Honeywell T5

[OlivierM]

Hi. First post here and a little help is needed.

I bought a Honeywell T5 thermostat (https://www.honeywellhome.com/en/products/thermostat/t5-touchscreen-7-day-programmable-thermostat) to replace an old Chromalox thermostat. Behind the old one, only 2 wires connected to the red and white terminals. So, as the Honeywell manual states, I connected those wires to the R and W therminals behind the new thermostat. Result, no heat. I don't really know where to look at and following that manual, I configured it properly. I attached some pictures to help.

Thanks for the help

Olivier

[Sergroum]

Out of curiosity and my apologies if the question is stupid, but did you turn the power off at your heating unit before doing the change over?

Are you getting 24volt at any of the two wires?

Did you connect to W, or W aux?

[OlivierM]

Hi. Yes, I turned off the power at the heating unit.

I connected to W.

[Admin]

Is that an electric forced air system?  If so don't forget to enter the System Setup options and adjust option 205 to electric forced air.

Slide the switch up to R.  See pic below.

[OlivierM]

Hi. It's an electric system in which the thermostat controls a relay that powers baseboards on the first floor. So, nothing special in that system.

The switch is in the upper position.

[Admin]

Normally baseboard thermostats use line voltage.  Your wiring looks like low voltage but what is the voltage reading between those 2 wires?

That thermostat isn't made for electric baseboards.

If you twist the 2 wires together and turn the power back on does it start to heat?

[OlivierM]

Voltage between the 2 wires with the power on and thermostat disconnected? Usually yes baseboards use line voltage but in that situation (don't ask me why), there is a relay (the Chromalox box) that activates the baseboards.

[Admin]

Yes, if you measure between the 2 thermostat wires with them disconnected and the power on.  I'm just curious if one of them is actually sending 24V.

[brad_monty10]

If it's a 240v to 24v transformer I've had it give you 12 volts on each wire

[Sergroum]

If it's a 240v to 24v transformer I've had it give you 12 volts on each wire

That's something else entirely. And I'm assuming you're measuring to ground.



Olivier.

with the wires disconnected and power on, if you measure between the two of them are you getting any voltage?

[OlivierM]

If it's a 240v to 24v transformer I've had it give you 12 volts on each wire

That's something else entirely. And I'm assuming you're measuring to ground.



Olivier.

with the wires disconnected and power on, if you measure between the two of them are you getting any voltage?

I just measured it and I've got 9 volts between the 2 thermostat wires, with power on.

[Sergroum]

Soo either your transformer is on a fritz, or the wire is exposed and worn somewhere and is really close to a metal edge.

[OlivierM]

So, why is my old thermostat working well? I will look at the relay if I have 24v or 9v where the thermostat wires connects.

[OlivierM]

Just to be sure, at the thermostat wires, should I get 24VDC or VAC?

[Frosty]

24v VAC

[Sergroum]

Is it? Working well?

If you take these two wires and twist them together, do you get heat?

[OlivierM]

It's working as it should with the old thermostat. I had an electrician here for other work and asked him. He told me it can't work well with a new thermostat unless I replace the relay. He also told me that it's a way better system than modern thermostats. So unless there is a problem with my heating system, I will not replace the thermostat, finally.