Hi there
I am wanting to build myself a heat pump but need to work out my heat load, and most compressors are worked out by the evaporating duty.
So if you have 100 watts evaporating @ 15 degrees, what would your discharge duty be at 43 degrees ?

Here are a few companys that may be able to help you on calculations. You can probably contact tech service or visit there web site.

Copeland Compressors Div of Emerson.
Bristol Compressors

And

Tecumseh Products Company | Compressors

In the long run its cheaper to buy a new system that is made to work and compatible with the rest of the system. Any compressor you buy will not have but a 1 year warranty and that's only if you can prove it was installed right by a certified tech, with you asking it makes one wonder if you are certified to work with the refrigerant side of the system. You know your breaking the law if your not.

Just to offer a little info as far as compressor warranties are concerned, most compressor manufacturers do offer an extended warranty. It's SOP for me to purchase it anytime I replace an OEM compressor.

Just a little info. If its designed for that system and installed by a certified tech.