Sub Panel

[Jim W in Tampa]

I will varify mine but might be a few months. I am just going by what my AC man (also friend and member of my club ) told me.
The way he exsplains it is that if temp gets below 32 the condencer would freeze up. Also when you get near freezing a heat pump is no longer cheaper to run. They work best at temps in the 40's and higher. If both compresor and heat strip can kick on at same time then we have both loads. Seldom a problem here in Tampa but up north things change.

 

[lakee911]

I will varify mine but might be a few months. I am just going by what my AC man (also friend and member of my club ) told me.
The way he exsplains it is that if temp gets below 32 the condencer would freeze up. Also when you get near freezing a heat pump is no longer cheaper to run. They work best at temps in the 40's and higher. If both compresor and heat strip can kick on at same time then we have both loads. Seldom a problem here in Tampa but up north things change.

That is correct. The manufacturer can give you a temprature where the effeciency line of the emergency heat and the heat pump cross. I think for my unit I was told that it is around 42 degrees and simply wouldn't work below 36 if I recall correctly.

 

[readydave8]

I thought that aux heat was only part of the strips, to get all stages to kick in have to move switch to emer?

 

[kwired]

I will varify mine but might be a few months. I am just going by what my AC man (also friend and member of my club ) told me.
The way he exsplains it is that if temp gets below 32 the condencer would freeze up. Also when you get near freezing a heat pump is no longer cheaper to run. They work best at temps in the 40's and higher. If both compresor and heat strip can kick on at same time then we have both loads. Seldom a problem here in Tampa but up north things change.

That is correct. The manufacturer can give you a temprature where the effeciency line of the emergency heat and the heat pump cross. I think for my unit I was told that it is around 42 degrees and simply wouldn't work below 36 if I recall correctly.

If temperature is below 32 degrees the coil will get ice on it, that is why there are defrost controls - to remove the ice. A heat pump will work down to very cold temperatures, just not as efficiently as it does at higher temperatures. The temperature point at which one should design to lock out the heat pump is a balance and will depend on if the unit can keep up with call for heat demand, as well as if the cost of operation is still below the cost of operating the back up heat.

cost of operation will depend on energy cost and will vary from one region to another.

I thought that aux heat was only part of the strips, to get all stages to kick in have to move switch to emer?

On all units I have seen it really depends on how you connect the aux heat control leads. If there is only one lead you get all of the heat. If there are multiple leads and you tie them all together you get them all. This is how you have to connect a gas aux heat system unless it has multiple stage gas valve.