Original message
| jc98250
 |  "temp. hold problem w/ Honeywell VisionPro"
, posted Tue 4 Jan 17:17  
I 'upgraded' my thermostat on my WaterFurnace Premier heat pump to a Honeywell VisionPro TH8320. Installation was a snap, but I noticed that the status LED was flashing whenever I manually adjusted the temperature above the currently programmed set temperature. During normal operation (ie no temporary hold) the LED doesn't flash.
The L terminal on the thermostat is connected to the system monitor output on the heat pump. The LED flashes because the heat pump is signaling that there is an error.
I used the diagnostic LEDs on the heat pump to see what signals the thermostat was sending:
normal 1st stage: Y1
normal 2nd stage: Y1+Y2
normal 3rd stage: Y1+Y2+AUX
manual override (temp hold): Y2 only
I see the 'normal' behavior when the thermostat is working on the programmed schedule as well as when I use the test functions from the installer menu.
I was able to remove the thermostat from the wall and use an ohmmeter to test the outputs of the thermostat directly and confirmed that anytime I manually adjust the temperature, it only energizes the Y2 output.
The flashing LED apparently indicates that the heat pump is reporting an error when the thermostat energizes Y2 without also energizing Y1. I have not been able to find any information from Honeywell about this behavior of their thermostat, but it seems like a 'bug' to me.
Or is temporary hold/manual override supposed to energize only the Y2 output?
thanks.
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