Ask Me Help Desk - Indoor Fan runs in Defrost Mode

I have an White-Rodgers 1F89-211 thermostat an aTempstar heatpump. I do not have an Electrical heating element in the Tempstar unit. When it goes into defrost mode the indoor fan turns on. This blows cool air until the heatpump is done with the defrost mode. The instructions on the 1f89-211 tell me to cut the "W904: lead if no emergency or auxiliary system is installed. Well, I cut the wire but the indoor fan still comes on when in the defrost mode. Is there something else I am suppose to do (like remove a lead from coming from the tempstar unit)? Or, do I have a bad thermostat?

Thank
Mike

The fan has to run in order for the defrosting action to take place properly. When it goes into defrost it has to have a heat source and the heat source is the air inside your home. That is why the fan is running inside your home during defrost. I suggest you study the defrost cycle in a course on heat pumps or find info on the net to study.

Quote:

Originally Posted by hvac1000

The fan has to run in order for the defrosting action to take place properly. When it goes into defrost it has to have a heat source and the heat source is the air inside your home. That is why the fan is running inside your home during defrost. I suggest you study the defrost cycle in a course on heat pumps or find info on the net to study.

I do not know were you learnd about Heatpumps but I would look for another source of education.

The following is a copy paste from InterNACHI:

(In defrost mode, this heating element will automatically turn on, or the interior blower fan will turn off. )

Note that they said "or the interior blower fan will turn off". If you do not have heating elements in your heatpump there is no need for the interior fan to run.
Your comment about needing to remove the heat when in the defrost mode does not make sense. Where do you think the coils are that needs to be defrosted? The heating coils are not the ones that need defrosting. They are not going to heat up in the defrost mode. They will instead get cold, because you have basically switched to the Air Condition mode.

Try again. I still need an answer.
Mike

The way the defrost cycle works is the unit is forced into A/C (cooling) mode, the outdoor fan is stopped, the indoor fan is stopped or electric heat is activated. The ice is melted off the coils and when the temperature sensor is satisfied, or the timer elapses if it is not satisfied or failed, the outdoor fan comes back on and blows the water vapor away and at the same time the unit is reversed back into heat mode.

In our area the indoor fan is always left running since electric resistance heat is needed to prevent to far of a temperature swing and also to keep the air temp up. Obviously your area is different or your temps are not so extreme.

I believe you have to flip a switch on the stat for the operation you are looking for. Since I have never cut off the electric resistance heat.

Try this on the subbase switch.

HP-SS SWITCH AND FAN SWITCH

HP-SS Switch - If your system is a heat pump, the HP-SS
Switch must be set to HP (see Fig. 1). If your system is a single
Stage, the switch must be set to SS.

See link and figure 1 in link for location of switch.

I blew right by the fact that you mentioned you did not have emergency heat since it is so strange of an item not to have in this area. Good luck.

http://www.white-rodgers.com/wrdhom/.../0037-6997.pdf

Quote:

Originally Posted by hvac1000

The way the defrost cycle works is the unit is forced into A/C (cooling) mode, the outdoor fan is stopped, the indoor fan is stopped or electric heat is activated. The ice is melted off the coils and when the temperature sensor is satisfied, or the timer elapses if it is not satisfied or failed, the outdoor fan comes back on and blows the water vapor away and at the same time the unit is reversed back into heat mode.

In our area the indoor fan is always left running since electric resistance heat is needed to prevent to far of a temperature swing and also to keep the air temp up. Obviously your area is different or your temps are not so extreme.

I believe you have to flip a switch on the stat for the operation you are looking for. Since I have never cut off the electric resistance heat.

Try this on the subbase switch.

HP-SS SWITCH AND FAN SWITCH

HP-SS Switch - If your system is a heat pump, the HP-SS
Switch must be set to HP (see Fig. 1). If your system is a single
stage, the switch must be set to SS.

See link and figure 1 in link for location of switch.

I blew right by the fact that you mentioned you did not have emergency heat since it is so strange of an item not to have in this area. Good luck.

http://www.white-rodgers.com/wrdhom/.../0037-6997.pdf

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That would had been great info you gave if I had a Emerson 1FB-0211 thermostat. As I stated to start with, I have an WHITE-RODGERS 1FB-211 thermostat. It does not have an HP/SS switch in it. It has a W904 wire that I have cut per the way I interpret the instructions.

Mike