220 VAC Electric Baseboard Heater Without A Ground

Without access to the manufacturer's installation instructions it is difficult to say what would happen. That is why countries have electrical codes: to assure the safety of those using electrical installations.

From the description it seems that the installation is located on the North American continent, which certainly has a suite of electrical codes that a competent Electrician there would follow, thereby both assuring safety of the occupants and also maintaining a level of popularity with the building's fire insurers. If the installation is not to code, the assurance is lost and the risk of litigation in the event of an incident rises.

The same recommendations have been repeated in this forum countless times: if in doubt, consult a qualified local Electrician.

Here in the US, older systems do not need to be retrofitted as codes change,so there are lots of homes that do not abide by the current code. Is this a good idea? For people on a fixed income who can't afford continual upgrades, it makes sense to them. What it implies is that the new codes are not vital to safety.

You either do it properly, or risk killing someone....

Do ask your insurance company, this ensues an answer, but remember, they now know what to look for too!

This is my understanding of the building and electrical code. GA for bringin facts to the table!

Code 250.4

(4) Path for Fault Current. Electrical equipment, wiring, and other electrically conductive material likely to become energized shall be installed in a manner that creates a low impedance circuit from any point on the wiring system to the electrical supply source to facilitate the operation of overcurrent devices should a second ground fault from a different phase occur on the wiring system. The earth shall not be considered as an effective fault-current path.

What could possibly go wrong? If the heater has any exposed conductive parts that could possibly come in (electrical) contact with the wiring (if e.g. a wire became detached or damaged), there would be a potentially lethal voltage on that part or parts; without a protective conductor (ground) this would not be noticed until it was probably too late.

Is this safe? Maybe.

IMHO this is probably not safe. A more careful examination of the materials used by the heater and what the local power wiring standards are would be needed to determine if it is safe. Then there's the added uncertainty of how this heater was installed.

Along with the electrical safety concerns there can also be ignition problems from blocked airflow or flammable materials coming in contact with HOT elements. Space heaters are one of the most frequent causes of fires.

The heater is an electrical heater that does not use any flammable fuels. I replaced an existing heater, similar type that did not have a ground terminal. The condo was built in the early to mid 60s and the heater and thermostat are original.

I dunno. Is Russian Roulette a safe way to use a gun? At least in Russian Roulette you know the odds and something of the timing.

Disconnect this potentially deadly device and call an electrician to properly install it....You're playing with fire, quite literally....

I think you need to find a way to ground it.

You don't say what the breaker's specs are. Will it trip before the wires get hot?

I'm not an electrician but if the heater says to ground it, ground it.

Your insurance company will drop you like a hot rock if the unthinkable happens.

It's not a, " Hot Rock ".

It's a, " Hot Potato ".

Rock; potato. The insurance will drop him either way if the thing fails.

The breaker is 20A and if it throws, both hots throw. The unit is 1250W and runs 5.3A.

So a ground fault drawing less than 20 amps will not drop the breaker, but possibly make the frame live at 110VAC.....

I still don't get it. If I walk around the room with a hot 110V in my hand and I don't touch a neutral or ground, how can I get shocked? Same as the chassis on the heater being hot and not ground or neutral close by; what's the risk?

I could look at things from an extremely unlikely point of view - first, there would have to be a fault in the heater (very unlikely since it's a brand new heater, but we're clawing for a possible problem) or the hot wire gets loose (how it happens, I don't know, but we're using our imagination) or the romex outer coating and the coating on the hot wire is broken and shorts to the chassis (again unlikely since it's brand new romex and it has cable stress relief. Then we'd need someone running an electrical device such as a vacuum cleaner also with a defective cord or a neutral fault and the person would need to touch the vacuum cleaner and the heater chassis at the same time to get a shock. This is extremely unlikely and using logic, I figure 50+ years of nobody getting shocked is pretty good history for me.

See post 73

Probably mostly ignorance and sloth.

Nevertheless, I am in agreement with the safety concern. GA

The new lines I ran for the washer/dryer were permitted and they are up to code, or at least in 2006 when it was done.

I can't understand what makes the concept so difficult for you to understand. Wait, maybe this will help. Choose a large room in your house and stand in the center. I'll drop a hot straight down from the ceiling and you'll hold it in your hand. The wire will be let out to allow you to get as close a within 6 feet of any outlet, but you'll never touch it. Tell me how you get shocked and why this is unsafe? Where's the illusion?

I didn't say that I am in full compliance of code. I did it for a reason, so that this wouldn't be a discussion about code. What I wanted to know is what is the "real" safety hazard - where have I put people at risk? I really want to know, but nobody has showed me, except for the vacuum cleaner example. If that's the worst case, which is what my belief is, then I thank everyone here for their input and it's time to move on.

And just so you understand, I'll spell it out clearly, I DON'T TOUCH A NEUTRAL OR GROUND, BECAUSE THERE IS NONE IN THE VICINITY. One does not magically appear, so the "illusion of safety" is not an illusion, it's a reality. If not, prove me wrong.

I fully understand your reasoning. It was the prompt for my question about the electrocution in a totally isolated bath. The answer was that although there is no path to ground there IS a gradient from the hand to the feet. The difference in potential between the heart and the feet is often enough to kill, apparently. Even though the feet are isolated in rubber soled shoes. This concept is new to me as well. I still have questions as i know there are videos of people holding a hot electric fence wire and not getting a shock until the person on the end grounds themself. Never having tried this i don't know if the inbetween people feel any tickle prior to the grounding. After all, there is a gradient here. It may be that you don't necessarily feel anything when you are about to die from this small potential. The example of people dying when they are in the water at a marina when the water is electrified indicates just how small a current can be and still kill. I AM assuming that a hand held electric device dropped in the vast body of water produces a very small gradient across a body.

"...(if) there is no path to ground there IS a gradient...", no there is not (at these voltages); a gradient requires a reference point, otherwise how do you measure it. You can easily place your hand around a live 240V bare conductor, as long as your other hand is in your pocket and you're wearing sneakers while standing on a rubber mat. You will have no sensation at all because there is no path to ground. The only place where there is sufficient gradient across your body would be doing live-line maintenance on high voltage transmission lines.

Do not compare an electric fence (Cattle shocker) to house wiring, they are entirely different. Although the shocker use a much higher voltage (2-3kV or more depending on use) and is grounded, it uses a pulsing DC system (about 1pps) operating through a relatively high impedance to ground. This limits the current to a few milliamps, something that makes most animals avoid contact with the fence. Of course if the goal is to kill rather than deter, both voltage and current are much higher.

Your marina statements require clarification. People die because of the gradient difference across their body, coupled with their physical condition, their orientation, and their proximity to, and possible contact with, either a hot wire or ground. A droplight that falls 10ft into the water will have spherical field surrounding it that falls off as the square of the distance, and as you said, shouldn't be lethal. However if there is a grounded 50ft length of pipe near the droplight, the field will be very distorted such that swimming between the light and the pipe will prove fatal, while swimming on the other side of the light will hardly produce a tingle.

Thanks, that clarification tends to agree with my understanding. I guess then that people who die in the plastic bath have some sort of contact to ground. Either through running water, touching copper pipe connected taps, (ours now are plastic pipes ), metal drain fittings and pipes or by jumping out and putting one foot on the ground. Again this is a body making a circuit. The body in the marina isn't making a circuit. Similarly a person in a dry bed can die if, for example a doctor has just inserted an IV line and holds the needle with his/her thumb and asks a nurse to tape the line to the person. In doing so she makes a shadow over the site so the doc moves the lamp. The patient goes into arrest. The direct line into the bloodstream and the induced current from the lamp housing did the damage. Nowadays the docs all wear gloves, the lamp fitting is earthed and protected. BUT how did the people die if they were isolated? Jim

The patient's death in your scenario may have been caused by what is known as "microshock", a tiny amount of current that happened to flow through a catheter in the heart?

it is normal to find a patient in an ICU to be connected or hooked up to several pieces of electrically operated devices, such as bed, monitor, etc. Each electrical device although are grounded produces certain amounts of leakage currents. It is possible that the due to differences in ground resistances, some of the currents that leaked may seek the least resistant path and that may be the weakened patient resistance?

Unlike other possible currents, electric current flows through every resistant path not just the least resistant path. The least resistant path will carry the largest portion but current will flow through all paths.

Very true... yet imagining a scenario where just 7 patient connected lead wires pumping leakage currents, seeking a way of discharge via an already weakend and grounded patient.

I believe an algebraic net resulting current even in the micro-ampere range can cause a patient to fibrillate...

"The body in the marina isn't making a circuit"

Not in the conventional sense of, say, overtly touching a conductor, but it is part of a continuous, distributed circuit where the electric current flows through the volume of water. How well it flows through the water versus how well it flows through the body in the water is an important factor in determining lethality, among others.

If the water has fairly high resistivity, for example (fresh/rain water, 5-20kΩm), a body - which has a very low bulk resistivity, about 5Ωm - will tend to conduct more of the current than the water in its immediate vicinity. The electric-field gradient in the surrounding water is also greater due to the higher resistivity. Therefore, a body would tend to 'short' out the immediate volume of water it occupies.

If it's low resistivity water (seawater, about 0.2Ωm), less current will flow through the body than through the surrounding water, but in all cases current will flow through the body.

How much depends on a complex relationship involving the electric-field gradient in the vicinity of the body, its shape (nearby conducting/insulated surfaces versus open water), the current density, the orientation of the body with respect to the field, how much of the body is exposed (partially out of the water or wearing a wetsuit, etc. for example), the water's bulk resistivity, and so forth.

The symbol for ohm(s) is just Ω, not Ωm.

The SI unit for resistivity (not resistance) is Ωm. Ohm-metres.

Thanks. I read too quickly. (In the meantime, Redfred has also pointed this out.)

But then, aren't abbreviations nice--does nm mean nanometers, newton-meters, or nautical miles? Is lbf pounds (force) or pound-feet? Hyphens are sometimes nice.

Depends on the context and the author's degree of laziness. If the context makes the meaning clear, the hyphen or, more correctly, the dot operator (as in Ω·m, given the component units are multiplied) is often omitted.

The dot is good, and I could even prefer it to the older hyphen.

Newton-metres* are Nm, since the Newton is named after a person, the capital letter is retained.

n (lower case n) is nano or nautical

* note spelling. Meters are what one uses to measure things. Metres are a unit a length.

Too bad even Samuel Johnson caved on the French spellings.

The small m stands for meter. The unit for resistance is the ohm (Ω). Resistivity (ρ) is a different metric than resistance. The unit for resistivity combines two standard units of ohm meter (Ω m).

Very well put. GA to you!

You have some great questions about how someone gets shocked when not grounded. Your bathtub and jumping in a "hot" marina is a good question. You don't need to be grounded in a plastic tub to be electrocuted.

Since neither has to touch a ground, how do they get electrocuted?

Here's my best explanation - please note that I am not an expert, but this is the best that I remember from college. Current will flow from Left to right or right to left (or front to back or back to front to back) in your body (or even up to down or down to up). If enough current goes through your heart, it will kill you. If it goes along your skin (think high voltage like lightning) and doesn't go through your heart, you may live, but your skin will be burned. The high voltage could also cause some damage to your nerves and brain. Going back to college physics, you can think of the body as a resistor. The water around you is also a resistor. When you hook up power to both resistors (hot electric appliance falls in the tub or lagoon) some current will flow through your body and kill you. Think of the old circuits problem where a power source feeds two resistors in parallel. Current breaks into two branches and some current flows through each branch. One of the branches is your body.

Your example about the IV line is excellent! A very small current can cause your heart to stop, since the IV is run directly into the bloodstream and has a low resistance run to the heart. The heart gets a small voltage that's enough to cause the muscle to get thrown off beat = stops normal heart operation.

I hope this helps.

Excellent! The best explanation of current flow to ground I've read in a while. GA to you!

You need current flow to have a voltage gradient. Here's a way to think of it. If you have a resistor that has connectors coming out at random places along the length, then you can test the voltage gradient (when current flows). If you put another device (let's say a person) between two of the leads, current would flow through that device unless the resistance was too high. Think of a parallel circuit (two resistors in parallel).

If no current flow, there isn't a gradient. So in the case of the chain of people holding on to the one touching the electric fence. The people may feel a trickle if the power to the fence is grounded (one lead to the fence and the other to ground) and the resistance from their body to the ground isn't too high. Remember that high resistance will limit current flow e=i x r. e is the voltage at the fence = fixed amount, therefore if r is high, i (current) must be low (inversely proportionate to r).

I admit that I have no idea how an electric fence is wired. If it's wired to ground or are there two conductors in the fence (the person must touch both conductors to get shocked). My explanation above is based on one hot to the fence and the ground being the neutral.

And your question about the electric device dropped in the water creates a voltage gradient pattern from the device to the ground (water pipe or back to the device) - think of it like the ripples that come from dropping something in water. The gradient pattern comes from the resistance of the water - again, think of the water as multiple resistors in parallel. When a person's body is in the water, it's part of the "resistance" of the contents of the tub and does change the voltage gradient pattern compared to an empty tub. But the main gradient pattern is from the water itself, since it's what will complete the path to the power source.

You're thinking in terms of some form of fixed ground. The reality is that unless the room in question has no other outlets and the heater is at least 25 feet from the next nearest outlet, then a potential hazard exists. Why? Because plugging in anything with a cord on it brings a second conductor possibly closer to the surface of the enclosure. Since it appears that the wiring in the entire structure may not be up to code, then perhaps the vacuum cleaner is old of metallic construction, or someone plugs in an old laptop or TV that has metal trim or is connected through a non-galvanically isolated power supply.

Now I realize that all these conditions add up to be multiple unlikely conditions, but even if you don't mind putting your family at risk, you're still faced with having the violation corrected before you can sell the condo.

btw- even back in the 60's (actually much earlier) the NEC required bonding of the neutral bar in the breaker panel to a solid ground, which usually was the water pipe on the street side of the water meter, so it's unlikely that you have a totally ungrounded system. If your condo has ganged metering pans then the connection may not be obvious, and is made out there with a bare wire run to your breaker panel. Without a neutral conductor you can't have a 240/120 Volt service.

At last some common sense is prevailing here......

The nearest outlet is about 8 feet from the heater and it's behind the headboard, so it's not very accessible. The next nearest outlet is about 12 feet away and behind a large dresser. The closest outlet not blocked by furniture is about 15 feet away on the other side of the room.

The vacuum cleaner is provided by us and I got it about 1-2 years ago and of course it's made of plastic.

You are correct about the ground in the circuit breaker box. Well, it's actually the neutral bar and all the neutrals run to it. The neutral is grounded to the water main for the building. All the outlets, appliances and switches don't have a ground except for the new circuit I installed when I installed the washer/dryer.

You may ask why I installed the ground to the washer/dryer and not the baseboard heater. It's because I broke the lath and plaster wall to run the wire - I also ran a sub circuit breaker box as well. I only had to break apart a couple feet of lath and plaster, since I punched a good size hole in the wall to install the sub breaker box, so it was easy to run the wires up the wall - for me, it wasn't a difficult thing. Also, there is a large risk of shock, since the water pipes were in the closet with the washer/dryer.

When I ran the new romex to the baseboard heater, I used 12/2 romex with ground from the thermostat to the heater. The wires coming into the thermostat were original and there wasn't a neutral or ground. It's a pretty long run to the circuit breaker box and I didn't want to break apart all that lath and plaster to run new romex - up the wall to the ceiling, then across above a doorway, then all the way to the breaker box. I don't mind fixing drywall, but lath and plaster is a lot more work and it's also harder to break apart without running cracks down the wall.

It’s up to Autobroker if he chooses to flaunt NFPA-NEC code.

UK’s BS7671 is advisory, NFPA-NEC is statute law along with all the consequences and penalties that entails. As I pointed out Autobroker has broken a cardinal rule.

BS7671 is weird, if you end up in court it will be used as evidence for a conviction, usually a custodial sentence if a death is caused by a faulty installation.

This might be OK, but I am having a hard time picturing the installation. A quick diagram of the wiring would help.

I can't draw it on my tablet, but there is a diagram in the manual. Its a Cadet 72 inch 1250W 220V unit. Its wired just like the manual states except I don't have a real ground wire.

But I thought you said the romex was two conductor and a bare ground wire and that you grounded the bare wire to the frame of the heater? I think that is where I got confused.

Yabbut the heater is the only place that wire is grounded! The other end isn't connected (or rather it's only connected to the grounding terminal of the 'stat, which is floating).

424.19 purely academic musings, among the firestorm this post has generated :)....

I wonder if the built in high temperature switch on the heater in question counts as a supplementary overcurrent device, I think they are fairly standard on baseboard heat...

Section 110 seems to refer more to locking your electric rooms, it is unlikely that there is a lock mechanism installed on most residential panels, esp. on this age dwelling. Can you add one? Yes. Is it probable that one will ever appear? No.

There must be some other escape for the in-sight-of clause, or my 'lock' search skipped another synonym, in the 2011 code...

Don't think that the panelboard breaker counts as a unit switch, especially if more than 1 section of baseboard heat is fed from the same circuit..?

The built-in high temperature switch knows nothing about overcurrent, just high temperature. It's there in case somebody covers the enclosure with a rug, towel, etc such that the unit overheats from a lack of circulating air, something that a wall mounted thermostat would never sense (until the fire starts).

I still wonder if it counts... heat is heat, no matter what the root cause

High temperature cut offs have been required for about 20 years. Before that there were many fires caused by curtains, clothing, towels, rugs, etc. somehow finding their way onto space heaters and blocking the airflow.

"...heat is heat..." is true, but consider that the heater under consideration only draws 5.3A, therefore no overcurrent will ever exist even if it remains energized for years. It's the high temp cutoff that prevents the heater from ever getting hot enough to ignite whatever is blocking it.

Overcurrent due to a fault in the heater...

As RC says, it's heat that causes the fire. Overcurrent would not necessarily cause overheat - hence the temperature switch.

Overcurrent could cause an overheat in any of the wiring to the heater (which could also lead to a fire, not detected by the heater overtemp switch until way too late).

You are right.

If I remember correctly, most such devices (heaters, dryers and the like) have special, sometimes melting fuses, that once a specific over temperature is reached, remove permanently the mains or better said, break the circuit.

Some need replacing to repair the unit, some are resettable. Many different types.

Here are a few pictures of some of those:-

Or look here:-

Lebao Thermal fuses

I hope this helps.

Overcurrent by definition causes excess heat... Just an interpretation question, would it be considered supplementary overcurrent protection, not primary, supplementary...

My point was not so much whether or not overcurrent causes excess heat, but where it causes the heat. If in the wiring (due to a fault), a temperature switch inside the heater would not necessarily detect it (until, as I said, it's probably too late).

The temperature switch in the heater is primarily present to prevent overheating due to e.g. a blocked vent, which would not significantly affect the current either way (until, again, it's probably too late).

That is why it might be considered supplementary, not primary, jus' wondering if some one ever got a ruling on it, that's all...

I believe it would just be called overtemperature protection (in the Uk, anyway).

Speaking authoritatively about my fair city only, our electrical code makes no bones of the fact that NFPA 70e is adopted as the city's standard and is the only standard it will accept and the standard to which all electrical installations will be inspected.

I have a friend who is an electrical contractor. NFPA is the only standard he and his crews will work to. He sometimes loses work because he is not the low bidder.

His reputation is worth the loss of a few jobs. I know warehouse/property owners who won't let anybody else work on their buildings.

Do it to code and CYA.

Sir Robin said...

"Article 424.19 Disconnecting Means.

Means shall be provided to simultaneously disconnect the heater, . . .(and other associated stuff) from ALL ungrounded conductors. Where heating equipment is supplied by more than one source, . . . .etc."

We have a similar rule here in Canada, but it is meant to handle heating equipment fed with more than one branch circuit, which we are starting to see a fair bit of. I would not consider a 240V circuit fed from a double pole breaker as being fed from more than one source as it is only one source.

Having said that... I have no idea how this would be interpreted in the US under the NEC.

You posted:-

"I would not consider a 240V circuit fed from a double pole breaker as being fed from more than one source as it is only one source."

I find that to be 100% true, but will all here believe you/us? I seriously doubt it!!

Many still talk about "2" phases!!! Even though the subject has been covered several times, at least!!

How about pounding a copper rod about 6-8' into the ground next to your building. Then take that romex ground wire and connect it to a wire (of equal or larger dia.) which goes thru exterior wall and is connected to that copper rod.

You will now have a grounded baseboard heater.

The problem that i am guessing that you may have is the old two wire system that old homes had. there were no ground wires. The house i grew up in had the old screw in fuses... no ground.

disclaimer: i may be incompetent so don't expect me to be held responsible...

Exactly.

Of course its a "safety" cure, you are forgetting simple basic electrics! Portable generators often (should) have earth and neutral bonded, when used, by such a rod, but few actually do it!!

Assuming for the moment that the ground rod is making good electrical contact with "Mother Earth", (as it should be!) then the major part of the electrical safety needed has been achieved.

Because it means that (provided the earthing cable to that rod from the heater frame is thick enough to handle any/all of the fault current developed) the heater frame is now at earth potential and cannot shock anyone anymore.

There is now simply no potential difference between M.Earth and the heater frame.

With luck, maybe the fuses will break/trip as well, if the fault current exceeds their value and certainly any RCDs, properly installed, will remove power immediately with any earth to phase fault!! (as I have already posted days ago!)

Reminder:- An RCD or equivalent, monitors the current on the phase line and the neutral line (or the other side of the phase) and checks that the currents are equal. If they vary if value, more than that allowed by the design and local code rules, the breaker trips.

Trip is usually set in milliamps. A test button is often available, which simulates the minimum trip value and should be pressed once a year as a safety check!

What needs to be also done to make the earth rod 100% (assuming not already done), is to identify the neutral on that phase and bond it to that same earth rod.

BUT, if 110VAC is already available in the dwelling, this has most probably (should be) been done, maybe outside of the dwelling at the transformer?

But no guarantee (I did not do the installation!!)

It should be checked out. But remember, bonding earth and neutral twice on the same phase is seriously not a good idea from either a safety or code point of view, plus, it can theoretically even bump up the amount of electricity used, according to the customer meter at least, under certain circumstances.

I hope this helps. But if you need weblinks supporting this, I will supply some, just ask.

Have a great day.

I am not forgetting anything... in the context of what we are discussing (which is not generators), bonding the heater to a ground rod achieves nothing.

As to generators... if the neutral of the genset is to be bonded to ground or not depends upon the transfer switch used to connect it to a distribution system. Creating a redundant path for fault current is a bad thing.

I do not have time for more than this response at the moment.

If both earth rods have been correctly installed according to local code, there should be only a tiny resistance between them.

I made the question easier to understand and answer by placing a cable between them.

Have you an answer?

"If both earth rods have been correctly installed according to local code, there should be only a tiny resistance between them."

If both earth rods have correctly installed according to code they will be bonded and the question is moot. Thing is, they're not, and that's the problem: there is a resistor between them. A variable resistor whose value is at the whim of soil conditions. That is why code requires the rods to be bonded, to shunt that resistor. If soil resistivity made little difference, then why the requirement? Evidently somebody thinks that resistor is a hazard.

Andrew Westman wrote:-

"If both earth rods have been correctly installed according to local code, there should be only a tiny resistance between them."

If both earth rods have correctly installed according to code they will be bonded and the question is moot. Thing is, they're not, and that's the problem: there is a resistor between them. A variable resistor whose value is at the whim of soil conditions. That is why code requires the rods to be bonded, to shunt that resistor. If soil resistivity made little difference, then why the requirement? Evidently somebody thinks that resistor is a hazard.

Of course there are TWO resistances, just as I mentioned before, the cable connecting the two rods, (which I clearly mentioned, in the case where the installing engineer could not achieve a good enough ground connection!), and the earth resistance, between the rods in parallel to that.

But, in areas where getting a good ground, there may be many ground rods in usage. All in parallel.

Also, some countries (Germany for example), require that the ground plane used be made larger, not just a rod, and deeper. So deep and large sometimes, that it is quite expensive to achieve!!!

Also here, and I believe in other countries, there will be a physical cable ground connection to each house from the local substation as well....

For example, our house has two (either side of house) grounds for lightning conductors, also used for mains earth ground and water system ground!! Pus the connection to the substation.

There is a really good paragraph, amongst many others, here:-

Getting Down to Earth

Broadly speaking, “earth resistance” is the resistance of soil to the passage of electric current. Actually, the earth is a relatively poor conductor of electricity compared to normal conductors like copper wire. But, if the area of a path for current is large enough, resistance can be quite low and the earth can be a good conductor. It is the earth’s abundance and availability that make it an indispensible component of a properly functioning electrical system.

There should be a total resistance of less than 1 Ohm in most codes for the cable alone. Check your local code for more exact values for where you live.

That is so that a ground fault on equipment would/should run a really high current, blowing fuses and dropping breakers with a bit of luck. But even if it didn't, the unit would have a voltage on it well below danger level.

That voltage is easily calculated with Ohm's Law!

On a US system, either phase is at 110VAC to ground/Neutral connection.

It's only 220VAC between the phases.

So assuming 19.5 amps (20 amp breakers/fuses if I remember correctly) fault current, over 0.5 Ohms = Max 9.75 AC Volts on the heater frame.

Even if 5 Ohms, that is a fault current of 22 Amps, above that of the breaker used I believe....

With a 0.1 Ohm ground fault path, it would be under 1 volt!!

Also, if an RCD is installed, it would have tripped and removed the supply completely, possibly at a fault current of possibly only 30 milliamps!!

In the USA, it would appear that a higher value is allowed, "less than 5 ohms" is quoted in some US manuals....

Interesting reading with regard to grounding in US domestic situations can be perused here:-

US Earthing_system

If you have any questions, please ask.

You wrote:-

Yes it is, except that the author of the comment to which he (and I) responded wasn't doing that. In his comment the second rod was connected only to the heater and nothing else.

I know he does not intend to do that, but it is something he should be doing, and was, I believe, proposed by someone else here, that is to put an earthing rod in........correctly so, to my mind, for anyone who is safety conscious.

If an item, like any sort of electrical heater, is properly connected frame to ground, then it has the same potential as the ground. That is apparently not obvious to a few here.....

If that ground rod is fully and correctly installed, then there will be no danger to people touching that heater, after a short to earth has happened. The connection to the rod will handle the current, hopefully blowing/opening any fuses/Breakers/RCDs.

Though in my experience, even when there is no earth fault, certain electrical units, older sat receivers and the like, although double insulated, show a "charge" on the frame, when the aerial connection has not been made, one hand has the aerial lead and the other is touching the frame of the unit, then you get a tingle!

It has next to no current, but you will feel it, sweaty fingers will "assist".....depending probably more on the internal power supply design, which is probably why many modern sat receivers have an external "wall-wart" type power supplies nowadays....it removes the "tingle" that probably scares some users....I have never bothered to measure it though....

Because the sat antenna is usually connected on the cable shield, and to the house as well, thereby earthing the receiver, when the antenna cable is correctly installed..

Tingle gone!!

Hi Andy,

There were two comments along these lines where the authors proposed earthing the heater frame via a second, independent ground. One, by means of a "nail buried in the garden" (though possibly he meant a rod) and the other who said he wasn't an expert in these matters, implying (to my ears anyway) that the reader may wish to take his suggestion under advisement. In a correctly installed earthing system multiple rods would of course be bonded and the connected heater frame at earth potential.

Soil resistance can and does vary all over the map; it depends mainly on the moisture content and the electrolytes present but also what type of soil it is, if it overlays rock, and other considerations. In some areas of Hawaii, for example, the volcanic soil has a high resistivity even when wet because its is almost completely devoid of electrolytes. When dry the resistivity can exceed 100,000 Ωm. In such soil two unbonded earthing rods some distance apart are unlikely even to be at the same potential. It can be quite difficult to get the earthing resistance low enough, often involving building ground pits filled with chemicals and the occasional watering to keep the ions mobile.

Then we have prime bottom land, wetlands, etc., and areas near the coasts where the soil is infused with seawater, all typically having very low resistivities - a matter of a few Ωm at most, depending. In such places you could almost get away with no bonding conductor between rods. Almost. (as in 'nice try but no cigar until it meets code')

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Perhaps a wee bit off-topic here, but the U.S. Navy's VLF transmitters at Cutler, Maine and at Exmouth, WA, Australia are deliberately sited where the soil resistivity is especially low. These systems demand an excellent ground plane to function properly and the aerials themselves are huge. For many years Australia's was the largest man-made structure in the Southern Hemisphere. Cutler's is even bigger, comprising two full trideco arrays each about the size of Exmouth's. Both sites incorporate a system of buried copper radials called a counterpoise which consists literally of hundreds to thousands of kilometres' worth of copper wire (Exmouth's, 386 km; Cutler's, >3200 km of #6, covering pretty much the entire peninsula and extending into the ocean some distance from the shore). These together with the low soil resistivity serve to act as the grounded plate of a giant capacitor and have a net DC resistance around a milli-ohm or less. The ground impedance at operating frequency (24.0 and 19.8 kHz respectively) is a bit higher of course due to skin effect and other causes, but you can still bet it's way, way down there.

Its all off topic as in the case of a bad area for earthing, the engineer tasked with the job must simply work harder/better to achieve the local code requirements.

Its not as though such a person is allowed to say:-

"its a shitty place to make an earthing system, I have better things to do elsewhere, bye, bye!"

They have to achieve the correct result. PERIOD!

Now looking at those domestic Transformers that the US hangs everywhere, it would appear that generally speaking, a house is supplied by both sides of a single phase, a neutral and an earth.

As to how long this has been so, I cannot say, but someone here will know and supply substantiating links.

It also appears that the ground is run down the pole into the ground!!

Having having a ground and a neutral, coming into the house (apparently), means that a vast part of the safety side of things, should generally be already connected!

So earthing a heater frame should really only be a case of running an extra wire, back to the power/fuse/breaker box I would guess. Something any competent electrician should be able to handle.

Having a house ground plane also, is a requirement here, "belt & braces" so to say!! Whether US code does this, it was difficult to be certain, but it appears (as I have already mentioned) that at least 5 Ohms or less to ground is also needed.

There are also several good papers available on the way this should be achieved and measured. I knew that it was a job for an engineer here, it also appears to be similar in the USA, but that is just a guess on my part.....the equipment needed, is more of an engineer level it would seem too.

So continually "rabbiting on" about soil resistance does not help, as it is not showing a proper appreciation of the way things get done in a practical and useful way as mother earth grounding is only one part of the earthing safety aspect as a whole.

Furthermore, the fact that so many people, especially ones not really up to date with modern electrics (last 50 years or more!!!), who do not understand the extra safety that an RCD brings with respect to accidental electrocution of humans and pets, is really showing his ignorance of the matter.

Having accidentally tripped such a device about 20 odd years ago, with my right index finger, I can safely say that its painful, and not to be repeated if at all possible!!! But it saves lives.

That would be the cheapest and best alternative for this installation I feel, if cable laying is too much work!!

(Due to going to the Barbers, I finished the last post a little abruptly!)

With regards to the sighting of VLF (submarine comms) masts, what has that got to do with domestic electrical safety and code? If the Navy wants to do something that might be considered very dangerous, you don't think that there is an Electrical code to stop them, do you?

So a "WEE" bit off topic is .......simply untrue, its "WAY" off topic.....

All antennas (not that I am an expert, but I have a friend who is!), usually work better with a proper ground plane - but for the picky people, that is NOT the same as saying that all Antennas "NEED" a ground plane......some work well enough without, for the usage required.

Many, many years ago, I always sited my CB antenna to the rear of the car roof, to give me maximum range possible in a forwards direction. It appeared to work just as I wanted it to!!

Perhap if you had read my post more carefully, you might have noticed that I covered that....... Should I point out where for you in my previous post? I thought it was MOST obvious!!!

Furthermore, you must understand that we are/were very restricted here on how powerful a CB is/was transmitting, 2 Watts if I remember correctly, so you took all legal ways to improve range..... some took other "ways" and got all their gear confiscated!!

That you have no interest is one thing, but that is not necessarily a general opinion.

Furthermore, another Andy brought it into the mixing pot on CR4!!!

Try being "Happy" in the "New Year!" It also helps the digestion as well!!

<unsubscribe>

What ever...

No answer?

North of 60 wrote:-

Why would you care what I have to say on this or any issue? With my lack of understanding... I decide any further discussion with you on this topic is of no value to me.

You are quite correct, I do not care about or value your "knowledge", at least on house/mains electrics.......on other possible subjects, I am sure you are far better informed.

Thanks for your post!!!

Happy New Year.

Incompetence often rears its ugly head here.

Right now there's a thread about a plastic cover whose author might just fit that description.

All I know about electricity is that too much can render you permanently dead.

So a good rule of thumb is to avoid it, and other men's wives as both may carry the aforementioned penalty.

What many don't realise is that the actual, physical earth is not everywhere at the same potential. Two ground rods (one, the proper system ground) a distance apart can have a voltage between them - in some cases a considerable voltage - because of ground currents; the earth between them acting as a resistor. During a fault the current will flow into this suggested second ground through the earth 'resistor' into the regular system ground at its earth connection and we now have a voltage at the grounded frame with respect to whatever else is nearby that is grounded properly.

This is why it is important that all the bonding conductors terminate at a single ground point. During a fault there will still be a voltage from one end of the bonding wire to the other because of the resistance of the wire and its connections, but less than if trying to the pass the current through the earth itself, and much less between nearby bonds having a similar electrical distance from the system ground point. This would very likely not be the situation when a second ground point is introduced, especially under fault conditions and quite possibly even under normal conditions, given that earth currents flow for other reasons as well, both natural and man-made.

I believe that is the reason why equipotential must be checked /ascertained to eliminate or minimize ground loops in any properly designed electrical installations..

On a theoretical level you are right, but on a practical basis, usually not.

Yes, single point earthing is correct here also, but sometimes its impractical or difficult to achieve and provided a second earthing rod is correctly and deeply installed, as it will usually be "nearer" to the heater, than the "other" earth rod, it will bring the heater frame down to its "earth" potential. But not that of the other, farther away, earth rod.

But unless you can put one hand or foot on one and another hand or foot on the other, its hardly likely to be dangerous!!! If they are that close, you don't need two!!!

Naturally, also if the two rods are (stupidly!) placed, so that the original rod is nearer to the heater and the new rod, farther away, then there is a slight extra danger from this potential difference.

But it is unlikely that the potential difference will be high, as to my mind, that should be covered by code to reduce it to a safe level!!

Here, any earth rods have to be checked for full, good M.earth contact by a properly accreditted electrical engineer, with certain specialised equipment.

He may even require that one be made deeper or both be cabled to each other in areas where the earth has a high resistance for some reasons.

His word is literally LAW!!

I would think that in the US Electrical code would also require such safety features to be properly checked out and fixed if problems are noticed.....

"Here, any earth rods have to be checked for full, good M.earth contact by a properly accreditted electrical engineer, with certain specialised equipment.

"He may even require that one be made deeper or both be cabled to each other in areas where the earth has a high resistance for some reasons."

Yes but a couple of times now someone has suggested just driving a separate ground without it being so cabled to the regular ground, checked by an accredited engineer and so forth - in one comment, "a nail buried in the garden," (though possibly the author meant a ground stake/rod - I suspect a language barrier). Earthing systems involving multiple, bonded earth connections are fairly common, especially in areas of high soil impedance, but that's not case here. Just plopping down a stake wherever it's convenient and not tying it to the regular system ground is asking for trouble. I don't know what the soil is like where the OP lives, but here where I live (and in many other places in the world) it can be difficult to get a good, low-impedance earth connection. Here the soil is often just a few score centimetres deep before you encounter solid limestone. There is also a great deal of seasonal variation in the soil resistivity which can exceed 2000 Ω-m; in some places more. We also get a great deal of lightning here which brings its own barrel of worms.

You are correct. The ground wire is tied to the heater, but at the other end I connected it to the metal outlet box where the thermostat is connected. There is no "real" ground there.

There just might be a ground there. It is possible the house was wired with BX, a metal box connector could carry the ground through the armor back to the panel. People knew about safety grounding and the need for it certainly in the 60s, so I doubt it was ignored. The steel armor maybe not your best conductor, but lots better than nothing.

It's all romex. Back in Chicago, I remember everything running through conduit. Not here in CA.

I wonder if at that age of dwelling in the US if perhaps they used BX, he did say he had a metal box. Not necessarily the best ground, but perhaps passable...

The thermostat for this heater should be double-pole, so that it opens both "hot" conductors. Or, alternatively, the thermostat controls a 2-pole contactor.

"Off topic", really...

There are 220 single pole thermostats and double pole thermostats. The manufacturer is okay with either one and the installation instructions cite both as okay.