Thermostat for swamp cooler - 2gig CT100?

Other Devices & Integrations Climate Control & Temperature Sensors
1

I have a swamp cooler with a MasterStat CC2000A thermostat.

The MasterStat has only 4 wires, labeled YWRG. There is no 24v com wire.

The CT100 can be operated via 4 aa batteries, so no requirement for the 24v com wire.

The install guide for the CT100 shows a wiring install diagram for a 4-wire, WYRG, system.

Does anyone think that a CT100 could successfully control a swamp cooler?

I have searched, but have not found any threads that have any information on a working
z-wave thermostat for a swamp coller.

2

AFAIK, the MasterStat is a line-voltage thermostat. You can’t simply replace it with a standard low-voltage thermostat like the CT100.

3

Thanks for the reply kkl.

The below paragraph is copied from the installation instructions for the MasterStat cc2000a.

" Determine which knockouts you will use for
electrical wiring (always use the knockout
marked “Thermostat Wire” for the 4-wire low
voltage wiring to the wall thermostat inside of
the house)."

The above quote from the MasterStat manual sounds like the thermostat wiring
is low voltage, and therefore got me hopeful that something like the ct100 could be used.

4

Perhaps I misunderstood your question. I thought you wanted to replace your MasterStat with a CT100. I see that you’ve already found the existing thread on this topic where someone tried using a 3rd party thermostat without success. I have nothing helpful to add. The YWRG wires don’t make sense to me since W is generally used in the heating mode which doesn’t apply to a swamp cooler.

5

After looking at the photo in the other thread, I see that YWRG refers only to wire colors, and they are non-standard: Y - fan, W - pump, R - 24V, G - com.

There is a Nest thread where someone was successful:

I was able to get my swamp cooler to work with NEST. I have a low voltage White Rodgers thermostat with 4 leads (red - power, white - pump, green - fan, yellow - fan speed). You have to fool the NEST a bit, due to the fact that connecting to "Y1" is mandatory and it is also used to draw power. I connected yellow to "y1", white and green to "g", and red to "Rc". Fortunately this unit has a built in fan delay - so the water runs for 60 seconds before the fan actually goes on. I give up the ability to adjust fan speed (which I never did anyway) and the ability to run as fan-only (I may decide to put in an external switch for that someday). Otherwise it is working very nicely!

Proceed at your own risk.