Multiple Radiator Air Vents Hissing/Sputtering and Spraying Steam after Insulating

scottroberts3

Hello everyone,
I've been lurking on the forum for a couple of months but finally needed to make a post in hopes of troubleshooting this new issue.

Steam Boiler: SlantFin GXH275
One Pipe Steam

Background: Recently purchased a home and inherited a steam heating system (no prior experience with steam, but learning all I can) I've read Dan's "We got Steam Heat" and just started working my way through The Lost Art of Steam Heating.

In October, after moving in, I flushed the system, cleaned the sight glass, blew out the pigtail, and tested the low water cut off/auto feed. Everything in working condition, though the water was extremely dirty and I doubt the previous owner ever did any maintenance. Filled her back up and turned her on for the heating season. Keep my thermostat at 69 degrees at all times. Everything worked great, besides a couple of minor hissing noises from a couple radiators.

Fast forward to this past week, the arctic winds blew in and the boiler has been working overtime. The more I learn about steam heat, I realized that insulation on the mains and near-boiler piping is very important. In the photo you can see no insulation, however last week I went ahead and insulated the riser and header up to the main take-off. That's when I noticed issues with the radiator air vents.

Ever since I insulated the near-boiler piping, and this arctic air moved in, a majority of the radiator air vents in my house (5 on first floor and 4 on second floor) began hissing like crazy and spewing steam! Very loud! (Most of the radiators have Hoffman adjustable air vents) I understand that this is due to the vents being stuck open and not closing properly when steam hits them. But what has caused them to all get stuck open at one time? High pressure? Dirty water? This has been causing water loss of about half a gallon per day and triggering the LWCO, leading to feeding fresh water. Yikes... I have pulled a few vents off and cleaned them, soaked in vinegar and readjusted, they still spew a ton of steam.

During a heat cycle, it appears that the boiler maintains pressure between 0.5 and 1 PSI, though towards the end of the cycle, it jump to 2 PSI and the pressuretrol triggers the boiler to shut down. Since the thermostat is still sending a signal to the boiler to run, when the pressure falls back down the boiler then kicks back on and runs until either:
A.) Pressuretrol triggers another shutdown, or B.) the thermostat is satisfied.

• Now with my limited knowledge, my first thought was bad air vents! But for all of them to go out at the same time, when they were all working fine the week before?
  

• My second thought was, bad main vent? Do I not have enough venting on the mains? (Currently my main goes into two branches and there is only one main vent located at the end of the first branch right before the wet return drip, see attached photo)
  

• And my third thought was, too much pressure! But why?? My Pressuretrol is set to .5 PSI and 1 on the differential wheel. Always has been, nothing changed. I even removed the pigtail again and ensured it was clear.
  

The only two things that changed since everything was working fine are, the installation of the insulation on the near-boiler piping and this arctic weather.

So I'd really like to get things back to normal and get the air vents from loudly spewing steam. (I can't sleep!) My questions are this:

1. Did insulating the near-boiler piping some how have an effect on boiler pressure?
2. Is there a need for a second main vent?
3. Does the gas heat on the boiler need to be adjusted (is it over sized or firing too hot now that pipes are insulated?)
4. What would you do??


Thanks for reading and any advice would be appreciated. Thank you all!

(and yes I know the pressure gauge is crap, installing a low pressure 0-3 today!)

ethicalpaul

1. No
2. You probably need two main vents, that pictured one is crusty and had low capacity even when new
3. No adjustment is needed due to the insulation, I can't speak to if adjustment is otherwise needed
4. See what pressure the boiler is really running at, verify the pigtail is clear. Make sure the pressuretrol is set for the lowest pressure it can reliably be set to

Tezak

I’m having a similar experience during this cold snap (Chicago). It’s happening mostly at the end of the longer cycles needed during this weather, especially if I use any amount of setback. Only happening with my adjustable vent-rite #1s. My Maid-O-Mist vents aren’t hissing and seem to be functioning fine.

My pressure settings are the same as yours. Current fixes I’m thinking of: increase my main venting (although it’s not bad), get a vaporstat to run at even lower pressures, swap out the vent-rites, just wait out the cold snap lol. 

Good luck, from another new steam system owner.

scottroberts3

ethicalpaul said:

1. No
2. You probably need two main vents, that pictured one is crusty and had low capacity even when new
3. No adjustment is needed due to the insulation, I can't speak to if adjustment is otherwise needed
4. See what pressure the boiler is really running at, verify the pigtail is clear. Make sure the pressuretrol is set for the lowest pressure it can reliably be set to

Do you have a good recommendation for a replacement main vent, and where to purchase? I think I will start there.

dabrakeman

OP: Check your thermostat settings . Sometimes in extreme cold weather you might need to reduce the swing temperature setting or depending upon thermostat increase the cycles per minute.


OF course it helps to not have oversized boiler and good working main venting.

ethicalpaul

Yeah the real cause of both of your issues is probably oversized boilers. But by managing your maximum pressure, you can do OK. Setbacks (returning from them) will exacerbate these issues.

By insulating your pipes in the basement, you have effectively made your boiler more oversized (by slightly reducing the available radiation of your system).

Did you say how long and what pipe size your mains were?

I like the Maid O Mist or Gorton #1 (these are functionally equivalent), or the Gorton #2 if you have a lot of volume in your main pipes.

BobC

If you decide a new main vent is needed it has to move, Once you get the old Hoffman out (not the easiest job) use a short nipple and then a elbow pointing back along the main. A 10-12" nipple (longer would be fine) and then an elbow that you can put that new vent on. Make sure that final elbow points to a void between floor joists and make sure this new pipe has slope so water finds it's way back to the boiler and does not puddle up

Bob

KC_Jones

The OP has a boiler rated for 706 sq ft of radiation connected to 9 radiators. I don't know your actual system EDR, but unless every radiator is the size of a Mack truck, that boiler is ridiculously oversized.

Going to need some aggressive main venting, and I would even suggest the fastest radiator vents that still allow for balance. That may allow you to tame that beast, the ultimate solution is to put in a properly sized boiler when that one fails.

scottroberts3

ethicalpaul said:

Did you say how long and what pipe size your mains were?

Both mains run approx 45' with 2.5" pipes coming off 3" header/main intake from the boiler.
There is about a 15' section on one of the mains that has no insulation and I ordered some owens corning 1" fiberglass to remedy that, should have that installed by next week.

ethicalpaul

Are those the nominal pipe sizes (like you'd order from a supplier) or is that what you measured?

Either way I'd start with a Gorton #2 on each.

And to follow what @KC_Jones said, you should calculate the EDR (sq feet of radiation) of your radiators in total so you can have an idea of how oversized your boiler might be. There are many threads about that on this forum that you can search

scottroberts3

KC_Jones said:

The OP has a boiler rated for 706 sq ft of radiation connected to 9 radiators. I don't know your actual system EDR, but unless every radiator is the size of a Mack truck, that boiler is ridiculously oversized.

Going to need some aggressive main venting, and I would even suggest the fastest radiator vents that still allow for balance. That may allow you to tame that beast, the ultimate solution is to put in a properly sized boiler when that one fails.

Thanks for the insight!
I have 18 total radiators, (1 in basement, 9 on first floor, 6 on second floor and 2 on third floor). 9 of them just happen to be hissing/have steam coming out of the vents very loudly (5 on first floor and 4 on second floor).

ethicalpaul

And to say it again so that it really sinks in, no matter how oversized a boiler is, no steam system should have any vents hissing. It indicates too high of pressure (See my #4 answer above). Your pressure control device should shut off the boiler if it sees any significant pressure that would cause hissing (like 1.5 psi maximum--but even 1.5 is ridiculously high pressure for any residential system)

And no vent anywhere on your system should ever let steam out. If it does, it's broken and needs to be replaced immediately.

scottroberts3

Just an update on this. I do believe this was a venting issue / bad air vents and maybe a mix of dirty boiler water.
Actions I took:

1. I replaced 6 of the radiator vents (w/ 3x 1A adjustable vents and 3x #40s). I also removed the hoffman main vent, hit it with a brush to clean it off and soaked in boiling vinegar for 30 min, gave it a real good clean and rinse.
   
2. I also ran some 8-way through the system and let her run over the last week, drained and flushed, repeat, drained and flushed. (lots of sediment came out).
   
3. I ensured every radiator in the house was pitched correctly (used these nifty things from amazon and found they were the perfect height (https://a.co/d/7KwvXKG)
   

I noticed I was still losing some water somewhere, but not nearly as much. I then discovered a few leaking radiator valves, and repacked with graphite. Fixed.

I now have a completely silent system. Pressure is steady at 4 oz, and has not gone above 1/2 PSI during a heating cycle. Sight glass level is steady when boiler is firing, and all radiators get hot. The house has been heating perfectly ever since. I also ordered a new main vent (I noticed that it doesn't close properly and lets out a little bit of steam, but with a slight bang of a wrench, it usually finds its seat) and will be installing that this week. Thanks for all the input from everyone. Cheers to hopefully lower gas bills!

ethicalpaul

Nice. If you got the water nice and clean put a little 8-way in there to get the ph up to 10-11 and your boiler will generate far less rust/mud.