I have a breaker panel with one open breaker. Problem is I was going to add a heat pump to my seasonal cottage but it requires 220. Will I need to replace entire panel to accommodate this heat pump? It's a 100 amp max box as well. Cottage is 1200 square feet. Don't know the code for this rural town in Maine. Will need to get this. Thanks
It looks like your old Westinghouse panel will accept breakers from Eaton or Cutler-Hammer (but check at place of purchase). If so, this tandem breaker can serve two circuits but use only one slot in the panel.
This is different from a double pole breaker which takes two slots like you would need for a 240 volt appliance:
To use the tandem, pull out a pair of single pole/non-tandem breakers (and discard), connect the two circuit wires to the tandem and insert. Voila! You have freed up an extra slot.
Depends on your other loads/circuits.
You might be able to combine some things and free up a second breaker, but the total load will matter quite a bit; and you might NOT be able to combine things, depending on what you have.
If the total load capacity and service capacity of the present panel allows, you might be able to relocate some circuits to a sub-panel. If you shift 3 or more circuits to a sub-panel you'll lose two spaces for the sub-panel feed but gain enough spaces for your heat-pump in the main panel. But this is pointless if the loads exceed the panel capacity.
Then again, some panels ("Federal Pacific Stab-Lok" for example) simply should be replaced (even if you are not adding loads.)