Circulator pump only works for a brief period


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Old 02-26-15, 08:18 PM
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Unhappy Circulator pump only works for a brief period

Hello, Long time lurker you guys have some great info.

So at my house in Passaic NJ I have a Untica SVB4 Boiler. It worked great up until the nightmare deep freeze a few weeks ago. During the night a pipe froze. Popped a joint between two PEX pipes. I fixed that, ran a space heater in the crawlspace where the pipe froze. Boiler started working. I was happy.

Then I noticed that it was taking forever to get the temperature back up. After long hours spent sitting along with my boiler, I have figured that the circulator pump seems to shut off midway through the warming cycle.

Here's what happens:
Pre-purge or whatever, the blower spins up
Boiler fires (jumped thermostat wires)
Feeder pipes get nice and hot, return pipes warm up.
Boiler teperature stays flat at 155. Stay flat for like 4 or 5 minutes.
Then the tempertature starts to spike. 156. 157. 158. 30 seconds later the boiler goes over max temp setpoint and cuts the gas.
Has a brief Post-Purge phase
Then it just sits there until the BT drops back under the low setpoint. It does not continue to circulate, though as I mentioned I jumped the thermostat wires.
All of the baseboards - every single one - gets warm, but not hot like they did before the deep freeze. So it's pumping, but only for those few minutes.


The system is 1 zone, but that 1 zone splits off to heat upstairs and downstairs. As I said, used to be the house was nice and toasty. Now I can barely walk around downstairs.

Specs -
As I said, this is a Utica Boiler SVB4.
Honeywell Boiler Control had a long number printed on the lable - 50045578-006

Taco Circulator Pump had the number 007-F5 printed on it.

This is one of those systems that pulls at the return instead of pushing at the feed.

Wanted to mentioned I have bled the air out of it.

Can anyone help me demystify?!

Thanks
 
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Old 02-26-15, 09:06 PM
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First thought is an air trap, seems most logical
Second, check for power at the pump. Make sure there you visually see if there is power or not when you feel the circ is off.
It's not like a Taco to start and then stop at some point during a run. They just don't do that, unless they really overheat.
If the power stop then you will have to trace it back to the boiler. In the mean time you could wire it to run 24/7 as long as it's a system pump. Is there an indirect DHW Tank ?
 
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Old 02-27-15, 09:44 AM
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Do you have this info ? It states that the circulator should be running as long as the Tstat is calling for heat,check the circulator supply voltage at the controller and monitor it, then check at the cir. to see if it is constant there, it seems that the cir. is fed from the control by a harness with a molex connector on it,make sure that is securely connected .
http://www.ecrinternational.com/secu...ument/3626.pdf
Geo
 
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Old 02-27-15, 06:51 PM
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OK so I stick a voltmeter in the two contacts where the circulator pump plugs into the control board? Where the molex connector is? And how would I force it to run all the time? Is there a point on the board where I can jump the power to the connector?

I'll test the power. I should have done that before posting. Appreciate the answers! Will post the voltage response over the weekend.
 
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Old 02-27-15, 07:18 PM
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If the board is putting out voltage, check at the pump. You could have a bad connection at the molex. To save trouble, you might want to start at the pump & work your way back if needed.
 
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Old 02-28-15, 07:00 AM
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If you jump out the Tstat the circ.should be running constantly as stated in the sequence of operations,test for voltage at the board under this condition.
Geo
 
 

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