Convert PC8900 to Nest

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Old 12-15-16, 09:43 PM
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Convert PC8900 to Nest

Hi,
I have Honeywell PC 8900 system, it is proprietary. I have tried 2 times to replace it with a nest and have had no luck. I have 4 wires coming into the honeywell, and they are labeled 1,2,3 and 4. I called nest support and they told me that i need to have the HVAC guy bypass their system, can anyone tell me how the HVAC guy does that? The guy came this week, thought he had it running, but the stat is not working as it is cold in the house and there is an error code on the nest. Any input is greatly appreciated.
 
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Old 12-16-16, 12:23 AM
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Welcome to the forums.

I see you posted in the other thread on this topic. Did you read it ???

I requested the member to take pictures of what he had as well as we need to know
everything about the system. http://www.doityourself.com/forum/el...-pictures.html

We need the make and model of your equipment.
Furnace with split A/C or heat pump system with back up electric ?
Humidifier ?
Remote sensors ?

You had an HVAC tech that couldn't do the install ??
The conversion is fairly straightforward and easy however four wires between the stat
and the equipment is usually not enough wires for the job. Plus..... the old EIM needs
to be completely removed from the system.
 
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Old 12-16-16, 06:49 AM
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Just a side note, but in my humble opinion the Nest is a terrible choice for a heat pump. There are much better options from Honeywell that will actually decrease your utility usage
 
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Old 12-20-16, 08:01 PM
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Can you please elaborate as to why the Nest is a bad choice for a heat pump system?

Thanks
 
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Old 12-20-16, 08:33 PM
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Heat pumps run best and most efficient when they are either left set to a constant temperature or used with a thermostat that can lock out the aux heat based on outdoor temp. The Nest cannot do this. Actually, the nest cannot do things that most basic Honeywell products can.
IMO, it's a very basic product with a large marketing budget and a fancy looking wrapper.
 
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Old 12-20-16, 10:31 PM
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Terrible and bad are hard words. The nest isn't terrible it just isn't the most cost saving stat to use.

As a rule... a heat pump should not be setback. It's far more efficient to have the heat pump generate the heat rather than the electric heating strips. With most thermostats.... when the room temperature is 3 degrees or more below the set temperature.... the heat strips are activated.
 
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