Single Pipe Steam Main Air Vents

northeastconfederate

Hello, I have a ~100+ year old farmhouse which has long ago been chopped up into 3 apartments and is heated by single pipe steam radiators, supplied by a large, gas-fired boiler. The main steam header is 2"; the pipes leading to the radiators are 1-1/4", as is the condensate return pipe. There are two main air vents, both located after (downstream) of the farthest radiator pipe. These are about 12" apart from each other, and have 1" Threads, so are bushed down from 1-1/4" to 1".

I found one of the main air vents, the first one in the flowpath, badly rusted, and showing obvious signs of water running down the body of it. I confirmed this happening while observing it emitting what I thought was a large quantity of steam during a firing cycle, and so I replaced both main air vents prior to the heating season. My understanding - possibly incorrect - is that there should never be steam emitted from the air vent, only air. That once the air is purged, the vent should close.

I recently observed the new "number one" (first in the flowpath) air vent doing the same thing the old one did: blowing a pretty large quantity of steam during a firing cycle. Are my main air vents undersized? If so, how are these properly sized? Is the number one air vent simply faulty? Is it maybe located too close to the last steam pipe?

Also, since the boiler cycles are determined by pressure setpoints, and the air vent is allowing steam to escape - therefore reducing system pressure - aren't I losing efficiency?

Any help would be greatly appreciated. This building costs a fortune to heat. I am trying to reduce the operating costs as well as improve the comfort of the tenants. I plan to install a Tekmar 279 outdoor temperature reset controller with condensate temp sensor as well as indoor temps sensors, which seems like it should go a long way to improving both efficiency and comfort over the existing thermostat. But the air vent blowing steam makes me think I'm wasting steam as a result of a faulty or vent and therefore spending extra money for nothing.

acwagner

You are correct--the new vents should not be releasing steam. They may give off a hint right before they close, but not continuously.

Can you post picture of the vent setup? What kind of vents did you install?

Also, is this a one pipe or a two pipe system? It's hard to tell from your description.

I'd focus on updating your venting before moving to the advanced controls. I know multifamily units can be hard to please everyone, but it sounds like your system needs some basic TLC first.

KC_Jones

The pressure in the system is supposed to be set by proper boiler size and proper venting. The presuretrol is supposed to be a safety device not an operating control.

You don’t want much pressure in a steam heating system, more pressure means less efficiency. High pressure can also kill vents.

All that said most of the time on here we see boilers that are oversized causing excess pressure which forces the pressurtrol to become an operating control. What is the setting on the pressurtrol?

For venting you need to measure the length and size of the mains and we can recommend how much venting you need. If you currently have Gorton #1 vents most likely you don’t have close to enough venting, unless the mains are less than 10’ long.

I’m curious why you think the tekmar will do anything for your application? Keep this in mind, any control is just an on and off switch for the boiler, it will do nothing for how the house heats other than controlling cycle times. I would strongly suggest you hold back on that until you get all venting corrected, which is always the first step. Controls won’t fix balance issues.

northeastconfederate

Acwagner: It's a single pipe system. See discussion title. Attached is a photo of the main air vents. I am 90% sure they are Hoffman brand, but don't know what size, except for the 1" pipe.

KC Jones: the main is 2" and is approximately 50 feet long. Actually, there are two branches of the system, and two condensate returns. Most of the 2nd branch is in a crawlspace, and I haven't crawled in there to get a look at it yet. But the longer main, and the one with the steaming vent, is around 50 feet.

The pressure limits are - I think - 5psig on the high side and 3 psi on the low side. Not 100% sure if I'm remembering this correctly, but I think so.

As for the boiler being oversized, it must be: a boiler man I had come look at it last year remarked that it is "huge."

KC_Jones

50’ of 2” main needs ~4 times the amount of venting you have there. That is a Hoffman #75 vent. The main in the crawl space needs to be measured and venting added or corrected. This is the first step for any steam system. I would suggest 2 Gorton #2 vents or a single big mouth vent for the 50’ main. The other we can recommend once you get dimensions.

5 is way too high. To give perspective, the pressure isn’t created at the boiler, it’s actually the back pressure created by the system slowing the steam movement down. So the more pressure the more the system is holding the steam back. Adjust the presuretrol as low as you can get it, get the main venting fixed and then you can concentrate on balancing the radiators.

Gsmith

Take and post pictures of the boiler and near boiler piping. That will help those here to guide you.
What is the pressuretrol set at?

northeastconfederate

Why I think the Tekmar will help: Please correct me if I'm thinking about this incorrectly. And please keep in mind that I've spoken to the technical assistance people at Tekmar, who confirmed that my thinking about this is sound. I got the idea from older discussions on this board, and did more research on it.

The current thermostat is the very basic, round analog dial with setpoint showing at the top and room temp at the bottom. It is in the apartment farthest from the boiler and controlled by that tenant. This apartment is on the south end of the building, and exposed to direct sun most of the day. There is no insulation in this building at all, except for one room which I renovated on the third floor on the north end of the building.

What I think is happening is: The thermostat can only see the temp in the room in which it is placed. This temp is not representative of the "average" building temp. That is one issue. I think by the time it sees the temp meet the setpoint and signals the boiler to cycle off, thermal inertia causes room temps throughout the house to rise significantly higher than setpoint. I know it's quite hot in some rooms, and in fact, the tenants have the windows open a couple inches because it's too hot. I've been in the apartment (Unit 1) with the windows open, and it is definitely too hot. This does not seem to be because the tenant with the thermostat (Unit 3) has it set too high. In fact, Unit 2 often complains of it being cold. There were clogged air vents in his radiators, which I replaced, which should have solved his cold problem, but the "hot" problem is still an issue in Unit 1.

What I hope the Tekmar unit will do for me: For one, it will remove control of the Tstat from one tenant and maintain a steady setpoint. With the indoor temp sensors, the controller should maintain a better average building temp rather than relying on a Tstat in a single location. Some tuning of the boiler run time curve, along with input from the indoor temp sensors will hopefully increase the comfort of the tenants (the "average" comfort?) while at the same time reducing operating cost. I have seen claims of pretty major fuel savings just from switching to an outside temp control system over a Tstat. With indoor temp sensors, the savings are supposedly greater.

KC_Jones

Oh to add to the pressure comment. If memory serves radiator vents are only rated for 3 PSI main vents I can’t remember. So at 5 PSI you are at least risking all the radiator vents, but I speculate it’s also the issue you are having with that main vent.

northeastconfederate

Here's a pic of the building, if it helps in any way. Unit 3 is at the far left of the building, and is 1st and 2nd floor. The Tstat is located on the 1st floor.

northeastconfederate

I may well be remembering the pressure settings incorrectly. i'll look at that next time I'm at the building and report back. I make take a trip there today specifically for that reason as well as to get pix of the piping near the boiler and the boiler itself, as requested above. I'll be able to estimate, at least, the piping in the secondary header.

Another question about the venting: I need 4x the venting provided by the two Hoffman #75 vents? If I replace both of those with a pair Gorton #2 vents in the existing location, that would provide adequate venting for that 50' 2" line?

Presumably, the other line has its own vent(s) as well?

acwagner

The Tekmar won't work if your system isn't balanced and operating correctly. Your pressure is entirely too high and is likely the reason why your main vents are failing and your bills are so high.

What you're describing is a classic balancing problem. You need to first lower the pressuretrol like @KC_Jones recommended. Then increase the main venting on both main branches. Then adjust your radiator venting so they all the radiators get heat at the same time. What kind of radiator vents do you have?

northeastconfederate

I just replaced all (almost all - there are a couple of radiators I haven't gotten to yet) with Hoffman adjustable vents. I wish I knew the size... But the top screw acts as a lock nut, and the cap beneath it rotates and is marked "1" through "6".

northeastconfederate

This is the radiator vent: https://www.supplyhouse.com/Hoffman-401422-1A-1-8-Adjustable-Angle-Steam-Radiator-Air-Valve-3516000-p?gclid=CjwKCAiA27LvBRB0EiwAPc8XWaqfiKPYHxvkto1kNv4Lvq8zQucsDKeMacnYBF47DwnUSA2mISWwrhoCe7sQAvD_BwE

KC_Jones

I see 1 Hoffman in the picture you posted, if that’s the 50’ main my comment is needing 4 times in that location, so 2 Gorton #2 vents or a single big mouth in that location. The crawl space main is a separate discussion.

acwagner

The Hoffman radiator vents are good for balancing. Each radiator will need it's own setting. "1" is the slowest venting and "6" is the highest venting. Radiators that are heating up quicker than the others need slower venting settings and the opposite for the radiators that are lagging. This will take some trial and error to get it right.

But, you really need to lower the pressure first. Most vents are rated for higher pressures, but you risk damaging them if your pressure is operating between 3-5 psi.

northeastconfederate

It's difficult to see because of the poor lighting, but I circled both vents in this one. You may need to zoom in to see the 2nd one.

Let me verify the pressure settings. I'm going to take a ride out to the building today to get thos pix and at least estimate the size of the other Lego's piping and vent.

So... back to venting the 50' line. 2 Groton #2 vents in the locatons of the 2 Hoffman #75 vents will provide adequate venting? It will be difficult to get a larger vent in the location of the 2nd one; the building's framing is quite close to it. I think I'm going to be reconfiguring the pipe a little bit to fix this.

northeastconfederate

Thanks for the input so far.

How do the air vents work? What causes them to seal once air is purged? Is it thermal expansion once steam gets there?

acwagner

Here's a video that shows how the type you have work. There's a cut away towards the end of the video.

https://www.youtube.com/watch?v=t7NiIyvDLbU

KC_Jones

On the tekmar or any control for that matter. If the temp varies by, say 5 degrees across the building, all controls will vary by that same 5 degrees across the building. No control can fix this, unless you use TRV’s at the radiators. The problem you are having is venting balance not a control issue, at least by the description.

I will reiterate the control will not fix any of the temperature issues you are describing. You must fix the venting before even thinking about new controls.

KC_Jones

Forgot to mention, even with TRV’s you have to balance the system first, this is a critical step no matter what you do.

northeastconfederate

Ok, one step at a time: venting first. I'll post again in a few hours after I've gotten out to the building. Thanks again for the help on this.

And thanks for the video, acwagner.

northeastconfederate

Here are some pix of the Booker and the piping near to it, including condensate piping.

What is the name of the steam loop installed at the boiler? A plumber once told me, along with the fact that it's safety requirement, but I disremember the name of it.

I have some more pix if needed, but didn't want to muddy the waters.

northeastconfederate

The pressuretrol setting is definitely 5psig, with a differential of 1.5.

Does the differential mean that the hi and low limits are 6.5 and 3.5, 1.5 either way? Or are they 5.75 and 4.25, for a total delta of 1.5?

northeastconfederate

Forgot to attach a pic of thenpressuretrol.

KC_Jones

You want to set the pressurtrol as low as it can go without disengaging the internal linkage and the white wheel inside should be set to 1.

I’d have to pull up the Burnham manual, but I’m pretty sure that boiler piping is incorrect. Mainly I think Burnham requires more than a single 2” riser. What model Independence is that?

Also you have reductions with bushings in the horizontal which makes water pool.

I would suggest the high pressure setting was someone’s attempt at overcoming the piping and poor venting, which is pretty typical of someone who doesn’t understand steam.

Hap_Hazzard

northeastconfederate said:

What is the name of the steam loop installed at the boiler? A plumber once told me, along with the fact that it's safety requirement, but I disremember the name of it.

Does the name "Hartford" ring a bell? Just remember the insurance company logo.

northeastconfederate

Happy Hazzard, yes, Hartford DOES ring a bell.

KC, are you talking about the tee circled in the picture when you refer to reductions with bushings in horizontal piping?

northeastconfederate

I believe this is the model number: 8141076R4

northeastconfederate

I just realized my phone auto corrected HapHazzard to "Happy Hazzard".....

I forgot to post the picture of the other steam loop, which has no main vent. It looks like there is a provision for it which has been plugged. There is currently only 1 radiator on that loop, on the 1st floor. There was a 2nd one in the room above it at one time, which was removed and the pipe capped before I got the place. In the pic the riser can be seen going up to the radiator above; the fitting with the plug where it looks like a vent could be; and then the elbow and 1-1/4" condensate return, which appears to be run well below grade.

KC_Jones

Yes that is the tee, reductions in the horizontal that go against the condensate flow are strict no no’s on steam.

Are you sure that’s the model number and not the serial number?

northeastconfederate

No, that's not the model number. I found it:
Model: SIN8LNC-LE2
Serial: 65062114

northeastconfederate

I'm pretty sure that's all the same size pipe - 2 inch. I guess I could be wrong, but it almost looks like an oversize tee was used, and bushed down to meet the 2" pipe?? If that's the case, whoever piped it must have used what he had on his truck....

Looking at the pic of the second loop, it, too, has a bushing reduction where it goes from steam to condensate. How else would I make this trnasition?

Also, could you recommend a specific "big mouth" vent? I looked up the Gorton #2, and while there's room in one of the current vent locations, the other has no room for that. I'd prefer to use a single vent so I don't have to re-do the piping back there.

acwagner

Getting a copy of the Lost Art of Steam Heating will be a worthy investment of both time and money.

You should have space to pipe over into a joist bay to put in a #2. If you don't have enough height, you use 3 Gorton #1's together. That's called building an "antler". You can search this site for examples.

KC_Jones

IN8 is supposed to use 2-2” risers with a 3” header. That boiler is far from correct piping and you may never be able to get it to perform properly. If it’s too choked down you might end up having to keep the pressure high just to get it to run long enough to heat the house. Whoever installed that boiler left you in a bad place.

Hap_Hazzard

northeastconfederate said:

I just realized my phone auto corrected HapHazzard to "Happy Hazzard".....

So you made me happy. Thanks!

KC_Jones

Big mouth is made by Barnes and Jones, they sell them on amazon.

gfrbrookline

Once you correct your near boiler piping I would add one Big Mouth to each of your mains and see how you balance out. You will likely need to reduce the venting on the radiators closer to the boiler to push steam to the end of the line. My rule of thumb is to set them to the middle setting, if the room is above the Tsat setting turn it down, if it is below turn it up but only after you run a heating cycle after you reduce the warm rooms venting.

northeastconfederate

> @KC_Jones said:
> IN8 is supposed to use 2-2” risers with a 3” header. That boiler is far from correct piping and you may never be able to get it to perform properly. If it’s too choked down you might end up having to keep the pressure high just to get it to run long enough to heat the house. Whoever installed that boiler left you in a bad place."

I'm I'm whoever installed it tied into the existing pipe system. Not that that makes my situation any easier to swallow.

So.... I'm obviously not going to re-pipe it this season. But if it will improve the performance and the economics of operating it, I might do it next year during the summer. Would it be worth it? The branch lines that go to the individual radiators are 1-1/4". I could replace the 2" header with a 3". I'd have a union at every branch, but...... Worth the trouble?

In the meantime, I'll get a big mouth vent and see what happens. I gotta do something to stop steam from blowing out the vent.

And, should I add a vent to the secondary line that feeds a single radiator?

northeastconfederate

> @gfrbrookline said:
> Once you correct your near boiler piping I would add one Big Mouth to each of your mains and see how you balance out. You will likely need to reduce the venting on the radiators closer to the boiler to push steam to the end of the line. My rule of thumb is to set them to the middle setting, if the room is above the Tsat setting turn it down, if it is below turn it up but only after you run a heating cycle after you reduce the warm rooms venting."

You just answered one of the questions I just posted, thanks. I'll get a couple of big mouth vents.

KC_Jones

To be clear I circled what is your header in red. I circled in blue what are your mains. Also in a re pipe those mains should attach to the header individually not tee’d together like they are now.

northeastconfederate

Thank you for clearing that up. So, using the proper terminology, it seems that correcting the header isn't as much of a project. I was thinking the mains needed to be re-piped. I could probably correct the header on a warm-ish day before it gets consistently cold.

Just so I understand correctly:

I should have two 2" risers connected to a 3" header, and the mains should connect to that 3" header individually. I got that clearly. Now, what about the size of the mains? Are 2" mains OK?

Also, this boiler has a second 2" steam outlet. i looked briefly at the manual which I found on Burnham's website (assuming I was looking at the right one), and it showed the second steam outlet as being "optional." So, KC, are you saying I should use that optional connection for the second riser? Which would mean that I would have three 2" connections to the 3" header: two 2" risers out of the boiler; and the third one from the Hoffman loop.