one thermostat for two ac units in the same room


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Old 05-10-18, 02:58 PM
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Unhappy one thermostat for two ac units in the same room

hello I live in a country with a very hot climate in summer and fairly good in the winterIn the living room I have two split duct air conditioning with two separate controller (thermostat)
24v both of them are career units 1.5 ton and 2 ton systems and both blowers are setup in the same locations .
i want to control the room with one nest thermostat is it possible
and yes i have C wire
single speed fan , but the fan can be 3 speed capable just need extra wires
 
  #2  
Old 05-11-18, 08:52 AM
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Welcome to the forums.

Yes.... it may be possible to do.

Most split systems like that use a proprietary thermostat. That means they won't work with an aftermarket thermostat like the nest. If you know for sure the nest can be installed on your unit... then two additional relays would be needed to control the second unit.

For further help.... I'd need to know the model number of the split unit and the thermostat.
 
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Old 05-11-18, 02:37 PM
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Its duct system

carrier ducted split system air conditioner
with three speed fan carrier (unit) not sure about the model but both of them are the same only diffrent is the outdoor unit power (tons). One (1.5 ton and 2.5 tons )
the indoor fan
look like this
https://files.carrier.com/building-s...ia-328x328.jpg

The thermostat is 24v each
 
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Old 05-11-18, 02:43 PM
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I need detailed technical information to help. I'm not aware of an aftermarket 24vac thermostat that has fan speed controls on it. It sounds like your units are connected with the Carrier communications system.

There may be a wiring diagram posted on your unit or inside the service cover.
 
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Old 05-11-18, 08:00 PM
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I have aftermarket thermostat installed I will post a picture
 
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Old 05-11-18, 08:40 PM
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I post the picture of the diagram latter
 
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Old 05-13-18, 11:46 PM
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sorry i couldn't go there to take the pictures i need some equipment that i dont have
 
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Old 05-14-18, 06:44 PM
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I can work with what I have. Since there will be one stat to replace two please name them.
It could be stat A which will be replaced and stat B which will be removed,

What color wires are connected to stat A's terminals ?
What color wires are connected to stat B's terminals ?
You will lose the sensors if those terminals are now wired.
Do you need the one nest to control heat and cooling ?

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Old 05-14-18, 07:39 PM
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This would be a tentative diagram.
1 - nest
3 - 24vac N.O. (normally open) relays.

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Old 05-15-18, 12:35 AM
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you just save a hole day of researching '
i have identical AC units 2 blowers indoor and two outdoor units .
thank you again i think this diagram well save the day
 
 

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