Low Water in Boiler - Wet Steam Likely

joshpjost

Been long time reader, first time post. Before I get into my question, here's my setup. Utica PEG150CIDE steamer, one-pipe system installed in 2006. NBP is actually quite good (except for insulation). Never had problems heating house or with water hammer. Main vents are adequate, could certainly use a Big Mouth, but I have measured the time it takes steam to reach the vents with and without them installed and its nearly the same, so I think I'm good there. LWCO probe type. No auto feeder. Boiler has never build any pressure during normal burns (got a 0-3 psi gauge on there). One time I ever saw it build pressure was during storm last year and it was running for a good hour, still only .5 psi max.





I have noticed water slow to return to boiler. Most times, boiler shuts off after 15-20 minutes because LWCO trips. Last year I had our friend Ryan at New England SteamWorks out for maintenance and he disassembled the wet return (which is all above ground by the way) and found some sludge. He added spigots at each 90 for flushing. Didn't really have too many LWCO occurrences. I did however notice water level surging so I skimmed 4-5 times. Still notice a lot of water "spilling" into the sight glass so I installed a ball valve on the lower portion of my sight glass to check for wet steam. 9/10 times when its steaming and I close lower sight glass valve and open ball valve, I get a slow trickle of water. Never added any additives to boiler water. Always flush with utility pump once a year in fall. Just flushed now and wet returns are clean, no blockage.

I'm thinking wet steam is the culprit. Water level generally is pretty stable when its steaming, bounces the normal +/- 1/2". As you can see in pictures, I don't have it over filled, its right in middle of sight glass. Boiler won't run more than 20 minutes without LWCO now. Soon as it trips, water returns back to normal level within 5/10 minutes.

I know that this boiler with the side tappings are nobodies best friend, especially steam's. Anyone got any ideas?

joshpjost

She just fired up and soon as steam is produced, water level surges a good 1" in sight glass. This time, no LWCO, stat turned it off. As soon as boiler shuts down, water level drops more.

Jamie Hall

Can you get Ryan back? You should get him back to clean and adjust the boiler and burner anyway, if you haven't...

nicholas bonham-carter

Let’s see a picture of the main vent, as I think the culprit could be a residual vacuum holding the water up in the dry returns. Maybe your main vent is not opening soon enough at the end of the burn.—NBC

joshpjost

Here are the main vents. I only have one main. Only had the VentRite No. 35 on there for the longest time until I got smart and added more.

nicholas bonham-carter

How long is your main, plus dry return?
Do you ever see the gauge needle moving below positive pressure, at the end of the burn?--NBC

joshpjost

Estimated 75' main and dry return. Most of main is 2", last 30 feet reduces to 1 1/4 copper. Pressure gauge needle always rests on the stop.

gfrbrookline

You are still way under vented with those G1's. If you have 75' of main and return you need at least I Big Mouth or 2 G2's plus 1 or 2 of your G1's to properly vent your system.

EBEBRATT-Ed

I agree with @Nicholas Bonham-Carter that it could be vacuum in the system hanging up the condensate. Maybe at the end of the dry return install a good quality Y pattern check valve on a tee near your air vents. Check valve must be level 1/2" ips is ok. Or you can buy a steam vacuum breaker. This will let air in if you system goes into a vacuum

Fred

Do you have any pitch on that return and on that vent antler? They look pretty level and it may be that the return condensate does flow as quickly as it could with a near level return.

joshpjost

NBC/Fred, believe you guys might have helped me here. I added a support on the return line which looked like it needed pitch, and last two burns have been turned off by tstat. I am still noticing the water level dropping more after boiler shuts off. This trips the LWCO. I’ll try to get on Ryan’s long list of low priority jobs and see when he can come consult.

I can hear the main vents hiss considerably as soon as boiler turns off.

Fred

One other thing I'm noticing. That Hartford Loop looks to be well above the boiler water line. If so, that may be letting pressure push water away from returning to the boiler. When was the last time the pigtail that the Pressuretrol is mounted on, was cleaned out? If it is clogged, the boiler pressure may be higher than you think, adding to the problem and maybe why the main vents are noisy at the end of the heating cycle, sucking air back in.

joshpjost

I replaced the pigtail last year which was in fact completely clogged. Haven’t taken it out this year yet but will check soon.

Fred

What about that Hartford loop? Is it above the boiler water line?

joshpjost

Just measured and It’s 2” below the waterline which is in the center of the sight glass.

Fred

joshpjost said:

Just measured and It’s 2” below the waterline which is in the center of the sight glass.

That's good then.

EBEBRATT-Ed

@joshpjost,

Let me have your ear for a moment. You have a few decent clues the way I am looking at it.

1. slow condensate return...could be a vacuum issue
2. Noticeable hissing steam vents on shut down... air trying to get in to break the vacuum
3. Water level drop and trips LWCO on shut down.....When the burner shuts down the steam in the boiler and piping condenses and pulls the system into a vacuum. The reduction in volume of changing steam to water is a reduction in volume of 1700. The rapid drop in pressure from a positive steam pressure to a vacuum causes some of the water in the boiler to instantly change to steam as the pressure drops and this steam quickly causes water in the boiler to evaporate lowering the water level.

Could it be another problem? Yes But to me it points to vacuum

joshpjost

Makes sense to me. Barnes & Jones vacuum breaker right next to the main vents?

joshpjost

EBEBRATT-Ed said:

@joshpjost,

Let me have your ear for a moment. You have a few decent clues the way I am looking at it.

1. slow condensate return...could be a vacuum issue
2. Noticeable hissing steam vents on shut down... air trying to get in to break the vacuum
3. Water level drop and trips LWCO on shut down.....When the burner shuts down the steam in the boiler and piping condenses and pulls the system into a vacuum. The reduction in volume of changing steam to water is a reduction in volume of 1700. The rapid drop in pressure from a positive steam pressure to a vacuum causes some of the water in the boiler to instantly change to steam as the pressure drops and this steam quickly causes water in the boiler to evaporate lowering the water level.

Could it be another problem? Yes But to me it points to vacuum

I put a ball valve at the end of the main vent antler and opened it right as the tstat shut her down. No change to water in sight glass, still dropped after shutdown and triggered the LWCO, not that it matters. I still plan to put a check valve there on the antler just in case there is a vacuum condition.

Could the surging I notice once it starts steaming be the rise in water level with the nucleation of water vapor bubbles? This would also explain the water level decrease when the boiler shuts off. I've skimmed twice already this year just to confirm no oil in the water.

Fred

How did you skim and for how long? The skim has to be very, very slow and can take several hours. Surging, low water, water droplets on the top portion of the sight glass are all indications that a skim is needed. Did you skim after the antler or any other piping work was done? Even the little new piping for that antler will put oils back into the water.

JUGHNE

You could try the vacuum breaker or equal measures at the boiler itself. See if that does anything different. I tried a vac bkr at the boiler but it takes a high level of vac to pull it open.

It is a long ways from the air vents back to the boiler gauge.