Brad, you've done one thing I don't agree with and I think you made one mistake. In your calculation, you have 2400VA for the water heater, yet you said it was 4500VA. Perhaps you're thinking that only one element is used at a time (which is true), but usually a 4500W heater will have two 4500W elements, of which either the upper or lower one is used (but not both).
What I don't agree with is the 220.30(C)(4) usage. This only applies to the optional calculation, not the standard method that you used. You can recalculate using the optional method, but that still brings up whether you should be using 65% or 100% of the heat pump rating. Try to talk to the HVAC guy, but most heat pumps run the electric heat when the heat pump is in defrost mode or when the outside temperature is below the "balance point". If this is a cold area (like noth of Georgia), I would hope the electric heat and compressor run at the same time. There is also emergency heat, which runs all the electric heat but without the compressor. It is possible to have X KW for defrost, Y KW supplemental heat (when its real cold), and Z KW for emergency. So its difficult to say how much of the installed strip heat is being used in each mode, unless there is only 1 strip. If you can't get answers to this, I think you need to assume that all the strip heat could be used with the heat pump compressor.
[This message has been edited by markp (edited 04-08-2005).]
