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BOILERMAN856, HVAC Technician
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what is a good temperature to set the furnace lockout at

Resolved Question:

what is a good temperature to set the furnace lockout at? I have my heat pump lockout set to 35 degrees. Should it be 35 degrees or X degrees more than I set the heat pump?
Submitted: 8 years ago.
Category: HVAC
Expert:  BOILERMAN856 replied 8 years ago.
Are you talking about the outdoor temp that you switch from heat pump to fossil fuel?
Customer: replied 8 years ago.
I have a Bryant HP & 90+ furnace with an Evolution thermostat. Thermostat setup has lockout setting under furnace setup (>x degrees) and lockout setting under heatpump setup (<x degrees). I don't have an explanation of either setting.
Expert:  BOILERMAN856 replied 8 years ago.
can you tell me the model numbers for both units and t-stat?
Customer: replied 8 years ago.
Furnace is 355AAV0420
HP is 265ANA030
Thermostat is just marked Bryant Evolution. Only have s/w version in installation summary screen.

Customer: replied 8 years ago.
Found TS manual - SYSTXBBUID01-A
Expert:  BOILERMAN856 replied 8 years ago.
I cannot find tech info for these units and bryant does not provide any info on the website only what you have. But if your t-stat has an outdoor sensor you should be able to set the temp that the heat pump cuts out at and the furnace starts. 35 deg is a good place to star for shutting down heat pump and going to fossil fuel. there are a lot of variable like localutility rate, building heat load, geographic location... etc. these can be calculated by a local hvac tech. Tempstar has a valueable tool on the dealer website that can calculate this temp for you. I hope this helps. Thank you
Customer: replied 8 years ago.
What's the furnace lockout temp for? furnace is a 2 stage.
Expert:  BOILERMAN856 replied 8 years ago.
it is usually to allow the 1st heat ( heatpump, radiant, solar etc.. )stage time to bring the temp up in the building before second stage kicks in. or to set the temp or time range before the second stage kicks in. with out the technical literature it is hard to tell for sure. I will try my local distributor tommorrow for some info on that model. Thanks
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Customer: replied 8 years ago.

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