Air vents hiss whenever boiler is working

Abracadabra

heatinghelp819 said:

someone banging on the metal

banging as in tapping with a screwdriver or a fork? (expansion)
or
banging as in a sledgehammer swinging at the pipe? (water hammer)

Sailah

The beauty of the vari vents is that you can tune them according to what your system needs. To replicate what you had, you simply would screw the cap down. I don't have an exact position for you but if you screw the cap clockwise (down) until you hit the bottom, it will essentially be closed. It's not a perfect seal as air can still get past the threads in the cap but it's basically closed. The thermostatic mechanism in the vent will still work normally, independent of the cap, but you've essentially throttled the air capacity of the vent by 99% or so.

Try screwing the cap down a fair bit, say 50%, and see if that changes your situation.

It sounds like increasing the venting has exposed another weakness in your system and that is now showing it's head.

heatinghelp819

I do think it was water hammer (sledgehammer sound) Have only heard it a few times, and have been listening closely for it. Also, the water feeder meter rose another point (first time since the thorough boiler clean by Dave) so maybe there is/was water stuck somewhere. Is it possible that water hammer can resolve on its own after several days, since I didn't hear it at all yesterday?

I also noticed yesterday steam (and water droplets) coming out of the B&J varivent on one of the mains (I have one vent that is sort of up above the ceiling and one that is not; I'm not able to really see the screw cap on the high one, but can see the other). This was while it was huffing and puffing. This shouldn't be happening right?

@Sailah I screwed the cap down a fair bit on one of the vari vents last night. I will observe to see if there is improvement on those rads it feeds. @Fred thank you for clearly isolating the different and perhaps unrelated issues. For the short cycling, I had attributed the short cycling I had experienced after the boiler clean to the setback I had in my thermostat, but I guess it could have also been because of the small main venting I had. I may not be remembering correctly but I think I had changed the thermostat setback around the same time I replaced the main vents. I have to go back and check. I am worried about back pressure if closing the varivents too much and will keep an eye on the short cycling.

Another theory as to why the huffing and puffing had disappeared for a week would be that the boiler clean had temporarily fixed it, but the boiler is somewhat dirty still and needs another clean. Maybe some sludge or dirt came back to the boiler through the wet return after that week of silence?

I can't figure out where there might be a sag in the piping, but I am clearly not the right person for the job. It's not helpful that the vast majority of our piping (aside from the mains) are behind walls. FWIW, Dave also said that he didn't notice anything sagging when he was here for the cleaning, so he doesn't think that's the issue.

Fred

@heatinghelp819 a good boiler cleaning is great but it isn't going to fix an over-sized boiler or that piping configuration at your near boiler. A single 2' riser and a 2" header on that boiler is the source of your radiator vent noise. The reason your radiator vents were silent for the week after cleaning is plain and simple. The main venting was inadequate and slowing the steam down enough that you didn't have the huffing noise. The wet steam, resulting from the velocity of the steam coming out of that boiler needs to be fixed before the radiator vent noise goes away or you may temporarily slow the steam down by minimizing the main venting again, as a temporary fix. As I said earlier, that has its own set of issues.
The things you need to do to fix the problems once and for are include:
- Do a complete and thorough assessment of all the main and run-out piping to make sure there are no sags and/or incorrectly pitched pipes. If you have intermittent hammer, something is likely sagging or pitched wrong, maybe only slightly but it will come back.
- Stop using any setbacks at all. That only adds to the number of short cycles an over-sized boiler goes through.
- Correct the piping at the boiler. A single 2" riser into a 2" header is problematic and needs to be addressed.
- Verify the radiator EDR (Dave indicates that the boiler is well over-sized) and if it is actually well over-sized, have him add a two stage gas valve and do a combustion test on each stage. If the boiler is in good shape, this investment is well worth it.
- If the boiler is old and its condition questionable, consider a replacement , right-sized boiler, properly installed and with properly sized risers (both) and header.
You always have the option of living with what you have until your boiler dies but you must understand that means the system isn't likely to be perfect and you will live with some trade-offs like you are now experiencing.

heatinghelp819

@fred I must have misread your earlier post, as I thought the pipe sizing and size of boiler wouldn't have caused this venting noise problem. I'm not sure we can afford the piping fix right now, as it is very expensive, so we may just have to live with this until we can.

Many thanks to all.

Fred

@heatinghelp819 , My earlier post indicated the noise was not indicative of the hissing typical from the system being over pressured. That was verified when Dave said he calibrated the Pressuretrol and it shuts down at 1.5 PSI. I believe the noise you hear at the radiators is the result of the steam velocity. Unfortunately, that is directly related to the near boiler piping/single riser out of the boiler and the size of that riser and header.

heatinghelp819

@fred do you think the wet steam issue which you talked about is the reason I'm seeing steam and water droplets come out of my B&J varivents, or should that not be happening regardless?

Fred

heatinghelp819 said:

@fred do you think the wet steam issue which you talked about is the reason I'm seeing steam and water droplets come out of my B&J varivents, or should that not be happening regardless?

I think @Sailah from Barnes and Jones can best answer that question but I would think that, if the steam holds enough water, it may well cause the vent to not close completely because it is looking for actual steam temps to close it completely and the water droplets in wet steam may counter those temps. Let's get Sailah's take on that. He designed both the Bigmouth and the Vari-vent and has done extensive testing so he'll know.

LionA29

@heatinghelp819 from my personal experience from my NBP that was not up to specs, it's caused an enormous amount of wet steam all the way up to the 3rd floor. After a complete re-pipe and adequate main venting all of my problems were eliminated. Based upon the feedbacks from all the more experienced HH members on here, I think that's the direction you are pointed towards in addition to Mr.@Fred recommendations.

Sailah

> @Fred said:
> @fred do you think the wet steam issue which you talked about is the reason I'm seeing steam and water droplets come out of my B&J varivents, or should that not be happening regardless?
>
> I think @Sailah from Barnes and Jones can best answer that question but I would think that, if the steam holds enough water, it may well cause the vent to not close completely because it is looking for actual steam temps to close it completely and the water droplets in wet steam may counter those temps. Let's get Sailah's take on that. He designed both the Bigmouth and the Vari-vent and has done extensive testing so he'll know.

You shouldn't be getting steam or water out of the vents. Those vari vents we make exactly the same as the units we install on military sterilizers operating in foreign theaters. I suspect all your symptoms are manifested from this wet steam issue. The banging, water in the vents, is all symptomatic and increasing your venting, which is a good thing, has amplified these issues.

The vents aren't designed to hold back water, by their nature they will try to get rid of it as the water in the vents cools the thermostatic element. If you had dry steam they would be tighter than a snare drum.

I would approach this from fixing that basic issue and I suspect these issues will subside. Or you can do some experimenting with closing the cap to try and slow the venting down. You may be able to increase the venting from what you had originally but may not be able to run them at 100% due to your system not tolerating that increase due to wet steam.

But again I'm just speculating from what I'm reading.

heatinghelp819

@Sailah i will email you

Thanks everyone