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Old 11-25-2007, 05:59 PM   #1
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taco 700 constantly running....


I have an old series 3 model HE-4 weil mclaine boiler. It seemed like I was using way too much propane. so, after some investigating I noticed that the boiler was running what seemed like a lot. I disconnected all the thermostats so as not to have any signal telling the boiler to fire. It fired anyway after the temperature dropped. This is normal I know but what got me is that there was no need for it to heat the water in the boiler. This is when I heard the taco circulator pump running...it was very quiet and I am lucky I noticed it at all. I just bought this house last year and have never had forced hot water for heat so I'm really new to this. What it looks like is happening to me is that the circulator pump is running dead headed to 2 zone valves that are closed. any how, my question is...should this taco pump be running all the time? is that normal? and if not is it the pump or the sending unit on the boiler thats causing this? and how can I determine which one it is? also, if its the sending unit is that a part I can pick up at my local Lowes? or will I have to go to a specialty place like Webb? I know I rambled a bit but this is my first post. Any help will be greatly appreciated. Thanks in advance!

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Old 11-26-2007, 12:34 AM   #2
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taco 700 constantly running....


It is not normal for the circulating pump to be running unless the thermostat is calling for heat. Not sure what type of zone valves you have, but if the motorized type, such a s Honeywell, the thermostat simply opens and closes the zone valve. In turn, there is an end switch on the zone valve that opens and closes the circuit that powers the circulating pump. If you have this type of zone valve, check for a faulty end switch that keeps the pump running even if the zone valve is closed. Disconnect one of the end switch wires from one zone valve and see if the pump quits. If not reconnect, and try the other one.

If none of the zones are calling for heat, the furnace should not fire when the temp drops below low temp set point. There is a relay in the control that tells the furnace to fire when the water temp drops ONLY if the circulating pump is running. Since yours is running all the time, that is probably the reason the furnace fires when it shouldn't.

In one case however, I saw a system that did not have the relay to perform the function discussed above. It was simple project to add the relay.

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Old 11-27-2007, 02:42 AM   #3
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taco 700 constantly running....


I replaced the transformer and relay pack that was in the boiler to no avail. In looking closer I tried removing wires from the transformer until the cirulator pump stopped running. Traced this back to a zone valve for my hot water tank. off of the zone valve there were a bunch of wires there, at the tank itself only two. while moving the wires to get a better look at them I noticed sparks from a blue wire, there was not a blue wire at the tank. Removed the blue wire from the setup and the pump turned off. I think I had multiple issues here...first being the transformer...the bolier now is turning on and shutting off at more regular temps. I think before it was running until it was too hot and then shutting down from temp to high and not the high set point. it was getting as hot as 220 before now only 190. also this blue mystery wire was telling the circ pump to run constantly. both issues are gone now so I think I fixed it by accident.
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Old 11-27-2007, 07:03 AM   #4
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taco 700 constantly running....


It's always great to solve a problem, even if by accident.

About the extra wires, it's been a long time since I've come in contact with zone valves that were activated by a heat motor and can't recall the way they were wired. If your system shows evidence that the zone valves were replaced at one time with the motorized style, assuming that's what you have, you may have some extra wiring that powered the old style. You may want to trace them back and eliminate before giving further trouble.

Regards
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