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[loneryder]

I don't expect anyone will have an answer to this but furnace won't shut off tonight.  I noticed house getting real warm so checked the thermostat.  Temp was 77 with setting on 69.  So I shut it off at the thermostat.  Just kept running and blowing heat.  I had to shut off the breaker to get it to stop.
My setup has a 3 way thermo valve in the line to cut HW on/off to the furnace xchger.  When the Thermostat calls for heat it opens after a delay to allow HW to the furnace.  It's designed to keep HW from the furnace if the fire goes out when I'm out of town.  Problem is the furnace blows cold air for 1-2 min before the water goes in and then it blows hot air for a very short time.  The house stays at temp so I haven't worried about it.  When I'm home all the time I get tired of it blowing cold air longer than it blows warm so I flipped the switch on the thermo valve to open thinking it would feed hot water to the furnace all the time and the blower would run shorter times.  I did that today..the only thing different that I've done.  I flipped the switch back to auto but nothing changes.
Any ideas??

[Scott7m]

Hmm....   That's odd

So why do you not want the water going through the coil when your away from home?

[RSI]

I am a little confused here. Does the blower run all the time of just when calling for heat? What exactly is supposed to happen when the thermostat calls for heat?

Was the switch that you flipped a mechanical lever on the zone valve? If so, it might have jammed and not closed again.

[victor6deep]

Sounds like your thermo valve contact isn't closing.

[loneryder]

Hmm....   That's odd

So why do you not want the water going through the coil when your away from home?

Electric heat takes over and don't want it to be heating the circulating boiler water.  I think the Taco 500 series valve has gone bad, possibly the power head.  Do you think if I dis connected the wires to the power head, that would let the furnace shut down?

[loneryder]

I am a little confused here. Does the blower run all the time of just when calling for heat? What exactly is supposed to happen when the thermostat calls for heat?

Was the switch that you flipped a mechanical lever on the zone valve? If so, it might have jammed and not closed again.
[/quote
Normally the HW is circulating from boiler thru HW exchg and back to boiler.  When heat is called for the 3 way zone valve opens and allows the HW to flow to the furnace and then back to boiler.  There is a delay where the furnace runs, blows cold air for 1-2 min before the valve opens and heats up the furnace exchg.

[RSI]

What is used to control the blower and make it delay?
We need to know how it is wired to find the problem.

[victor6deep]

It is obviously stuck in the open position. If it requires voltage to open and close which it sounds like I would say you have a bad solenoid or there might be a voltage issue maybe a 24v transformer gone bad? I don't know what voltage that solenoid requires tho. Check for power first and then go from there. If your tstat isn't shutting off I would think solenoid issue.

[loneryder]

What is used to control the blower and make it delay?
We need to know how it is wired to find the problem.

The zone valve is wired back to the furnace...2 wires.  Maybe bad relay or solenoid?

[Scott7m]

But you said the fan would never shut off as well?  Hmm


I always wanted a bit of heat being sent out to the boiler, if it were -20 and no one home for a week, a bit of heat going back to the boiler would be some awesome antifreeze

[loneryder]

But you said the fan would never shut off as well?  Hmm


I always wanted a bit of heat being sent out to the boiler, if it were -20 and no one home for a week, a bit of heat going back to the boiler would be some awesome antifreeze

The fan won't shut off unless I flip the breaker.  T stat is off.  I'm wondering if I unhook the wires back to the furnace if that will allow it to shut off??

[Scott7m]

It's hard to say without seeing it, I don't think it would hurt a thing to try it and see

But, if it kept heating as well as the fan running, something is powering them, bad stat maybe I donno

[victor6deep]

Is the stat on fan or auto?

[RSI]

I too am guessing a bad thermostat but it could be a shorted wire. I would start by removing the G wire at either the thermostat or furnace. See if that makes it shut off.

I would rewire the whole system while you are at it so you don't get the cold air out the vents that you don't like. I would wire the zone valve to come on at the same time as the fan and put a strap on aquastat on the line from the OWB so when the water is cold it over rides the thermostat and falls back to electric with no water flowing through the heat exchanger.

I would probably also look into adding another sensor for low temp to turn it on if the water gets too cold so nothing will freeze.

[loneryder]

It's hard to say without seeing it, I don't think it would hurt a thing to try it and see

But, if it kept heating as well as the fan running, something is powering them, bad stat maybe I donno

Just unhooked the wires to the zone valve and no difference.  I'm wondering if stat is bad.  I'm also wondering what I'm going to do tonight. Can't leave breaker on.