Calculating offset temperature profile for steam boiler

Hello! First just wanted to say that I love Beestat—it’s the best part about owning an Ecobee thermostat.

I was having trouble understanding the temperature profile for my (aux, used to be primary) steam boiler for my old 1900’s steam radiators. It seems like, despite the boiler being way oversized for the home, Beestat calculates a negative heating delta for temperatures below 48º which seems incorrect.

I started by investigating the thermostat detail and found that, while the boiler is running, the temperature is still continuing to drop until the radiators heat up. By the time they do, the boiler cycle is done and the rads stay hot for an hour and a half or so until the cycle repeats. This matches my real-world observations as well.

(image below, forum won’t let me post two images at once)

I’m wondering if this is expected (I assume so, since it’s calculating the profile based on the same logic as heat pumps and furnaces) or if there’s something I can do to offset the calculation of heat gain. It seems to me that all steam and hydronic systems would have the same issue, but posting here to see if anyone else has advice or suggestions.


Beestat doesn’t do a great job with analytics on radiant heat systems. It captures incorrect data because all of the heat comes after the actual heat cycle is over.

I haven’t spent a ton of time thinking through this particular problem. The simplest idea is to just offset the sampled data until the temperature starts to rise. Definitely something that I would like to improve.

That makes sense. I think a configurable offset would help.

In my case, it seems like the temperature starts to rise when the heating cycle ends, and (typically) continues to rise for about the same time as the cycle ran for.

Not very scientific and doubt that’s how other homes work, but I could probably make do with a static offset and duration to get in the ballpark.

(fwiw, also probably not terribly urgent for me since this is aux heat)

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