Sharing a main electrical panel for 2 central air units

I just finished a service entry for a house with an attached dwelling. The main house wanted more than 200 amp capability, so the decision was to have 320 amp service to the house and separate it into 2 - 150 amp panels. One of the panels will provide for the attached dwelling with a 100 amp sub panel and the remainder of that 150 amp panel will provide for the main house mechanicals.

A point of debate now is whether to have two AC units on the same 150 amp panel. This is a question that a friend posed (who is not a professional electrician, but an engineer), who was concerned of the possibility of current overload of that whole panel, in the case the two AC units ever experienced LRA current draw at the same time. The ACs are both 3 ton with LRA of about 60 and MOP of 30. The reason I am defending the position to keep the two on the same panel is for organizational cleanliness.

I would love to get others input.

Thanks for the thoughts.

Unless the panel is undersized for the total connected load the two units that you’ve mention will never be a problem. I wouldn’t even look at the locked rotor current because it probably will never be an issue.

Explain to me what “locked rotor current” is?


Thanks for the input Rob. I don’t think it will ever be an issue, but wanted to take into account others opinions. What about the possibility of lights dimming? That would also infer the total load on the panel is too much, is that correct?

Not likely, it would be more of a condition of the conductor size used to feed the unit.

The bigger question (not asked) is what is your calculated load on each panel?..has anyone actually done a calculation in order to speculate a concern?

Paul your disclaimer appears to be /maybe written wrong.

These two units have a full load current of less than 20 amps each. As I said prior unless the panel is well undersized there isn’t even an issue to consider.

Nope…written as i like it…;)…My opinions and ECA are one and the same !