Lowered Pressure, but Vents Still Hiss

Frank_63

are fine, as far as I can tell. I have a 50 foot, 2 1/2 inch main for a four story, four unit apt bldg. I've got one Hoffman 75 and three Gorton 1s on it. I've been down there when the boiler has been cycling on, and the vents don't hiss and they are hot. Based on past threads on this board about this problem ((http://forums.invision.net/Thread.cfm?CFApp=2&&Message_ID=431535&_#Message431535), I don't think the main vent is where the problem is.

Frank_63

Narrowing the Problem

I lowered the pressure to 12 oz cut out, and 3 oz cut in, but still have a hissing valve problem. Two of the new Gorton 4 valves that I purchased and installed over the weekend are hissing, and emitting hot air, which I presume is steam. I cleaned out an old valve with vinegar, and a lot of gunk did rinse out of the valve, but that valve still hisses as well.

At the lower pressure setting, I think the boiler is now cycling off because of pressure. Twice during the current cycle, I've heard that sucking sound of air entering the valve when the boiler shuts off, but the t-stat is still calling for heat.

One positive is that installation of the smaller sized valves has reduced my apt overheating problem. So that is a bit of good news.

Michael Wilson

Check the Main Vents in the basement

It sounds like the air isn't getting out of the mains fast enough..

I'd look for the main vents in the basement... see if you have any. If so, check their condition.

If you can't find them or don't have any installed you'll need to add some

Mike

Steve Garson_2

Your boiler might be a bit oversized and generating steam too fast. I had this problem with a new boiler and resolved it by reducing the firing rate by 10%. That did the trick.

Steve

Kool Rod

Reducing Firing Rate

I'm willing to try it, especially if it can be done easily. Can I do this myself, as a layman, or do I need to have a professional do it?

nicholas bonham-carter

hissing vents

remember that a 4-story length of pipe will have some serious vacuum in it at shut-down. it appears that only the vents your apt. have been renewed, so they may be doing all the work of vacuum relief. this may be a case where you have to treat this problem as a whole instead of just in pieces. i suggest putting new high capacity vents on the top floor, and smaller vents on the lower floors.

you have been down around the mains, when it cycles on, but what about when it cycles off? try switching it off when its been up to pressure, and listening for the mains hissing, while checking your low pressure gauge for the needle going over "to the other side" of zero into vacuum.--nbc

Kool Rod

vacuum relief

My most pressing concern at the moment is not hissing when the system shuts down and the air vents suck in air. I'd like to know why the vents are hissing hot air, which I presume is steam.

The top floor has a Gorton D valve on each radiator, and I've got three 4s, one 5, and one 6 on my rads, and all of them hiss regularly. Are you talking about something different than Gorton Ds on the top floor, and 4s or 5s on the lower floor when you are talking about high and low capacity vents?

I will go down into the basement and check the main vents to see if they hiss when the boiler shuts down.

I've since turned the pressure back to 16oz/4oz, since the hissing continued at the lower pressure and the boiler seemed to be cylcing off due to pressure before the t-stat was satisfied, something that I don't think was happening before the pressure was lowered.

nicholas bonham-carter

hissing vents

at your low pressures, fully functioning vents should have no trouble in closing quickly, and completely when steam arrives, no matter how over-fired the boiler may or may not be. all the vent can see is 210 deg steam at 3 oz. then only boiler problem affecting it might be a long run of under-insulated pipe.

one way to tell when steam has arrived is to use a non-contact IR thermometer [which have become so inexpensive lately]. use of this could enable you to check the thermostatic operation of the vents. they probably do not close at 212 deg, but maybe 200. that way the bad eggs could be discovered easily and replaced. there was a description here of piping for vent-testing in the boiler room which could be very useful to have.

as far as vent sizing;write down a list of what vents are in the building on all the radiators. by consulting the "venting...." e-book, you can find the highest capacity group for the top floor, and the next highest capacity group for the 3rd...etc. it would be a very good idea to have all the top floor vents the same at least, even though you may have a different mix on other floors. that would be a good starting point to get all vents doing the same work together. if they all close simultaneously, then there will be no stragglers to hiss their complaints! in addition, they will all begin to heat at same time, which is good for eveness of heat.--nbc

Kool Rod

Maybe I'm Not Understanding Something

I think I'm missing something here. I understand your saying that a fully functioning vent should close quickly upon the arrival of steam. But you also say I should test to see when the vents close, and that maybe they're closing at 200 degree, rather than 212. But if the valve is emitting steam, wouldn't the temp inside the valve be at a degree point where it should be causing the valve to close? Something is stopping it from closing.

I spoke to Ken at Gorton, and he said, from my description of the problem, that it sounded like the steam was wet, and that a valve has trouble closing when the steam is wet. I don't know if that is the cause of my problem or something else.

If my valves are losing steam, I'm losing heat and condensate that should be returning to the boiler. Nobody else in the building is complianing about too little heat or hissing rads, although my neighbor on the top floor said that two of her rads are hissing when I asked if she had any hissing rads. I'm just trying to minimize the loss of heat, and making sure the system is running as smoothly as possible.

Thanks again for your time.

PS: Just did a google search for the non-contact, infrared thermometer. What a neat toy.

Kool Rod

Lowered the Pressure Again

Decided to give a second try to lowering the pressure, down to 12oz/4ozs on Sunday. If today is any measure, the vents seem to hiss less now as compared to the higher pressure setting. The temp has been much milder; I don't know if that makes any difference.

I also think that there is less hissing of steam. I was listening to the rads when the boiler turned on from the evening set back. The largest rad, in my bedroom, started hissing and hissed for a few minutes, then stopped. After that, it would hiss intermittently, hissing for between 20-40 seconds, then stop, be silent for a while, and then hiss for 20-40 seconds. Is this how a valve is supposed to work, as it closes and drops due to temp?

Something, though, is causing some moisture to collect in the valve once the steam hits it. I can hear it and sometimes see it in the form of a tiny drop that will appear right below or in front of the air hole on the valve.

I also did not hear any swoosh of air entering the valve when the boiler turned off in the morning after the setback, like I had been hearing at the higher pressure level.

Kool Rod

No Hissing

My big rad did hiss a little as the steam filled the rad, after the boiler fired from the evening setback, but after that it was quiet. The rads were so quiet that I went into the basement to make sure the boiler was working, and it was. It cycled off while I was down there, but came back on a few seconds later, which I thought was weird. I was in my bedroom when the boiler turned off after the t-stat was satisfied. I did hear air enter a rad to fill the vaccum, but it was a softer sound and lasted a little bit longer, it seemed, than when I had the pressure set higher.

The boiler is also much cleaner now than a few weeks ago. The sight glass is clear when the boiler runs. No more muddy water. I guess that helps too.