HVAC pro’s: please chime in

[StolenFox]

Morning all and Happy Fathers Day (where applicable)! I need a little guidance here regarding thermostat wiring or more specifically interrupting the 24v circuit. I have two heat pumps, one package unit and one split unit and they are on separate thermostats.

I need to determine the best methodology for installing interrupt switch in the thermostat circuits that will immediately shut down both units (package and both parts of the split) immediately.

The reason for this is I’ve installed a 26kw Generac generator and its transfer switch has an onboard load shedding feature for the HVAC units. The shedder is nothing more than a logic controller for a series of switches that interrupt the 24v for the thermostats. So do I do this at the units themselves or just go to the t-stats themselves?

Any tips or ideas would be appreciated!

S.F.

 

[Zeke]

Whichever is shorter/easier. The 24v originates at each unit and of course has the hot/common and control wires for heat/cool/fan. You can tap into the hot wire with your switching. Wherever you do this is a matter of ease. Too bad it can't be done with RF. Or maybe it could but that's added expense.

 

[StolenFox]

Whichever is shorter/easier. The 24v originates at each unit and of course has the hot/common and control wires for heat/cool/fan. You can tap into the hot wire with your switching. Wherever you do this is a matter of ease. Too bad it can't be done with RF. Or maybe it could but that's added expense.

Thanks for the reply Zeke!

I think I have a plan now: The package unit is sitting right next to the transfer switch so I’ll add a small flex conduit (with the 2-wire thermostat wire inside) from the P.U. to the transfer switch. I’ll then just “insert” the load shed module in-line using the new wiring.

As for the split unit: The air handler is in the garage on the opposite end of the house. It already has the 24v circuit separated to facilitate a condensate drain pump’s ability to shut down the Split unit if the condensate pump fails. I’ll just run a new 2-conductor thermostat wire from the load shed module through the crawlspace and tie it in series with the condensate pump shut down circuit.

Does this plan sound viable?

Thanks!
S.F.

 

[Zeke]

Sounds good. As I said, take the short route even if it's pump fail switch. We used to put these systems in markets so all the refrigeration equipment didn't start at once. Involved at lot of low voltage and relays. You've got it easy since the LV is already there.