15 Amp - How much is too much?

Topic: 15 Amp - How much is too much? (Read 1285 times) previous topic - next topic

Re: 15 Amp - How much is too much?

Reply #25 – July 14, 2017, 11:35:14 am

You'd probably want to run the single AC that is NOT on inverter power and switch off the breaker feeding your inverter so you can run your house power circuits off your solar via the inverter. That would give you full functionality of any AC powered equipment you need for work without running more amps thru your extension cord. If your batteries run down, no worries as you can simply charge them off the 15 amp circuit at night once the need for AC has ended.

Re: 15 Amp - How much is too much?

Reply #26 – July 14, 2017, 12:52:43 pm

One issue that hasn't been discussed is under voltage from the house during hot weather due to the house air conditioning unit coming on. This will be dependent on how a particular house is wired. This is why our experience with 15 amps was hit or miss over the years.

It wasn't only a matter of starting the RV (coach/trailer) air conditioner. The coach air conditioner was being added to the load on the house, and the house supply had to also start the house AC.

Depending on how the house is wired things like house AC units can cause the lights to dim while the house unit is starting up. If the coach unit is starting at the same time that might cause issues.

When our house AC is running I've noticed that the voltage available to the coach is reduced. The coach is plugged into a dedicated 30 amp circuit wired with appropriate sized wire for the length of the run from the breaker to the 30 amp outlet. Still the voltage available at the coach is reduced when the house AC is running.

With a 15 amp circuit it could be hit or miss and there were several times our Progressive Industries EMS would cut power to the coach because of under voltage when the house AC came on.

With a 30 amp circuit it's never been a problem even if the voltage drops a little.

Chris

Re: 15 Amp - How much is too much?

Reply #27 – July 14, 2017, 01:49:26 pm

I would have both our EMS and autoformer on the setup.

Actually on the dual input cheater cord if two circuits are available

Re: 15 Amp - How much is too much?

Reply #28 – July 14, 2017, 09:47:49 pm

Just installed a 220VAC 50 Amp service after suffering with overloaded extension cords. I was tired of:

- 20 volt drop from my 15 Amp outlet.
- Three heavy-duty extension cords, all of which got warm. Even a short cord had a 10 volt drop.
- Worrying about an electrical fire. Extension cords are TEMPORARY: not designed for full-time use. The two little contacts on a 115VAC extension cord get HOT.

It is totally worth installing a 220 Volt system, where both ACs can run and share the cooling load.

Re: 15 Amp - How much is too much?

Reply #29 – July 14, 2017, 10:15:22 pm

Just to clarify, what Tim (hopefully) installed was an RV 120/240 VAC outlet with this wiring:

Outer straight #1 hot from L1
Outer straight #2 hot from L2
Center straight neutral
Center round ground

Re: 15 Amp - How much is too much?

Reply #30 – July 14, 2017, 10:40:06 pm

I use a cheater usually a 30 and 20a, it will usually run both airs. However the 2 outlets you plug the cheater into have got to be on different legs. If not it will trip the breakers for the outlets.

Re: 15 Amp - How much is too much?

Reply #31 – July 15, 2017, 01:11:27 am

Cheater cords that connect two different outlets into one 50-amp connection are useful. The two male ends can be 30 or 15 amp plugs and can be used in any non-gfci outlets. Each leg of coach outlets and loads must not exceed the breaker rating of the individual campground outlet it is plugged into. There is no need for the campground outlets to be on separate legs. Knowing what coach outlets and loads are on each of the 50-amp legs, and managing coach loads is the secret to using these gadgets.

Re: 15 Amp - How much is too much?

Reply #32 – July 15, 2017, 08:04:49 am

What is original LRA (AC) of the roof air?

Re: 15 Amp - How much is too much?

Reply #33 – July 15, 2017, 08:16:39 pm

Two years ago we "boondocked" in the yard of some friends. We only had a 20A outlet available, so we used that overnight and in the morning - no a/c. When it got warm enough to need the a/c I unplugged from the outlet and the coach and ran the generator. This was at a rural church (our friend was the pastor) so running the generator during the day didn't bother anyone.

Re: 15 Amp - How much is too much?

Reply #34 – July 17, 2017, 08:53:48 am

Quote from: Tim Fiedler – July 13, 2017, 08:44:57 pm

RLA of 12.1.

Whoops I missed this before. Yes this appears to be true - I was giving you Magnum display reading of the battery draw when run on battery power, which apparently includes the ~20-30% loss due to inverter.

Re: 15 Amp - How much is too much?

Reply #35 – July 17, 2017, 08:57:15 am

Quote from: Numbers – July 14, 2017, 11:20:42 am

James,

Do you all have one of the new Hybrid style inverter/converters you? \

No, no hybrid. I actually originally ordered a hybrid unit, but was concerned about some of the failure rates we were reading about, and went with the tried-and-true MS2812 instead.

Re: 15 Amp - How much is too much?

Reply #36 – July 17, 2017, 11:00:26 am

James,

Well... How did plugging into 15 amp service work for you?

Chris

Re: 15 Amp - How much is too much?

Reply #37 – July 17, 2017, 12:35:31 pm

You know.... we ended up not needing to... Unexpected cold front moved in, thunderstorms during the late night . Instead of a high of 97, the next day was a high of 82. I can deal with 82 using the Kool-matic and a fan or two...

But I will post back eventually - I'm sure the need to try it will arise eventually.

Re: 15 Amp - How much is too much?

Reply #38 – July 17, 2017, 12:39:09 pm

Quote from: Tim Fiedler – July 14, 2017, 11:26:35 am

One air will work fine - question is, how do you do anything in coach other than a PC etc. since shore power is connected, Invertor will be in standby on all the circuits, correct? So cool inside, but not much else.

You'd be surprised how tiny of a power draw the PC is. Daylight, so no lights needed. Fridge (and hot water if needed) on propane. A high powered laptop is 5-6 DC amps, monitor is another 2-3, Mobley might as well be 0. Works out to be negligible.

Re: 15 Amp - How much is too much?

Reply #39 – July 17, 2017, 02:11:56 pm

I have rewired the main AC power panel and added a second neutral #8 wire from the power panel to the service bay. Installed two 30 amp twist lock receptacles in the service bay. I split the neutral bar in the power panel into two neutral bars, one for the red hot circuits and one for the black hot circuits. With separate red & black neutral wires from the power panel to the service bay 30 amp receptacles, I can plug in two 30 amp extension cords, one for red hot and one for black hot even if the campground plugs are ground fault protected. You cannot do that with a 50amp / two 30amp cheater.
I can still use the 50 amp service bay receptacle but not when a 30 amp cord is plugged in.

Re: 15 Amp - How much is too much?

Reply #40 – September 06, 2017, 12:17:44 am

Tried starting a single ac on a 15 amp circuit with everything else off. Transfer switch chatters like crazy but won't start. Contacts shot? Todd engineering PS-250, with a warning if a malfunction blow out terminals with compressed air due to dust. Junk it or tear it apart to attempt clean/repair? Thanks

Re: 15 Amp - How much is too much?

Reply #41 – September 06, 2017, 12:24:37 am

Are you letting the transfer switch lock on before turning on the air?

Re: 15 Amp - How much is too much?

Reply #42 – September 06, 2017, 01:28:45 am

Yes, let it lock, check for good voltage, switch fan on and recheck voltage, and then enable the compressor. Same circuit I run a 14" steel chop saw on. A/c units have hard start cap.

Re: 15 Amp - How much is too much?

Reply #43 – September 06, 2017, 03:51:01 pm

Likely this 15 amp is not enough to consistently start such a load. Voltage may be dropping too low to keep transfer switch coil energized. Also if voltage drops too low roof air compressor and fan motor can be damaged. Low voltage is always problematic to motors. And chattering transfer switch points may be arcing and damaging points. Many roof air conditioners draw more than 15 amps to start.

Re: 15 Amp - How much is too much?

Reply #44 – September 06, 2017, 04:00:23 pm

Without some more facts, we are speculating here.

If you do have 15 amps AT 120 VAC (not 108, 102, etc) and nothing else is running, you are fine to run one roof A/C.

Please do post what voltage is before you turn on the A/C and after. Very likely your shore side wiring is not sufficient to provide the 15 amps at 120 VAC.

As said, you can do a lot of damage to electrical equipment running on sub-par voltage.

Re: 15 Amp - How much is too much?

Reply #45 – September 06, 2017, 04:21:48 pm

Are you using the coach power cord or an extension cord? If you use an extension cord it must be 12 ga. or better

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