Is there a digital thermostat that can run two AC units simultaneously or is there another solution using one thermostat?

Answer 1

Simple SolutionJust get two new thermostats with auto changeover. Simply set the temperature range that you want, for example 68-72 and the thermmostats will do their thing. when it gets cool out it will kick the heat on. when it gets warm it will start the cooling.

yes , a thermostat ,digital, with the option of 2-stage cooling sub - base would do what you want . most likely a honeywell or Johnson controls brand.

edit this would require a professional to wire as the units both supp;y their own control power and a 2-stage theremostat has aprrox a 2 degree spread on the stages which would cause 1 unit to start then the second when it gets 2 degrees warmer

the best solution would be to use a single stage stat and have the professional upgrade the transformer in 1 unit to a higher VA then use relays to start both units together ( i would also use a small time delay in 2nd unit about 1 min to prevent high voltage spikes on start up)

I have used the contactor contacts of the first unit to power a relay that would energize the contactor (or the transformer) of the second unit. The relay coil voltage could be 120v or 240v and you avoid the larger transformer issues (they are $$$). Yes, you could just energize the second contactor, but the relay allows better flexilbilty on the coil voltage(s) choice.

I would ask myself this: If your house is large enough for 2 separate A/C units, why would you want to control a second space by the temperature in another part of the house? Each unit should have it`s own thermostat located in the space that it serves. By doing what you are asking about you are not only inviting comfort issues but also wasteful usage of your energy dollars.

Here's why: Many two story houses have separate heating and A/C systems for upstairs and downstairs. In Texas where I live, it may be 90 degrees one day and 40 the next. We flip the swith from heat to cool many, many times each year. Most of my family does not understand that both these units need to be switched together. If someone switches the upstairs unit to cool while the downstairs unit is on heat, I end up with a thermostatic blackhole that sucks my money in as fast as it can. Since cool air sinks and warm air rises, neither unit will ever shut off. I have been unable to find a thermostat that will control both units, but I will post here if I do. As it stands, I must run up (or down) the stairs everytime I change one of the thermostats to make sure I haven't created this horrible blackhole. I need to keep as much monay as I can.