I recently installed a 2nd generation NEST thermostat. I'm not home very often, but I was paying particularly close attention to the furnace after installing this thermostat and I noticed that the fan would not shut off.
Thought it was a faulty NEST so I put the old honeywell back on and same problem.
The furnace is set to a 60 second delay so the fan should shut off 60 seconds after temp (heat) is reached.
I opened up the furnace and i found a relay (p283-0294) that has terminals 4 and 6 jumped from "line" (110v). when the coil at 1 (24v heat) and 3 (neutral) is energized (heat is on) then 5 (red, low fan), 6 circuit is completed. When heat is off 4 and 2 (black, high fan) circuit is completed.
I went in and removed the wire from terminal 5 and now it behaves as I would expect.
Why is this relay in place? Why would anyone want the fan to be on all the time like that when there is no heating nor cooling and the fan is set to
This system does have a white-rodgers electronic controller. The only connection to this board from the relay is the heat connection on terminal 1. The connection for 4/6 is pigtailed off of the line connection to the board. The neutral is pigtailed to neutral.
I feel like i just saved myself a bunch of money by not having the furnace fan running all the time but did I create a different problem?
furnace is a york gas upflow model P3URC14N09501C. i inherited it when we moved in. The only service I have not done on it myself is had the main fan wheel blade assembly replaced when it somehow got warped a couple of years ago.
no error codes / lights on via board diagnostic led.
Edit: should the red wire i pulled off of relay's terminal 5 be going to the board controller instead of directly to the fan? seems logical to me that the board would decide when to run that fan speed instead of all the time.