Home charge 30a TT on 20a breaker

[murbot]

Hi,
Been running at home on a 15a breaker that tripped if anyone visits and ran AC in summer or a space heater in winter. Will install 50a next year. I upgraded the 15a breaker (and cable) to 20a yesterday and it seems to be better. TT is the only thing on this circuit.

My question is (and pardon any stupidity I might be showing here), now that it's cooled some outdoors, but still not winter, am I really getting an accurate test when I run the AC at 60° in 65° weather?

Doesn't trip now, but it repeatedly tripped during 90°+ temps in summer so I'm not sure I'm really getting a good test today.

Thanks for any tips or suggestions.

[carybosse]

The breaker typically will trip when the AC is starting up - the AC starting current is the highest load from AC. There should not be a significant difference in that current draw at 65 or 95 degrees. I presume you saw the 15 amp breaker kicking when the AC would startup.

One of the things I would try to insure is that you are using minimal other items with the AC unit on. If you are going to fire up the microwave, turn off the AC. If you have other electric appliances, turn them off. If you just have guests at the house, can you turn off the refrigerator, etc., and plan for them to just come get their drinks from the house?

[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.

[Crasher]

When the AC is running, it will use the same amount of amps regardless of the OAT. However, @90, there is a heavier load on your neighborhoods incoming power that could lower the available voltage a little causing everything to draw more amps. If your unit is drawing close to the 20 amps @ 65 degrees, it will draw more amps should the available line voltage drop due to heavier demands.

[wolfe10]

What is VOLTAGE with the heaviest load you plan to run???


Just check at any outlet in the RV with device(s) on.

[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.

[bigb56]

You don't mention the size of your roof air but I can easily run my Coleman 13,500 BTU on a 20 amp circuit, along with the fridge and the converter, TV and lights. If we need to use the microwave we just shut the air off or wait till it cycles off. It's true that the startup current is greater than the running current by a large factor (up to 5-6 times running current) but most modern circuit breakers are HACR rated and even if not the trip curve will still allow the large inrush without tripping because it is so brief.
Watching voltage is a good idea in case the circuit is too long and you get excessive voltage drop, has not been an issue with mine so far at 4 different 20 amp locations.

[twinboat]

Originally Posted by Crasher

When the AC is running, it will use the same amount of amps regardless of the OAT. However, @90, there is a heavier load on your neighborhoods incoming power that could lower the available voltage a little causing everything to draw more amps. If your unit is drawing close to the 20 amps @ 65 degrees, it will draw more amps should the available line voltage drop due to heavier demands.

I don't think that's accurate, ACs draw more amps in hotter weather.

[twinboat]

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.

He said he upgraded the wire.

[twinboat]

I just left my daughters house where I run my 15,000 btu AC on a 20 amp circuit, along with most other stuff except the microwave/convection oven. Shut the AC off to do that. Hot water is tankless gas only.

I run 200 feet of 10 guage wire from a 20 amp outlet, next to her main panel, out to my RV. Works fine.
May upgrade to a 30 amp breaker and outlet next year.

[Gary RVRoamer]

Originally Posted by twinboat

I don't think that's accurate, ACs draw more amps in hotter weather.

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.

[Persistent]

Originally Posted by twinboat

I don't think that's accurate, ACs draw more amps in hotter weather.

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.

[glwinger]

Originally Posted by twinboat

I just left my daughters house where I run my 15,000 btu AC on a 20 amp circuit, along with most other stuff except the microwave/convection oven. Shut the AC off to do that. Hot water is tankless gas only.

I run 200 feet of 10 guage wire from a 20 amp outlet, next to her main panel, out to my RV. Works fine.
May upgrade to a 30 amp breaker and outlet next year.

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.

[Ray,IN]

IMO your most important thinking should be about running your air conditioner on low voltage, causing the breaker to trip.
This will slowly destroy your compressor motor due to irreversible damage.
OTOH, a resistance space heater will not be damaged from low voltage, only inductive motors and sensitive electronics.