You want to move the two existing wires so they both terminate into a subpanel? You can't feed the subpanel with two circuits. You can, however, simply replace one of those 240v breakers with a larger breaker and run a NEW wire (correctly sized) to a subpanel.

Ok thanks. Is there a reason why 2 circuits can't feed a subpanel, just like to understand. I will change the approach then

Separate but related .... Am building a shop and plan to have the following circuits (3) 20a, (2) 15a, (1) 30a and perhaps an extra one for future

What size of wireshould I run from house?

Tx

Is there a reason why 2 circuits can't feed a subpanel
Basically, you can't combine circuits to make bigger ones. Two 30A circuits don't make one 60A circuit. If a load is drawing 40A, there is no guarantee that the wires of the supplying circuits will evenly split the required power. So each wire must be sized to supply the whole requirement.

Plus, if those 30A circuits are 240v, then they don't have a neutral wire. In order to have 120v circuits, you'd need a neutral wire.

That is about 125A that could be used for other areas
What crazy math did you use to come up with that number?!? :)

That makes sense about no guarantee which circuit carries. Thx

My crazy math - the two 220v have 4 wires so they could be (4) 30a 110

For the shop, recommendation on the size of wire but will just do the (3) 20a and (2) 15a. I will redo the 30a in the garage for the rv

Tx

I'm surprised none of the electricians that are regulars have jumped in here to answer your question.

My non-professional opinion is that a 60A subpanel would probably be enough for your needs. That would be fed by 6 gauge copper wires, I believe.

If you wanted 100A then it would be 2 gauge.

Those are probably the 2 common sizes for subpanels.

This post was edited by greg_2010 on Wed, Jul 16, 14 at 16:01

If the 30A circuits are not run with a neutral (four wire circuit) you can't feed a subpanel of any capacity with them. If we were talking individual conductors in a conduit, you might be able to canabalize conductors from one to augment the missing neutral for the other.

As already mentioned, you can't "parallel" your 30A conductors to get more capacity.

How much you need to run the circuts really depends on what they are. Electrical load calculations is not the matter of just adding up all the circuit ratings.