Best way to interlock AC and Heat

[LonArcvarden]

Hi there, I have to do an interlock for a new AC unit and two 15A 2P circuits for 4000W of forced air heaters. The AC will be on a 30A breaker, so im realizing I cant just use a switch since they arent the same amperage.


Could I simply put the two heating circuits on a contactor and use the call for AC to trigger that, or will it not have enough power to trigger a low voltage relay? Would I do it instead with 30A rated relays? (the amperage of the AC will probably be less then 20A).


Thanks

[princemeraj]

Get a contractor with normal open and closed contacts. Run a wire from the ac on the control side to open the contact for the heating load so it can’t run.

[ayawoalhassan]

A small 2‑pole contactor driven by the AC’s control circuit usually keeps things clean: coil on the AC call, contacts breaking the heater feeds. Just make sure the contactor is rated properly for the heater load. For installs where space was tight, I’ve had pros handle the wiring while they were already doing commercial plumbing upgrades phoenix az for me, and it saved me a ton of hassle.