Replacing a Honeywell PC8900 to NEST thermostats

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Old 02-17-14, 02:33 PM
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Replacing a Honeywell PC8900 to NEST thermostats

I've got a Honeywell PC8900 and I'd like to replace it and try the NEST thermostats. But of course, the PC8900 has proprietary wiring to it's thermostats and so it's not a simple wall change. The wiring at the wall is 1,2,3, and 4, but what I need at the wall is G, Y, W, etc..

I'll need to unwire the PC8900 control box and connect the wires to the wires that are running down the walls to the tstat locations. Has anyone done this successfully? I don't want to mess anything up in case I need to return back to the old system, but there's got to be a way to do it.

Here's a link to the manual for the PC8900:
http://www.alpinehomeair.com/related...t%20System.pdf

Here is a picture of one of the controllers (I have two, one for upstairs and one for downstairs)
Name:  PC8900_Controler.jpg
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Thanks,
seddleman
 
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Old 02-17-14, 04:47 PM
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Welcome to the forums.

I'm not the expert in this forum and especially with this particular system but I have a few question that will need to be answered. This is not your standard thermostat changeout job so be sure you document where ALL the wires are connected to now.

Are you replacing both of these systems or just one now ?
Post the wires and the colors that are currently connected to your control unit. We already know the 1-4 thermostat wires.

G - green
Y -
etc.

Since that Honeywell system could be configured/wired for many systems we also need the make and model of the furnace and A/C system.... or if it's a heat pump with electric heat coils, etc.
 
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Old 02-18-14, 06:42 PM
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I can't see the left side very well but it appears that you may have a humidifier and outside air damper connected to your existing control.

Can you post a better shot of the left side?

 
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Old 05-14-15, 10:27 AM
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Saddleman, did you get this working? I too want to replace a PC8900 with a newer thermostat with conventional wiring. I would appreciate it if you could post a photo of where you hooked your wiring into to work with the Nest.
 
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Old 05-14-15, 01:46 PM
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GO with a pro 8000. Much better stat
 
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Old 05-14-15, 02:51 PM
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Welcome to the forums.

Saddleman has not been back since he posted that. You could click on his name and send him a PM. If you'd like our help you'll need to post a picture like he did of your control board. Each installation is different so his wiring may not be the same as yours.

http://www.doityourself.com/forum/el...rt-images.html
 
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Old 12-15-16, 07:45 PM
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Seddleman or ElliottM, were you able to replace the PC 8900 with the nest? I am trying to do the same thing, any input is appreciated.
 
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Old 12-16-16, 10:16 PM
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I have replaced that stat with a Nest before.

You must remove the existing equipment interface module along with the existing thermostat.

The Nest thermostats performs better if you have an extra wire that you can connect to C.
 
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