Hello I am looking for some guidance regarding wiring a sub panel into my porch. My home is close to 40 years old and never had heating or plumbing. I recently had to build a porch to allow for these upgrades. This sub panel is to accommodate an electric hot water heater, water pump outside plug for vehicles a washer and dryer a gas furnace and an outside light along with outlets for heat tape for my water lines and sewer pump out. I had a gentlemen come and wire everything but he wasn't sure what amp breaker he should use to run power off the main panel because the sub panel is a regular panel with a 100 amp main. If you can help me this would be greatly appreciated as I need this done before winter sets in and everything freezes.

What size feeder wire has been installed from the main panel to the sub panel?

I will assume the gentleman that did the wiring is not an electrician.

If he does not know how to size a circuit breaker, how does he know how to wire the panel?

He is a fourth year journeymen but has done just industrial over the last four years. I believe the feeder wire is a 6, it's the thickness of a roll of nickels. I purchased all the material under the direction of an electrician. He initially recommended a 40 amp breaker on the main panel. Does this sound right?

A 4 yr app should know how to use Table 310.16 in the Code.

Depending on the type cable installed, a #6 Romex can use a 60 Amp breaker, and MC cable can use a 70 Amp breaker.

You may use a 40 amp CB, but doubt that would carry the load you mentioned.