Is my generator big enough?

[jungleexplorer]

I have have a Coleman 2500 watt generator and I am wondering if it will pull my rooftop AC on my 19ft travel trailer? My rooftop AC is a Duo-Therm Model: 57915-541. It does not say how many watts it pulls on the plate that I can find. What do y'all think?

[pianotuna]

Hi,

It is almost certainly too small to operate the air conditioner if you intend to run the generator on propane. Output may be reduced by one fifth, so it is now a 2000 (surge) VA generator, not a 2500 (surge) VA unit.

Be aware that output also drops with altitude, so what will work at sea level, won't in the mountains.

[Arizona_Kid]

Like I said, If you put the capacitor in (cheap) it should work. It's really hard for members here to give you an answer because all gen-sets, and AC's are different. The only sure way is to test it.
Ethanol can cause problems, but most carb gumming comes from sitting too long, and not properly exercising the gen-set, which will also cause rust on the windings, and rings.

[jungleexplorer]

Thanks for all the advice. The reason I can't test it is because the carburetor has been destroyed by this insane ethanol gas (that we are forced to use now days) that has destroyed the carburetors on almost every small engine I own. I refuse to fix them so they can be destroyed again and I just convert them all to run on propane and never have another problem. I have dual 30lb propane bottles on my TT with a good space between them and the trailer, where I plan to mount a generator and run it off of propane. Before I go through all the trouble of converting this 2500 watt Coleman and mounting it I want to make sure it will do the job. This is why I have not tested it yet. I have a 5000 watt Coleman that I converted to run off of Natural Gas as a backup for my house in case of a prolonged power outage, but it is louder then a bulldozer with no muffler and I don't want to use it for my TT.

[ScottG]

It will be close. Coleman generators have very poor surge capacity and that's whats needed to start an AC (or residential fridge).

[Sandia_Man]

It will be close but I don't understand why you can't just test it if you have the generator, even can be done if stored somewhere. To have reliable success you have to have virtually nothing else drawing 120Vac, 2500 watts is borderline and as stated above most generator wattage claims fall short of actual output. Good luck!!!

[Arizona_Kid]

A general estimation for stating watts, is to double the BTU's of the AC so 13,500X13,500=27000. Using this formula you will need a 2,700 watt gen-set.
If you add a hard start capacitor you will probably get by, but won't be able to operate much else.
Just Google hard start, also referred as a soft start, capacitor.

[azrving]

The reason I kept saying check the amps is because you may not see a voltage drop. I can watch my Progressive ind. Ems and the volts will stay up while I'm pulling 23 amps on my Honda 3000 while running 2 battery chargers and 80 dc amps hitting the batteries.

[azrving]

My 13,500 want's 3,500 watt gen also....well...they aint gunna git it. 3000 or nuttin.

[azrving]

Looks like your compressor load is 11.3 amps and a minimum generator size of 3,500.

So....they want 3500 divided by 120 = 29.16 amps. They cant be sizing it by locked rotor because that's about 60 amps. They are sizing it at 1/3 of total capacity?

Manual

[pianotuna]

Hi,

Yup, they say watts on the label but when you look in the owner's manual it may very likely specify VA. It will also very likely be the surge rating.

For example the Honda 2000 watt is really only 1600 VA continuous. It is about marketing not "real life" numbers.

By way low I mean below 107 volts--and staying there for more than one second.

jungleexplorer wrote:

pianotuna wrote:
Hi,

Generators are rated in VA not watts.

Well, it says 2500 watts on the label. Maybe they have a different standard in Canada.

[azrving]

I have ran a 13,500 for a short time on a 14 gauge extension cord. I tried it but didnt do it long.

14 gauge is normally good for 15 amps. 15x120v=1800 watts. Not good but it ran.

My guess....your genny will do it but you may be borderline. Again, I would go by the amp draw.
I see you are in Texas so say it's 95 degrees and you see 8 amps running. That would be about 50 % of your gen capacity and would probably be fine to run it there. You then want to see what the amps are when the thermostat cycles off and a little while later it kicks back on. That's the amp surge that it will see over and over. Just guess and say it's 12 amps, you would probably still be ok. BUT, I'm not an ac guy and none of us are charging you anything either. 🙂

[azrving]

jungleexplorer wrote:
I know AC units have a start up and run amperage. They pull 30% to 50% more at start up then they do running. It is the start up that I am worried about. Most AC units, that I have seen, state what their start up and run amperage or wattage is. This one does not, or I have not found where it states it. That is really what I need to know.

Right. I'm no ac guy but the ambient will matter too. I think the amp draw is much more when it's 95 vs 60 which is probably what I'm seeing when I tried mine tonight.

[jungleexplorer]

I know AC units have a start up and run amperage. They pull 30% to 50% more at start up then they do running. It is the start up that I am worried about. Most AC units, that I have seen, state what their start up and run amperage or wattage is. This one does not, or I have not found where it states it. That is really what I need to know.

[azrving]

You probably actually have about 2200 or 2300 watts. 2500 is probably surge.
Generators will be rated in watts and your manual probably says that if you have a 13,500 btu ac it requires a 3500 watt gen. Many will run on less.

They are saying that if you check your system voltage as the ac works you can see if the voltage drops too low.

2300 watts divided by 120 volts equals 19 amps.
If you can borrow a clamp on amp gauge it would be good to check amp draw. You want to see starting amps and amps as it cycles on and off with compressor head pressure.

Remember that your converter and anything else on 120 v will add to the ac load. Put the frig, water heater on propane

You dont want to run maxed out because it's hard on both pieces of equipment.

I just checked my rig and the ac was pulling 5 to 6 amps but the ambient is only 60. I have seen it pull more but cant remember how much.

Beg borrow or borrow a clamp on amp meter.

[ed6713]

By "way low" he means 110volts or less. Voltage this low will cause long term damage to electric motors.

Your a/c unit is a 13,500 btu unit. I do think your generator is adequate,just watch the voltage.