Honeywell T8775A 1009 - not working

Jshine

Post transferred from "The Wall"



  I have a gas boiler/steam heat system.  The current thermostat is a t87f (2 wire - 1 connected to pressure control - 1 connected to low water cut off) - and works ok but we thought we'd install a new digital display to make it easier for us to read.  I bought a Honeywell T8775A 1009 - installed the only 2 wires that were connected to the T87F to the only 2 terminals R and W on the digital - but it didn't work.  The display would repeatedly light up after a few seconds (but not when you depressed the button to manually backlight) and then display blank - the little burner flame indicator came on ok - but down at the gas furnace - I noticed the damper was continuously cycling.   The damper was actually slowly turning a full 360 degrees and the electronic ignition never kicked in to start the furnace.  I tried changing the dip switches back to off and tried reversing the 2 wires - no good - still the same results - no ignition and the damper kept revolving.  I called the Honeywell help line - described the situation - and they said it was a bad thermostat.  I have a replacement coming - but I'm thinking there might be more to it - maybe a need for one of those "isolation relay" setups that I read about. Maybe not.  Anyone have any ideas on this?

Thanks - John

Thermostat  - <a href="http://yourhome.honeywell.com/home/Products/Thermostats/Digital-Non-Programmable/Digital+Round.htm">http://yourhome.honeywell.com/home/Products/Thermostats/Digital-Non-Programmable/Digital+Round.htm</a>

will smith_4

Control problem

Hi John-

I tried logging on to the Honeywell site to see if there was something unusual about the setup of your stat, but I kept getting knocked out. You mentioned that the damper keeps turning on a call for heat-are you talking about the flue damper? If so, it could be that the proving switch isn't making. The problem might be with the damper-not the stat. Check to see if you can lock the damper in the "test" or "service" mode, and see if the system will fire.

A sure fire way to see if the stat is at fault is to remove it, and jump out R-W. If your system works fine that way, the problem is with the stat. If it still acts up, the problem is elsewhere.

All the best!

Jshine

Honeywell t8775a

Will - thanks for the reply -

I actually put the old t87f thermostat back in place and everything worked ok as before - and yes - it is the flue damper that I was talking about.

I guess I'll just try the new replacement and see if it works.

John