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Correct wiring for aquastat?

AdamInEvergreen Member Posts: 42
edited January 2023 in THE MAIN WALL
Hello all!

I am helping a friend replace an aquastat on on a Crown CXE-7. The prior aquastat was more basic than the replacement, which is a L8124A1007. I installed it using the same wiring pattern as the old one. It works fine for all the zones but on the indirect water heater it will get up to temp then shut off the main circ pump (and the boiler) before the water heater is satisfied. Slightly confusing it appears if a single zone for anything else is running the boiler will behave more as expected; boiler and circ pump running until the boiler hits the high limit then the circ pump will continue after the boiler shuts off. I don't know why they would be different...as far as I know the boiler sees all the zones as one.

Currently in the install the ZR and ZC terminals are empty. 

High limit is 190 (were at 8000 feet), low limit 140 and I think thr differential was 15

Ran out of time today, heading back tomorrow.

A) previous aquastat operated without recognizing the dhw loop as different. It just operated like other zones. With the new aquastat do I need to hook up the dhw water heater separately?

B) why is the water acting different than other zones? There are only two 
wires connecting to the T terminals from all the zone valves. 

C) what else should I be looking at?

D) what info do you need to understand the situation? 


  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    What model number is the old aquastat? What are all the settings.
    Sounds like you have the wrong aquastat. You don't need a low limit if your indirect is on it's own zone.
    Why didn't you replace like for like?

    There was an error rendering this rich post.