Wireing 24 volt dump zone on PB 105

just installed another PB 105 and customer has a 24volt zone valve for the dump zone. since the boiler supplies 120volts when it overheats is there any reason why I cant just put a Taco transformer in that circut to power up the valve. I did it...made it overheat to check it....it worked...BUT now the customer says the dump zone is open all the time now. He disconnected it and is waiting for me to return. is there a wireing problem ...thoughts???

Ice, I would verify his findings. What you did was fine so if there really is a problem maybe it was coincidental. Maybe valve is stuck? I would like to know how you make out.

that should work I agree with centurion about the valve being stuck

Did you resolve this? I am having the same issue - blue wire always energized regardless of water temperature. Control board problem or what?

Yes I did resolve the problem. His dump zone was a zone valve powered by another 24 volt transformer. although the secondary windings on the transformer I installed was not enough to activate the zone valve...they were enough to hold it on after it was activated. all I needed to do was install a relay (normally open) in the circuit and loose the transformer I installed. when the blue wire became energized it closed my relay...when it (blue wire) went dead the relay would open...killing the dump zone. the blue wire MUST go dead when unit is not overheating.

Why would a pellet boiler ever overheat? Isn't the fire controlled by the aquastat and that starts and stops the pellet auger feeding the fire? I can see an overheat in a wood fired boiler where you can't really control the heat except with the automatic damper which is quite inefficient.

Was this just something they wanted for a safety thing in case the pellet furnace had a run away for some reason?

Check the valve and make sure that there is t another set wires running to it from another transformer, say from the other boiler... Both systems need the valve to work and both need to power it.

Pellet boilers still over shoot. Boiler is going full bore, then power goes out, pump turns off with a huge flame inside, bam overheat.

If the power goes out, the dump zone valve and circulator won't work, either. You'd have to open the valve manually to get gravity feed and that's something less than efficient to cool down an over heat.

I would have my dump valve a normally open valve... So when power goes out, it opens. And is always held closed while there is power.

Agreed, and that is what I had on my HS Tharm wood furnace, but gravity feed is poor for cooling a hot boiler at best. It takes a l-o-n-g time. Maybe OK for a pellet furnace seeing the fire will die quickly when the power goes out. Better make sure that valve coil is continous duty rated and has the ability to shed the heat from running 24/7.

Oh **** moment, is oh **** moment =/