I'm upgrading my older Aprilaire thermostat to the Honeywell Prestige HD. My unit is an American Standard HP with Aux heat and 1 stage cooling. I've read up on everything I can find and have the majority of things figured out, but there's one thing I'm not positive about:

Wires are connected to the following terminals on the old thermostat:

Terminal - Wire color
C - blue
R - red
Y - yellow
E - brown
G - green
W2 - white
O - orange

On the Honeywell most things make sense, but the terminal configuration is a little different. The two wires I'm concerned about are the E & W2 wires. The new thermostat has a AUX/E terminal which is also labeled W2 on the conventional hookup side. There is no dedicated E or W2 terminal to put the current wires. After reading everything I've read, I was going to hook up the current W2 (white) wire to the AUX/E terminal. But this leaves the E (brown) to hook up, so, really it seems I don't know which of these two wires to stick where. Any help or information would be appreciated.

Old thermostat: Aprilaire Model 8355
New thermostat: Honeywell Prestige HD THX9321R5000

 

Old---------New
C - blue----C
R - red-----R/RC
Y - yellow--Y1
E - brown--E
G - green--G
W2 - white-Aux
O - orange-O/B

 

Thanks for the reply and info!! I have one question though.

On the Honeywell the AUX terminal is the same as the E terminal. (Labeled AUX/E). Does this mean that both my W2 wire and existing E wire go into the same terminal?

Thanks!

 

I to go and take a look at the manual for this stat, I am shocked that they used Aux and E together! I would of think this high end t-stat has it on it's own.......


Guess you'll have to put both wires on it togther...

 

Thanks again for replying. I have one more question... If I wire the Honeywell Prestige HD as suggested and connect both the brown and white wires to the AUX/E terminal, will everything perform as expected? The HP will come on by itself as required and the auxilary heat will come on as required and the emergency heat will come on only by demand when called for by user input?

Thanks again for your patience and understanding.

 

Everything will work as it should till you get the need of Aux and E heat.

With the two together, they are going to be on at the same time where the old on by itself on X and W2, it came on in stages.

Is it a bad thing? Not really, you'll have more heat at once than in stages. I like stages for comfort reason.