Generator/AC/converter questions

[coolmom42]

My travel companion and myself are going to buy a generator for use on an extended trip this summer. It will definitely be an inverter type, and we are looking at the Champion models. We just need to figure out which one we need.

So help me figure out some things here:

1) A generator with 3100 watts peak output at 120V can produce 3100/120 = 25.8 amps. Is this correct?

2) The Advent 13500 BTU AC info we have says "12.4 amps is the load associated with the AC." So 12.4 amps X 120V = 1488 W. Is this the starting amps or running load?

3) The converter is a WFCO 8955. According to the WFCO website, the power input is 950 W. Is this what it will pull off a generator?

4) So if we plug into the generator and run both the converter and the AC, power consumption would be 2438 W. Is this correct?

5) Assuming a 10% "efficiency" loss, 2438 W/0.90 = 2700 W that would need to be supplied by the generator. Is that a reasonable assumption?

6) Is there any way to turn off the converter draw if the AC is running?

We are looking at the 3100 watt dual fuel Champion generator at Costco. According to Champion, it has:

gas--3100 peak, 2800 run
propane--2800 peak, 2520 run

Trying to decide if the propane would be adequate. Looks like it would be IF the 12.4 amps is the starting load from the AC unit. Otherwise, not.

If not, we will go with the single fuel 3400 peak version from Tractor Supply (best price we've found.)

Any input appreciated!

[Lantley]

Don't be too quick to pass on the propane model. Propane is much easier to transport than gasoline. I would also suggest consider your usage.
If you plan to run genset occasionally hours at a time propane is fine.
If you plan to run genset regularly days at a time go with gas.
If genset is use frequently gas is fine however if it will be idle and stored for long periods propane wins

[coolmom42]

If we were going to be running at sea level, we might be OK with the smaller dual fuel. But a lot of places we stay are 5000 feet or so.

The remote control is a consideration too, I admit. We definitely want electric start as both of us have some shoulder problems---not bad, but don't want to aggravate with a pull rope, either.

[enblethen]

Only 2880 on LPChampion 100264
If you are happy with it so am I!

[rirish1]

Model #100264, 3500 watt Dual Fuel Inverter.
Doesn't make 3500 watts on LP, yet meets my needs. Is pretty darn quiet also.

[enblethen]

ririshi:
What is model of your genset?

[rirish1]

I opted for the champion dual fuel because of the hassle associated with carrying gasoline. I carry an extra 20lb propane tank in the truck bed along with the generator. My past experience with ethanol/gas mixture gumming up carburetors in small engines helped me make the decision. I plan on never using gasoline in the generator. I have had good luck running my 15K BTU A/C and have also used my microwave at the same time. I am running this generator at close to sea level and expect to have some problems when I get to higher elevations. So far I am very pleased with the generator.

[TurnThePage]

The technical stuff has been well covered. I will share that I chose the 3400w version of the Champion with the remote start, which is not available in a dual fuel version. I really wanted the dual fuel for the same reasons as you, but have discovered that the remote start is SO worth it. One year in and no issues with pollution as it were, or being pinched for power. One caveat is that we do have solar panels helping to keep the batteries fairly well topped off, so the converter is unlikely to demand very much power. We're very happy with our set up. My wife loves that she can fire up the gen from inside to use her blow drier.

On edit, I think it's worth mentioning that the generator has enough reserve, that it doesn't even hiccup when the AC compressor kicks in. This is so much more generator than my old Yamaha 2800i.

[MrWizard]

the 12.x is running, compressor start surge could be anywhere between 40 & 50+
the LRA (lock rotor AMPS) is on the tag on the compressor

the 3100 will do it but the 3500 is a better choice

the trick is to start the genny, turn the A/C on high fan only
let the converter charge for 15-30 minutes
then turn the A/C to cool
turn it all they on high until the rv cools down, then dial it back for cycling if needed
short cycling with a hot RV is going to cause an overload signal on the genny
cycling the hot compressor back on too soon

i did some Pf, VA charging tests, but i don't remember the exact results
i dont recall if PF meant the VA was higher than the rated watts
or that the out put was only 0.7 of the rated input power used

PF gets tossed around a lot on this forum, but i have found that PF at the genny changes when the A/C is also running and not near as drastic as a 'converter' only power user

i have several post on these forums regarding those measurements
and they were made using champion inverter generators
maybe somebody has the links

[BFL13]

VxA = W only if PF is 1. The WFCO converter has a PF of 0.7

[coolmom42]

pianotuna wrote:
Hi Coolmom42,

Generators are rated in VA.

I strongly recommend spending the extra money for the larger Champion.

I do not recommend the dual fuel option because it will go through propane extremely fast.

The converter may draw a maximum of 950 watts--but if the battery bank is fully charged it may only draw 50 watts.

The start up surge from the roof air can be up to 4 times the running amps.

OK this make sense.

I thought that sounded like a lot of propane. The advantage of propane is how clean it runs... but doesn't seem that this version on propane will have enough power.

If we get the 3400 W gas only generator, the price is about the same as the smaller dual fuel. So the decision is really whether to go with dual fuel or not. Probably NOT.

Correct me if I'm wrong--but doesn't volts X amps = Watts?

[BFL13]

The converter at 950w has a power factor of 0.7, so it will draw approx 1357VA from the power supply as input at full converter DC output.

Kill-A-Watt on a different 55 amp converter powered by a Honda inverter generator showed:

124.7v, 11.06a, 980w, 1383VA, PF 0.71 when DC output was 56.8a, battery voltage 13.7 and rising, converter set to 14.8 volts

[DrewE]

pianotuna covered things fairly well.

The 12.4A rating would be a running rating, though the actual consumption is variable depending on various things such as the outside temperature and the circuit voltage. It's likely a worst-case (or approximately worst-case) running current rating at the nominal rated voltage, presumably 120V.

The converter rating is a worst-case rating, i.e. the maximum consumption. The actual power consumption depends on how much power it needs to put out, which in turn depends on the charge current if any going to the battery and the 12V power consumption. I think my converter (a different brand) uses less than 25 watts when the battery is fully charged...indeed, the entire RV uses about that, for the converter loafing along and the microwave clock and other such "phantom" loads.

There's no need to assume a 10% efficiency loss; the generator is rated in what it puts out. Typically that would be used for an inverter to figure the power consumed from the batteries.

I'd think the 3100 generator should be sufficient (but not offer much leeway), but I'm no expert nor can I speak from personal experience on that. My 4000 watt Onan does start my air conditioner without any hardship, but that's not a very useful data point for your investigation. 🙂

[enblethen]

3100 peak, check the specs it is probable close to 2800 continuous. Oops I see that later in post.
AC unit is rated for run not for start up. Could hit 15 amps start up.
Converter output will vary bases on the condition of the batteries.
No, you should not shut off converter. You can by shutting off 120 volt circuit breaker feeding it.
You should have somewhere around a 3500 genset.

[pianotuna]

Hi Coolmom42,

Generators are rated in VA.

I strongly recommend spending the extra money for the larger Champion.

I do not recommend the dual fuel option because it will go through propane extremely fast.

The converter may draw a maximum of 950 watts--but if the battery bank is fully charged it may only draw 50 watts.

The start up surge from the roof air can be up to 4 times the running amps.