Help me understand this heat pump

zippo · 01-10-2011, 11:42 AM

I just don't get this heat pump and trying to figure if it or me has a problem.

#1. If I set the thermostat to electric at say 73 is the heat pump suppose to run and when it senses the electric can't keep up let the gas furnace come on??

This is what happened this morning. When we got up it was 41 outside and 65 inside. The thermostat was in the off position. I set the thermostat to electric at 73 degrees. After 2 hours neither the electric of gas heat came on and the outside temperature was now 44. So I set the thermostat back to off and right back on to electric at 73 degrees. Bingo the heat pump came on. I thought because it was 65 inside and I had set the thermostat to 73 the gas furnace should have come on but never did. The heat pump brought the temperature up to 73 and shut off. Since it has came on and off as needed to maintain 73. But why did I have to turn the heat pump off and back on before it would start??

If you experts out there need more info just let me know, I would sure like to understand this heat pump. But keep the answers simple as you can please.

DancinCampers · 01-10-2011, 06:01 PM

If you have the basement unit, my guess is the infamous thermostat contacts. Sometimes I need to wiggle or turn it back off, then on for it work.

Navy Flier · 01-10-2011, 10:08 PM

Since I do not know which coach you have I can only tell you in general what should happen.
You are correct that with that 8 degree (65-73) requirement the heat pump should come on within two minutes followed by the gas furnace. Both should run until the temp reaches 73. If the heat pump does not come on within two minutes I would do as you did and cycle the on/off switch. The thermostat is not perfect and, in the past, I have had to cycle the switch one or twice.
Also, if the heat pump cannot satisfy the thermostat within 20 minutes the gas furnace should start. If this happens twice in a row the heat pump is locked out for two hours. This happens to us quite often with the outside temp below 40.

KIX · 01-10-2011, 10:30 PM

We've had to replace our t'stat in our coach. The newer t'stat has a different algorithm which operates as Navy Flier stated. The older Winne/Coleman-Mach (original in our coach) could be set up to 4* above inside temp. and the set temp could be raised as the inside temp rose. That will not work with the newer algorithm as there is a 20 minute limit on satisfying the t'stat.........if the 20 minute limit is exceeded the gas furnace will start and the heat pump will shut down.
Also, with the older t'stat you could simply set the call temp. 5* or more above room temp. and both heat pump AND gas furnace would operate simultaneously to satisfy the t'stat. Sure do wish we had the older t'stat.

zippo · 01-11-2011, 09:20 AM

Quote:

Originally Posted by DancinCampers

If you have the basement unit, my guess is the infamous thermostat contacts. Sometimes I need to wiggle or turn it back off, then on for it work.

Yes mime is a basement unit and is in a 2008. From reading the other replies it sounds like mine may be running normal. This morning was 41 outside and 67 inside. Setting it to 73 and moving the setting to electric it started right up. With the 20 minute delay, that must be why yesterday morning the gas never came on as it may have closed the gag in temperature before the 20 minutes was up is that makes sense.

Thudman · 01-11-2011, 06:40 PM

I have a new (Oct 2010) R-410A Basement Air unit. But did not change out the T-stat, so have the old algorithm. Also having issues of Elec/Gas heat, operating in & out of each mode. Called RVP today & spoke w/Tech and also Elec Engineer. Told me the Elec mode has three strikes before it goes into lockout mode. Mine seems to be doing neither, that is, operating properly in Elec mode, w/3 strikes. Temp now is 40* (Destin, FL) & Elec mode works sometimes. Last few weeks the Elec mode worked continuously (without going to Gas) down to 30* but now decided it's going to refuse at 42*. And Gas mode does not come On til a 5* temp spread is reached. Strange.

Also put in a spare T-stat but same as above occurred.

Anyway, the RVP Elec Eng is doing some research & will call back tomorrow after some tests. Will advise.

Thudman

KIX · 01-11-2011, 07:32 PM

Quote:

Originally Posted by Thudman

I have a new (Oct 2010) R-410A Basement Air unit. But did not change out the T-stat, so have the old algorithm. Also having issues of Elec/Gas heat, operating in & out of each mode. Called RVP today & spoke w/Tech and also Elec Engineer. Told me the Elec mode has three strikes before it goes into lockout mode. Mine seems to be doing neither, that is, operating properly in Elec mode, w/3 strikes. Temp now is 40* (Destin, FL) & Elec mode works sometimes. Last few weeks the Elec mode worked continuously (without going to Gas) down to 30* but now decided it's going to refuse at 42*. And Gas mode does not come On til a 5* temp spread is reached. Strange.

Also put in a spare T-stat but same as above occurred.

Anyway, the RVP Elec Eng is doing some research & will call back tomorrow after some tests. Will advise.
Thudman

Looking forward to hearing what you hear. Thanks

DancinCampers · 01-11-2011, 09:33 PM

This is from a 2008 post, it applies to older tstats, mine is original 2003. It appears newer tstats a different, but my second reason near bottom of post may still apply.

QUOTE
There are 2 different ways the gas furnace turns on when the thermostat is set for electric heat.

The following is one way, which is when the heat pump can't keep up with the set temp:

Heat Pump Example To Bring On Gas Furnace As Backup Heat

Setpoint Indoor Temp. Operation
70 70+ No functions occur
\\\ 69 Heat Pump turns on (Primary heat source)
71 Heat Pump turns off (Thermostat satisfied)
69 Heat Pump turns on
65 Gas Furnace turns on, Heat Pump turns off (Heat Pump not able to satisfy Thermostat) (First strike for backup heat counter)
71 Gas Furnace turns off (Thermostat satisfied)
69 Heat Pump turns on
65 Gas Furnace turns on, Heat Pump turns off (Heat Pump is again unable to satisfy Thermostat), (Backup heat counter reaches 3rd strike and Heat Pump is locked out for 2 hours), backup heat counter is reset if Heat
Pump is running for more than 20 minutes and does not call for backup heat
71 Gas Furnace turns off (Thermostat satisfied)
69 Gas Furnace turns on (Becomes Primary heat source)
71 Gas Furnace turns off (Thermostat Satisfied)
\\\ After 2 hour lockout
69 Heat Pump turns on (Resumes as Primary heat source)
65 Gas Furnace turns on, Heat Pump turns off (Becomes Primary heat source) (Heat Pump is locked out for another 2 hours)
71 Gas Furnace turns off (Thermostat Satisfied)
\\\ After 2 hour lockout
69 Heat Pump turns on (Resumes as Primary heat source)
71 Heat Pump turns off (Thermostat Satisfied) (Backup heat counter is
reset any time Heat Pump satisfies thermostat setpoint and does not need Gas Furnace)
The word "DIFF" will display on LCD when backup heat is operating and the heat pump is locked out. There is a 30 second delay between
Stage 1 and Stage 2. There is also a 3 minute anti-short cycle delay time for cooling.

The second way is when the outdoor freeze sensor opens & shuts down the heat pump. Under this condition, the gas furnace will operate. BUT, according to the manual, in this case it will come on when the indoor temp reaches 45 deg F & turn off when the indoor temp reaches 60 deg F. At this time the thermostat should be changed over to gas.

I did have this happen to me once. Took me awhile to figure out. Once you change the tstat to gas the thermostat will operate as you have set it.

Hope I haven't confused anyone.
UNQUOTE

zippo · 01-12-2011, 08:55 AM

I thought I had got a little better understanding of how this heat pump operates. But after last night I'm not sure I understand anything about it.

When we went to bed it was 32 outside and the heat pump was on and doing a great job of keeping us at 73 without the gas furnace kicking in. I wake up at 4 am freezing, no heat.
The outside temp is now 29, thermostat set to heat pump and 73 degrees. The inside temp has dropped to 57 yet there is no heat. I thought the gas furnace was suppose to start if the heat pump couldn't keep up. So I switched the thermostat to gas and the furnace came on and it warmed up and stayed that way. Does this sound like the way the heat pump system is suppose to work?? This is our first run of temps this low and I can't say as I'm to happy if this is the way the heat pump is suppose to operate. It's now 34 outside and I just switched the thermostat back to the heat pump and it doesn't run. It seems a little crazy to have to be switching between gas and heat pump all the time trying to stay warm.

DancinCampers · 01-12-2011, 10:06 AM

I believe your unit went into the default gas mode, the second way I mentioned above.

Thudman · 01-16-2011, 06:04 PM

"Looking forward to hearing what you hear. Thanks" ----Kix

The guy did not call back. I'll try Tuesday.

Thudman

KIX · 01-16-2011, 07:33 PM

Thudman,
Earlier this week I called RVP and spoke with an electrical engineer named Gahlen. He said he has heard form others about deficiencies in their current t'stat algorithim. He advised that he was going to talk with his boss and determine if reprogramming the algorithim is warranted. He promised to call me next week. Please advise whatever your hear and I'll do the same. Thanks

Janjanjan · 01-17-2011, 09:01 AM

Another thing we've found is that neither the heat pump nor the gas furnace will run if our fan is on low. We leave it on high all the time now. May be peculiar to our system, but you may want to check if you're unable to set the thermostat to make the system work.