[t84a]

3 of these thermostats have failed in the last year. 2 were installed by the contractor who installed the system and 1 by a second installer. Both companies are well respected and have been in the business for decades. I emailed Honeywell and they wouldn't discuss my problem.

In any event, I don't think I'm going to attempt to fix my problem but am looking for possible problems that may have been overlooked. I also have a Aprilaire humidifier.

The labels on the board in the furnace are:

O
YLO
Y
B/C
G
R
W
W2
DEHUM

on the back of the thermostat (Conventional Columns) are:

Left side:
Y2
W2
S1
S2

Right side:
RC
R
W
Y
G
C

Can anyone shed some light on this or perhaps let me know if this thermostat is incompatible? When it worked, it seemed to work fine. Thanks

 

[hvactech126]

yes, it will work.... when you say the thermostat failed, how did it fail, screen go bad or blank or did heat or air stop working? How is the humidifier wired?

 

[t84a]

The screen just scrolls through unreadable screens. The first failure, the heat came one and heated the house until I shut the furnace down. It was like 80 in the house. The second time, the heat didn't come on, the last time, I just happened to walk by the thermostat and it was blank. The best I can tell, the thermostat has 2 wires going to a transformer and 2 going to some type of relay that then one wire comes back hand hook to the RED wire coming from the thermostat and then connects to the R terminal. I'm hesitant to touch anything because I don't want to have to pay for a replacement. Thanks for the quick reply.

 

[hvactech126]

thermostat = furnace

Rc and R = R
W2 = W2
W = W
Y = Y
G = G
C = B/C


These are the standard connections that should be hooked up.......without knowing if you have a heat pump or 2 stage a/c I cant tell you what else should be hooked up. The humidifier should really have its own transformer. Do you have a lot of power outages or spikes?

Screen was blank..........did you check the batteries in stat if applicable? Stat may not be receiving 24V from furnace.

 

[t84a]

Thanks. The latest thermostat lasted maybe a week. I have a 2 speed A/C unit outside if that answers your question. Like I said, there is some kind of extra relay or something on the side of the unit that has some fat wires that connect to the humidifier, some of the thermostat wires (either coming from the thermostat or going to the outside compressor) and the control board.

 

[hvactech126]

there may be an excessive amp draw though one of the components........the tech should check for that due to excessive amount of failure