problem managing G wire on an electric furnace with nest


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Old 09-30-13, 08:47 AM
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problem managing G wire on an electric furnace with nest

Hello guys,
new to this forum!

I have an electric furnace and have replaced my 2 wire thermostat with a nest one!
The problem is that the G wire is detected by the thermostat but it tells me that he is not powered and there is no way to manage it from the thermostat! The other problem is that when I hit the switch to on the blower starts immediately no matter if I call for heat or not ( the elements are connected and operating well)

My electric furnace has a Honeywell control fan center Fan Center R8222B and has everything needed in order to control the fan by the thermostat but I suppose that the connection is done to suit the old 2 wire thermostat and not a new one!

P.S. The problem is not with the thermostat as both acting the same way and when the furnace is on the fan is always on!

Any help would be greatly appreciated
 
  #2  
Old 09-30-13, 10:49 AM
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Welcome to the forum!
What other wires do you have connected to your thermostat? How are you powering your Nest? On most applications, a Nest will operate with just batteries but some applications require the common wire be connected from the transformer to the Nest.
 
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Old 09-30-13, 09:45 PM
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The Nest has a chargeable battery and relies on the resistance in the relay(s) to charge. Basically it steals power when the relay is in the active state. That means it only charges when the thermostat is calling for heat, cool or FAN ON.
 
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Old 10-03-13, 05:55 AM
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Name:  fan center.jpg
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Size:  20.8 KBHello again and thanks,

I have a Honeywell control center and have connected Rh (28 volts) W and also G in order to control the fan but the nest gives N26 error if I'm not mistaken no reply or something like that, so it is 3 wires! Nest is working well charging everything on that side is ok. Anyway What I'm sure is that is not the thermostat!

No my system is turned off by the switch on the furnace, nest is off too but it is charging only with Rh! It gives message no power only when I turn off the power to the furnace from the electric board

There is some kind of bypass somewhere in the furnace in order to fit the old thermostat and I cant find it...!

On the fan center there is a blue wire connected to 'C' that goes down to the coil of the relay and then it continues to the fan limit switch ( the part that senses the temperature) and then it goes to Rh on the control center! I was thinking to take that wire from 'C' on the control center and move it to the G!!!??? I don't know if this is good but it seems logical to me!
On the other side, the relay is SPDT and when the coil is engaged the relay can switch between low and high speed of the blower but there is no neutral position!!

I'm sending the photo of the fan center, the blue wire from the bottom right coil is going to the limit fan switch and then goes back to the Rh! So do you thin that I can transfer the 'C' blue wire to G??
 

Last edited by ivailosavoff; 10-03-13 at 07:52 AM.
  #5  
Old 10-05-13, 05:10 PM
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hello,
Nope, not a tstat problem, but more wiring as the old acts the same!! The wires go from the equencer otn the relay that is powered from one side and fro mthe other there si 2 options closed one low speed (starts uppot engage on button ) or open circuit fast speed !
Was liek this before and I reall y don't know what to do! I 've tried some things today no succes!

Thnaks anyway
 
 

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