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Help with 240V heat relay
I am working on heating a 3 room cabin in PA. There is 200 amp service - so plenty of juice to heat it.
The house will only be occupied 1/2 the winter - and internet is available, so an app can tell the 2 nests to call for heat so the homeowner can turn up the heat on the way to the cabin. Each zone has UFH (under floor electric heat) and a 240V 20 amp in wall electric heater. The homeowner would prefer to only use the wall heater as supplemental aux heat if necessary. See diagram
1. The aux will need a 240 relay - no 24VAC transformer is necessary - which one(s) should I consider. Is there a reliable honeywell like RC840T-240 but without a transformer?
2. Am I missing something?
The house will only be occupied 1/2 the winter - and internet is available, so an app can tell the 2 nests to call for heat so the homeowner can turn up the heat on the way to the cabin. Each zone has UFH (under floor electric heat) and a 240V 20 amp in wall electric heater. The homeowner would prefer to only use the wall heater as supplemental aux heat if necessary. See diagram
1. The aux will need a 240 relay - no 24VAC transformer is necessary - which one(s) should I consider. Is there a reliable honeywell like RC840T-240 but without a transformer?
2. Am I missing something?

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Comments
If you have the space, why not use a traditional transformer and 2 contactors.
Albert Einstein
As @Zman mentioned above, a 24 volt transformer would make this problem go away and open you up to any kind of solution you felt was best.
For the transformer:
Packard PF42440 Control Transformer Class II Foot Mount 40VA 24V. Given that I am powering 2 nests, and 4 contactors (Packard C140A 1 Pole Contactor Coil Contactor, 40 Amp, 24V) , how many transformers will I need given each transformer is 40VA?
I assume the contactors are 24VAC even though they just say 24V?
Thanks again for all the help!
WRT the Nest stat, the specs only say that it's 1.21" deep, 3.3" tall, and also (can you believe it!) 3.3" wide. In any case the detailed specs tell me that it's 3rd generation, stainless, and has a 24 bit color display. Oh, and it uses less than 1 KWh/month. You're probably ok with ignoring the load of the nest stats. The internal battery should carry it through the times that the transformer is heavily loaded, if any.
The Nests should be capable of switching those contactors, they appear to be pretty standard. The real question is how much current does the Nest need. They're not going to want to tell us that, because it changes pretty drastically. Idle current, i.e. nothing calling, will be less than one VA; however all the current required for the outputs needs to be accounted for in the total, as well as the charging current & (perhaps most significant) the power required when the radio transmits or receives. All those by rights should be added up & listed as "max power required" or some such, but that'd make it look like a small space heater, & since some of those are what's known as non-coincident (can't have heat & cool on at the same time for instance), they make it hard to find.