Heat Pump Question

[Monkei]

Why ... when  switch my heat pump on, does it go on for a about 3 seconds and then switch over to LP?  This morning the temp outside was around 50, the inside temp was around 56, I set the thermostat to 60, the fan is on auto, the speed on low (although I have had it on high just to see if it made a difference, slide the bar over from off to ELEC HEAT ... unit clicks on, then switches back to LP.  What am I missing?

 

[seilerbird]

Sounds like there is no electrical power to the heat pump. Are the breakers on?

 

[Monkei]

Sounds like there is no electrical power to the heat pump. Are the breakers on?

I don't think that is the problem, it cuts on, and then cuts off and switches to LP ... no breakers or fuses tripped.  I am assuming that if that was the issue "nothing" would happen ... but it "is" cutting on to Elec Heat and it starts blowing out up top, but then switches over to LP in about 5 seconds to LP.  I was once told that it would not work depending on the temps outside, but it's 50, the heat pump should work at that outside temp.

 

[lavarock1210]

Possibly a weak power source.  Check your voltage while the heat pump starts.  I suspect it (voltage) goes too low and then the system transfers to LP.

 

[ua40j]

In the Winnebagos, the thermostat has a 5 degree differential between the heat pump and the gas furnace.  So if you set your thermostat to 54 degrees (if the ambient air is 50) then only heat pump comes on.  If you set it to 60 degrees, then the heat pump cycles and kicks on the gas furnace.

That's the way it works in most of them.

 

[Monkei]

In the Winnebagos, the thermostat has a 5 degree differential between the heat pump and the gas furnace.  So if you set your thermostat to 54 degrees (if the ambient air is 50) then only heat pump comes on.  If you set it to 60 degrees, then the heat pump cycles and kicks on the gas furnace.

That's the way it works in most of them.

So if that is the case I could only hope to be 5 degrees warmer inside than outside?  So outside 50, inside 55 ... if I want it warmer we are talking LP then?

 

[ua40j]

Once the temperature in your coach gets to within 4 degrees of the set temp, then the gas furnace will shut off and the heat pump will continue to the set temperature. 

This works for most conditions unless your outside air temp is below 38 or so.....then the heat pump won't (shouldn't) come back on and the gas furnace continues to run.  I'm not sure where the transition point is for the heat pump when the outside air temp is below 38.  I've never paid much attention.

Hope this helps.

 

[Dar]

So if that is the case I could only hope to be 5 degrees warmer inside than outside?  So outside 50, inside 55 ... if I want it warmer we are talking LP then?

The 5 degree variant is with the set tempature inside. Here is a quote from our Adventurer manual concerning the heat pump;
"This system is set to automatically start the gas furnace to assist the heat pump if room temperature cools to 5 degrees
or more below the thermostat set temperature. You may wish to manually switch to furnace heat to maintain a higher temperature when outside
temperatures begin to reduce the efficiency of the heat pump. The heat pump will not operate when the outside temperature falls below 36 degrees F."

 

[Monkei]

well ... I cut the heat pump back on this morning.  It was 58 outside, it was 60 inside the coach, so I set the thermostat to 62 and once again, heat pump cut on and then switched over to LP in about 3-4 seconds. 

The A/C works fine, the LP works fine.  I am assuming that since both of them work ok that there is no electrical issue ... doesn't the heat pump work on the same electrical circuits as the A/C does?  I am also thinking I can rule out the thermostat since the A/C and LP work (cut on and off depending on setting). 

If anyone else has any idea or thinks that my assumptions are wrong, please let me know.  At this point I am in the "ruling out" stage.

Thanks

Keith

 

[ua40j]

Well, Keith...I guessing now.....but it sound like you've got a thermostat problem.  Or a problem with the reversing valve. 

Good luck with resolving this...sorry I couldn't be more helpful.

 

[Monkei]

Well, Keith...I guessing now.....but it sound like you've got a thermostat problem.  Or a problem with the reversing valve. 

Good luck with resolving this...sorry I couldn't be more helpful.

OK, I am sure you know more about this but I wonder ... if the LP and A/C are working correctly, would they not be using the same thermostat?    The reversing valve, where is that located and is it something that anyone could replace?

 

[John Canfield]

The reversing valve is plumbed into the freon line and it is not something you could replace.  Find your service manual here at RVP's web site.  You could have a thermostat problem or a wonky circuit board on the basement unit itself.

 

[ua40j]

Ditto on what John said.  When I said a problem with the reversing valve, I should have said that it may be 'stuck' in the cool position causing it to report that it can't make heat and thereby kicking in your gas furnace.  An electrical problem could cause this either on a circuit board or in the thermostat.

If you can't find some troubleshooting steps in the manual that John referenced, I would call RVP directly and work through their customer service.  I understand they've been very helpful to folks who call in.

 

[howdymi]

I have talked to Winnebago and the manufacturer about our heat pump.  How they tell me it's suppose to work and how it works at times is not the same.    There is myself and 3 close friends that all have heat pumps and at times they all do not function as they are suppose to.  I have seen mine produce good heat with the outside temperature at 24 degrees and the LP never came on.  I have also seen the outside temperature at 41 and the heat pump would switch to LP.  I have gone to bed with the heat pump on and set to 68 degrees working fine, only to wake up freezing.  The heat pump not running or the LP.  It's like it has a mind of it's own at times.  98% of the time the heat pump works great, but waking up freezing, I don't care for the 2%.  I talked to my dealer and he tells me he hears the same complaints often.  I take it in to be checked out and it works great for them.  I guess it's waiting for the warranty to expire and then fail.  We had a heat pump in our old 2000 model and it never missed a beat for the 6 years we had it.   

 

[Monkei]

I just called the technicians about 10 minutes ago ... of course it worked first time on the phone with them, but then again we are working with a temp of 70 in the bus and 73 on my room setting vs 50 an 53 like this morning.  Nothing left to do but try it again tomorrow and it does not work correctly, into the shop it goes per their instructions. 

Thanks everyone for trying to figure this out!

 

[Pubtym]

A couple of items....

I see you are wintering in Port St Lucie Fl, where the humidity varies from 65-98 %, and dew point runs high 70s too.

a. High humidity like that with high dew points tend to sometimes favor early icing in the condenser coils..which really shuts down heat pump's heat extraction from the outside ambient air. If your condensing coils have not been cleaned in a while..icing occurs in the coil earlier in lower temp-high humidity, high dew point scenarios...especially as night falls and into the early morning. Suggestion, with the unit not operating...get some Simple Green and a small hand sprayer. Dilute the SG about 3oz to ten oz water. Starting at the top of the coils..gently spray SG solution so it travels at least 3-4 inches into the coil banks. Work your spray across the coils eventually all the way to the bottom. Wait 15 minutes. Take your water hose and very gently, rinse the coils clean starting at the top and flushing all to the bottom. Try the heat pump again when it's a 65-70 degrees and lower humidity (50%) and dew point. Watch the coils  to see if any icing occurs.

b. Check that both compressors come on line during Heat Pump demand temp. # 1 compressor should start within 15 secs and be indicated at the power panel by about 12-14 amp draw. About 30 secs later # 2 compressor should start and the power panel should indicate 22-24 amps.

c. Have you checked your AC current input to the coach at your park. Usually heavy (park & neighbors) A/C and Heat Pump ops will really suck down the incoming voltage (108-105V) to your rig too and this really cripples the Heat Pump start up cycle. You should always have 120 +- 10 Volts.

Quote from Unit Manual:HEAT PUMP OPERATION (HEAT MODE)
1. Begins with a call from the thermostat, 12 volt positive (+) to terminal #8 (W) in the 9-pin connector. (White with Black stripe
wire at the thermostat). The Ground (-) is Blue in terminal #4.
2. The p.c. board takes over at this time and controls all functions of the heat pump.
3. 115 VAC should appear between the T18 and T19 Rev Valve Out terminals.
4. This voltage continues to the reversing valve solenoid coils and switches both reversing valves to the heat position.

The way the reversing valves work is the solenoid valves open pressure ports to operate a nylon slider in the cylinders. This sleeve can jam or bind half way (called "wind milling") and will over heat the compressor in a few minutes. Once this happens there is little chance that the valve will work again.

d. Have you checked your A/C unit air filter lately? Change it...Is there something (suitcase, case of beer, paper bag etc) blocking/restricting the inside air intake of the A/C unit.

Keep us updated.

Charlie

 

[Monkei]

A couple of items....

I see you are wintering in Port St Lucie Fl, where the humidity varies from 65-98 %, and dew point runs high 70s too.

a. High humidity like that with high dew points tend to sometimes favor early icing in the condenser coils..which really shuts down heat pump's heat extraction from the outside ambient air. If your condensing coils have not been cleaned in a while..icing occurs in the coil earlier in lower temp-high humidity, high dew point scenarios...especially as night falls and into the early morning. Suggestion, with the unit not operating...get some Simple Green and a small hand sprayer. Dilute the SG about 3oz to ten oz water. Starting at the top of the coils..gently spray SG solution so it travels at least 3-4 inches into the coil banks. Work your spray across the coils eventually all the way to the bottom. Wait 15 minutes. Take your water hose and very gently, rinse the coils clean starting at the top and flushing all to the bottom. Try the heat pump again when it's a 65-70 degrees and lower humidity (50%) and dew point. Watch the coils  to see if any icing occurs.

b. Check that both compressors come on line during Heat Pump demand temp. # 1 compressor should start within 15 secs and be indicated at the power panel by about 12-14 amp draw. About 30 secs later # 2 compressor should start and the power panel should indicate 22-24 amps.

c. Have you checked your AC current input to the coach at your park. Usually heavy (park & neighbors) A/C and Heat Pump ops will really suck down the incoming voltage (108-105V) to your rig too and this really cripples the Heat Pump start up cycle. You should always have 120 +- 10 Volts.

Quote from Unit Manual:HEAT PUMP OPERATION (HEAT MODE)
1. Begins with a call from the thermostat, 12 volt positive (+) to terminal #8 (W) in the 9-pin connector. (White with Black stripe
wire at the thermostat). The Ground (-) is Blue in terminal #4.
2. The p.c. board takes over at this time and controls all functions of the heat pump.
3. 115 VAC should appear between the T18 and T19 Rev Valve Out terminals.
4. This voltage continues to the reversing valve solenoid coils and switches both reversing valves to the heat position.

The way the reversing valves work is the solenoid valves open pressure ports to operate a nylon slider in the cylinders. This sleeve can jam or bind half way (called "wind milling") and will over heat the compressor in a few minutes. Once this happens there is little chance that the valve will work again.

d. Have you checked your A/C unit air filter lately. Change it...Is there something (suitcase, case of beer, paper bag etc) blocking/restricting the inside air intake of the A/C unit.

Keep us updated.

Charlie

Thanks Charlie for the explanation on how the system works.  I am anxious for tomorrow morning to come to see if it works again.  The coils are clean, I did them back in October in Tennessee before we came down to PSL.  We have not had a run on "humidty" lately down here! 

We own the lot here at the resort and we have really good electrical setups ... I don't think that is the problem either.  But I know what you mean about some parks and the electricity ... but believe me this is not one of those parks.

I can only assume, here again it is just my computer related trouble shooting skills that since it worked fine when on the phone about 2 hours ago with the technician, then the valve is not the issue either.

 

[Pubtym]

Thanks Charlie for the explanation on how the system works.  I am anxious for tomorrow morning to come to see if it works again.  The coils are clean, I did them back in October in Tennessee before we came down to PSL.  We have not had a run on "humidty" lately down here! 

We own the lot here at the resort and we have really good electrical setups ... I don't think that is the problem either.  But I know what you mean about some parks and the electricity ... but believe me this is not one of those parks.

I can only assume, here again it is just my computer related trouble shooting skills that since it worked fine when on the phone about 2 hours ago with the technician, then the valve is not the issue either.

Good link! Check humidity and dewpoints vs OATs.

http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=KFLPORTS41

Charlie

 

[tomsm]

My heat pump has never given me a problem so my troubleshooting skills are low, but here's something to consider... Something (thermister) back there determines when it's too cold for the heat pump to operate. I know mine has shut down in low temps. I usually try it even on cold mornings (too cheap to use LP if I don't have to). What if the thermister or whatever makes the "too cold" decision is out of calibration. It would be OK when you talked to the tech in the middle of the day, but say "too cold" in the morning temps.

 

[John Canfield]

Here's the Wiki that describes thermistors which in this application are commonly referred to as freeze switches.  As far as 'going out of calibration', I'm not sure if that can happen, but when they fail, I don't know if they go open, or change resistance.  A long time ago Winnie factory service replaced our thermistor when they were trying to fix an intermittent problem (which didn't fix the problem, BTW.)