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Circulation Pump Aquastat

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ScottMcNab
ScottMcNab Member Posts: 50
Hi
I recently had an L6006C aquastat installed to control the circulation pump for my Biasi cast iron conventional boiler (propane). What would be the best setting for the circ pump to come on and the correct differential? Want boiler protection to prevent condensate but don't want to waste fuel either. The boiler is a cold start and controlled by the house thermostat.
Thanks

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  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
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    What other aquastat is on the boiler?

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  • ScottMcNab
    ScottMcNab Member Posts: 50
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    L4006A that is the high limit for the burner. Thermostat calls for heat, burner turns on and runs until thermostat setting has been satisfied (68 Fahrenheit). Circulation Pump won't come on until the set temperature on the L6006C. Just not sure where to set and if a low or high differential is better. Have it set now for 160 to come on and 130 to shut off.
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
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    Probably fine. You could try lowering it to 150°. Anything closer than 20° between the settings could cause problems. I assume this is a strap on? I'd double check the settings against the actual water temperature to make sure you are setting it where you want it.
    If one or the other breaks, get a modern aquastat that has circulator hold off, low water cut-off. Probably the same price.

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  • ScottMcNab
    ScottMcNab Member Posts: 50
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    Yes it is a strap on. I'll have to get something to test the water temperature to make sure the aquastat is working like planned. Maybe should try 150 with 25 differential? What temperature will the return boiler Water condense when the burner is on?
  • HVACNUT
    HVACNUT Member Posts: 5,863
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    You should maintain a minimum 135° for condensate protection.
    I might get yelled at but if you have an indirect water heater, I typically set the high limit and let the boiler cycle off the water heaters aquastat. No low setting. Cold start.
  • ScottMcNab
    ScottMcNab Member Posts: 50
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    No domestic heating coil. I use the boiler as a cold start and I'll set the circulation aquastat to not circulate water below 135. Before it kept the water temperature hot instead of a cold start but wasted a lot of propane.