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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 5648
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have a Lux dm2110 thermostat and am replacing it with a

Customer Question

I have a Lux dm2110 thermostat and am replacing it with a basic Honeywell programmable RTH221B. The wireing is similar but there is a purple wire in the E slot of the Lux but there is no E slot on the Honeywell. Where does this wire go. Thanks Robert
JA: Just to clarify, do you think this is a larger HVAC problem, or something specific to the thermostat?
Customer: I think its just the thermostat
JA: Do you plan on doing the work yourself?
Customer: Yes
JA: Anything else we should know to help you best?
Customer: Just where the purple wire marked E goes
Submitted: 6 months ago.
Category: HVAC
Expert:  Phil replied 6 months ago.

Hello, the E stands for 'emergency back up heat'.. its an option needed to accommodate **heat pumps**

I need to know if you have a heat pump system where the outside unit runs in the winter as well as the summer or not... these thermostats in most cases can be wired for either option, I need to know which option in your case

We can go from there

Customer: replied 6 months ago.
It is a Goodman heat pump with emergency heat option. The air handler is in the attic with the heat strips there
Customer: replied 6 months ago.
The heat pump does run on both seasons. The emergency heat only comes on in extremely cold weather
Expert:  Phil replied 6 months ago.

Hello, the E stands for 'emergency back up heat'.. its an option needed to accommodate **heat pumps**

I need to know if you have a heat pump system where the outside unit runs in the winter as well as the summer or not... these thermostats in most cases can be wired for either option, I need to know which option in your case

We can go from there

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