The relay I used is quite small and should fit inside your breaker box.
I removed the wire from the AC dedicated breaker and put it on one contact terminal and ran a 4 inch long wire from the other terminal to the breaker.
When the relay "makes" or "picks up" you then are connecting the Cooling unit to the breaker.
Set the cooling unit thermostat to max cool and the fan speed where you like-we use low.
Run a wire from the Y terminal on the Hunter thermostat to the coil contact on the relay.
Run another wire from the other coil contact to battery ground to complete the coil circuit.
When set on cool the Hunter thermostat calls for cooling,sends battery voltage to the relay coil (via the Y wire),the relay connects across the contacts and sends power to the cooling unit which then comes on.
When the set temperature on the Hunter thermostat is reached it turns off the Y wire, the relay drops and power is removed from the cooling unit.
Hope this was helpful ,
Mike