DFAA084BBTA, HW-T-stat, heater won't turn off

[DejaVuToo]

Just installed Coleman DFAA084bbTA oil heater with AC unit to be added (AC unit is not in place) and installed Honeywell PRO TH3000 series nonprogrammable thermostat. When thermostat is set, for example to 75, heater comes on and does not turn off no matter how hot it gets until the switch on the thermostat is turned to "Off."

Installer says "might be bad thermostat," "might be wiring," "don't know."

Any thoughts, any ideas at all be will be extremely helpful and much appreciated. Thank you in advance for the help.

[Robert]

Hi,

Well, is the RH to W on t-stat opening when room temp is satisfied ?


If not, t-stat has a problem.


IF it does, then gas valve would be next place to look.


That is component end. Wiring is simply a shorted wire somewhere keeping circuit energized.


IF when room temp is met, gas valve is still receiving 24vac, then problem lies in t-stat or wiring to GV.


If not and no 24vac at GV, then GV is suspect.


Thanks,
Robert