Aquastat L8148E: Circulator shuts down prematurely


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Old 01-28-17, 12:11 PM
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Aquastat L8148E: Circulator shuts down prematurely

Quick and to the point.
I recently replaced relay and damper. Now the circulator pump shuts down the same time as the burner. I ran a jumper from L1 to C1 so the pump just runs continuously, (hopefully just temporary).

I've checked, double checked and triple checked the wiring and connections, and everything seems to be right.

Shouldn't the pump run until it hits its low limit?
Is there a low limit setting that I'm missing?
 
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Old 01-28-17, 02:36 PM
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The circulator will only run until the thermostat is satisfied. If the thermostat is still calling for heat after the burner shuts down the circulator should still run.
 
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Old 01-28-17, 03:26 PM
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That aquastat is a high limit only made for cold start applications which means there is no tankless coil on your boiler. That being said the circulator will continue to run if the boiler reaches high limit and the stat is still calling for heat. Other than that it will come on with the burner and shut off with the burner if the burner shuts off because the call for heat is satisfied.

If it didn't do that before you may have had a different model control with a low limit.

Hope this helps a little.
 
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Old 01-29-17, 07:44 AM
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Thanks Spott and Grady
I removed the jumper and verified your responses. Also, I replaced the relay and damper with identical parts.

After removing the jumper I ran it through a cycle, keeping the thermostat high. The pump continued to run after the boiler came to temp. The issue I was noticing was when the pump shut down with the boiler up to temp, the pressure and temperature continued to rise. SO, to rectify THAT situation, I've turned the high limit to 170 degrees. It's still keeping the house warm.

Next question: If I leave the limit at 180, and the rises to to 190, would that cause any issues?

FYI: the boiler is 100000 Utica purchased new in 2008

Again, Thanks
 
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Old 01-29-17, 08:42 AM
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No issues at all. That is only residual heat in the boiler that is heating the now stagnant water. The better the boiler the higher the res. heat because it is staying in the boiler and not going up the chimney.

It was common to run boilers at 180 & 200 back before the rise in oil prices years ago. Now everyone is trying to run lower temps to save money which is fine as long as you're getting enough heat output.

The data on baseboard BTU output is all based on 180 water going through it. Higher temps will produce more and lower will produce less. Hot water tankless coils and indirect water heaters are all based on that 180 also.

Water does not turn to steam until about 240 deg. at 12 PSI so you can safely run up to that temp on the boiler which if you notice is your max high limit setting anyway although running lower temps puts less stress on the cast or steel.
 
 

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