Using datalogging thermometers and spreadsheet to diagnose bad rad vent

Jells

My tenant complained that their bedroom was cold. I've been driven crazy in this 4 unit house by the heat issues, and have 10 datalogging thermometers at various points, like on riser pipes, sitting on radiator valves and the boiler header, as well as just taking room and outdoor temps.

So I graphed the room temp, outdoor temp, the rad in question and the riser feeding it. It became clear the damn MoM vent was sticking intermittently, in the 3rd quarter of the graph where the riser (black) is cycling but the rad (red) stays cold. There were other instances of this other than the 60 hrs I show here.

There's still some interesting artifacts to figure out, like why the boiler is running continuously in the 4th quarter of the graph, and then without the outdoor temp rising, return to a normal sine wave pattern. The odd 'boiler off' section on the left side I think is because the tenants in the unit with the thermostat were cooking in the kitchen off the living room where the thermostat is. When I checked the log on the Nest thermostat, there was no heat call during that time!

I have no idea how else I would have figured this intermittent failure out in a house I do not live in.

jesmed1

Nice use of data loggers to figure out the problem. Over the years I've been troubleshooting the heating system in our 4-unit condo building (hot water, not steam). We've had similar problems with uneven heating because the owners in the units with the thermostats were cooking, or had auxiliary heaters running, etc. When I moved in, I found the thermostats had been mounted on walls directly in front of the risers, causing the boilers to short cycle when the risers began heating the insides of the walls. I wouldn't have figured that one out without an infrared imager. Modern electronics have definitely made troubleshooting easier.

There's a similar thread to yours ongoing, with a multi-unit building owner trying to troubleshoot uneven steam heat using multiple data loggers. His tenant in the one unit with the thermostat has had erratic habits including leaving windows open in cold weather, cooking and overheating the thermostat, etc. That was another case where multiple overlaid temperature graphs helped diagnose the problem.

https://forum.heatinghelp.com/discussion/194427/unbalanced-heat-in-4-unit-with-1-thermostat/p2

In the 4th quarter of your graph, you observed that the boiler was running continuously for an unusually long period. Maybe your tenant also left a window open near the thermostat?

Jells

jesmed1 said:

In the 4th quarter of your graph, you observed that the boiler was running continuously for an unusually long period. Maybe your tenant also left a window open near the thermostat?

On the Nest log it's calling nearly continuously that day, 21.75 hrs! But the datalogger in the same room shows it rock solid at 70 the whole time, inconsistent with an open window. If it's a response to the outside dropping to 30, I'm worried that I'm going to fall short of heat like I did before getting the burner properly tuned last spring. Time to brush the boiler...

BobC

Before i bought this palace i was living on the first floor of a standard, for the Boston area, two family house. I noticed some large swings in temperature but ignored them because i spent a fair amount of time in the kitchen close to the beer chest. Lots of these old houses did not have radiators in the kitchen, they thought heat from cooking would be enough, so the kitchen stove often had a vented gas log on it. These had a standing pilot so did not need any power to run, very handy if a snow storm knocked out power. The thermostat for the steam boiler was in the living room so any heat from that gas log was unlikely to affect it.

One day while stripping wallpaper in the living room I noticed the wall the thermostat was mounted on was pretty warm, the landlords boiler was running and a steam riser was right behind my thermostat. I moved that thermostat to a different room and my temperature swings were a thing of the past.

back in the early 70's the house had a pair of Delco 4 section steam boilers that were twice the size needed and when I bought this house it to had a Delco 4 section steam boiler. Those were a pretty robust boiler BUT did not have a LWCO and thats what killed most of them, even so most made to 40 years or so.

Bob

jesmed1

Jells said:

On the Nest log it's calling nearly continuously that day, 21.75 hrs! But the datalogger in the same room shows it rock solid at 70 the whole time, inconsistent with an open window. If it's a response to the outside dropping to 30, I'm worried that I'm going to fall short of heat like I did before getting the burner properly tuned last spring.

Yes, I see. Well, your 2nd floor ambient temp went up from 65 to 75 during that long boiler run, so you still have some excess capacity at 30 degrees. Hopefully that's enough.

Jells

jesmed1 said:

Jells said:

On the Nest log it's calling nearly continuously that day, 21.75 hrs! But the datalogger in the same room shows it rock solid at 70 the whole time, inconsistent with an open window. If it's a response to the outside dropping to 30, I'm worried that I'm going to fall short of heat like I did before getting the burner properly tuned last spring.

Yes, I see. Well, your 2nd floor ambient temp went up from 65 to 75 during that long boiler run, so you still have some excess capacity at 30 degrees. Hopefully that's enough.

The variability of that room is messy. Dropping below 70 even when the rad is cycling, but then sometimes up to mid 80s! I have no idea what to do about it. Oddly, the identical room on the floor below is much more even. I think I don't even have a port screwed into the vent valve on that one.

jesmed1

Jells said:

jesmed1 said:

Jells said:

On the Nest log it's calling nearly continuously that day, 21.75 hrs! But the datalogger in the same room shows it rock solid at 70 the whole time, inconsistent with an open window. If it's a response to the outside dropping to 30, I'm worried that I'm going to fall short of heat like I did before getting the burner properly tuned last spring.

Yes, I see. Well, your 2nd has floor ambient temp went up from 65 to 75 during that long boiler run, so you still have some excess capacity at 30 degrees. Hopefully that's enough.

The variability of that room is messy. Dropping below 70 even when the rad is cycling, but then sometimes up to mid 80s! I have no idea what to do about it. Oddly, the identical room on the floor below is much more even. I think I don't even have a port screwed into the vent valve on that one.

I wonder if your MoM vent that's obviously sticking during that one cycle is also partially sticking during the second set of three burns. Notice the second set of three burns has lower peaks for the riser and rad temps than the first set of three burns, and as a result of that plus the falling outdoor temps, the room temp drops below 70.

Not an expert on steam heat, but you might find that replacing that one vent clears up both those artifacts.

Like some famous detective said, once a thief is caught, a string of crimes is often solved.

Jells

jesmed1 said:

Jells said:

jesmed1 said:

Jells said:

On the Nest log it's calling nearly continuously that day, 21.75 hrs! But the datalogger in the same room shows it rock solid at 70 the whole time, inconsistent with an open window. If it's a response to the outside dropping to 30, I'm worried that I'm going to fall short of heat like I did before getting the burner properly tuned last spring.

Yes, I see. Well, your 2nd has floor ambient temp went up from 65 to 75 during that long boiler run, so you still have some excess capacity at 30 degrees. Hopefully that's enough.

The variability of that room is messy. Dropping below 70 even when the rad is cycling, but then sometimes up to mid 80s! I have no idea what to do about it. Oddly, the identical room on the floor below is much more even. I think I don't even have a port screwed into the vent valve on that one.

I wonder if your MoM vent that's obviously sticking during that one cycle is also partially sticking during the second set of three burns. Notice the second set of three burns has lower peaks for the riser and rad temps than the first set of three burns, and as a result of that plus the falling outdoor temps, the room temp drops below 70.

Not an expert on steam heat, but you might find that replacing that one vent clears up both those artifacts.

Like some famous detective said, once a thief is caught, a string of crimes is often solved.

I don't think that's the case, if you look at this one with the rad from the room below in green and the room tempo there in light blue, the graph is similar, though inexplicably about 10 deg cooler, both loggers are sitting right on top of the shutoff valve.