I have a TT with a 13,500 BTU Dometic AC and am struggling with finding a good way to power it. My off grid property has an Onan 5.5 KW propane generator for use when the solar system needs charged or additional power is needed. I tried to use a a 100' 10/3 extension cord plugged in before the transfer switch that feeds the house and nothing is drawing power in the house. This resulted in 115 volts when the AC compressor is not on but once it turns on it goes down to 99 volts after a couple of minutes making the fan run slower so I cut it off. There is a bit of additional solid copper from the generator to the outlet I am using of about 30' plus the 30 amp RV plug which is 25' if I remember right.My question is, is the voltage drop due to not a heavy enough gauge extension cord? If so, I can run some romex under the grass and install an outlet near the camper so what gauge would be recommended. My power draw is 11 amps when the AC is running plus another 2 for misc items.Thanks in advance.

Do your calculations here:Southwire calculator

Yes, your wire is too small. I'm kind of surprised because I've run my air conditioner on 125' of 12 gauge extension cord plus the camper's #10 cord and it worked fine. My voltage stayed around 104 - 108 if I remember correctly.I wouldn't run romex under the grass, it's not rated for outdoor use or wet locations. You would want to run UF cable in that application or better yet, run PVC conduit with individual conductors.According to Southwire's calculator #10 should be large enough. So, maybe you have some other high resistance wire problem or a generator problem. If you run new wire I would at least go to #6, it's not much more than #8. If you went even bigger to #4 you would see a bigger price jump.

When the A/C was at 99 what was the source voltage? Seems like a larger drop than would be expected. Possibly a loose connection at some point. Extension cord connectors are notorious to cause trouble.The other issue is why did the power fade with time? Is it source regulation? Connection getting hot and loose?If this is to be used often I would hardwire #6 copper.

I think that's too long for #10. The post above reports 104-108v. I would not be comfortable with that.

Big fat wire. Aim for a 1% voltage drop. Move the generator closer.

Running AC from Generator 150 feet away | Good Sam Community

29 Replies

greenrvgreen
Explorer
Aug 02, 2017
I was under the impression that the freq had to be insanely high (radar) for a coil to affect voltage. What kind of real-world results did you find? (AWG, footage coiled, A, V, etc)

Thanks!
flylipsdaddy
Explorer
Aug 02, 2017
Just a Thought from an open minded person - Are you coiling up ANY OF YOUR CORD? a friend showed me that just a couple coils on my cord Resulted in Reduced voltage,After we Straightened out my "Neatness" the AC ran fine.Knew 12 volts did that,but didn't know that 120 volts would do the same.
marcsbigfoot20b
Explorer
Aug 02, 2017
Try to adjust the voltage on page 35 or 6-5

Manual for you gen model
Kayteg1
Explorer II
Aug 01, 2017
The older gensets had adjusting screw on governor/carburetor linkage.
If you find it - adjust to get 62 Hz
Newer generation does everything electronically and I hate those things.
Hopefully you can figure it out.
Than seeing 115V no load, your generator might have bad coils.
mtnman1000
Explorer
Aug 01, 2017
I need to head to Montana for a few days so will try ramping up RPM this weekend to see what happens under load.

The 115V is due to the length of cable but is 117 V at the house and I've never seen it higher.
Bird_Freak
Explorer II
Aug 01, 2017
Bipeflier wrote:
Dennis12 wrote:
Sounds to me like you have a CHAMPION and don't like the noise. Buy a Honda and sit it right beside your unit.

I nominate this post for the LEAST HELPFUL in the past year!
Agree, just another Honda troll.:S
MEXICOWANDERER
Explorer
Aug 01, 2017
Do some observation to see how the governor moves. Repeat the test. With a lot of care noodge engine speed a little higher and see if voltage tracks upward. Turn off or unplug all sensitive electronics before you do this. Short sleeve shirt. No watch. I have seen bad voltage regulators droop engine speed and voltage.
marcsbigfoot20b
Explorer
Aug 01, 2017
No load the gen should be at 120-123 volts and 62-63 HZ.
mtnman1000
Explorer
Jul 31, 2017
There is a house wired to the generator via a transfer switch but I turn off all breakers to the house when testing so no load there.

The genset is an Onan 5.5 HGJAE. L1 output at 120V is going to the transfer switch. L2 at 120Vis going to the outlet I am using for the TT. Bear in mind my Honda 3k has 0 issues running everything.

Here are the results of the frequency tests over a 2 minute period:

115V @ 60hz with no load

101V @ 58.7hz once AC kicks in

100V @ 58.6hz

99.5 @ 58.6hz

99 @ 58.5hz

At this point I shut it down. Is this possibly a governing issue as Kayteg1 had mentioned? I can find no info on adjusting in the owners manual.
MEXICOWANDERER
Explorer
Jul 31, 2017
Cheaper and easier to use is a handheld digital multimeter. Shows instant readings to point one Hz least significant digit. Ex= 59.6 Hz.