Weird behavior with new thermostat

itsmehli

Replaced Lux (LTX9600) with Emerson Sensi thermostat.

New Sensi thermostat will control heat but have unexpected behaviors like:

when thermostat turn on and off heat there is a momentary grinding noise at the beginning and end.
unable to configure WiFi without heat turning on with constant grinding noise
When power to furnace is turned on the gas burner will turn on for 2-3 secs before shutting off. Thermostat will be set to no heat or room temp below set temp so burner is not suppose to turn on at all.
Previous thermostat do not have WiFi and did not exhibit the above weird behavior

Wiring from transformer to thermostat:
Transformer - thermostat (wire)
Y - W/E (red)
W - RH (white) C - C (cyan)

Previously with Lux thermostat there was no common connected.

Tried swapping the RH and W/E but thermostat will not turn on furnace.

Opened ticket with sensi in case the thermostat is faulty.

Furnace is Weil McLain EG - gas steam.

https://www.weil-mclain.com/products/residential-boilers/gas/steam

https://www.luxproducts.com/wp-content/uploads/2017/07/tx9600ts_manual_en.pdf

https://www.luxproducts.com/wp-content/uploads/2017/07/tx9600ts_manual_en.pdf

EdTheHeaterMan

Your post is difficult to understand.
did you take a picture of the wires before you disconnected them from the Lux (LTX9600)?

if you did, can you post it here?

There is a good chance you have incorrectly wired the thermostat.

EdTheHeaterMan

I looked at the wiring diagram for your heater. I see your problem, and unless you are qualified to rewire the safety devices on your heater, you will need a heating equipment professional (that understands steam heating system wiring) to install the thermostat



Since the R from your thermostat does not go directly the R on the boiler transformer, there will always be a problem with normal operation. R will be disconnected every time the LWCO detects a low water condition. This will break the connection from the R to the Thermostat and the thermostat will detect that as a fault. This will send error codes to the microprocessor on the thermostat, and it may not recover from the error.

If you get a professional to rewire the LWCO so the R from the transformer is wired directly to the R on the thermostat, your problem will be resolved. as illustrated here.



Don't try this at home. Safety circuits must be tested after rewiring to be sure the safety and operating controls function properly.

Jamie Hall

And yet one more reason why power stealing thermostats drive heating pros crazy.

EdTheHeaterMan

Yup @Jamie Hall

"You got to use your head in the big stuff!" quote from a mechanic I used to work under as an apprentice