Steam boiler timing controls

jesmed1 · January 9

I'm still helping a friend troubleshoot the steam heat in his rented shop in a 100-yr-old multi-use building with storefront units on the first floor and residential units on the second floor.

Indoor temperature inside the shop sometimes spikes around mid-afternoon to 80+ degrees. There is no thermostat in the shop, so it must be somewhere else in the building. Other shop owners don't know where it is either, and they also report poor temperature control. Landlord has been unresponsive.

Heating pros here have suggested that someone with the thermostat in his/her unit is propping open a door or window for an extended period, causing the thermostat to get cold and call for a too-long boiler run that then overheats all the other units. This sounds likely to me, but now we have to figure out who is doing it.

One odd thing I noticed is that the first two spikes (on different days) happened at exactly the same time of day, within 1 minute of each other per the data logger. Which suggests some kind of timer/automatic control is involved. So I'm trying to figure out if this is a human problem, or an automatic control problem, or both.

I'm still learning about steam heat, so I don't know much. But I have seen mention of CPH (cycles per hour) thermostat settings for steam boilers. So if someone propped open a door at, say, 12:50 pm on one day, and then propped open the same door at, say 1:05 pm on the next day, could the thermostat CPH setting make the boiler start running at the exact same time, say 1:15 pm, on those two different days? Or is there some other automatic timer possibly involved?

ethicalpaul · January 9

To my knowledge the CPH setting is just a sort of different way to describe the "swing" of the thermostat and is not based on actual timing. (I will be corrected if I am wrong about this)

If the thermostat setting is higher than the current temperature it should call for heat. If the setting is lower than the current temperature it should not call for heat.

As for if there is some other timer, or if the thermostat is programmed with some setback or whatever, I couldn't say from here

jesmed1 · January 9

Thanks, Paul. As luck would have it, I finally found the maintenance guy today. He said the thermostat is in his "office," which is apparently a windowless room on the second floor, in the residential unit area.

I explained the problem and said I suspected cold air was blowing on the thermostat, causing the boiler to run too long and overheat the building. (I forgot to ask him if there was just one boiler for the entire building, but since he only mentioned one thermostat, I guess that's the case.)

So the entire building must be getting overheated during these spikes. Maybe the first floor shops get it worst because they're closer to the boiler, but I assume the upstairs residential units would get overheated too.

I guess everyone is so used to poor temperature regulation in the building that no one ever bothered to figure out what was happening.

Anyway, he seemed willing to try to do something about it. He said there was a transom window above the doorway that leads into the hall, and maybe cold air from the hall was spilling in through the transom. He said he'd try to seal the transom. We'll see.

jesmed1 · January 10

@ethicalpaul Thanks for your informative radiator pitch video. I'm thinking that my friend's "problem radiator" may also have condensate in the bottom from incorrect pitch. (The rad is pitched minimally in the right direction, but the horizontal feed pipe is pitched badly the wrong way.)

Comparing a screen shot from your video to my IR pic, I think a see a similarity, in that steam is not flowing along the bottom channel. So I think probably my friend's radiator has water pooled almost uniformly along the bottom, and that raising it and pitching both it and the inlet pipe would be the fix.

ethicalpaul · January 10

Maybe, but if it's anywhere close to level, even pitched slightly the wrong way I don't think you'll gain much by changing the pitch.

It's hard to say from here, but your IR photo looks to me like the radiator vent is too fast. The steam is moving too fast along the top and then going out the vent and closing it before the steam has a chance to heat up the rest of the first sections.

My vent in my video was set real wide open just so the video wasn't even longer.

jesmed1 · January 10

https://forum.heatinghelp.com/discussion/comment/1833608#Comment_1833608

OK thanks. I'll try a different vent setting and see what happens.

ethicalpaul · January 10

OK very good. But remember, be driven by your comfort in that room. The goal isn't necessarily a full radiator, the goal is that room's comfort level according to the residents

jesmed1 · January 10

https://forum.heatinghelp.com/discussion/comment/1833627#Comment_1833627

Yes, thanks. The room is generally underheated, so we're trying to maximize average heat output.

That is, except for the times when cold air from the entrance hallway blows on the thermostat in the maintenance guy's closet, in which case the boiler runs too long and overheats the building. Which is a different problem…

jesmed1 · January 10

@ethicalpaul

Here's an update. With the air vent turned down to 4, I got a good series of IR pics as the radiator filled with steam. It took about 5 minutes to fill, and with the vent turned down (4 now vs, 7 before) it got even less filled with steam. So slower venting did not make the radiator heat up more, it made it heat up even less.

Which further supports the theory that the improper pitch has the bottom of the radiator filled with condensate.

The first pic below shows the radiator after filling with steam at a vent setting of 7. The second pics shows with a vent setting of 4.

So slower venting makes the underheating problem worse, not better. The only other explanation I can think of is condensate in the bottom of the radiator, because of the incorrectly pitched inlet pipe.

pecmsg · January 10

that’s not condensate backing up it’s just less steam getting in!

ethicalpaul · January 10

I'd forget worrying about the condensate if I were you. It's not an issue.

It could still be too fast. I don't know what vents you're using but "setting 4" vs "setting 7" doesn't mean much to me.

I still see the steam racing across the top and down to closing the vent.

Ironically, with a slower vent you can get more steam in the radiator but yes it takes longer. It takes longer to fully heat a radiator than what you are showing in your pictures. Heating stuff takes time!

Are you usually heating these up from dead stone cold 60 degrees? Is that the typical usage pattern? If not, then your test isn't great because in most cases in the winter, a call for heat will come with some warmth still in the radiators—it's abnormal for the steam to have to come into a 60 degree radiator.

jesmed1 · January 11

@ethicalpaul OK, it's not condensate, it's the vent. It's a Vent-Rite #1 adjustable, with a setting range of 1 to 8.

And the steam is not racing across the top of the radiator, it's crawling at a snail's pace. I took a series of 10 IR images (not shown) at 1-minute intervals beginning from when the steam started to rise. It took 2 minutes for the steam to rise the 2 feet from the inlet to the top of the first section. That's a rate of 1 foot per minute.

Then it took another 4 minutes for the steam to advance 4 feet across the top gallery of the radiator. Again, that's 1 foot per minute. That's crawling, not racing.

Then it took another 2 minutes for the steam to crawl down to the vent at the end. Then it took another 1-2 minutes for the vent to close. In all, it took 10 minutes of agonizingly slow steam "crawling" to advance from the inlet to the time the vent closed. And the IR pics I posted above show the 10-minute point, just after the vent has closed. After that point, no more steam enters the radiator. So that's as hot as it gets. And a large portion of it is still cold.

Meanwhile, the other radiator in the room, with its vent set to maximum, has already vented smoothly and quickly, and is completely filled with steam and uniformly white-hot.

So I go back to my original observation in the other post, which was that the vent is clogged. It goes "psss…psss…psss" when the steam rises, and also when the radiator cools and sucks air back in.

Since the vent is clogged, it doesn't matter whether I set it to 7 or to 4, because the clog is now the limiting factor. So turning the vent from 4 up to 7 makes little difference.

So you and @pecmsg have convinced me that condensate is not the problem, it's a clogged vent.

ethicalpaul · January 11

ok that’s good data collection. Did you try swapping the vents yet? There are other things that could be at play.

jesmed1 · January 11

https://forum.heatinghelp.com/discussion/comment/1833781#Comment_1833781

I'm not going to wrench on it because it's my friend's landlord's property, and the way the vent threads look rusted I think there's a good chance they'll break off.

I just wanted to have a good diagnosis for my friend so he can tell the landlord what needs to be done. Thanks again for your help.

LRCCBJ · January 11

@jesmed1

You have to ask yourself a question:

If that radiator is a proper steam radiator, with NO connections across the top, how could the steam heat the top of the radiator all the way across?

It can't.

What you have appears to be a hot water radiator where the steam can fly across the top of the radiator and not even bother with anything below the top 1/3.

Such a radiator will never have anything close to the rated output before the vent closes.

pedmec · January 11

it sounds like to me like your getting thermal gains from the sun and it's not the system. What side of the shop faces the sun. You can have large thermal gains from windows facing the sun.

If your not filling the radiator all the way across and down it could be due to the fact the boiler is shutting off before it fills the radiator. Its a system problem that could be causing the issue, not your radiator.

And I'm not buying the cold air blowing over the thermostat in a windowless room? that makes no sense. you would have to leave the door open and wait for the room temperature to drop which would take a little while for the thermostat to react. Then when the door is shut its not recovering temperature?

jesmed1 · January 11

https://forum.heatinghelp.com/discussion/comment/1833839#Comment_1833839

This is another interesting rabbit hole. I'm just learning about steam, so take this with a grain of salt. But I have looked at other radiators in the building, and they all seem to have connections along the top as well.

The following blog seems to have a good description of the different radiator types.

https://ecoradinc.com/blog-hot-water-vs-steam/

Most of the radiators in the building seem to be of the type shown in the last photo, with connections at the top, and port locations for either water or steam. I've lived in the Boston and NY areas and have seen a fair number of old steam systems, and I don't recall ever seeing a purely steam-only radiator with no connections at the top. Most of them seem to be the "hybrid" type designed for either hot water or steam. This post says that change from steam-only rads to the hybrid type happened around 1905:

https://heatinghelp.com/systems-help-center/steam-radiator-vs-hot-water-radiator/

I would guess my friend's building was built in the 1920's or 30's, at which point it was presumably common to use the hybrid-type radiators for steam.

In fact, here is an IR pic of the other radiator in my friend's shop, which is one of those hybrids with connections along the top, and it has no problem filling completely with steam:

Interestingly, I live across the street from my friend's building in a 1920's or 30's house with the same type of hybrid radiator in a hot water system, except they're tapped for the air vent at the top instead of the air vent halfway down.

LRCCBJ · January 11

The steam radiators connect at the top, great! But that’s not all.

Once I read this in the cited article, that was it. Another individual who has no idea what he is talking about.

You have observed the result of using steam on a HW radiator. You probably will get not more than 1/2 the output from it.

Why would the steam, which is lighter than air, go down to the bottom of the radiator? The only way the bottom half will heat is via conduction from the CI at the top.

jesmed1 · January 11

https://forum.heatinghelp.com/discussion/comment/1833848#Comment_1833848

I've stood in the room while the temperature spikes happen, with my thermal imager. It's not solar gain, it's the radiators cycling repeatedly and cranking out the heat.

And there is a second radiator in the room that vents smoothly and fills quickly and completely with steam. See IR pic in my previous post.

So the boiler is heating the other radiator in the same room, no problem. It's not the boiler. It's this one radiator that isn't filling. As I already said, the vent is venting only intermittently (psss….psss…psss) and the radiator is taking nearly 10 minutes to fill. By contrast the other radiator fills almost immediately with no problem.

As for the thermostat, I agree, the maintenance guy's theory was lame. He doesn't strike me as the sharpest tool in the shed. I suspect there are multiple wireless sensors throughout the building, and somewhere someone is propping a door or window open and letting cold air blow onto one or more of the sensors. There are workers going in and out of the building rehabbing some of the residential units, and they may be opening windows or doors.

LRCCBJ · January 11

The only possibility that the one rad heated all the way through……….and it clearly did……….was the velocity of the steam entering that rad was sufficiently quick to flow all the way along the bottom before rising. It must have a fairly large vent to allow this.

This radiator will be difficult to control with venting as the moment you slow the rate of steam into the rad, the output is going to drop dramatically due to the steam rising up the first column and crossing at the top, and avoiding the majority of the remaining columns.

It's doable but certainly not what is preferred.

jesmed1 · January 11

@LRCCBJ said:

The only possibility that the one rad heated all the way through……….and it clearly did……….was the velocity of the steam entering that rad was sufficiently quick to flow all the way along the bottom before rising. It must have a fairly large vent to allow this.

I agree with you. The vent on the rad that fills quickly and heats evenly has a Vent-Rite #1 adjustable that's now set on 7 (8 is max). It vents quickly and the radiator fills fully.

The other (slow-filling and unevenly heating) radiator also has the same Vent-Rite #1. But that vent is partially clogged. It goes psss….psss…psss…when filling with steam, and also under vacuum when re-admitting air.

So that vent is clogged, making the radiator fill very slowly and unevenly. And I think we are both agreeing now that a non-clogged vent would allow that radiator to fill faster and more fully with steam.

LRCCBJ · January 11

If you can get them to perform…………that's all that matters.

But do understand that the radiator will eventually present a 200F temperature to the IR camera if the system runs long enough. Conduction in the CI will make that happen.

If the steam cycle is of shorter duration (in the warmer ambients), this radiator may present a totally different IR result.

pedmec · January 11

Is it a thermostat or a central heating control like a Heattimer steam boiler control or a Tekmar. If it is a thermostat with remote sensors then the sensor location and operation need to be checked. The control needs to be specified. It will make a difference. A faulty sensor will cause a system malfunction.

jesmed1 · January 11

https://forum.heatinghelp.com/discussion/comment/1833880#Comment_1833880

Understood. The room is chronically cold (except for the one-a-day temperature spike which is a different issue), so I'm just trying to maximize the heat output of the one under-performing radiator. Per thermal imaging, one radiator is clearly filling with steam almost immediately, and the other takes 10 minutes to fill partially. So putting a new vent on the slow, partially filling radiator with a clogged vent seems a no-brainer.

jesmed1 · January 11

@pedmec That is what I'm trying to find out. I managed to find the maintenance guy and talk to him briefly before he had to run off, and he wasn't particularly helpful. He did say there was a locked thermostat inside his maintenance closet, and that the thermostat is now controlled remotely by the new owners.

Obviously one thermostat inside a closet cannot be controlling the heat for an entire sprawling building with 30 residential units plus commercial shops on the first floor. So there has to be more to the story, but this guy had to run off before I could get it all out of him.

Steam boiler timing controls

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