I was told that I should be able to tell by the model number what size unit I have at my house. The M/N = 13hpd-036-230-14. Can someone tell me what size unit I have please?

Looks like 36,000 BTU or 3 ton.

I have a model # 13HPD-036-230-14 heap pump cooling and heating split system. When my air handler shuts down, my compressor outside keeps running for at least an additional 15-20 minutes. Is this normal?

I have a model # 13HPD-036-230-14 heap pump cooling and heating split system. When my air handler shuts down, my compressor outside keeps running for at least an additional 15-20 minutes. Is this normal?

Under most circumstances it is not normal.