EWC ST 3E and sensi wifi thermostats

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Joined: Mon Nov 21, 2016 10:23 am

EWC ST 3E and sensi wifi thermostats

Post by pjaewc »

I have the ESC ST 3E control and 3 sensi wifi thermostats.
The old thermostats were LUX PSP511, and were working fine (3 zones).
I bought 2 Honeywell wifi thermostats, and the main ("master"?) location worked, but the other one did not. The main/master one has the usual common, green, red, white, yellow... But also had orange and brown hooked up to the O and B on the old thermostats. The other 2 had the usual wires but not orange or brown.
Honeywell help had me hook up but leave the brown disconnected on this unit. This worked on the main Honeywell thermostat. The other did not work (you could hear it click when I bumped up the temp above the current temp.. but the furnace did not turn on).
Honeywell had meeasure the voltage across a couple wires (I think common and red?) and said it had to be 24v. The main was was.. the other 2 were not.
I uninstalled the new thermostat and replaced the 2 old ones.. now the 2 old ones were not working either (think the main one was left as the new thermostat).
I returned the Honeywell units and saw the Sensi wifi units that said they do not require the common C 24v wire. Thought I'd try them.
Got 3... Hooked up the mainaster the same way (leaving off the brown wire).. and the main worked fine. Hooked up the other 2, and same issue.

Could something be wrong with the control unit, caused by changing from old to new thermostats?

Paul Z.
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Joined: Thu Dec 08, 2011 3:05 pm

Re: EWC ST 3E and sensi wifi thermostats

Post by Paul Z. »

Give me a call have a few questions 1-800-446-3110 X490.
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