Two "Chuffing" steam vents in one-pipe system

jch1

I apologize in advance for the long post, but I'm going to try laying out all the information at the beginning.

As some have seen over the years, I have a Peerless boiler that was installed in 2014. The near-boiler piping is correct (though no drop headers were added), and the system is certainly adequately vented. I have three Big Mouth vents and four Gorton #2s on a tee. Perhaps it's overly vented, but that's a discussion for another day. Here are details of my radiators:
- 1st floor: five radiators with different Gorton vents. Specifically, one rad, which is near the end of my main pipe loop, currently has a Gorton #6 on it. The others have G4s or G5s.
- 2nd floor: five radiators, two of which are in our main bedroom and are attached to TRVs. These radiators are either near the end of the main line loop, or they are fed by a pipe that exits the main loop almost immediately and simply goes up through the wall. One of the main bedroom vents has a Gorton #4, the other has a Gorton #5.

Prior to this morning, the last time my heat kicked on was 8am yesterday. I have the heat currently set at 70 over night, and 72 during the day. This morning, when the heat kicked on, I was awoken by "chuffing" from the radiator vent having the G5 on it. I assumed this is just air leaving the pipes as steam is being generated, but I went into the basement to explore the system. The bedroom radiator with the G5 was beginning to heat up, but the one having a G4 was still cold (and silent). This is when I also realized the first floor radiator (having a G6 on it) was also making this chuffing sound and beginning to heat up. When I went to feel the main return to see how far the steam had progressed, the pipes leading to the main vent tree were still cold to the touch.

With all that, I think the solution here is to just drop down to a smaller vent on those two radiators, but could I have another problem that's causing steam to make it to the radiators before even reaching the main vents?

nicholas bonham-carter

The main vents should close before the radiator vents.
You may have a sagging pipe trapping water, impeding the air, which must be pushed out before the steam can rise into the pipes.
Are the pipes insulated? If not, then you can more easily use a level to make sure there is a constant slope towards the main vents.--NBC

jch1

Thanks for the reply. The pipes in the unfinished half of the basement are insulated, but are not insulated in the finished half. I'll check the levels of the pipes. Also, I should mention that all the radiators are pretty aggressively angled so the vent side is higher than the valve side.

jch1

From what I can tell using the level, there is n fact a constant slope towards the main vents.

I have a follow-up question. You mentioned the main vents should close before the radiator vents, but is it normal for the radiators to begin heating up before the main vents close? I'm envisioning a scenario where steam progresses to the radiators while also progressing to the main vents, but just so happens to reach the radiators first. Maybe this should never happen, and it means I need to reduce venting at the radiators?

ethicalpaul

My theory:

On a cold startup you are going to get a lot of steam collapsing (condensing) as it heats up the main from cold. It advances a bit, pushing the air, then immediately condenses when it hits the cold steel, causing a partial vacuum that reverses the air flow back toward the boiler. These repeated pressure changes in the main (and really in all your pipes) are going to push and pull the air around in your system.

Hopefully most of that "chuffing" (a great word and I know exactly what you are talking about) happens at the main vents, and with your amount of main venting, I would think most of it would happen there.

But you can't prevent those pressure waves from making their way really to every radiator.

Insulating your mains will minimize it during the heating season, but I don't know what you can do to prevent this during a cold startup.

I think your radiators' slopes are unrelated to this phenomenon.

jch1

@ethicalpaul That was my exact theory as well, and I specifically didn't suggest it to see if someone else would. I told my wife this morning that I'd expect that not to happen when it's consistently cold and the heat is on more often.

You described what I could essentially hear happening. I'd hear two or three "puffs" of air escaping the vent, then silence for a few seconds, and it would repeat. Eventually, the entire length of the radiator was warm, the vent closed, and the sound stopped. And yes, I did hear a similar sound at the main vents, though I'll note that the Big Mouth vents appear to take more time to close than the G2s, despite those vents being "first" on my vent tree.

Sounds like I'll need to just live with it for a bit, try changing the vents, and possibly delaying when I turn up the heat until a bit later in the morning when I'm actually awake.

ethicalpaul

To come back to something that @nicholas bonham-carter said, though... do double check your pipe slopes to make sure that the steam can freely flow everywhere.

It is a little strange that one or more of your radiators is getting hot before the main vents close, but steam goes where it wants to. I think slowing down some of the fast radiators might be something to try, one at a time.

I wasn't happy with my Big Mouth vent, and I took it out of service.

Jamie Hall

I'm thinking that somewhere on that main that isn't heating up there is a low spot. Maybe not much of a one... that sort of chuffing is, as @ethicalpaul suggested, often the result of hitting a pool of water. But on another topic -- don't be surprised if a radiator heats, or rather starts to heat, before some of the main does, if its a shorter distance -- and particularly if most of its route is insulated, but the more distant main isn't.

jch1

I've taken my level to all accessible sections of the main line, and it does appear to be properly angled and free of low spots. I'm going to plan on slowing down some of the radiators via differently-sized gorton vents, and see what happens when the temperature drops enough for my system to still be warm when it restarts.

As always, many thanks for the helpful info!

JUGHNE

You could try smoke or a flame on the chuffing vents to see if, while doing their thing, the vent is inhaling air and then exhaling.

Fred

You've got some large vents on those radiators. Steam is going to take the path of least resistance and that may be some of those run-outs to the radiators (especially those closer to the boiler), even though you also have a lot of Main Venting, the mains are larger than the radiator run-outs, which also means there's more iron to heat, heading to the main vents. In reality, this probably isn't the best time of the year to try and balance a steam system. We are in the "shoulder" season and the boiler run time simply may not be long enough to allow the entire system to heat and stay relatively warm between cycles. I wouldn't try to balance a system until I got to what is a more normal heating season.
The other comment I would have is: A sag in a pipe is not limited to the areas of the pipe that you can easily see or that is easily accessible.
Also check the pitch of the radiators. Any that are level or pitched the wrong way will hold some water and may also cause "chuffing" at those radiators.

jch1

Thanks, @Fred - all my radiators are pitched (in some cases, aggressively) towards the valve, so I don't think the radiators are holding water. Also, I actually raised both ends up with hopes of eliminating any sags in the piping near the radiator.

ChrisJ

Just curious, what does the water in the gauge glass look like?  Is it nice and clean?

jch1

Good question, and one I hadn't considered. I haven't done a flush or skim in a while, and haven't yet this season, but I'd say this looks pretty good (1 or 2 steamaster tablets). 

ChrisJ

jch1 said:

Good question, and one I hadn't considered. I haven't done a flush or skim in a while, and haven't yet this season, but I'd say this looks pretty good (1 or 2 steamaster tablets). 

Doesn't look like a problem.  Just be warned the color of steamaster fades over time but it's effect doesn't. Meaning don't add more without draining and refilling with fresh water first.

jch1

I didn't realize that, thanks! 

neilc

let's take another look at that sight glass,
that little scum line up about a half inch, looks, scummy, oily(?),
and do we see a drip running down from the top?
Do you have? and it might be worth your time skimming, and again,

motoguy128

I’ve found on my boiler the “chuffing” only occurs in the big mouth main vents and it’s from water shouting up into the header which momentarily slows the steam flow and causes a slight vacuum to form for a moment while a slight in pressure Inside the boiler itself.

I agree that skimming would probably help.

motoguy128

I find that a #5 size I only use on radiators fed with 1-1/2” pipe, a Hoffman 40 equivalent (a Gorton 4.5 if you will) for those on 1-1/4” and smaller radiators get a #4. I find the pipe size feeding it will somewhat balance the venting rate as well. Meaning a radiator on a 1-1/2” pipe will vent faster than one with a 1-1/4” even though they both have a #4 vent.

jch1

Thanks, guys. I will skim in the next few weeks. I think I took my Hoffman 40s and 1as off because they clicked too much for my liking. I just want super silent vents, especially in the bedrooms. 

ChrisJ

My system breaths in and out as the steam goes down the mains.    It's not loud and it's kind of slow sounding.    It's never caused ann issue and in my case is from the steam condensing and pulling more steam in so it " inch worms" down the pipe.

jch1

Just wanted to update everyone who is interested - I've been skimming the boiler now for about two hours, and I'm about to finish up, but I had one question. I will obviously drain the excess water from the drain pipe, but would it be prudent to completely drain and refill (and perhaps pop in one steamaster tablet)? 

jch1

Well, the skimming went fine, but I guess the bottom of the boiler is filled with gunk because when I went to drain it down to the fill line, nothing happened when I opened the valve. Ugh. Fortunately there's another drain below the sight glass I can use, but I'm slightly disappointed that I may need a new valve. 

Jamie Hall

More likely the valve is gunked up. Try seeing if, when open, you can thread a stiff wire through it -- that sometimes works.

JUGHNE

That lower boiler drain is probably plugged.
You can back flush the drain with a garden hose connected to house water pressure.
A double female connection (washer hose works for that).
With house pressure connected then open the boiler drain a few times to blow out any gunk.
Don't let the boiler water get into the house supply....hard to do as it is pressurized.

Then with the boiler drained you can change the drain valve.
A 3/4" brass nipple connecting a full port ball valve with hose adaptor and cap is good for a long time.

jch1

I overreacted, as usual - I was able to clear the valve by jamming some a stiff brush into the nipple. Cleaned out the pigtail and pressure gauges while I was at it, and will fire it up shortly. Thanks all for the help!