Steam heat: room temperature spikes

jesmed1 · January 8

I'm still trying to troubleshoot the steam heat at my friend's shop. The condensation turned out to be from a 5" crack in one radiator that I fixed (so far, anyway) with JB Weld.

The other ongoing problem is occasional temperature spikes. Here's the background:

-Two 1-pipe radiators with Vent-Rite 1A adjustable vents

-Shop is in a big old mixed-use building, probably 100+ yrs old, storefront shops on first floor with residential apartments above

-Shop is typically underheated (61-68 degrees) on cold Boston days, even with vents maxed out.

-But occasionally, room temperature spikes to 80+ degrees.

-Data logger graph below shows two such spikes: one last Saturday afternoon, and one this afternoon (Tuesday)

-Both spikes happened around 2:00 pm, with similar graph shapes. A boiler cycle before noon causes an intermediate spike up to 71-72, then the following boiler cycle around 1 pm causes a massive spike up to 81-85 degrees.

-Vent on one radiator sounds like it's venting air cleanly with no obstruction.

-Vent on other radiator sounds like it vents sporadically, making interrupted psss….pssss…pssss…sounds while the steam is rising. I can also hear constant burbling in that rad while the steam rises, as though there's pooled condensate in the horizontal pipe feeding that rad.

Because both spikes happen at the same time of day and show the same behavior (one lower spike to 70+ followed by the big spike to 80+), that makes me suspect some regularly scheduled boiler event, like a pressure increase? But why wouldn't it happen every day at the same time?

Also, if the boiler pressure was spiking, wouldn't that cause the vents to stick closed even harder?

Room Temperature Graph 1_3_25-1_7_25 - Google Sheets.pdf

jefftk3 · January 8

You mention large mixed use building, and two radiators in the shop. Are other radiators for other tenants sharing the same boiler / heating system? Where is the thermostat, and/or sensor for the thermostat?

Is data logger located next to the thermostat?

EdTheHeaterMan · January 8

It could be that the Patriots are having a bad season this year 4 -13.

If you were in Philadelphia however we are having a great season 14 - 3, so we get more chances to Spike the Ball at the end zone!

🦅 Go Birds!

jesmed1 · January 8

https://forum.heatinghelp.com/discussion/comment/1832723#Comment_1832723

I assume one boiler for the entire building, or at least he's sharing a boiler with several other units. In any case, there's no thermostat in the shop, so no control except for the adjustable vents. The data logger is about 5 feet away from one radiator, sitting about knee-high on an unplugged, not running dehumidifier.

jesmed1 · January 8

https://forum.heatinghelp.com/discussion/comment/1832724#Comment_1832724

I'm from NY originally, so both the Pats and the Sox are...unprintable. 😀

But your Birds plug reminds me of a funny sign that says: "It's hard to soar with the eagles when you work with turkeys!"

jefftk3 · January 8

I'm no expert, probably wont be helpful in diagnosis any real system problems if there are any - but, my first inclination would be to find out where the thermostat and/or its sensor is. The landlord at least ought to know that. I could imagine that it could be as simple as some other shop or common space, which happens to have the thermostat, is leaving a door open for some delivery, or window for whatever reason for exhausting some dust/fumes (no idea what kind of shops are in question here).

bburd · January 8

A tenant who opens a window near the thermostat could cause the observed behavior. The Germans have a tradition of opening windows for a few hours for ventilation even in winter; maybe this is part of the tenant's housekeeping routine.

jesmed1 · January 8

https://forum.heatinghelp.com/discussion/comment/1832732#Comment_1832732

OK, then that brings the next question. The air vents close pretty quickly. Then the rads heat up as the steam condenses, the vents open, and no steam comes back until the next boiler cycle 2 hrs later. So the air vents usually only cycle once per boiler run.

So if someone has a window open, say, near the Tstat, then the boiler keeps running, cycling on pressure, and the shop radiators presumably fill with steam, condense, and repeat several times? So that overheats the radiators and thus the whole shop?

jesmed1 · January 8

OK, that makes sense.

The other problem is that, without a thermostat, the shop is typically underheated. Would the erratic venting from that one radiator contribute to underheating? Is it worth me trying to replace the vent and/or repitching the radiator and/or replacing the valve if that is partially obstructing the steam?

Jamie Hall · January 8

https://forum.heatinghelp.com/discussion/comment/1832747#Comment_1832747

yup

bburd · January 8

https://forum.heatinghelp.com/discussion/comment/1832747#Comment_1832747

The shop probably underheats frequently because of the flow of outside air from opening and closing of the entrance door. If the thermostat for the whole building is upstairs among the residential units, it will not see that load and reheat the shop; and even if it did, it would overheat the apartments.

Supplemental heating in the shop on a local thermostat could fix that.

jesmed1 · January 8

There isn't really much traffic in and out of the shop, unfortunately, so the underheat condition I think is mainly due to the large plate glass display windows that are thermal sieves, in combination with the lack of thermostatic control.

He does have an electric supplemental heater that he left turned off while I recorded with the data logger so I could see the effect of the radiators alone.

I guess I'll try to replace the vent on the radiator with the intermittent venting, and see if I can figure out where in the building the thermostat is, and who is opening the window/door near it for an hour after lunch…

EBEBRATT-Ed · January 8

I would check the pitch on the rad that gurgles and also the pitch on the runout. Not that that is likley your problem if your overheating.

yellowdog · January 8

You need to find the thermostat before you start changing vents.

jesmed1 · January 8

Here's another piece of the puzzle. I went over this morning and took thermal images of both radiators during a morning boiler cycle. The one radiator that I JB Welded is not filling completely with steam. As I mentioned earlier, the air vent vents sporadically in both directions (venting out and venting in). And although the radiator itself is pitched slightly in the right direction, the horizontal feed pipe is pitched towards the radiator, producing a low spot at the valve/spud area right at the radiator entrance.

By contrast, the other radiator shows completely white on the IR image, and its vent is venting smoothly, so I know that radiator and vent are fine.

So here are IR pics of the problem radiator. Vent is at far end. Second pic shows vent end of radiator.

Does this prove conclusively that the vent is partially clogged, and that's the reason for only partial filling?

ethicalpaul · January 8

it shows me the vent is working, possibly too fast

If the vent were blocked you’d see no red in the radiator

jesmed1 · January 8

https://forum.heatinghelp.com/discussion/comment/1832818#Comment_1832818

The vent is working, but slowly, because I can hear it venting intermittently (psss…psss…psss) on both the exhuast and intake cycles.

By contrast, the other radiator has the same vent, on the same setting, and vents smoothly and quickly, filling the radiator and giving a totally white IR picture. Same vents, same setting, one venting smoothly and filling the radiator, one venting intermittently and not filling the radiator.

So doesn't that tell us that the intermittently venting vent is the culprit? And possibly also the incorrectly pitched inlet pipe?

jesmed1 · January 8

Here's a pic of the other radiator, with the same vent, same setting, venting fast and smoothly, and filling completely.

ethicalpaul · January 8

I'm not sure we can know that the "panting" you are noticing is the vent's fault. It could be there is water trapped in the radiator's supply pipe due to a sag, or who knows, something completely different.

But you can swap the vents to possibly rule out the vent as a cause

The reason I suspected that the vent was too fast is because if it were indeed slow, the steam wouldn't race across the top and down to the vent. It would slowly heat one section of the radiator at a time (at least in my current mental model of How This Stuff Works™—subject to change!)

The advance and retreat of steam (panting) is often due to the collapse of the steam as it hits a cold section. In a nice slow radiator, these advances are small, and the panting is not noticeable. So that's why I wonder if it's due to over-fast venting.

jesmed1 · January 8

@ethicalpaul OK, thanks.

I can see how trapped condensate would cause intermittent venting as the radiator fills with steam.

BUT…I can also hear the vent operating intermittently (psss….pssss….psss) while the radiator is cooling and sucking air back in. And I can't see how that could happen except for the vent itself being partially clogged.

Anyway, I've gone as far as I can with diagnosis. It's up to the landlord to fix it, so I'm going to recommend (1) a new vent, and (2) raising the radiator so that the horizontal inlet pipe is pitched correctly. The vent is probably 20 years old anyway, so even if it isn't the problem, it can't hurt to replace it.

Steam heat: room temperature spikes

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🦅 Go Birds!

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