View Full Version : Generator will run A/C but not Heat?

10-31-2016, 06:18 AM
Our HB has a 12.5kw Westerbeke genset. Initially we had some issues which ended up being caused by the lack of a fuel/water filter.. No idea how it ran for nearly 20 years without a filter but anyway...

Its been reliable for us for 8 years now. Normally we only run the A/C (typical heat pump setup with an air handler inside) but for the first time since the family has owned it, we tried running the heat while out on the lake. The heat pump tries to kick on but Im assuming it kicks out on low volts. The fan starts spinning then the unit almost immediately kicks off back off.

We tried the A/C just to test it and it kicks right on no problem.

I know the first thing thats popping into everyones head is the AUX coils are kicking on thus pulling more load. This MAY be the issue IF the coils are kicking on without saying AUX on the thermostat. Ive made 100% sure that it does not say AUX when were turning the heat on.

Anyone have any ideas? Why would a heat pump use more amps to kick on when in heat mode vs ac mode? Assuming the coils aren't kicking on... Im not sure if the air handler has a breaker for just the coils but its something I could check. Turn the breaker off for the coils and try it... From what I can tell by the temp of the air coming out of the vents when on shore power, they only kick on when the thermostat says AUX. I suppose its possible they could kick on for a short moment without saying AUX, but idk why they would do that....

10-31-2016, 08:30 AM
Sometimes the contactor / relay for the heat strips energize and then get stuck in the closed position.
This allows them to be on all the time. Then when the compressor also tries to energize, you are overloading.
Does this also occur when connected to shore power?

Recently, a buddy had this problem during the summer, his power bill more than doubled. He was baffled and spent allot of time trying yo figure it out.
At the end of the day, when the thermostat called for cooling, the heat strips also energized.

10-31-2016, 09:50 AM
Funny you mentioned that. I googled 'heat pump using more amps on heat' and one of the posts talked about the coils coming on with the A/C... That would be a mess. I had never heard of that happening and now Ive read about it twice in the same day...

Everything works as it should on shore power.

Its pretty easy for me to tell when the coils AND the heat pump is running. The amount of heat output is dramatically more with both on. When on shore power it all seems to work as it should. Coils only come on when the 'set' temp is 3 degrees above 'room' temp OR the unit is defrosting. Either way, I would think the genset would be able to run the heat pump and the coils. The short power is 50amps and the genset is 50amps.

The stove top actually works better when using the genset. Sometimes shore power wont boil water...

10-31-2016, 12:07 PM
I had this problem on a mobile home heat and air outside unit. When you turned the heat on the air also came on. Very high electric bills, The wires on the thermostat were crossed be and EXPERT a/c company. Air would work fine by itself but heat setting also turned on the ac.

10-31-2016, 12:12 PM
The transfer valve could be sticking is a possibility. If you have the old thermostat on the wall switch over type the thermostat switch could be sticking. Beat on it with the handle end of a butter knife.

10-31-2016, 01:46 PM
When all else fails, reboot the computer.

Haha, just kidding.

11-01-2016, 07:17 AM
What brand of AC are you using? May be nothing more than a bad Thermostat causing this problem (happened here in my house).

11-22-2016, 08:14 AM
Honestly cant remember the brand of the heat pump. It doesnt have it on the unit anywhere but I knew at one point.. Since I dont see a sticker on the unit everytime Im there I forget what brand it is....

The thermostat is just a digital thermostat.

Its a good possibility that the valve is sticking. Not sure how to check that other than replacing it.

May just live with using AUX heat till the unit goes bad or the boat is sold... We rarely ever take the boat out when heat is needed anyway.