New air vents leaking

GregM

Hi folks -



I can't tell you how many times this board has helped me fine-tune my heating in the various places I've lived over the last decade, so first off, thank you!



First, some back story:  I just moved into a new place this fall, and have a one pipe steam system that had been sorely neglected.  I believe the piping is the "circuit" configuration, with a mix of 100 year old and 10 year old radiators from an addition.  The boiler is a 10 year old Weil-McLain with a Honeywell pressuretrol piped into the top of the low water cutoff (McDonnell & Miller series 67.)  The main circuit appears properly insulated and is around 40 feet in length.  It has a single Hoffman 75 vent furthest from the boiler above where the circuit drops back to the floor to re-enter the boiler.



I had a local heating company come out and clean the unit in September.  Unfortunately when the guy cleaned the pigtail he didn't notice that the right angle connecting the pigtail to the low water cutoff was completely corroded shut.  At the time of this service I lowered the pressure on the pressuretrol to 1.5 PSI with a subtractive 1 PSI differential.  Of course since the line was corroded shut this had no effect... 



I then proceeded to replace a half dozen radiator air vents with new Hoffman 1As as the old ones were damaged or showed signs of leaking.



Fast forward to December when the heating season really started to ramp up here in Michigan, and I noticed the boiler was continuing to fire even after all the rads had steam.  Investigating I found the clogged pipe beneath the pigtail.  I then replaced all the piping coming out of the low water cutoff with a new pigtail, a proper vaporstat (Honeywell L408J1017) and a 0 - 3 psi pressure gauge.  Vaporstat is set to break at .75 PSI and make at .25PSI.



The firing cycle seems reasonable to my untrained eye - it takes around 30 minutes for the radiators to fill with steam, during which time the pressure gauge reads 0.1 PSI or less.  Then as the radiators' air vents (those Hoffman 1As) click closed the pressure rises rapidly to 0.5 PSI or so.  However, before I get to the vaporstat cutout several of the 1As begin (I think) to break open and leak steam.  So my question is, have I destroyed the new air vents I put on by running the system without a working pressure cutout and thus need to replace them?  Or should I lower the vaporstat cutout to something less than 0.75 PSI?  At 0.5 PSI cutout the system starts to pull a vacuum within 20 - 30 seconds, which isn't enough time for the boiler to cycle back on again.



I can post pictures of anything if it's helpful.



Thanks!

Greg

Dave in QCA

Leak Steam means?

When you say the the 1A vents click back open and leak steam...   do that again click and go closed?  It is normal for them to open and close after the radiators are filled with steam.  Your steam pressure is very low and seems reasonable. 

Zarbal

Property manager

I have a steam radiator vent leaking water, I have changed the steam relieve vent and tilted the radiator towards the steam inlet return still it leaks can you please tell me what is causing that and what else should I do

Zarbal

Property manager

I have a steam radiator vent leaking water, I have changed the steam relieve vent and tilted the radiator towards the steam inlet return still it leaks can you please tell me what is causing that and what else should I do

BobC

Try a couple of new vents

Depending on how high and for how long that pressuretrol was offline because of the clog you might have damaged the vents on some radiators. I'd try replacing one or two and see if that solves the problem.



Lowering the cutout below 0.75PSI is not going to help those vents, they are rated up to 3PSI.



Error!  I just checked a new one i have downstairs and they are rated up to 10PSI according to the info sheet that comes with them. Do you know if your pressure ever got up that high?



For what it's worth the VentRite #1's are a better air valve but not very common.



Bob

GregM

Re: Leak Steam means?

I hear them click closed (the sound is loud and unmistakable!)  Then after a minute or two I hear them begin to gurgle/hiss and steam starts to leak out - I can see it if I look very carefully or just barely feel it if I put my hand near the vent.  I do not hear them click back open again at all.  Some of the vents in the house do cycle open and closed, but the ones I'm having trouble with do not seem to.

GregM

Re: Try a couple of new vents

Bob - I can't say for sure how high the pressure got.  The pressuretrol likely spent more than one heating season clogged shut, but the new 1As have only been on for a few months.  It certainly seems possible to have hit 3+ PSI during that time though.  10+ seems less likely but maybe?  I think the main vent is rated for 15 PSI so it makes sense that the rad vents would fail first.  I'll try swapping out one or two vents like you suggest and will report back.  Thanks!

nicholas bonham-carter

vents leaking

i would guess that it is the main venting which needs some improvement. the hoffman 75 is much less capacity than our favorite gorton #2, and so i would put one of those along side the hoffman. you could then reduce the settings on you vaporstat to cut in at 3 ounces, and cut out about 12 ounces.

the hoffman radiator valves are pretty tough, and well made. they may not function well above 3 psi, but in my experience are not permanently damaged.--nbc

GregM

Update

Just wanted to post an update - after replacing the leaking air vents, repitching one radiator, and doubling the main venting I've got things working much better.  On really cold nights the system runs for half an hour before cycling on pressure, and the pressure drop after the boiler cuts off is around 0.5 PSI / minute by my watch, much slower than it was.  The main is filling in around 60 seconds now too, vs. a couple of minutes before.



Two things to note: when I replaced the leaking vents most of them were Hoffman 1As, and were set to 5 or 6.  I think this violated the "vent the mains quick and the rads slow" mantra, and was causing a lot of water/spitting in the air vents that might have contributed to their inability to close.  I have most of them set now to between 2 and 4, with one huge rad out on a long run at 5.  The system seems much quieter and happier.



Second, after fixing all the leaking vents I've discovered a radiator with a leaking section (rats.)  That'll be another post though...



Thanks for the help!

Abracadabra

don't hijack someone else's post

please start a new thread with your question.  Don't ask it in somone else's post.











Thanks!