Low limit water control doesn't kick when no one is using hot water


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Old 08-18-07, 10:07 AM
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Question Low limit water control doesn't kick when no one is using hot water

I have a L8124C aquastat control on my V68 Weil Mclain furnace. During the night or during the day when nobody is using hot water, the temp of the water decreases beyond the low limit (160F) to around 110F while the low limit control doesn't kick.I manually override the burner and the water starts heating up. While the water temp is within the range of Hi (185F) and Low (160F), and I keep using the hot water, the low limit kicks in and heats up the water. I did buy a new L8124C control and replaced control but same thing happend.
Do you think is something related to the immersion Well where the bulb goes in and some how when water moves out it feels the temp difference and while it is static can tell the temp difference?

Thanks for your advise.
 
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Old 08-19-07, 06:06 PM
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L8124c

The problem could be the well, the domestic coil, or the aquastat itself. When you installed the aquastat did you use the heat conductive paste included with the control?
 
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Old 08-22-07, 06:59 PM
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Low limit..

I suspect (Grady, correct me if I am wrong) that when you are using hot water the burner demand is continuous, and the variation you are seeing is the Hi Limit differential coming into the play--NOT the low limit "working."

Unless my thinking is wrong, the lack of thermal paste would have boiler running longer and hotter since the bulb would be cooler than the boiler water.

Pete
 
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Old 08-23-07, 03:44 PM
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Aquastat

With the limits set at 160 & 180, the temperature should never drop to 110.
Here is a link to Honeywell's page on the 8124:
http://customer.honeywell.com/techlit/pdf/60-0000s/60-2061.pdf
 
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Old 08-23-07, 04:44 PM
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Originally Posted by Grady View Post
With the limits set at 160 & 180, the temperature should never drop to 110.
Here is a link to Honeywell's page on the 8124:
http://customer.honeywell.com/techlit/pdf/60-0000s/60-2061.pdf
Hi Grady

He mentioned that the Low Limit seemed to be working when the DHW demand was present. I think what he is seeing is the differential on the High Limit. There's no reason why the low limit would work only during a DHW call that I can see. I suspect the Low Limit isn't working in either scenario?

Peter
 
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Old 08-23-07, 05:36 PM
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Low Limit

I've had aquastats do wierd things. Some will seem to work just fine with a call for heat or if there is relatively little time between calls but not work well after a longer "rest" cycle. The only thing to which I can attibute this is a weak relay. A crude but often effective test is done when the burner first starts. It involves whacking the control side with a screwdriver handle. If the burner drops out, whether or not it refires, the relay or relay circuit is bad.
 
 

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