Community Forums

timjet · 11-20-2020, 04:59 AM

I installed a power pole at home. A 50 amp outlet is connected to twin 30 amp circuit breakers with cabling suitable to carry 50 amps. So L1 is 30 amps and L2 is 30 amps. So I have 7200 watts of available power because the CB is 30 amp and I'm using a 50 amp outlet.
Is my thinking correct?
I think so because I use both my air conditioners without issue.

KanzKran · 11-20-2020, 05:21 AM

Yes, that's fine, as long as you keep the current under 24A on each leg for continuous loading.

But I just gotta ask - if the wiring is suitable for 50A, why use a 30A breaker?

Sbrownstein · 11-20-2020, 05:21 AM

Why did you use a 30 amp duplex breaker if the cable is good for 50 amps?

timjet · 11-20-2020, 05:31 AM

Yes, good question.
The RV power pole receives power from a circuit breaker box located in my detached garage. That CB box (garage) receives power from twin 40 amp breakers located in the house CB Box.

I could have used 40 amp breakers for the power pole but I have a wood shop in my garage and I wanted 10 amps reserve for use by some power tools.

Sbrownstein · 11-20-2020, 06:08 AM

Quote:

Originally Posted by timjet

Yes, good question.
The RV power pole receives power from a circuit breaker box located in my detached garage. That CB box (garage) receives power from twin 40 amp breakers located in the house CB Box.

I could have used 40 amp breakers for the power pole but I have a wood shop in my garage and I wanted 10 amps reserve for use by some power tools.

Breakers in a box do not have to add to the service amperage. You could have used a 40 amp duplex for the RV anyway.

Winemaker2 · 11-20-2020, 06:19 AM

Quote:

Originally Posted by timjet

I installed a power pole at home. A 50 amp outlet is connected to twin 30 amp circuit breakers with cabling suitable to carry 50 amps. So L1 is 30 amps and L2 is 30 amps. So I have 7200 watts of available power because the CB is 30 amp and I'm using a 50 amp outlet.
Is my thinking correct?
I think so because I use both my air conditioners without issue.

I'm no electrician but my understanding that putting a 50A device on a 30A circuit is against code... even if you install lower Amp breakers.
Will it work - Absolutely but it will not pass an inspection.

wolfe10 · 11-20-2020, 06:26 AM

Don't know about meeting the electrical code where you are (suspect Don may be correct), but you are fine with your modified 30 plus 30 vs 50 plus 50 setup as long as you are aware of its capacity limitations.

twinboat · 11-20-2020, 06:34 AM

Quote:

Originally Posted by Winemaker2

I'm no electrician but my understanding that putting a 50A device on a 30A circuit is against code... even if you install lower Amp breakers.
Will it work - Absolutely but it will not pass an inspection.

If he installed a 240 volt 30 amp outlet and used an adaptor it would be fine but not install a 50 amp outlet in its place ?

twinboat · 11-20-2020, 06:36 AM

I'll bet your generator is close to that wattage ( 7200 ) and everything works fine.

MtCamper · 11-20-2020, 06:41 AM

You should be just fine, but just for kicks and giggles, check the gauge of the wire on your 40 amp garage circuit. You may have the capability to increase your amperage on that circuit. I had to do something similar this year using a 60 amp breaker on a 100 amp cable because the 100 amp ones were not available anywhere. 40 amp circuits are kind of odd to my thinking. I've only seen those on some ranges and on HVAC units. That implies 8 gauge copper wire to me and I find 8 difficult to obtain in my area. Someone could have used 6 or even 10 gauge wire just because they had a 40 amp breaker. Just curious, but then I am not an electrician so maybe someone will chime in with why a 40 amp sub-panel would be used.

Teamfoxy · 11-20-2020, 06:53 AM

If you have a 5500W generator, the 2 breakers on the output are 30A. I expect that the breakers on your AC units are 15A. The problems come if you add an electric water heater and another high draw appliance to the AC units at the same time.

twinboat · 11-20-2020, 07:25 AM

Quote:

Originally Posted by Teamfoxy

If you have a 5500W generator, the 2 breakers on the output are 30A. I expect that the breakers on your AC units are 15A. The problems come if you add an electric water heater and another high draw appliance to the AC units at the same time.

You can keep adding things until the breaker trips. That's what they are there for.
Then you learn what not to turn on, no problem.

twinboat · 11-20-2020, 07:37 AM

Quote:

Originally Posted by KanzKran

Yes, that's fine, as long as you keep the current under 24A on each leg for continuous loading.

You do understand that continuous loading is 3 hours or more of a constant steady load.

If the load is cycling on and off, or less then 3 hours, you can go to the breakers amp rating.

https://www.ecmweb.com/basics/articl...ircuit-breaker

KanzKran · 11-20-2020, 08:11 AM

Quote:

Originally Posted by Winemaker2

I'm no electrician but my understanding that putting a 50A device on a 30A circuit is against code... even if you install lower Amp breakers.
Will it work - Absolutely but it will not pass an inspection.

It's not actually a code violation. It may not be good design, but it fits a particular need, and doesn't actually break any rules if the load is managed. NEC 210.21(b)(1) requires that a single receptacle on a branch circuit* have a rating not less than the circuit ampacity (paraphrasing). 210.21(b)(3), however, does require receptacle outlets to match the circuit ampacity, for the most part, by reference to a table** when there is more than one receptacle on the circuit.

The need to manage the load is hardly unique, either, as anybody can plug two space heaters into a single 15A wall receptacle circuit and pop the breaker. Happens all the time in office spaces and cubicles, in fact, and they're 20A circuits. My 50A 240V welder is plugged into a 6-50 receptacle on a 30A circuit because I only use it at low output current (<120A) and it's more than adequate. OK, I also had miles of 10-gauge already laying around. The OP, in fact, already has to practice load management in his garage with only 9600VA available.

An inspector may take issue with it, for reasons that don't always hold up to strict scrutiny, but it's much better than wiring a 30A circuit and receptacle and then adapting up to 50A. IMHO at least.

*It's arguable whether an RV power pedestal is a branch circuit or a feeder outlet, but that depends on what's plugged in, not on the circuit as wired.
**Table 210.21(b)(3) allows 15A receptacles on 20A kitchen counter circuits when there is more than one, and even just a duplex counts as two. Higher circuit ampacities require matching receptacles, at least until you get to 40A.