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Optimizing Run Times With Cold Weather

Today we saw our 68F target tenant sensor apartment room temp using our Tekmar was only 63F with the colder Milwaukee, WI weather the last few days at our 5 unit apartment building, which had us wondering. Our single-pipe steam system WMC EG-75 (Water Feeder picture below for reference). We watched the gauge glass refill with condensate from about 2-6 minutes after the burners shut-down and stopped about 80% refilled on the gauge glass full water line at 6 minutes for a few cycles while we observed. Does that suggest moving the delay for the water feed from 10 minutes to 8 minutes was a good idea (or didn't make a difference if one of the things was the limiting factor)? We kept the feed amount to "LWC" rather than a fixed 1, 2, 3, gallons, etc. as labeled inside on the tiny tabs for the settings.

We're not sure if the system shut off on low water, pressure (operating pressuretroll at 0.5 psi cut in/1.5 diff. for 2.0psi cut out to give it some room to run & secondary safety pressuretroll 2.0psi in/3.0psi out with 1.0 diff), although I don't have a lot of faith in those tiny millimiters representing 1 psi getting us a very accurate reading). Although our 0-3psi pressure gauge shows it operating under/up to 2.0 psi range during the cycle.

The lockout differential was 8F, so we lowered it to 5F to let things run earlier after shutting down each time. I think our steam established was/is at 135F for now. The last radiator with the tekmar thermistor sensor was fully hot across all sections & comfortable in the hallway room when we observed it today, so not sure if we really need more heat for the entire building, or the apartment with the thermostat sensor is colder for some reason.

Any guess on what caused out heat to not be as high as usual? We've never had a problem with heat being acceptable in past cold spells eventually. The cold spell makes sense just not sure how to best adjust things (more/faster water, wider pressure operating range, less time/temp drop for tekmar lockout differential setting, or another tekmar setting?)


  • nicholas bonham-carter
    How capacious is your main venting? If it’s up to snuff, all the radiators should receive steam simultaneously.
    Therefore everyone would have been equally cold, assuming the radiators had been properly sized for each room.
    Is the steam arrival setting of 130 degrees enough?
    There is a lot to be said for managing the system the old fashioned way-a thermostat sensor in the most exposed room.—NBC
  • cubicacres
    cubicacres Member Posts: 358
    edited February 2021
    Our main venting is pretty good/maxed out with Gortons, with the exception we have a longer loop out of 4 basement main loops that takes a few minutes longer to heat up than the larger diameter shorter main branches from the boiler. The coldest room/thermostat sensor room is on this long smaller line. Adding riser vents & splitting the long main loop would be our next major improvement project. We have vari-vents, so maybe the thermostat room is set at a 1 or 2 & could use faster venting? So far it's been ok with 68 the coldest room/thermostat sensor room target and 1-2 degrees variance between 67-69 all season until yesterday. We'll keep an eye on it and see if it's closer to the 68 target tonight.
  • bburd
    bburd Member Posts: 918
    Unusually high winds can mess up an outdoor thermostat based control system.

  • cubicacres
    cubicacres Member Posts: 358
    Looked good at room temp 68F yesterday, so maybe our adjustments helped or it just needed some time to get back up to target temp in the apartment with the indoor senor.