Home charge 30a TT on 20a breaker

[murbot]

Originally Posted by Argosy

What I’d be concerned about is the wire size from the breaker to the outlet you’re using. The breaker is in the circuit to protect the wire, if the breaker is oversized for the wire you could have a problem, especially as your RV seems to be overloading the circuit already.

Correct ! I upgraded from 14 to a 12 awg cable running from the breaker to the outlet. This outlet is mounted only 6' from the breaker so it this was a simple swap. Using the dogbone to connect to the TT's 30a charge cable.

[murbot]

Originally Posted by tom92

Did you actually replace the wire from the breaker box to the outlet? If not you are running 20 amps through 14 gauge wire which is only rated for 15 amps. The wire needs to be 12 gauge for 20 amps or you are risking burning your house down when the wire in the walls heats up.



If you did actually pull new wire, and there are no other outlets on that circuit, you should have used 10 gauge so you could have put in a 30 amp breaker with the appropriate 30 amp socket.

You're correct on all points. I did upgrade the cable from 14 to 12. The outlet is only 6' from the breaker so not a big deal to swap again.
I plan to install a 50a on the other side of the wall (outside of the garage and next to the TT) next year. This way I can plan for an EV in the future as well as a nice add on when I want to sell some day.

[twinboat]

Originally Posted by Persistent

Small differences can occur. A hot motor has higher resistance. However, hot weather run current is essentially the same for any given voltage. Compressor runs for longer time periods in hot weather.

As the temperature outside goes up during the day, the condenser coil has a harder time dissipating the heat.* Because the refrigerant is now at a higher pressure (pressure/temperature relationship law), that causes the compressor to work harder to continue to pump refrigerant through the system, thus causing an increase in current draw for the compressor.

[twinboat]

Originally Posted by Gary RVRoamer

Why is that? The a/c fan & compressor are either cycled on or off because of the ambient temperature, but when on the static power draw (watts) are the same. Likewise the start-up surge is essentially the same. Maybe you could measure some differences in a test lab, but there would be no practical difference.


What increases in hot weather is the kilowatt hours consumed. It runs more hours.

As the temperature outside goes up during the day, the condenser coil has a harder time dissipating the heat.* Because the refrigerant is now at a higher pressure (pressure/temperature relationship law), that causes the compressor to work harder to continue to pump refrigerant through the system, thus causing an increase in current draw for the compressor

[twinboat]

Originally Posted by glwinger

If you are adding a 30 amp breaker to the panel and plan on using 200 ft of wire, I'd go to #8. With #10 at that distance and a 20 amp load, you will lose about 10% of the voltage. That doe not take into the factor of the start current of the AC compressor which may be as much as 45 amps. At that point the voltage at the AC unit will be below 100volts while the compressor is starting.

Actually the voltage drop at 20 amps will be 8 volts with 200 feet of 10 guage, leaving me 112 volts, well within the limits.

I'm good with the 10 guage I already have, 8 guage will cost as much as a new A/C unit.

[Astasoftride]

have you considered getting a soft start for the RV A/C?

[Psneeld]

Tiny point, but was the outlet changed too?

If originally a 15A breaker, probably a 15A outlet.

Seen a few melted outlets as sometimes they are the first to overtemp before the breaker goes if it does at all.

[bigb56]

Originally Posted by Psneeld

Tiny point, but was the outlet changed too?

If originally a 15A breaker, probably a 15A outlet.

Seen a few melted outlets as sometimes they are the first to overtemp before the breaker goes if it does at all.

Good point, even though code allows a 15 amp duplex on a 20 amp circuit it would be wise to change to a 20 amp, or a single 20 amp receptacle instead of a duplex. However this will not solve the issue of the plug only being rated for 15 amps and to my knowledge there are no 20 amp rated adapters for RV hookups.
There are also no 20 amp single receptacle GFCI's and depending on the location of this receptacle is may be required to have GFCI protection, which then could be done at the panel.

[Psneeld]

Originally Posted by bigb56

Good point, even though code allows a 15 amp duplex on a 20 amp circuit it would be wise to change to a 20 amp, or a single 20 amp receptacle instead of a duplex. However this will not solve the issue of the plug only being rated for 15 amps and to my knowledge there are no 20 amp rated adapters for RV hookups.
There are also no 20 amp single receptacle GFCI's and depending on the location of this receptacle is may be required to have GFCI protection, which then could be done at the panel.

I have a 20-30A adapter and that of course can have a 30-50A adapter added.

My real point is often the connections are weaker than the wiring and CB , heat builds up.

Aren't most outlets only rated for something like 80% of their breakered load
by the NEC?

[bigb56]

Originally Posted by Psneeld

Aren't most outlets only rated for something like 80% of their breakered load
by the NEC?

All electrical components are rated to carry their full rated load for up to 3 hours. 3 hours or longer is considered a continuous load. NEC requires circuits and their associated devices to be rated at 100% of the non-continuous load and 125% of the continuous load.

Other loads such as electric space heating also have the 125% requirement.

Sometimes construction design specifications will require 125% oversizing for non-continuous loads but not NEC.