The larger wires were for a unit that operates on a higher amperage than the unit you are installing. The biggest concern arises when the unit you are installing decides to have a problem, and the breaker that is presently installed does not trip as soon as it should.
What you need to do is look on the unit you are installings' manufacturers tag and find out what the amperage rating is and then compare it to the breaker that is presently installed. Most likely there will not be a problem.
If you like please post this information and I will be able to tell you if they are a go, or a no go.
Well the 40 amp breaker is twice what you need to operate the unit.
I would have an electricXXXXX XXXXXe it to a 20 amp breaker, and put the other 40 amp to a single pole 40amp breaker. (eg:20 amp for the new unit and 40 amp for the other unit if you are going to still have one. If not just replace the dual pole with the 20 amp). Considering that the wires were getting fried in the wall it would probably be a good idea to change them to the proper guage at the same time you change the breaker.
Of course you could just hook it up as is and not have a problem. But if it were me I would definatly do the change. If anything just for the peace of mind.
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