My new Payne 3 ton Heatpump has 15KW electric heat for auxiliary/emergency heat.
In emergency mode I get 20 degrees of temperature rise from the electric heat. The installer confirmed that the 3 elements of the heat strip were working.
I was expecting more from the electric heat. Should I?
It all depends. slow the fan speed and you'll get more heat rise, but lose cfm. Emergency heat is just that....not meant to constantly heat your home, just keep you alive. A manual J is needed for actual heat loss.
If your air handler is providing 1200 cfm in emergency mode, then with a 15kw heat strip, you should be getting
(15kw * 3412btu/kw) / (1200cfm * 1.08) = 39.5°F
If you are getting only 20°F temperature rise, something is wrong unless your air handler is providing 2400 cfm of air flow (it's not).
Where are you measuring the temp at.
It should be measured at the unit, not the regs in the house.
It may be cycling the strips.
What type of duct do you have, if its sheet metal is it insulated, and is it in an unconditioned area.
All of the above, plus-
it may be that it's wired such that you get 15kw for aux heat, but only one bank for emergency heat (not that you would want it wired that way, but it could happen).
Don't forget that there are typically sequencers on heat strips, so it will have to run for several minutes before it reaches its full wattage.
The question of where you measure return and supply temperatures is important; if you have a return leak and are sucking in cold outdoor air, the temperature rise may be way more than you'd assume it is.