Tekmar 564 compatible with Steam system 2 wire heat only?

Chris_108

I would like to order this stat but cannot find any info on if it plays nice with steam boilers? I have a Weil Mclain Peg 200k BTU steam boiler and also was wondering if i would need a different transformer or relay other then what boiler came with to hook up the 3 wires from the Tekmar control module to boiler?

thx in advance!

Chris

EdTheHeaterMan

This seems like OVERKILL if all you are connecting is a steam boiler.  If however you are also connecting humidifier/dehumidifier, air conditioning, or fresh air HRV equipment now, or in the near future then it has more capabilities than most of the popular smart thermostats like Ecobee, Nest and Honywell.

You need to program the thermostat to operate on the Radiant Floor Heat option YES in the setup menu.  That is the closest to Steam Heat as the settings will allow.  If that is not comfortable then set it to NO. there are other parameters that can be adjusted to get the steam boiler to operate to your liking.

EdTheHeaterMan

Since the Weil McLain wiring design is not compatible with using the C wire from the boiler transformer to power up a C terminal on a smart thermostat I suggest that you count on using a separate transformer and Isolation relay like this:

If you have the older boiler (Series 1 or 2) that has the simple wiring, I have a diagram that reworks the LWCO and vent damper settings and you can use the boiler transformer. If you have the newer control with all the LED indicator lights, then you must use the isolation relay.

109A_5

@EdTheHeaterMan

What's the difference between your added isolation relay and just using Rh1 and W1 ? It seems like Rh1 and W1 are isolated contacts.

EdTheHeaterMan

https://forum.heatinghelp.com/discussion/comment/1830988#Comment_1830988

I didn’t look that closely

You are absolutely correct