RVP Heat Pump Question

[Gary RVRoamer]

When in Heat (reverse cycle) mode, my RV Products heat pumps sometimes have difficulty starting. Sometimes the compressor may fail to start several times before it gets going, while other times it kicks right in. In cooling mode, they seems to work fine all the time. Does anybody know if the RVP's start capacitors are different in the two modes? Or something else different (other than the reverse cycle itself)?

[Gary RVRoamer]

When in Heat (reverse cycle) mode, my RV Products heat pumps sometimes have difficulty starting. Sometimes the compressor may fail to start several times before it gets going, while other times it kicks right in. In cooling mode, they seems to work fine all the time. Does anybody know if the RVP's start capacitors are different in the two modes? Or something else different (other than the reverse cycle itself)?

[Petro]

Gary;

I am not a Tech. but I believe the compressors operate the same. A valving system reverses the flow of freon. If I am wrong hopefully some will jump in here and correct me.

Don

[two2go]

I have to set our thermostat temp to within 4 degrees above the room temp on "Electric Heat", or the gas furnace will start instead. The heat pump starts fine if it is maintaining room temperature. Check your thermostat function first before trouble shooting at the A/C unit.

[JoeT]

My RVP Heat Pump compressor wouldn't start recently. Just the fan ran. I think it was about 35 degrees outside. Later in the day when it was warmer it started just fine. My guess is it has to be above a certain temperature to start.

Does your problem happen only in very cold weather?

The compressor uses the same start capacitor for both heat and cool.

[RV Wizard]

Gary, Joe is on track with the problem. The problem with the heat pump units on these coaches is that there is no crank case heater like you would find in a fixed building heat pump. The viscosity of the oil in the compressor and the migration of the refrigerant into the oil causes this and other problems. Many of the units do not incorporate an outdoor thermostat either to prevent the unit from being at least tried to start below what is called the balance point. If the outside temp is lower than 45 degrees, I will not attempt to start the unit up. This is not to say that you do not possibly have a weak start capacitor, you could but it is still strong enough to crank it up in warmer weather.
What is the out door temperature when you are having the problem?

[Gary RVRoamer]

Sorry for the long delay in response. Have been busy and away from the coach. Now it's cold here again and I have some recent data.

two2go: Mine system fires the furnace if 6 or or degrees difference between interior temp and "set" temp. The heat pump also runs at the same time.

JoeT: American Coach says my RVP heat pump is good to about 35 degrees. RVP says it's heating capacity begins to go downhill below 42 degrees but doesn't give a lower limit. I'm not sure if there is a temperature where it locks out completely, but I haven't reached it. I don't turn it on when below 40 or so, but it may reach a lower temperature overnight when I'm asleep.

Mike: I start to experience the problem in the mid 40's and the front unit is worse than the rear. It happens even if the unit has been running off and on all day. This week, at about 45 degrees, the front unit cycled over a dozen times to start. Each time the compressor stayed "in" a second or two longer, starting at about 3 seconds and gradually building to about 12-13 seconds before it engaged and stayed engaged. The rear unit only took about 4 cycles to get to normal operation. Once they get going, they produce plenty of heat at those temps.

I had the front unit checked this spring at the American Coach factory, but it was a nice warm day and it worked flawlessly on heat & a/c.

I'm thinking a weak capacitor in the front unit, coupled with the oil viscosity issue you described. Once they get going and warm up, they usually start first or second try.

[GaryKD]

Hi Gary,
Consider doing nothing until you see how the units work when the temps are in the 50s. My front unit does the same as yours. I figure it's just too cold and leave it at that. I do not use my units below 50F.

I do not mind using the furnace. It doesn't get much work. The few times a year it is used at least confirms it works.

[Meandering Retiree]

We are camping a Twin Creek in Gatlinburg, TN, and it got down to 16* last night. The heat pumps worked until the temperature reached about 25* and then the furnace ran off and on during the night. Today, when the temperature reached the 20s again, the heat pumps took over and are still cycling on and off now.

[historyljc]

My heat pumps don't work below 40 degrees. They'll run, but they'll blow cold air. If I'm expecting anything lower than about 42 I'll switch over to propane heat.

[RV Wizard]

Gary, I would check the start capacitors and the voltage you are at under load to determine if you have a problem. If the compressors have been running, even off and on, it is not so big a deal with ambient temps and you can continue to get heat out of the outdoor air down into the twenties but the outside coil may freeze up, especially in higher humidities.

[Alfa38User]

Hi All,

Since your unit is an RVP you likely have an RVP thermostat as well.

Before chasing ghost problems,voltages, bad caps etc, be sure to read the booklet that comes with the thermostat, the sequence chart is very revealing as to how the thermostat/air conditioner/heat pump and furnace are expected to function together under these conditions. Once the process is understood, troubleshooting will be a lot easier. Be aware that BOTH compressors have to operate for the heat pump to function. This usually won't happen on a 30 amp AC supply.

BTW despite RVP statement that the heat pump works to 35 degrees, it does not do well below 45 degrees and will call in the furnace automatically if it can't keep up. The thermostat booklet is quite specific.

[Gary RVRoamer]

I have an Atwood Comfort Control System t-stat, not the RVP (Coleman) one, but I am familiar with it's manual. However, I don't get your point. I don't see what the t-stat has to do with the heat pump compressor cycling. Once the t-stat calls for heat (or cool) to the a/c, it's pretty much on its own as to how to provide it. Only when the temperature difference exceeds the 4 degree threshold does the t-stat do anything different, and then it just calls for furnace heat in addition to the heat pump.

[Gary RVRoamer]

Mike,
When this happened this past week I had excellent voltage to the coach - mostly 120-122v. However I have not checked directly at the a/c itself - could be a voltage drop up there. I'm away form the coach for a few days, so can't check on it now.