Circulator pump not turning on when t-stat calls for heat.

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Old 10-30-10, 06:23 PM
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Circulator pump not turning on when t-stat calls for heat.

I have a honeywell L8148A aquastat and a Tace pump. The boiler turns on when the low limit is reached and turns off when the high is reached. No volts on the C1-C2 circuit in the aquastst even when the boiler is on. I checked the pump and it works when I wire directly to a separate 120V. The (4) zone valves have 24V coming from the transformer and the valves opens when the t-stat calls for heat. Is it possable that all 4 zone valves are bad or is it the aquastat?
 
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Old 10-30-10, 06:50 PM
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When you say "the boiler turns on", you mean that the BURNER fires, correct?

I don't understand what you mean by "when the low limit is reached", there is no low limit control on the 8148A aquastat. There IS a fixed 'differential', is that what you mean?

If the burner is firing, but the pump is not running, and you do have an L8148A (not a typo), then the problem is in the aquastat. Probably either toasted contacts on the relay, or a bad solder connection on the pc board.
 
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Old 10-31-10, 08:44 AM
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Thanks, Looks like I'll be changing the aquastat before it gets to cold since I'll have to drain the boiler first.
Correct the burner fires.
Correct this aquastat is a fixed differential type and the model number is correct.
 
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Old 10-31-10, 08:53 PM
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You should not need to drain the boiler to change the aquastat. The well should be sealed...
 
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Old 03-05-11, 04:17 AM
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Thumbs up Easy free fix!

I just encountered the same problem (no continuity between L3 and C1). I disconnected hot, neutral and ground, bent the four metal chassis tabs straight, tipped the circuit board out and found a bad solder joint behind the solenoid. Reassembled and it works perfectly. This is apparently a common problem with these Aquastats...
 
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