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Rick, HVAC Supervisor
Category: HVAC
Satisfied Customers: 21351
Experience:  40+ yrs. experience as a licensed oil & gas technician.
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I have a burnham v-16-a-t oil fired tankless coil system.

Customer Question

i have a burnham v-16-a-t oil fired tankless coil system. Last year I replaced the thermostat control unit ( rebuilt) my circulator pumps do not turn on unless the unit has fired regardless of temp. I also have to keep the hi and lo setting at 140 H and 120 L to keep it from going over 180. Is the thermostat control bad?
Submitted: 1 year ago.
Category: HVAC
Expert:  Rick replied 1 year ago.

Welcome to Just Answer, my name is ***** ***** I will do my best to help you with your issue. If my initial response doesn’t answer your question then let me know and we can continue our conversation.

Could be a bad control or at least one that's out of calibration (nothing you can do to re-calibrate). Keep in mind the circs won't run unless the boiler temp is above the lo limit set point. The lo limit is what maintains boiler water temp for DHW. The hi limit is the space heating function.

Customer: replied 1 year ago.
if the lo limit is set to 150 and the hi limit is 180 and the water temp is 160 the circs should run, even if the calibration is off. so what is keeping them from running? and why do they only run once the unit has fired?
Expert:  Rick replied 1 year ago.

Yes, if the control is functioning as designed. The circs should run as long as there is a call for heat (unless the boiler temp is below lo set point). The burner runs when there is a call for heat and the boiler temp is below the high limit. During a call for heat once off on limit the burner won't fire again until temp drops below hi less diff. Lo should always be set below hi less diff.

Customer: replied 1 year ago.
right now I am 180 hi 150 lo and 15 on the dif. and the heat wont circ. when I turn on thermostat, is my control unit bad? It only activates the circ. pumps while fired.
Expert:  Rick replied 1 year ago.

What's the boiler temp? If it's below 150 the circs won't run and the burner should be firing.

Expert:  Rick replied 1 year ago.

The only time the circs will run and the burner not fire is if there is a call for heat and the burner runs up to hi limit then shuts off on limit. While the temp is falling back to hi - diff only the circ will run.