208v feeding to 240v Subpanel

T

TowerDawg

Member
Location
Michigan
Occupation
Telecom Electrician
Hello,

I need to confirm some things and hope you guys can help. I have a 40 Amp 208v single phase receptacle I need to convert to a small 240v subpanel. The receptacle has 2 hots and a ground. If I add the 120/240v subpanel can I do so without a neutral? I will only have 3 small circuits / breakers each pulling less than 7 amps on a 120v. How can I wire up the 120v component? It would be 1 hot, 1 neutral, and 1 ground. How is the neutral wired from radio, without one coming in from main and without changing 1 Hot to neutral at main panel?
 
Previous question worded better -

I need to confirm something and hope you guys can help. I have a 40 Amp 208v single phase receptacle I need to convert to a small 120/240v subpanel. The receptacle has 2 hots and a ground. If I add the 120/240v subpanel: I will only have 3 small circuits / breakers each pulling less than 7 amps on a 120v. In order to wire up the 120v component, I have to have a neutral - correct? It would be 1 hot, 1 neutral, and 1 ground wired from radio transmitter. This is the only correct way, right?
 
TowerDawg said:
Previous question worded better -

I need to confirm something and hope you guys can help. I have a 40 Amp 208v single phase receptacle I need to convert to a small 120/240v subpanel. The receptacle has 2 hots and a ground. If I add the 120/240v subpanel: I will only have 3 small circuits / breakers each pulling less than 7 amps on a 120v. In order to wire up the 120v component, I have to have a neutral - correct? It would be 1 hot, 1 neutral, and 1 ground wired from radio transmitter. This is the only correct way, right?
Click to expand...
Yes. You definitely need a neutral for the 120V loads.
 
TowerDawg said:
Previous question worded better -

I need to confirm something and hope you guys can help. I have a 40 Amp 208v single phase receptacle I need to convert to a small 120/240v subpanel. The receptacle has 2 hots and a ground. If I add the 120/240v subpanel: I will only have 3 small circuits / breakers each pulling less than 7 amps on a 120v. In order to wire up the 120v component, I have to have a neutral - correct? It would be 1 hot, 1 neutral, and 1 ground wired from radio transmitter. This is the only correct way, right?
Click to expand...
2023 NEC TX
Do you want to boost the 208 V single phase voltage to a 120/240 volt circuit?
What is the voltage of your service entrance?

Another important question is the voltage of the radio transmitter?
You said "wired from the radio transmitter".
So you want a 120/240 panel?
What is the rating of the sub panel?

Respectfully, something does not make sense.
You want to change a receptacle to a sub panel?
I don't know anything about the radio transmitter, except if it runs on a different voltage that's different from your service, sounds like you need a buck / boost transformer found in 450.4 also known as a autotransformer.
Seek help from a licensed electrician!

TX+MASTER#4544
 
Yes, it sounds like you need to feed your new small subpanel with 1 hot, 1 neutral and 1 ground, no need for 240 volt correct? Just tie the two bus bars together, no multi wire branch circuits of course.
 
TowerDawg said:
Previous question worded better -

I need to confirm something and hope you guys can help. I have a 40 Amp 208v single phase receptacle I need to convert to a small 120/240v subpanel. The receptacle has 2 hots and a ground. If I add the 120/240v subpanel: I will only have 3 small circuits / breakers each pulling less than 7 amps on a 120v. In order to wire up the 120v component, I have to have a neutral - correct? It would be 1 hot, 1 neutral, and 1 ground wired from radio transmitter. This is the only correct way, right?
Click to expand...
I feel you man, I have lots of years doing telecom but really, this is a job for an electrician. Imagine a sparky asking for help with SIP configurations converting a multi path paging to unicast.

Are you asking if you can feed a sub single phase panel with your 40A branch? Is the 40A receptacle being abandoned?
 
TowerDawg said:
I have a 40 Amp 208v single phase receptacle I need to convert to a small 240v subpanel.
Click to expand...
So basically you only need a 120 volt panel. Yes you can convert the existing 40 amp, 208 volt branch circuit to a 40 amp, 120 volt feeder. What is the existing wiring method for the 40 amp receptacle?
 
Depending on wiring methods it can potentially present code issues with identification requirements of grounded and ungrounded conductors, but yes the thing to do is make one conductor grounded and the other ungrounded. I'd rather see that violation than to use the EGC for normal current carrying purposes.
 
kwired said:
Depending on wiring methods it can potentially present code issues with identification requirements of grounded and ungrounded conductors
Click to expand...
That's why I asked what the wiring method is. A cable will already have the correct colors for 120 volts.
 
kwired said:
Depending on wiring methods it can potentially present code issues with identification requirements of grounded and ungrounded conductors, but yes the thing to do is make one conductor grounded and the other ungrounded. I'd rather see that violation than to use the EGC for normal current carrying purposes.
Click to expand...
I never knew people cared so much about that color coding portion of the code until I got on the internet. I have never met a person in real life that would have a problem with some white tape on a #8 THHN. Only one inspector ever even mentioned it, and that was while letting it slide.
 
CoolWill said:
I never knew people cared so much about that color coding portion of the code until I got on the internet. I have never met a person in real life that would have a problem with some white tape on a #8 THHN. Only one inspector ever even mentioned it, and that was while letting it slide.
Click to expand...
Most inspectors won't let it slide at all for a new installation.

Re-purposing something that isn't simple to swap out to the right thing? You may find some that will allow it, only with their permission for that one installation.

Any that don't even mention anything about it, have to question their credibility as an inspector, they should at least tell you they are letting you get by but is not correct.

If you let people cheat like that they tend to think they can always do what they did. Should only be a one time allowance when it does happen.
 
kwired said:
Most inspectors won't let it slide at all for a new installation.

Re-purposing something that isn't simple to swap out to the right thing? You may find some that will allow it, only with their permission for that one installation.

Any that don't even mention anything about it, have to question their credibility as an inspector, they should at least tell you they are letting you get by but is not correct.

If you let people cheat like that they tend to think they can always do what they did. Should only be a one time allowance when it does happen.
Click to expand...
I just think most people understand that there is not a huge threat to life safety if some white tape is put on #6 but it's perfectly OK with #4. This is one of those rules that should be ignored because it is dumb.
 
infinity said:
Yes SE cable could be an exception. When hear radio transmitter I don't think of SE cable but it is possible.
Click to expand...
If it's a radio site it will either be pipe and wire or possibly MC. I suppose maybe TC but I have never seen it on sites. But people do a lot of crazy things on sites because electrical inspectors seldom venture to the tops of mountains
 
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