Off-Road Lanes for Cycling in Kildare and Wicklow

Lane from Barretstown to Bishopshill Commons. © Eugene Brennan

I'm always on the lookout for new trails and farm lanes for cycling on. Some are marked with a cul-de-sac sign, and just end up at farmhouses. However, others actually link two roads. Usually, there’s no sign at the junction where they meet a main road, or even a road number, so it can be a mystery where they go. The best way to work out whether there's a through route is to check old maps and Google satellite imagery. (The road layer of Google Maps sometimes only shows sections of a lane). I've found around six of them in the Kildare/Wicklow area. This is one of my favourite trails that runs between the Ballymore Eustace–Barretstown Castle road and the Ballymore–Bishopshill road. (The back road to Blessington which runs at the rear of the Russborough House estate.) It's only really passable in dry weather, as like many of these lanes, it gets flooded at several points and it's  necessary to climb up into the ditch through briars to avoid the floods. Also the ground on such lanes can be hard going as the surfaces are usually untarmacked, potholed and sometimes the surface is churned up by horses' hooves. The screenshot map at the end of this post shows a Google My Map I created. You can zoom into the map when you visit it at this link, or by following the link in the map's caption.

The ground that this trail passes over is hilly and rocky. Looking at the Geological Survey Ireland bedrock map, it appears that the rock in this area is slate and greywacke. The formations here are called the "Glending Formation" and the "Slate Formation". Greywacke is currently quarried north of Blessington near Rathmore and slate was also extracted at least as far back as the early-19th century, resulting in the townland being named "Slate Quarries".

Bedrock geology in the vicinity of Barretstown. Contains Irish Public Sector Data (Geological Survey Ireland) licensed under a Creative Commons Attribution 4.0 International (CC BY 4.0) licence

 

Some nice off-road cycling routes. Image courtesy Google Maps.

Further Reading

Available Substation Capacity in Ireland

Information on substations. Image courtesy ESB Networks.

This interesting interactive map on the ESB Networks website shows transformer capacities. A "substation" indicated on the map could be an actual town substation like the one at Sunnyhill, with 1, 2 or more transformers and associated switchgear and circuit breakers, or a transformer in a cabinet or small building (common in the newer housing estates). A substation could also be a pole transformer. Demand Firm Capacity (DFC) is a measure of a substation's redundancy guaranteed supply available under a "single contingency" (fault). So while named capacity is the total output of a substation, (e.g. 2 MVA for a substation with two, 1 MVA transformers)., DFC is the max output with one of the transformers out of action.

Demand Capacity Available is the amount of spare VA capacity for connections.

In the first image, the popup shows the status for the substation beside Nolan's car park.

In the second image below, the spec is given for Kilcullen 38 kV Station at Sunnyhill. (ESB Networks have it in the wrong place. They haven't fixed it since I let them know). It has two 5 MVA transformers and one 10 MVA transformer. Demand Firm Capacity is 18 MVA. That's based on the larger transformer going off line. That leaves 2 x 5MVA = 10 MVA. The 18 MVA DFC assumes that it takes time for cooling oil to heat up, so a transformer can take higher loads and give overcapacity for a period of several hours until a fault is repaired.

Only 0.6 MVA or 600 kVA Demand Capacity Available is indicated for the town's substation. Also there's a Demand Parent Constraint from the substation's parent at Stratford.

This is a link to the ESB Networks available capacity heatmap.

View the Distribution Network Development Plan.

Information on substations. Image courtesy ESB Networks.

Further Reading

What Is the Ground Wire For?

© Eugene Brennan

What Is a Ground Wire?

The hot and neutral cores in a power cable are used to supply current to the appliances in your home. So what about the green wire? Why is it needed? This is known as the "ground" and is an additional wire that is included for the safety of you and your home.

Note: This article was written for a US audience, so I refer to the protective conductor as "ground". However, it is also called "earth" in other countries. Another difference is that the term "hot" is used, which is also known as "live". The third difference is that a split-phase 120/240 volt supply is provided to most homes in the US, resulting in a 240-volt supply between the two hots in addition to a 120-volt supply. This 240-volt supply is for powering higher powered appliances.

What is the ground wire for? © Eugene Brennan

What Are the Wires in a Power Cable?

Hot

This wire is at a potential of 120 volts nominal in the US relative to ground. Current flows out through the hot wire to an appliance. Hot is also referred to as "live" in other countries and voltage can be either 110 or 230 volts AC nominal.

Neutral

The neutral wire is at a voltage close to or equal to ground. The current which flows to an appliance via the hot wire returns via the neutral core in a cable. (See note below).

Ground

This is a protective conductor, included to prevent shock and/or fire. Ground is also known as "earth" in some countries.

The supply from the transformer feeding your home is split-phase and in the U.S., two hots in addition to a neutral are provided. Lower power appliances are connected between either of the hots and neutral and this gives a 120 volt supply. The voltage between the two hots is 240 volt for supplying higher power appliances.

Note: The electricity supply in our homes is alternating current (AC). So while we tend to think of current flowing out through the hot wire to an appliance and returning via the neutral wire, current actually flows both ways. So for one-half of what is known as a "cycle", current flows out through hot and returns via the neutral wire. During the second half cycle, the process is reversed and current flows to the appliance via neutral and returns via hot.

AC and DC voltage waveforms. DC voltage is constant over time. AC voltage and current change direction at a rate given by the frequency. This is 60 times per second or 60 Hertz (Hz) in the US. Each repetition of the waveform is called a cycle. © Eugene Brennan

Voltage supplies throughout the world. Somusde, public domain image via Wikimedia Commons

Ground: The Protective Conductor

The flex or fixed wiring supplying metal cased appliances includes a ground conductor (colored green in the US or green/yellow in the EU) in addition to hot and neutral. Inside an appliance, the ground core of the cable is connected to the outer metal casing. The connection may be made either using a screw terminal or a ring crimp and self-tapping screw or bolt. Spade crimps are generally not used to prevent a ground from being inadvertently removed instead of hot or neutral, and not replaced. Fixed (e.g. storage heater, kitchen range) and portable i.e corded appliances with extraneous metal which can be touched in normal use must be grounded. Ground acts as a "bypass" for currents in the event of a fault.

The fault could be due to:

• Conductors (e.g. wires, terminals, components) at hot or near full mains potential breaking, bending or detaching and touching the casing of an appliance
• Breakdown of insulation. For instance, insulation on cores of the power flex could become damaged inside an appliance or insulating spacers could become dislodged. Also, metal parts such as screws or nuts which have come undone could bridge the gap between hot and the metal casing
• Making contact with a power cable when drilling through a wall

Inside a microwave oven, the ground core of the power flex is connected to the casing using a ring crimp and screw. Note the symbol for ground. © Eugene Brennan

What Happens During a Fault if an Appliance Isn't Grounded?

If a fault occurs, the external metal of an appliance will become live and the voltage with respect to ground a person is standing one will be anything up to 120 volts (230 volts in the UK), depending on which part of the internal circuit touches the casing. If the metal isn't grounded and someone touches the appliance, current will travel through their body to ground.

If they are lucky and have rubber-soled shoes and are standing on a dry floor, they may just experience a tingling sensation. However, if conditions are damp, they have wet hands and are standing outdoors, they are more likely to experience a severe shock. If one hand touches the appliance and the other touches a grounded object (e.g pipework, poles, radiators or whatever), current will travel across their heart, a more dangerous scenario. If the person is unlucky or has a heart condition, this can kill.

Why Does Current Flow to Ground?

The reason why current flows to ground is that the neutral point in the supply transformer is connected via a ground conductor to a ground electrode. This raises the potential of the hot conductor to about 120 volts (230 volts UK) with respect to the ground surface. During a fault, or if someone touches a live conductor, current flows through ground conductors and the bulk of the physical ground (i.e the soil) back to the transformer. Safety transformers used in the UK, which are sometimes used for powering tools on construction sites and convert 230 V to 110 V, have the centre of the secondary grounded. This ensures that if another cable (potentially at a higher voltage) makes contact with extension leads connected to the output of the transformer, this voltage is pulled down to ground level and can trip breakers. Since the centre of the winding is grounded, either of the two 110 outputs from the transformer (there's no live and neutral as such) is only at a potential of 55 V, with respect to ground.

For more information on volts and amps, see my guide: 

Understanding Electricity? What Are Volts, Amps, Watts, Ohms, AC and DC?

Why Is the Supply Transformer Grounded?

Grounding the neutral of the supply transformer is a safety measure taken to eliminate dangerous rises in potential (greater than the hot voltage) on the hot or neutral conductors entering a home. This could occur for instance if a very high voltage power line (possibly hundreds of kilovolts) breaks and lands on a "low" voltage (120 volt) line. Another scenario is the insulation between the primary and secondary of the transformer being breached. This could allow the primary voltage (>10kv) to appear on the secondary. Yet another possibility is a lightning strike on the lines. Static charge can also cause a buildup of voltage on lines.

Basically, grounding the neutral pulls down the voltage of the line so that neutral is close to the potential of the earth which we are standing on and the voltage on either of the hot lines doesn't greatly exceed 120 volts.

The path of fault current when someone touches a non-grounded faulty appliance (2nd hot in U.S. wiring systems not shown). © Eugene Brennan

How Does Grounding Of Appliances Make Them Safer?

Grounding provides a bypass, shunt or shortcut through which electricity can flow, instead of passing to earth through the person who touches an appliance. Wires called equipment grounding conductors (EGC) are run from the electrical panel through the fixed wiring to all socket outlets, fixed appliances such as ranges or water heaters, light switches and ceiling roses in your home. In the case of a portable appliance, this grounding path continues from the pin in the plug through the flex, to the metal body of the appliance. At the electrical panel, all of these conductors are joined at the main grounding terminal. A grounding electrode conductor (GEC) runs outside the premises to a grounding electrode embedded in the soil.

When a fault occurs, current flows via the grounding conductor back to the electrical panel. If a TNC or TNCS earthing system is in use, all neutrals are joined to ground at the panel (or the neutral and ground may be joined at the output of the supply meter see earthing systems schematic below), and so the hot to ground fault at the appliance effectively becomes a hot to neutral fault, practically a short circuit. A large over-current flows and this trips the MCB (miniature circuit breaker) and possibly also the GFCI (whichever acts first) for the circuit, cutting power and making everything safe.

Grounding, however, also has another important function. Even if the current is insufficient to trip a breaker (in the case of a TT grounding system), the neutral conductor breaks outside the home, or stray currents in the neutral cause a dangerous rise in potential, it reduces the touch voltage between the casing of the appliance and the area on the ground on which the person is standing to a safe level. Both EGCs and the ground rod and the bulk impedance from the ground rod to the supply transformer effectively behave as a potential divider. Since the impedance of an EGC and ground rod are a lot less than the equivalent impedance of the soil between the premises and the supply transformer, and since the two impedances are in series, a much smaller voltage is dropped across the EGC than the total supply voltage and so the hazard is reduced.

The low impedance ground conductor shunts current away from the person touching the appliance, reducing the touch voltage to a safe level. (In reality the conductor passes via the plug and flex of the appliance and electrical panel to the ground rod) © Eugene Brennan

Naming Convention in the USA and UK

Equipment grounding conductors (EGC) = Protective earths (PE) in the UK.

Main grounding terminal = Main earthing terminal in the UK.

Grounding electrode = Earthing electrode in the UK.

Double-Insulated and Non-Grounded Appliances

Appliances such as hair driers, TVs, handheld kitchen appliances, etc. generally have plastic casings. If a fault occurs inside the appliance (e.g. a wire or component touches the inside of the casing), there is no danger since the plastic body is an insulator. These appliances don't have a ground wire in the flex. Some appliances such as power tools are not grounded and instead are "doubly insulated". This means that although the external casing of the tool or appliance may be metal, sufficient separation and isolation of the external metal from internal high voltages is effected to prevent electric shock. These devices don't have a ground wire in the cord either.

Double insulated appliances can be extremely dangerous if they get wet. This is because the casing is not grounded and can become live if water breaches the separation between live parts and casing. Also, the MCB is unlikely to trip and the GFI may not operate either.

Double insulated symbol. © Eugene Brennan

GFCI

A safety device called a Ground Fault Circuit Interrupter (GFCI) also known as a Ground Fault Interrupter or Residual Current Device (RCD) is likely to be fitted in most modern installations. This device monitors the current flowing out through the hot conductor and back via neutral. Normally these currents are equal. If current leaks to ground, not all the current returns through the GFCI. Electronics in the device detects this imbalance, and it trips out, shutting off the power. The trip current for a GFCI is normally 30mA but can be higher or lower depending on conditions.

A GFCI handles situations such as someone touching a live conductor, such as a damaged power cord with exposed cores, or the connector of a kettle left in a pool of water on a sink. (It may also even trip if damp bread gets stuck in a toaster and touches the element!)

A GFCI also responds to faults as described above where hot makes contact with the grounded body of an appliance. The device cuts the power if the MCB doesn't "get there first".

Another function of the GFCI is to prevent fire. Consider the situation where a damaged and exposed conductor makes contact with damp timber or grounded material, e.g. conduit or piping. This could produce sparks and start a fire if there is any flammable material nearby, e.g. sawdust, wood shavings or insulation. The current may not be sufficient to trip a breaker, however, the small leakage current to ground is more likely to be detected by the GFCI, making it trip and shut off the power.

GFCIs can be installed at the electrical panel, they are available in the form of a GFCI socket outlet, and you can also buy a GFCI adapter that plugs into a socket. An appliance is then plugged into the adapter. This is a worthwhile safety accessory for an extension lead if you use power tools in the garden.

Three Types of Grounding Systems

TNCS or PME (Protective Multiple Earthing)

This system uses a combined ground/neutral back to the supply transformer. This is then split into separate ground and neutral conductors after the meter. A hot to ground fault effectively becomes a hot to neutral fault, and since the impedance back to the transformer is low, the large, short circuit current ensures that an MCB for the circuit will trip. The problem with this type of system is that full mains potential could appear on extraneous metalwork of an appliance if the neutral breaks outside the premises. This is why the ground electrode is so important. The bulk of the earth between the ground electrode at the premises and the point where the supply transformer is grounded acts like a potential divider.

If someone touches a grounded appliance, the touch voltage between their hand and feet is equal to the voltage between the point at which the electrode enters the ground and their feet. Since this distance is likely to be a fraction of the distance to the supply transformer, the voltage is reduced proportionately. The electricity supply company may install multiple earthing or ground points from the neutral line between transformer and premises to reduce the consequences and hazard of a broken neutral (especially if they are widely separated)

TNS

The TNS system is often used when a ground can be provided by the armor of the supply cable. If the armor becomes corroded causing bad ground, this system can be converted to TNCS.

TT

The TT system is used when the power comes in overhead. The system uses the bulk of the earth as the return path for fault currents. It doesn't have the risk of a broken neutral. If a home is distant from the supply transformer, the fault current during a hot to ground fault may be insufficient to trip a breaker because the resistance of the earth is too great. Since the development of GFCIs which can detect small leakage currents to the ground, this is less of an issue. TT systems may be converted to TNCS systems where the ground and neutral are neutralized or joined together at the exit point of the meter.

Un-Grounded and Grounded Socket Outlets: NEC Regulations

In the U.S., both ungrounded and grounded receptacles are used. Ungrounded outlets are prohibited in new buildings but in the situation where an equipment ground conductor is not present, NEC code exceptions allow these to be replaced by either another non-grounded receptacle, a GFCI receptacle or a grounding type receptacle fed by a GFCI as long as the receptacle is marked "No equipment ground" and "GFCI protected".

2-pin in-grounded receptacles can be upgraded to 3-pin grounded receptacles with the addition of new ground wiring.

Bonding

Metal services such as water and heating pipes and hot water heaters are grounded with a heavy gauge wire routed back to the electrical panel. This ensures that if a hot wire makes contact with these services, a large current will flow and trip the breaker. The heavy gauge wire is rated so that it can carry the current which may flow if a hot from a high current circuit makes contact with the service. Also, the heavy gauge keeps the resistance of the cable low. This ensures that as current flows through this resistance, the resulting voltage rise is kept below safe limits. This is vitally important in bathrooms where everything is damp and we may be in our bare feet and making relatively good electrical contact. Everything such as radiators, water pipes, wall heaters and the drain in the bath/shower are connected together by a bonding conductor. This "equipotential bonding" keeps everything at the same voltage and there is no difference in voltage between for instance a showerhead and the drain.

© Eugene Brennan

Electric Wiring Color Codes

This Wikipedia article gives lots of info about wiring and color codes used in various countries around the world.

References

Fish RM, Geddes LA. Conduction of electrical current to and through the human body: a review. Eplasty. 2009;9:e44. Published 2009 Oct 12.

Kuphaldt,Tony R., Lessons In Electric Circuits -- Volume I - Chapter 3 - ELECTRICAL SAFETY. Copyright (C) 2000-2020, Revised November 06, 2021.

Disclaimer

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

© 2013 Eugene Brennan

Questions and Answers 

Cal Stowe from Houston, TX on August 12, 2019:

In my outside main breaker panel, the neutral bus is connected to:

1) the ground bus

2) earth electrode

3) conductor back to the transformer

4) 100 kva surge protector

This panel is connected to an inside panel with all the individual breakers.

The plumbing is connected to a separate earth electrode 4 feet away. Should the plumbing earth electrode be connected to the power earth electrode?

If they are separate:

1) Pipe ground fault voltage should be relatively high, current low, and breaker may not trip due to high impedance from pipe earth electrode to transformer earth electrode.

2) A high voltage surge would create high potential between connected devices and plumbing faucets, etc. There would be no potential plumbing to floor.

3) A lightning ground strike would create some potential between the two earth electrodes, and some potential between plumbing and floor due to voltage gradient.

4) Surge protector dump to earth will induce little voltage on plumbing.

If the earth electrodes are connected:

1) In the event of a ground fault, voltage will be low, and current high through neutral back to transformer. Breaker will trip.

2) A high voltage surge will not raise neutral and plumbing voltage?

3) A lightning ground strike will induce some voltage and current between the ground electrodes.

4) A surge protector dump to earth will induce some voltage on the plumbing?

Jim G on March 18, 2019:

Hello Eugene

I’m hoping that you can advise. I recently came into possession of an old film projector from the 1940’s. The projector is primarily made out of metal, has tubes, and a cord with no ground prong.

I plugged in the projector and turned it in and success the lights came on. But then I noticed a slight tingle when I touched the projector. Luckily I was wearing rubber soles. I opened up the projector and could not see any obvious wire touching the case, etc. I got my multi meter and ran a wire to the house ground which is close to my work bench. With my meter connected to the house ground I would read 120v from multiple locations on the projector.

I’m basically at my limit of electrical competence. Would replacing the power cord with a grounded cord solve my problem and make the projector safe to use.

Thank you for your advice.

Jim

Eugene Brennan (author) from Ireland on March 18, 2019:

Hi Jim, it sounds as though there's a hot to ground fault somewhere in the appliance. If you ground it by replacing the flex and plug, it would still trip a GFCI unless the fault is sorted. Another scenario with a three core grounded cord is that you could have a bootleg ground in one of your receptacles and if hot and neutral have been reversed, this would place live voltage on the casing of the appliance.

Another scenario is that there are EMI suppression filters used and with these, a terminal of the filter can be connected to chassis. The chassis in AV equipment is often ungrounded to prevent ground loops and hum. However, it's possible to experience a tingle when touching an aerial connector on a TV, because of a capacitor in the filter being connected to the chassis. However, EMI filters are unlikely to be used in vintage equipment such as your lamp.

Might be a good idea to take it somewhere and get it checked. I don't give advice online on these matters because something could be missed and there could be an unfortunate outcome!

Tyrone on September 11, 2017:

In the event of a fault it seems the circuit is not being completed via ground but via the neutral wire. Therefore the grounding on both the transformer and residence are stand alone and are only there to bring the neutral down to 0 volts?

Eugene Brennan (author) from Ireland on September 11, 2017:

A circuit is normally completed via neutral, but if a hot to ground (live to earth) fault occurs, there's also a parallel path for current to flow through via ground back to the transformer (and also the neutral conductor, if ground is connected to neutral at the panel).

Tyrone on September 11, 2017:

I'm thinking there wouldn't be much current travelling along the ground path because of the much higher resistance compared to the neutral wire?

Eugene Brennan (author) from Ireland on September 11, 2017:

It depends on the grounding system Tyrone. If TT grounding/earthing is used, the bulk of the ground may have a large resistance and so current would be lower than that in the neutral in a fault situation (possibly insufficient to trip an MCB, but when the installation is protected by a GFCI/RCD, this will trip). In a TN-S system, a large short circuit current will flow back via the separate ground to the supply transformer. In a TN-C system which has a common combined neutral/ground back to the transformer and appliance cases connected to neutral, a larger than normal current will flow on this conductor during a fault. A broken neutral conductor can cause a dangerous potential on the metalwork of appliances. A TN-CS system provides separate ground and neutral to appliances. If there's a fault, a large current will flow through the equipment ground (protective earth) back to the panel. This will be larger than the current flowing in the neutral core of the cable feeding the appliance, but will flow in the neutral conductor back to the transformer.

So it's really only TT systems where the resistance is high. The actual ground wire from the appliance back to the panel would have a low resistance.

Izhaan on August 28, 2017:

Plz tell me

How can i identify earth wire in household circuit.?

Eugene Brennan (author) from Ireland on August 28, 2017:

Hi Izhaan - This link shows the colours of earth wires in electrical installations:

https://en.wikipedia.org/wiki/Electrical_wiring#Co...

Earthing/grounding conductors may have a coloured sheath or be bare without a sheath in fixed wiring cables. The earth conductor in a flexible power cord supplying an appliance normally has an insulating sheath. In socket and lighting outlets and electrical panels, bare earth conductors are provided with a coloured sleeve to insulate them from inadvertent contact with live/hot parts and also to identify the conductors.

If you are considering making any electrical modifications, I highly recommend you consult a qualified electrician. A simple mistake can prove fatal!

Denise field on May 19, 2017:

Okay here goes my hairdryer lead (flex) has been chewed in half so I gave it to my neighbour (yes I'm rubbish!!)

He put on a new plug, the other one was fixed on the lead. But said its not earthed it only has 2 wires which were visible cutesy of the dog!! These visible wires are copper im not going to get electrocuted am I?

Eugene Brennan (author) from Ireland on May 19, 2017:

Hi Denise,

If the casing of the hair drier is plastic, it doesn't need to be earthed. I presume you mean the copper of the wires was visible? If there are still sections of the flex, after the plug was replaced, where the copper wires are exposed, the whole lead needs to be replaced (or possibly shortened if the bad bit is near the plug end).

Denise field on May 21, 2017:

Thank you so much Eugene. Youve really put my mind at ease. Unfortunately the lead has been shortened so no exposed wires!! But! It worked for about 1 minute then stopped. There was no smell indicating the motor burnet out no no bang no spark just stopped maybe the plug is old what do you think obviously without seeing it. Just glad to know I'm not going to be shocked etc.

Eugene Brennan (author) from Ireland on May 21, 2017:

Hi Denise,

Possibly there is invisible damage, i.e. broken wires, in the flex from the dog stretching it. Sometimes if the stranded copper cores in a flex are broken, the wires can be pulled until they snap and the lead then shortened. However the safest thing would be to completely replace the lead.

Ned Tallyho on April 10, 2017:

The green/yellow (EU) cable connecting copper pipes near my gas combi boiler is bent over to fit in but the bare wire can be seen where the cable has split due to being bent. Is this dangerous and should I get it changed?

Eugene Brennan (author) from Ireland on April 10, 2017:

Hi Ned,

The earth wire doesn't carry a dangerous voltage (at least it shouldn't assuming the earth rod is working properly and the touch voltage is below safe levels during a fault situation).

The covering on an earth wire is used for identification but can also give the inner core some protection from damage. It also acts as insulation if for instance the wire feeds into a socket outlet/light fitting. This prevents live parts/wires inadvertently touching the earth conductor when for instance socket plates are removed/replaced. Usually however live wires are insulated and live parts are shrouded, so this doesn't often happen.

I don't think it's a major issue if the cable insulation is split, in any case the pipes it connects to are uninsulated. I would be more worried that the inner core has been damaged and strands broken from the cable being repeatedly bent during installation/maintenance work. It may have just been chaffed when work was done, but it's no harm getting the cable checked by a qualified electrician.

MG Seltzer from South Portland, Maine on August 02, 2015:

This topic was just on my mind as our GCFI outlet in the bathroom isn't working, which means that the one near the kitchen door has kicked itself off. I had just been thinking, "I really need to understand how the current flows through the system." Also, years ago, a contractor told me the grounding plugs on adaptors were "useless," and could be pulled out with pliers to let a three-prong plug fit a standard outlet. And I remember thinking, "Now is this true?" I am bookmarking this Hub because I see lots of good detail that I think will answer my questions. Voted thumbs up, of course.

Eugene Brennan (author) from Ireland on August 03, 2015:

The older style NEMA 1-15 two pole socket was 15 amp rated and un-grounded. It is not permitted in new construction but there are probably lots of these still out there. If an appliance has a metal casing (e.g. a metal kettle), it needs to be grounded. The exception is double insulated appliances which have metal on their exterior but are not grounded. This is because the metal is separated from the inner workings to the extent that it is highly unlikely to become "live".

Ideally you should get your sockets upgraded to 3 pin grounded types...

Further Reading

Re-Discovering the Mill Stream Arch

One mill is marked on the OSI c.1837 first-edition six-inch map. Image courtesy the National Library of Scotland, licence CC-BY.

I hadn't seen it since around 1982 or '83. I thought it was covered with scrub and brambles over the decades, but not so. This is a good time of the year to investigate it before the brambles get going. My theory is that it could have been the opening to a culvert/mill race that diverted water to a second mill in the adjoining field beside the cemetery car park or it may have been the return feed to the stream. One mill is marked on the 6-inch, first-edition OSI map and was located just over the wall from where the bins used to be kept in the cemetery. The ruin is still there. There's an arched culvert under the Mile Mill road, south of the lodge, that fed water to this mill.
I think the arched opening into the stream is unlikely to be a latrine outlet or drain as it's too wide. I thought most of the arch was submerged below the waterline, but possibly the bed of the stream has dropped over the last four decades due to erosion. Anyway, I didn't have a camera with me. That's a shame because the arch was nicely lit up by the setting sun.
Will investigate further tomorrow and take some photos.

The map above is a ChatGPT-sharpened version of a screenshot of the c. 1837 first-edition six-inch map available on the National Library of Scotland website. The scans appear to be a bit clearer than those available on Tailte Éireann's Irish Townland and Historical Map viewer.
Map reproduction licence CC-BY, courtesy the National Library of Scotland.

Further Reading

YouTube Requirements and Broadband Speed

Connection speed required for YouTube. Image from Google Help

Unless you have lots of people in your home feeding off  your Internet service and sharing the bandwidth, ultra-high-speed connection promotions such as "Gigabit broadband" are just marketing hype. The table above shows the recommended connection speeds from Google for streaming video from YouTube. Vodafone keeps trying to sell me such a service using a fibre-optic connection that replaces copper wires to the cabinet and which would increase my speed from 100 Mbps to 1 Gbps, but I'm stubbornly refusing as the current speed is perfectly adequate. A faster connection probably increases upload speed (which I think is normally about one tenth of download speed), but most people aren't in a hurry when uploading, unless they can't wait to backup thousands of photos or put their latest video online. Eventually I'll have to give in, because copper lines, which Vodafone rent from Eir, will ultimately be replaced. The process is slow, because there are legacy systems that still require them. 
I ring Vodafone every year, three months before my contract is due for renewal and negotiate a loyalty discount, getting a six-month discount. It's only €5 per month for 6 months, but better than nothing.

Further Reading

A Child Can Push Harder Than a Lawn Mower Blade

AI image generated by Google Gemini.

Did you know that a child can probably produce more torque using their arm, than a lawn mower engine can generate to turn the blade? Surprisingly, the figure for the torque of a 5 hp engine used on a mower is 7 to 10 foot-pounds (ft·lbf) in the imperial system or 11.5 to 13.6 newton-meters (Nm). Applied torque is simply force multiplied by distance, so 1 pound-force applied over a distance of 1 foot from a pivot is 1 foot-pound. In the metric system, the unit of torque is the newton-metre (Nm). A torque of 1 Nm is equivalent to one newton—the SI unit of force—applied over a distance of one metre. The speed of a lawn mower blade is more important than torque, and blades are driven directly by the crankshaft without reduction or overdrive gearing. Blades typically spin at the engine speed of around 3000 RPM, giving a blade tip speed of around 200 mph, or 90 metres per second.

As we saw in the article Interesting Facts - What is Torque?

power = torque x angular rotation speed

So while a child may be able to exert more torque with their arm than a mower engine can exert on a blade, they wouldn't be able to match its power. Another piece of the jigsaw is that the quoted figure of 11 to 13 Nm is for the drive torque from the engine. Since a blade is spinning at around 3000 RPM, it has a lot of inertia. The technical term for this when a rotating body such as a flywheel or blade is involved is moment of inertia. When a blade slows down as it impacts grass, the change in angular momentum creates a force, just like the way a car or any linearly-moving object creates a force as it slows down due to friction, or when it hits something (think of the huge force produced by a hammer, typically many tonnes, when it hits a nail). So the force produced by a blade as it impacts and shears grass is much greater than the force that the engine itself could have generated.

Note: You may be wondering why "newton" in "newton-metres" above isn't capitalised.  The unit is named after the English scientist Isaac Newton. It's not a typo. In the International System of Units (SI), or Système international d'unités, units named after a person are not capitalised. However, the symbol is, N in this case, Units are normally lower case, as are prefixes. However, prefixes over one million are capitalised—so kilometres is km, but gigahertz is GHz.

Further Reading

Cantilevered Boardwalks For Motorway Bridges?

Bridge over M9 Kilcullen Bypass on Sunnyhill Road. Image courtesy Google.

When Kildare County Council, or whoever was responsible, produced the spec for this bridge, (and the one over the M7 at the Bundle of Sticks Roundabout outside Naas), they left out foothpaths. Maybe it was lack of common sense and an attitude of "Sure, only cars go out there". Or perhaps it was due to penny pinching and lack of foresight and a narrow bridge was cheaper than one a couple of metres wider? Anyway, I'm wondering could boardwalks/cantilevered foothpaths be fixed onto the sides, exterior to the parapets?
It would obviously be impractical to install foothpaths on the inside of the parapets due to to both lanes being reduced in width. As it is, cars can't pass pedestrians safely without partially moving into the other lane. An article by Paul MacDonald, Kildare National Roads Office, on the construction of the M7 Newbridge Bypass and M9 Kilcullen Bypass is available on the Kilcullen Diary here.

The section about the earthing of the steelwork of the underbridge for the River Liffey is interesting—High voltage pylons can induce voltages and currents in conductors, potentially leading to different and hazardous potentials between isolated elements of a structure. Bonding them together eliminates these voltages and earthing a structure pulls the voltage down to ground (similar to the equipotential bonding in bathrooms, where metal objects such as drains, radiators, towel rails, water pipes and metal baths are bonded together):

Bridge over M9 Kilcullen Bypass on Sunnyhill Road. Image coiurtesy Google.

Further Reading

How to Calculate Bolt Circle Diameter (BCD) for Chainrings and Bash Guards

Bolt circle diameter (BCD). © Eugene Brennan

What Is a Bolt Circle Diameter (BCD) or Pitch Circle Diameter (PCD)?

As you may be aware, if you've found this guide, a bolt circle is an imaginary circle that passes through the centre of the bolt or screw holes in a round pattern. This is typically a wheel hub on a vehicle, chainring on a bicycle or flange on a pipe. The diameter of this circle is known as the bolt circle diameter (BCD) or pitch circle diameter (PCD).

Typically, BCD is quoted for chainrings on bikes and the bash guards that cover them, and you can calculate it by measuring the distance between the mounting holes of the chainring on the spider. If you need to order a part for a bicycle or check the BCD of a flange and can only measure the bolt hole spacing, you need to know the formula for working it out. Alternatively you can skip to the end of this guide where there are tables for various bolt spacings.

Imaginary bolt circle. © Eugene Brennan

Working Out the Formula for Bolt Circle Diameter

I've given the formula further down this guide, but the math for working it out is fairly straightforward if you want to follow it through. To do the calculations, we first need to understand what sine and cosine mean.

A right-angled triangle has one angle that measures 90 degrees. The longest side opposite this angle is called the hypotenuse. Sine and cosine are trigonometric functions of an angle and are the ratios of the lengths of the other two sides to the hypotenuse of a right-angled triangle.

Let's represent one of the angles by the Greek letter θ (theta) as shown in the diagram below.

Side a is called the "opposite" side and side b is called the "adjacent" side to the angle θ.

"|" around the words below means "length of"

So:

sine θ = |opposite side| / |hypotenuse|

cosine θ = |adjacent side| / |hypotenuse|

Sine and cosine are sometimes abbreviated to sin and cos.

Sine and cosine for a right-angled triangle.. © Eugene Brennan

Angle Subtended by the Arc

Since there are 360 degrees in a full circle, then if there are N equally spaced mounting holes, the angle subtended by an arc (produced by joining the ends of the arc to the centre) on an imaginary circle passing through the bolt holes is:

θ = 360 / N

In the diagram below, there are six equally spaced holes, so:

θ = 360 / 6 = 60º

Angle subtended by arc. In this example, the angle is 360/6 = 60 degrees. © Eugene Brennan

Use Sine and Cosine to Work Out the Radius

We can draw triangles and use sine and cosine to solve the triangles and find the length of the radius R and, therefore the diameter D.

Working out bolt circle diameter (BCD). © Eugene Brennan

The simplest case is when holes are equally spaced around in a circle.

If we can find the radius R of the bolt circle, then this gives us the diameter D.

We calculated that:

θ = 360 / N

Also, A is the spacing between holes.

D is the bolt circle diameter.

Referencing the diagram above, a triangle can be drawn between the two ends of an arc on the bolt circle and the centre of the circle. This can be split up into two equal right-angled triangles. The length of the chord or line joining the two ends of the arc is the hole spacing A. (For more info on circles, see this guide.)

So from the diagram, we see that:

Sin (θ/2) = |opposite| / |hypotenuse| = (A/2) / R

Rearranging:

R = (A/2) / Sin (θ/2)

But D = 2R

So, D = 2 x (A/2) / Sin (θ/2) = A/Sin (θ/2)

But we worked out θ = 360 / N

So substituting for θ gives

D = A/Sin (θ/2) = A/Sin ((360 / N)/2) = A/Sin (180 / N)

Our final equation is:

D = A/Sin (180 / N)

Working Out the BCD for a Chainring or Bash Guard

All you need to do to calculate the BCD is measure the hole spacing A between adjacent holes, count the number of holes N and plug them into the equation above to calculate the BCD.

Tables of Bolt Circle Diameters

The tables below give the BCD for hole spacings from 10 to 200 mm, 1 to 12 inches and 3 to 8 holes.

Table 1: Bolt Circle Diameters for Hole Spacings From 10 to 200 mm

Table 1: Bolt Circle Diameters for Hole Spacings From 10 to 200 mm

Hole spacing	Number of holes
	3	4	5	6	7	8
10	11.5	14.1	17.0	20	23.0	26.1
11	12.7	15.6	18.7	22	25.4	28.7
12	13.9	17.0	20.4	24	27.7	31.4
13	15.0	18.4	22.1	26	30.0	34.0
14	16.2	19.8	23.8	28	32.3	36.6
15	17.3	21.2	25.5	30	34.6	39.2
16	18.5	22.6	27.2	32	36.9	41.8
17	19.6	24.0	28.9	34	39.2	44.4
18	20.8	25.5	30.6	36	41.5	47.0
19	21.9	26.9	32.3	38	43.8	49.6
20	23.1	28.3	34.0	40	46.1	52.3
21	24.2	29.7	35.7	42	48.4	54.9
22	25.4	31.1	37.4	44	50.7	57.5
23	26.6	32.5	39.1	46	53.0	60.1
24	27.7	33.9	40.8	48	55.3	62.7
25	28.9	35.4	42.5	50	57.6	65.3
26	30.0	36.8	44.2	52	59.9	67.9
27	31.2	38.2	45.9	54	62.2	70.6
28	32.3	39.6	47.6	56	64.5	73.2
29	33.5	41.0	49.3	58	66.8	75.8
30	34.6	42.4	51.0	60	69.1	78.4
31	35.8	43.8	52.7	62	71.4	81.0
32	37.0	45.3	54.4	64	73.8	83.6
33	38.1	46.7	56.1	66	76.1	86.2
34	39.3	48.1	57.8	68	78.4	88.8
35	40.4	49.5	59.5	70	80.7	91.5
36	41.6	50.9	61.2	72	83.0	94.1
37	42.7	52.3	62.9	74	85.3	96.7
38	43.9	53.7	64.6	76	87.6	99.3
39	45.0	55.2	66.4	78	89.9	101.9
40	46.2	56.6	68.1	80	92.2	104.5
41	47.3	58.0	69.8	82	94.5	107.1
42	48.5	59.4	71.5	84	96.8	109.8
43	49.7	60.8	73.2	86	99.1	112.4
44	50.8	62.2	74.9	88	101.4	115.0
45	52.0	63.6	76.6	90	103.7	117.6
46	53.1	65.1	78.3	92	106.0	120.2
47	54.3	66.5	80.0	94	108.3	122.8
48	55.4	67.9	81.7	96	110.6	125.4
49	56.6	69.3	83.4	98	112.9	128.0
50	57.7	70.7	85.1	100	115.2	130.7
51	58.9	72.1	86.8	102	117.5	133.3
52	60.0	73.5	88.5	104	119.8	135.9
53	61.2	75.0	90.2	106	122.2	138.5
54	62.4	76.4	91.9	108	124.5	141.1
55	63.5	77.8	93.6	110	126.8	143.7
56	64.7	79.2	95.3	112	129.1	146.3
57	65.8	80.6	97.0	114	131.4	148.9
58	67.0	82.0	98.7	116	133.7	151.6
59	68.1	83.4	100.4	118	136.0	154.2
60	69.3	84.9	102.1	120	138.3	156.8
61	70.4	86.3	103.8	122	140.6	159.4
62	71.6	87.7	105.5	124	142.9	162.0
63	72.7	89.1	107.2	126	145.2	164.6
64	73.9	90.5	108.9	128	147.5	167.2
65	75.1	91.9	110.6	130	149.8	169.9
66	76.2	93.3	112.3	132	152.1	172.5
67	77.4	94.8	114.0	134	154.4	175.1
68	78.5	96.2	115.7	136	156.7	177.7
69	79.7	97.6	117.4	138	159.0	180.3
70	80.8	99.0	119.1	140	161.3	182.9
71	82.0	100.4	120.8	142	163.6	185.5
72	83.1	101.8	122.5	144	165.9	188.1
73	84.3	103.2	124.2	146	168.2	190.8
74	85.4	104.7	125.9	148	170.6	193.4
75	86.6	106.1	127.6	150	172.9	196.0
76	87.8	107.5	129.3	152	175.2	198.6
77	88.9	108.9	131.0	154	177.5	201.2
78	90.1	110.3	132.7	156	179.8	203.8
79	91.2	111.7	134.4	158	182.1	206.4
80	92.4	113.1	136.1	160	184.4	209.1
81	93.5	114.6	137.8	162	186.7	211.7
82	94.7	116.0	139.5	164	189.0	214.3
83	95.8	117.4	141.2	166	191.3	216.9
84	97.0	118.8	142.9	168	193.6	219.5
85	98.1	120.2	144.6	170	195.9	222.1
86	99.3	121.6	146.3	172	198.2	224.7
87	100.5	123.0	148.0	174	200.5	227.3
88	101.6	124.5	149.7	176	202.8	230.0
89	102.8	125.9	151.4	178	205.1	232.6
90	103.9	127.3	153.1	180	207.4	235.2
91	105.1	128.7	154.8	182	209.7	237.8
92	106.2	130.1	156.5	184	212.0	240.4
93	107.4	131.5	158.2	186	214.3	243.0
94	108.5	132.9	159.9	188	216.6	245.6
95	109.7	134.4	161.6	190	219.0	248.2
96	110.9	135.8	163.3	192	221.3	250.9
97	112.0	137.2	165.0	194	223.6	253.5
98	113.2	138.6	166.7	196	225.9	256.1
99	114.3	140.0	168.4	198	228.2	258.7
100	115.5	141.4	170.1	200	230.5	261.3
101	116.6	142.8	171.8	202	232.8	263.9
102	117.8	144.2	173.5	204	235.1	266.5
103	118.9	145.7	175.2	206	237.4	269.2
104	120.1	147.1	176.9	208	239.7	271.8
105	121.2	148.5	178.6	210	242.0	274.4
106	122.4	149.9	180.3	212	244.3	277.0
107	123.6	151.3	182.0	214	246.6	279.6
108	124.7	152.7	183.7	216	248.9	282.2
109	125.9	154.1	185.4	218	251.2	284.8
110	127.0	155.6	187.1	220	253.5	287.4
111	128.2	157.0	188.8	222	255.8	290.1
112	129.3	158.4	190.5	224	258.1	292.7
113	130.5	159.8	192.2	226	260.4	295.3
114	131.6	161.2	193.9	228	262.7	297.9
115	132.8	162.6	195.6	230	265.0	300.5
116	133.9	164.0	197.4	232	267.4	303.1
117	135.1	165.5	199.1	234	269.7	305.7
118	136.3	166.9	200.8	236	272.0	308.3
119	137.4	168.3	202.5	238	274.3	311.0
120	138.6	169.7	204.2	240	276.6	313.6
121	139.7	171.1	205.9	242	278.9	316.2
122	140.9	172.5	207.6	244	281.2	318.8
123	142.0	173.9	209.3	246	283.5	321.4
124	143.2	175.4	211.0	248	285.8	324.0
125	144.3	176.8	212.7	250	288.1	326.6
126	145.5	178.2	214.4	252	290.4	329.3
127	146.6	179.6	216.1	254	292.7	331.9
128	147.8	181.0	217.8	256	295.0	334.5
129	149.0	182.4	219.5	258	297.3	337.1
130	150.1	183.8	221.2	260	299.6	339.7
131	151.3	185.3	222.9	262	301.9	342.3
132	152.4	186.7	224.6	264	304.2	344.9
133	153.6	188.1	226.3	266	306.5	347.5
134	154.7	189.5	228.0	268	308.8	350.2
135	155.9	190.9	229.7	270	311.1	352.8
136	157.0	192.3	231.4	272	313.4	355.4
137	158.2	193.7	233.1	274	315.8	358.0
138	159.3	195.2	234.8	276	318.1	360.6
139	160.5	196.6	236.5	278	320.4	363.2
140	161.7	198.0	238.2	280	322.7	365.8
141	162.8	199.4	239.9	282	325.0	368.5
142	164.0	200.8	241.6	284	327.3	371.1
143	165.1	202.2	243.3	286	329.6	373.7
144	166.3	203.6	245.0	288	331.9	376.3
145	167.4	205.1	246.7	290	334.2	378.9
146	168.6	206.5	248.4	292	336.5	381.5
147	169.7	207.9	250.1	294	338.8	384.1
148	170.9	209.3	251.8	296	341.1	386.7
149	172.1	210.7	253.5	298	343.4	389.4
150	173.2	212.1	255.2	300	345.7	392.0
151	174.4	213.5	256.9	302	348.0	394.6
152	175.5	215.0	258.6	304	350.3	397.2
153	176.7	216.4	260.3	306	352.6	399.8
154	177.8	217.8	262.0	308	354.9	402.4
155	179.0	219.2	263.7	310	357.2	405.0
156	180.1	220.6	265.4	312	359.5	407.6
157	181.3	222.0	267.1	314	361.8	410.3
158	182.4	223.4	268.8	316	364.2	412.9
159	183.6	224.9	270.5	318	366.5	415.5
160	184.8	226.3	272.2	320	368.8	418.1
161	185.9	227.7	273.9	322	371.1	420.7
162	187.1	229.1	275.6	324	373.4	423.3
163	188.2	230.5	277.3	326	375.7	425.9
164	189.4	231.9	279.0	328	378.0	428.6
165	190.5	233.3	280.7	330	380.3	431.2
166	191.7	234.8	282.4	332	382.6	433.8
167	192.8	236.2	284.1	334	384.9	436.4
168	194.0	237.6	285.8	336	387.2	439.0
169	195.1	239.0	287.5	338	389.5	441.6
170	196.3	240.4	289.2	340	391.8	444.2
171	197.5	241.8	290.9	342	394.1	446.8
172	198.6	243.2	292.6	344	396.4	449.5
173	199.8	244.7	294.3	346	398.7	452.1
174	200.9	246.1	296.0	348	401.0	454.7
175	202.1	247.5	297.7	350	403.3	457.3
176	203.2	248.9	299.4	352	405.6	459.9
177	204.4	250.3	301.1	354	407.9	462.5
178	205.5	251.7	302.8	356	410.2	465.1
179	206.7	253.1	304.5	358	412.6	467.7
180	207.8	254.6	306.2	360	414.9	470.4
181	209.0	256.0	307.9	362	417.2	473.0
182	210.2	257.4	309.6	364	419.5	475.6
183	211.3	258.8	311.3	366	421.8	478.2
184	212.5	260.2	313.0	368	424.1	480.8
185	213.6	261.6	314.7	370	426.4	483.4
186	214.8	263.0	316.4	372	428.7	486.0
187	215.9	264.5	318.1	374	431.0	488.7
188	217.1	265.9	319.8	376	433.3	491.3
189	218.2	267.3	321.5	378	435.6	493.9
190	219.4	268.7	323.2	380	437.9	496.5
191	220.5	270.1	324.9	382	440.2	499.1
192	221.7	271.5	326.6	384	442.5	501.7
193	222.9	272.9	328.4	386	444.8	504.3
194	224.0	274.4	330.1	388	447.1	506.9
195	225.2	275.8	331.8	390	449.4	509.6
196	226.3	277.2	333.5	392	451.7	512.2
197	227.5	278.6	335.2	394	454.0	514.8
198	228.6	280.0	336.9	396	456.3	517.4
199	229.8	281.4	338.6	398	458.6	520.0
200	230.9	282.8	340.3	400	461.0	522.6

Disclaimer

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2018 Eugene Brennan

Further Reading