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MDH33
01-13-2009, 10:36 AM
I tried replacing the mercury/bimetal thermostat in my house with a digital unit. Seemed simple enough, only two wires, but the new unit does not seem to be controlling the boiler. The digital readout was measuring temp, but not kicking the boiler on as temps dropped. It's 58 in here now... I tried putting the old mercury unit back on, and it's not working either. Think I fried something??

It's a hot water boiler with a pump and two zones on two thermostats.

Anyone have any info on how to connect this, or reset the system?.. I'm totally unfamiliar with heating systems and I can't afford to call in the pros.. :o

Air Randy
01-13-2009, 11:27 AM
I assume you've checked the onvious stuff like the new unit probably has a switch on it somewhere that says "Heat-Cool-Off" and make sure that is set to Heat. It may also have a setting that says Fan Hi-Lo-Auto-off. Make sure that is set to auto.

You may also want to check your boiler to see if it has a reset button it. Sometimes they are real sensitive and it easy to trip them.

When I've had similar issues in the past, I've also gone to where the 2 wires from the thermostat connect to the furnace or boiler. If you jumper across those terminals it will bypass the entire thermostat circuit. If it lights/starts then the problem is in your thermostat or related wiring. If it doesn't light/start then the problem is in the furnace/boiler itself.

If you need real time help call me at 303-319-8976

MDH33
01-13-2009, 12:46 PM
Thanks Randy.

Here's some more info:

Rheem boiler with Honeywell Synchron Zone controls.

There are two zone valves (A & B). Zone A is working fine and responding to the thermostat.

I checked the valve on B and it's staying open unless I disconnect the white wire from it's thermostat, then it closes.

Only zone A seems to be communicating with the boiler and firing it up. Since zone B is staying open, I am keeping the pipes warm by cranking the heat in zone A for now.

Any thoughts, I'm not sure what to try next.

Air Randy
01-13-2009, 06:01 PM
Is there a choice on the thermostat for either hooking it up as "normally open" or "normally closed"?

I'm assuming there is no reason for you to have zone A creating heat but not zone B at the same time? If that is the case, do you have the wires for both zones actually hooked together or do they go to separate terminals on the Tstat?

RockRunner
01-13-2009, 06:14 PM
I may have bad news for you. First of did you buy a dig unit for a boiler? If not that may be it, they need special units.

Next, you can fry the switch on your heater, DA Sharon HSK :eek: We had the same thing in out town home, two wires so she thought "how hard can it be" I was busy so she figured she would do it. $150 later and a visit from the Sears guy, 12 years ago, we were back in business.

Check the switch on your heater that turns on the boiler and pump, you may be able to "hot wire" it for now.

I really hope I am wrong but while typing this I remembered the same thing happened to my parents unit, they have hot water heat with baseboards.

Good luck, I will keep my fingers crossed as will Sharon :o

MDH33
01-13-2009, 09:22 PM
I think you are right Tom. The new T-stat seems to have killed the switch in the zone valve. I called my plumbing and heating guy and he walked me through the diagnostics. The valve opens and closes, but when open the internal switch is no longer turning the boiler and circulator on. Unfortunately it's an old unit and may require draining the entire system to replace the valve... We just had the system drained last year when we had to have a couple of fittings replaced... looks like another $500 repair bill is in my future. :(

MDH33
01-13-2009, 09:30 PM
Is there a choice on the thermostat for either hooking it up as "normally open" or "normally closed"?

I'm assuming there is no reason for you to have zone A creating heat but not zone B at the same time? If that is the case, do you have the wires for both zones actually hooked together or do they go to separate terminals on the Tstat?

Two thermostats. When the T-stat is "running" it should complete the circuit and open the valve.

Until I get it fixed, I have the faulty valve manually locked open and am running the heat in the other zone, which is helping to circulate hot water through both zones. No temp control in the faulty zone, but at least the pipes can't freeze.

Thanks for the help Randy. :thumb:

RockRunner
01-13-2009, 10:37 PM
Martin,
Sorry to hear the bad news. I don' like to be right when it is bad. Just wondering how old your system is? Sounds like you can still get parts for it and or is still serviceable. I have drained my parents system in previous years without much trouble and replaced the pump and valve. I don't know what type of system you have but have you looked at doing it yourself?

Maybe when you have it apart you could add some in-line valves to shut the water off if this or something else occurs. It may not be cost effective just a thought. Maybe post up some pictures somebody may be able to steer you in the right direction and or help.

Corbet
01-14-2009, 10:14 AM
I can't help but understand as my heating guy just left the house 30 minutes ago. At least we have heat again. :)