Garage sub panel

[Eddie_T]

They may have changed here too but I don't know why. I gave my temporary service pole to a friend and he had to get it rewired so that may have been the reason.

Here's a quote from 2021;

A standard drop is comprised of three cables, called conductors. Two are insulated “hot” cables, each carrying 120 volts of electricity. A third cable, typically bare (uninsulated) aluminum, works as the neutral conductor and offers structural support for the entire service drop.​

I always chuckle at the 'each carrying 120 volts of electricity' in realty they carry current from a 240v transformer from which 120v is derived via a grounded center tap.

 

[bud16415]

Not that I’m suggesting this to the OP but a long time ago I had a situation where a friend had a water well pump house that was a good distance from his home and had a 240v pump motor and the run to it was similar to what is shown here two hots and a ground. My friend wanted to add a light and a outlet to the pump house and asked me if he could just use the ground and one of the hot legs. I told him it was not to code or safe and the ground leg was not insulated as here.



I went to work and asked our senior plant electrical guy and he said the same. I asked him if it could be done with a transformer and in effect produce 120v with a common at the building out of the 240v. He seemed to think that would work. My friend never did anything so I can’t vouch for how this would work or what parts would be needed.

Maybe some of the pros could weigh in on if this could be a way around running another conductor.

 

[Eddie_T]

It's not as unsafe as it sounds. My cook top is wired with SE cable 2 conductor with braided ground. So effectively the chassis is connected to the neutral but it's grounded so no problem. It met code at the time of installation.

 

[PJB12]

It's not as unsafe as it sounds. My cook top is wired with SE cable 2 conductor with braided ground. So effectively the chassis is connected to the neutral but it's grounded so no problem. It met code at the time of installation.

The reason a neutral is now required is because if something that you can touch while touching the cook top is grounded better than the cook top, you will carry the unbalance from whatever the 120 volt loads are (timer, lights, etc) through your body. So, if your cook top is near something grounded, like a refrigerator or faucet, you can become a conductor.

If there is a dedicated neutral, the neutral will carry the current, not the frame, nor you. Clothes dryers were the impetus for the code change because the grounded washing machine was often next to the dryer. Dryers have 120 volt lights, timers & such.

I'm not a residential electrician, just industrial and some commercial, but I've seen the effects in commercial coffee urns. When they were 3-wire, 208 or 240 volt, one could put a voltage meter on the case of the urn and on something grounded, like a water pipe or the stainless counter, and read voltage when the 120 volt pump was running.

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With much respect, GPGLinka, you might be wise to turn this project over to an electrician. Should there ever be a fire or someone gets shocked, you won't be liable and your insurance company won't refuse to pay.

Insurance company adjusters work hard to find reasons not to pay. Even if your work was not the cause for a claim, they can declare your policy void due to non-inspected work discovered on the premisis. At the very least, I'd suggest obtaining a homeowner's permit and having the job inspected. Again, this is suggested with no disrespect to your abilities.
Paul

 

[PJB12]

Not that I’m suggesting this to the OP but a long time ago I had a situation where a friend had a water well pump house that was a good distance from his home and had a 240v pump motor and the run to it was similar to what is shown here two hots and a ground. My friend wanted to add a light and a outlet to the pump house and asked me if he could just use the ground and one of the hot legs. I told him it was not to code or safe and the ground leg was not insulated as here.



I went to work and asked our senior plant electrical guy and he said the same. I asked him if it could be done with a transformer and in effect produce 120v with a common at the building out of the 240v. He seemed to think that would work. My friend never did anything so I can’t vouch for how this would work or what parts would be needed.

Maybe some of the pros could weigh in on if this could be a way around running another conductor.

That is a very good suggestion, Bue16415!
Yes, an isolation transformer would do the job that Bue16415 illustrated because an isolation transformer will create its own grounded circuit conductor (neutral) for the secondary.

For safety, you must use an isolation transformer & not bond the secondary's neutral to ground at the transformer. Ground the transformer to earth in the same manner as is required for the service because the 120 volt load is now considered by code as a "separately derived system".

Your new "system" is treated pretty much the same as if it were the main service to the premises. Bond the neutral and ground in the circuit breaker panel that is supplied by the transformer. And be sure to use ground fault circuit interrupters where required or wise.

Although they are far cheaper, don't use a Buck-Boot transformer because the neutral will still travel on the equipment grounding conductor to the main service. As mentioned, you need an isolation transformer.

Enjoy This Day!
Paul

 

[bud16415]

That is a very good suggestion, Bue16415!
Yes, an isolation transformer would do the job that Bue16415 illustrated because an isolation transformer will create its own grounded circuit conductor (neutral) for the secondary.

For safety, you must use an isolation transformer & not bond the secondary's neutral to ground at the transformer. Ground the transformer to earth in the same manner as is required for the service because the 120 volt load is now considered by code as a "separately derived system".

Your new "system" is treated pretty much the same as if it were the main service to the premises. Bond the neutral and ground in the circuit breaker panel that is supplied by the transformer. And be sure to use ground fault circuit interrupters where required or wise.

Although they are far cheaper, don't use a Buck-Boot transformer because the neutral will still travel on the equipment grounding conductor to the main service. As mentioned, you need an isolation transformer.

Enjoy This Day!
Paul

Thanks for confirming the idea and yes an isolation step down transformer would be the correct choice.



When my friend first asked about just lighting in the pump house with just 240v with no neutral I thought about suggesting he wire two 120v lights in series as a cheap work around. I held my tongue for the reasons you mentioned where down the road he have an issue or he go to sell his place someone is going to ask what the heck is this.



If you can, could you find a 240/120 isolation transformer that a homeowner could easily get his hands on that would supply such a setup? Might be good information for someone finding this thread in the future with a similar problem.

 

[Eddie_T]

Any potential on my cook top can only reflect the return current of the fan and indicator light times the resistance of 20ft of braided ground/neutral to the panel resulting in maybe a few tenths of a volt to ground.

 

[Eddie_T]

240v LED bulbs are available but I haven't done a search for fixtures. Most are for bright lighting but some are as low as 3w.

 

[gpglinka]

I was told I could cap off one of the hot wires and use the ground as my neutral. Basically using the panel as a junction box. Will this work?

 

[PJB12]

I was told I could cap off one of the hot wires and use the ground as my neutral. Basically using the panel as a junction box. Will this work?

You really should have an insulated neutral. The ground and neutral must not be bonded together until they reach the load center that has the first disconnecting means after the service. (That's why sub panels are fed with 4 wires and the first panel from the service entrance is fed with three.)

 

[PJB12]

If you can, could you find a 240/120 isolation transformer that a homeowner could easily get his hands on that would supply such a setup? Might be good information for someone finding this thread in the future with a similar problem.

Thanks for suggesting that an example is posted here for the future, Bud. That's very considerate of you.

I suppose that since only lights are required by the original poster a small one is sufficient, so I'll give a couple of examples.

A plug-in model would be simplest, but not considered permanent wiring by the NEC.
For an example, check McMaster Com and search for item 70245K81. This little one can handle 100 VA (about 80 watts) which is a whole lot of LED lighting.
The installer would put the appropriate breaker in the local panel and install a receptacle for the transformer's primary. This one is probably NEMA 6-15 plug & receptacle. Then the lights would be powered by a cord plugged into the transformer.

CAUTION! This plug-and-cord set up is by no means code's version of permanent building wiring, so be sure not to attach the wiring or light fixtures. Use a String-O-Lights plugged into the transformer's receptacle instead.

A hard wired transformer is appropriate for permanent installations.

You can get VA ratings from tiny to millions of VA in hard wired units.
An example of one that handles 1,000 va (about 800 watts) is McMaster Carr part number 7131K21

Check these two out at McMaster Carr and learn the specifications. Then you can shop where things are less expensive. Try Grainger, then when you find one your like, go to Zoro Com and type in the Grainger number. Zoro is Grainger's child and often has lower prices than the mothership.

Be sure to buy UL, ETL or CSA listed. There are a lot of scary imports on eBay and Amazon. (Unfortunately, there are also fake UL, ETL and CSA labels on some of this stuff.)

And, I recommend a permit & inspection for any permanent wiring.

I hope this is helpful to someone eventually. (We all have to learn before we can begin.)

Paul

PS: To know the watt rating of the transformer, you have to check the specifications from the manufacturer and find the Power Factor. Multiply the stated VA by the Power Factor to get watts. Then reduce by 20% for safety

 

[PJB12]

A "Why didn't I think of this sooner?" Thought:

If your 120 volt load is only lights GPGGinka, a 240 volt LED shop light would work. They look like the old-timey 4 foot fluorescent shop lights.

I've seen many with a switch mode power supply than accepts from 80 to 300 volt input. Simply run a 240 volt circuit to each light. Some even daisy-chain so you only need to run to the first fixture.

I've put many 277 volt versions in locations where only 480 volt 3 phase delta exists. It was far less expensive than a transformer and load center.

OR-
You could buy a power supply unit (PSU) for an LED strip light that allows 240 volt primary. Then put the needed receptacle for the PSU and some LED tape lights or strip lights.



Above, it was asked about 240 volt light bulbs.
You can get them & the lamp holder on line at places like 1000bulbs com. I'd stay away from the E26 and E27 bases because the bulbs fit each other. Someone will get confused and screw in a 120 volt bulb and have it go bad in after about second of very bright light. Perhaps an E14 base bulb & socket would be a better choice.

(E26 is the base on a typical 120 volt screw in A-Shape table lamp bulb like those we use in North America. E27 is the 230 volt version that is used in Europe and much of the rest of the world.

 

[gpglinka]

I capped off one of the 240 feed lines. Used the bare ground as neutral. When I turned on power I got no lights. Put the meter on lines and read 80 volts. Must be getting too much resistance from ground.

 

[Eddie_T]

Since the code doesn't apply to plug-in devices you might consider a plug-in lamp with a diode wired in series with the bulb to clip half the 240v waveform. If the lamp is LED the polarity of the diode might be critical.

 

[PJB12]

I capped off one of the 240 feed lines. Used the bare ground as neutral. When I turned on power I got no lights. Put the meter on lines and read 80 volts. Must be getting too much resistance from ground.

Sounds exactly like what you concluded- high resistance to ground.

This situation is the reason why 230 volt ranges, dryers & ovens now must have a real neutral. (4-wire)

With the the high resistance ground wire, you can become a conductor. Example: Operate, for example, a metal case electric drill when you are grounded better than the bad ground (damp floor) you carry 100 percent. In some instances you can carry 100 percent times the square root of 3.

Please run a neutral back to the panel at the service entrance or use 230 volt items only. Then, find and fix the reason for the poor ground. You need 25 ohms or less between the end and the main service grounding point.

Please be safe!
Starting on day one, I always taught students:
Electricity is an excellent servant, but a very bad master.

 

[Eddie_T]

If you had 25Ω resistance in the ground wire and shorted 120v to it it would draw 4.8A and not even blow a fuse or pop a breaker.

 

[Snoonyb]

Sounds exactly like what you concluded- high resistance to ground.

This situation is the reason why 230 volt ranges, dryers & ovens now must have a real neutral. (4-wire)

With the the high resistance ground wire, you can become a conductor. Example: Operate, for example, a metal case electric drill when you are grounded better than the bad ground (damp floor) you carry 100 percent. In some instances you can carry 100 percent times the square root of 3.

Please run a neutral back to the panel at the service entrance or use 230 volt items only. Then, find and fix the reason for the poor ground. You need 25 ohms or less between the end and the main service grounding point.

Please be safe!
Starting on day one, I always taught students:
Electricity is an excellent servant, but a very bad master.

When you view the photos in post #25, 27 & 29 the neutrals and ground are all bonded, with no other ground shown, however there may be a ground from the distribution panel.

AsI recall he had shown 120v to ground from both individual 240v legs.

 

[PJB12]

If you had 25Ω resistance in the ground wire and shorted 120v to it it would draw 4.8A and not even blow a fuse or pop a breaker.

The 25 Ohm is from NFPA 70 requirements, so I put it in there knowing the math does not work. I wrote it assuming the poster will have his work inspected via a permit.

 

[PJB12]

I made an Old Guy Brain Glitch mistake in Post $58, above, Eddie_T

The 25 Ohm requirement is for the Grounding Electrode System, not the Equipment Grounding Conductor. I apologize for the mistake.
Paul

 

[gpglinka]

Well I have 120 power, lights and outlets are good. Wired one leg as hot wire, capped off other hot wire and used ground as neutral. Didn’t work at first because ground was corroded at clamp. Thanks for all the advice.