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Old 08-15-2016, 12:20 PM   #1
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Portable Generator to run 13,500 Btu A/C unit on 2008 Georgetown 350

trying to find a portable generator/inverter that will be able to run one rooftop A/C. currently have a Guardian Generac QP65 (6500 watts) 120V/240V single phase 60 hertz. found few generators that have a 30 amp output but is only 120V. my ONE & ONLY question is do i need a 120V/240V generator to be able to run a 13,500 Btu rooftop A/C or is a 120V generator with a 30 amp output sufficient? for example will a "Champion Power Equipment 75531i" be good enough to run one A/C unit? i only need the generator on when i'm driving in the hot summer heat and one A/C will be sufficient. MH does not have an auto transfer switch.

Back story:
current generator has about 3000 hours on it and is backfiring like crazy (idle & under load). i've done the following and the problem still exist:

- changed both plugs (it'll run nicely for a few hours then problem starts again)
- changed air filter (nothing)
- changed fuel filter (nothing)
- cleaned combustion chamber with Mopar and water (it'll run nicely for a few hours then problem starts again)
- changed carburetor (new - ran nicely for a few hours then problem starts again)
- upgraded to 92 octane
- added Stabil, Seafoam, etc. (nothing)
- unplugged breather hose from intake (nothing)
- compression test (both cylinder good at approx. 122 psi)

one thing worth mentioning is when i pulled both plugs one of them seems to be really dirty. once i clean the heads or install new plugs it seems to run fine until the plugs get dirty again. there's something causing a bad combustion in that one chamber and i can't figure it out. I am out of ideas. the only thing left that i can think of is a faulty stator (not easy to get to).

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Old 08-15-2016, 12:29 PM   #2
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Originally Posted by crazyasian View Post
my ONE & ONLY question is do i need a 120V/240V generator to be able to run a 13,500 Btu rooftop A/C or is a 120V generator with a 30 amp output sufficient?
Not sure it that was one or two questions but;

A 13,500 unit will only draw 15 to 20 amps (max) at 120V.

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Old 08-15-2016, 12:50 PM   #3
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I have a champion 3100. Had a 120vac 30a RV connector. Runs one air conditioner just fine.
Vince and Susan
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Old 08-15-2016, 02:04 PM   #4
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Rather than drag a portable generator around, I would think it would be far more economical to have a good generator tech fix the problem. Not to mention the convenience factor. P/S a faulty stator Will Not cause fouled plugs. Are you sure you have the right plugs to begin with. Check the plug wires. If the compression is good as indicated, look for an ignition related problem,
Dennis & Carol
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Old 08-15-2016, 03:27 PM   #5
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i definitely thought about going the repair route but i keep coming back to the same solution of getting a lightweight portable genny. when this backfire issue started i thought i fixed the problem after replacing with new plugs. it ran normal for a couple of trips and a few months. then the problem started again. diagnostic alone will cost around $150 and any repairs will cost me at least $500 unless it was simple. and repairs aren't guaranteed. the problem could come back in a few months. i figured with 3000 hours its' not worth fixing unless i can fix it myself. plus new genny will be mounted on the hitch, therefore, won't be too bad and it's good for dry camping...a lot quieter and more efficient.
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Old 08-15-2016, 05:13 PM   #6
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Originally Posted by dennis45 View Post
?....Check the plug wires. If the compression is good as indicated, look for an ignition related problem,

This is my advice also.
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Old 08-15-2016, 05:14 PM   #7
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I gather this is RV has a 50A shore power system (a 4-prong plug)? But no transfer switch, so you have to plug the shore cord into a genset outlet to make things work? If so, it is still a 120v system. Any 120v portable genset that can supply about 3000 watts (peak) and 2400 watts continuous through a single outlet will work fine. Beware that many gensets with a high watt rating only supply that wattage at 240v through 4-prong outlet. You can use that, but only half the rated wattage is available on each of the two hot wires, and your a/c will be running off just one of the two.

You will need a suitable outlet wired to it to bridge between your 4-prong shore cord and whatever. Just what that is depends on the genset make & model, but most with 30+ amp outlets use twist-lock plugs.
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Old 08-16-2016, 03:45 PM   #8
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Hi, I would look for someone who services generators and not an RV dealer. I think RV dealers are hacks, well most of them. Try to fix your generator rather than get a replacement. I have an older 8hp portable that puts out 32.5 amps. Came out of an electric van. I'm selling it if interested. Live in IL.
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Old 08-16-2016, 05:06 PM   #9
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I'd get your current generator serviced.
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Old 08-16-2016, 06:33 PM   #10
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I would fix what ya got. I can run a 13000 btu AC off of a 20A outlet. With no other big load.

Ya got a generator. It almost sounds like valves not closing at the right time.

Try some of the slippery stuff and go to synthetic oil.
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Old 08-17-2016, 08:26 PM   #11
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Backfiring ?

It's an ignition issue. Either bad plug wires or ignition timing is off...or both.
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Old 08-18-2016, 07:48 AM   #12
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yes, i came to a conclusion that it's an ignition issue after replacing a lot of parts (which needed replacing anyway). the question now is what's the fix. i mistakenly said it could be the stator in my original post but what i meant was the ignition coil. the parts aren't that expensive ($125 for both) but getting to it is what i'm unfamiliar with. i'd imagine the cover has to come out and in order to do that the whole generator has to be dropped from the compartment.
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Old 08-18-2016, 09:08 PM   #13
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The genny is nothing more than a lawnmower...

If Onan it has a single coil that fires both plugs at same time.

Yiu say plugs dirty?

Fouled is correct term and if black damp and sooty it is a rich or no ignition condition.

Are both or 1 doing it?

If one plug wire is leaking to ground it could cause one side to miss fire as the spark is higher voltage on compression so the leaking side may not fire properly on compression.

Clean old plugs or get another set and after verifying gap pull one at a time and check to see what they look like.

If one is worse than the other then put them back and fire it up to confirm poor run.

Shut off and place new plug in and retest, if it runs better then stop and swap other plug and repeat.

If better yet stop and pull plugs to see what they look like.

If starting to look bad then confirmation that good plugs but something not right.

Confirm if electronic or points ignition and if points confirm condition.

Take one of th e old plugs and pull one plug wire and connect to old plug and rest it on t he engine.

Get a screwdriver and fire up the genny and with the screwdriver lift the plug to see how much spark.

Repeat for other plug.

The coil may not have enough spark.

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generator, tow

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