How does thermostat control circulator?

[srichardson]

I had a thread a couple of days ago - lost heat in top floor heating zone.

Bled (bleeder-less) baseboards and replaced power head on Taco 571 for top floor zone..........I thought it was working.

Now heat will still not get to top floor, circulator will not kick on. If I manually 'open' top floor valve and put heat on (turn up digital therm.) on main floor - the circulator will kick on and both main and top floors will receive heat.

I put the main floor power head on the top floor copper valve and turned up main floor thermostat, top floor heats - when power heads for main and top floors swapped, top now heats and main doesn't. I have to assume there is a wiring problem.

I have never had a problem until this year. My wiring is a rat's nest, but all thermostats and valves for all three zones are wired the same.


Any suggestions on why the circulator will not come on for the top floor thermostat?

I have a Honeywell L8124 Aquastat, the low-voltage transformer has two terminals - all (3) thermostat white wires are connected to left terminal of transformer, white wires to valves are wired to right terminal of transformer. Right terminal of transformer also has 1 of 2 wires from Aquastat. Black wires from valves are bug-nutted to 2nd wire from Aquastat. Red wires to valves are bug-nutted to red wires to respective thermostat.

This probably clouds the situation. The new power head on the top floor Taco 571 did have a 'burning' smell to it the evening that it was hooked up. I don't know if it 'burnt' out and that is why the circulator won't start. I power head was very hot, but water was not circulating. I assumed it was a 'new' smell from the heat.

Thanks -
Scott

[KField]

You have a bad head for the third floor. If you look at it undeerneath after you disconnect it, you will probably see the thermal paste that activates it all oozed out and looks like wax all over the piston. Just replace that head and you should be fine.

Ken

[srichardson]

Ken -

This was a brand new power head, there is a liquid all over the place and it looks like the top of the 'piston' is popped. Why would this happen to a new power head? Faulty?

Thanks -
Scott

[KField]

If you took it off the valve with power applied, you caused it. The only thing that keeps the piston from going ballistic is the resistance from the valve spring. All the paperwork that comes with the head and the tag that should be left there warn you about that. You should be fine after replacing it.

Ken