Omnistat2 - heat won't turn off

[bjdraw]

This Summer I purchased a new HAI Omnistat2 (RC1000 WH) thermostat and honestly once the AC worked, I never tested the heat. Well the first day the heat turned on last week (Florida) I noticed it got much hotter than I wanted the heat set point, in fact it got as hot as my cool set point. Upon some investigation I discovered that although my Heat Pump turns off, the blower and heat strip (I assume this based on the temp of the heat coming from the vent) continue to run until the house reaches my cool point when the thermostat turns on the AC.

I verified this by putting the Hold to On, and switching the mode from Auto to Heat and then turning the heat point one degree warmer than the current temperature. At that point the heat turns on, and I go outside to verify the heat pump is on. Then I switch the mode to off, at which point the heat pump turns off, but the blower continues to blow. So I wait 10 minutes and it never turns off. Now I switch the mode to Cool and turn the cool point to a degree cooler than the current temperature and the Heat Pump turns on and cold air starts blowing from the vent. Now I switch the mode to off and the entire system turns off.

I checked all the wiring and everything seems in order. The only thing interesting is that the white wire connected to #6 B runs to the air handler where it is wired to both the Heat Pump and the Heat Strip. But this all worked fine with my old Omnistat1, so I'm thinking either the thermostat is messed up or my Heater, not sure how to tell which.

Here are my components.
Goodman CPLJ48-1B (condenser/heat pump)
Goodman arpt049-00c-1a (air handler)
Goodman HKR-10A (Elec Heat)

Thanks

 

[sic0048]

Sounds like the 2nd stage heat (the heat strips) are incorrectly wired on the thermostat. Or perhaps the thermostat isn't properly set to run a 2 stage heating system. The cooling system in only a single stage which is why the problem never appeared in the summer.

 

[bjdraw]

Sounds like the 2nd stage heat (the heat strips) are incorrectly wired on the thermostat.

Ok, should heat strips be wired as a second stage? And if so which stage 1 or 2?

 

[bjdraw]

Ok, found the installation instructions for my system and the white heat strip wire is supposed to go to the Heat Pump as well -- although I don't understand why. But it is supposed to be wired to W2 of the thermostat, not to #6 B where I had it wired. So I switched the white wire from B to W2 and configured the thermostat to a dual stage heat pump and it seems to working now. If the issue crops up again I'll assume it is the system and call out a warranty tech.

Thanks
Ben

Here is a link to the installation directions for my Goodman system listed above if anyone else needs them.
http://www.hvacpartsshop.com/ckf%20series.pdf

 

[sic0048]

Glad to see you got it working. I wasn't sure exactly how to wire it, so it is good you found the solution in the manual.

 

[cornutt]

Ok, found the installation instructions for my system and the white heat strip wire is supposed to go to the Heat Pump as well -- although I don't understand why.

That's so the heat pump can turn on the strip heat during defrost cycles. It's a comfort thing; it keeps cold air from blowing out into the room during defrost.

I think I understand what was happening with your system. The standard heat pump has two wires that control it. There's one (It may be the "Y" terminal, but I can't remember for sure at the moment) that tells the outdoor unit "turn on". Then the "B" terminal tells it whether to cool or heat. It's energized for heating and not energized for cooling. However, when the "Y" terminal is not energized -- in other words, the heat pump is not being told to run -- there is no defined state for the "B" terminal. It may be energized or not, depending on the thermostat; the heat pump doesn't care.

So evidently what happened was that when you switched the system to heating, the first time the thermostat called for heat, it energized the "Y" and "B" terminals. This turned on the heat pump in heat mode, and since your strip heat was tied to the "B" terminal, it also turned on the strip heat. The combined system ran until the temp reached the heat setpoint, at which point the thermostat de-energized the "Y" terminal and the heat pump stopped. However, it kept the "B" terminal energized -- this is an artifact of how the thermostat's circuits are designed; the heat pump doesn't care what state the "B" terminal is in when the "Y" terminal is not energized. But, since your strip heat was tied to the "B" terminal, it stayed on. And evidently, your air handler has an internal safety thermostat that holds the fan on as long as the strip heat is hot, so the fan kept running too even though the thermostat was no longer calling for it.

So the room kept getting warmer. But with the room temperature reached the cool setpoint, the thermostat de-energized the "B" terminal in order to call for cooling. When it did that, the strip heat shut off.

 

[bjdraw]

So evidently what happened was that when you switched the system to heating, the first time the thermostat called for heat, it energized the "Y" and "B" terminals. This turned on the heat pump in heat mode, and since your strip heat was tied to the "B" terminal, it also turned on the strip heat. The combined system ran until the temp reached the heat setpoint, at which point the thermostat de-energized the "Y" terminal and the heat pump stopped. However, it kept the "B" terminal energized -- this is an artifact of how the thermostat's circuits are designed; the heat pump doesn't care what state the "B" terminal is in when the "Y" terminal is not energized. But, since your strip heat was tied to the "B" terminal, it stayed on. And evidently, your air handler has an internal safety thermostat that holds the fan on as long as the strip heat is hot, so the fan kept running too even though the thermostat was no longer calling for it.

So the room kept getting warmer. But with the room temperature reached the cool setpoint, the thermostat de-energized the "B" terminal in order to call for cooling. When it did that, the strip heat shut off.

That makes perfect sense since B is defined in the Omnistat2 installation instructions as "Energized in Heat" and my Goodman system only requires the valve to be energized to cool (so O is connected directly to the condensor).

Ultimately the problem is that I didn't know about the heat strip since the mention of a two stage heat pump in the installation instructions refer to gas and I knew I didn't have gas, so I assumed I had a single stage heater. It wasn't until I took the panel off the handler today to trace each wire that I noted the part number on the heater strips and identified it.

Thanks again for everyone's help, believe it or not I spent most of the day crawling in the attic and reading how heaters work. Good stuff.