Short cycling steam boiler with water level that rises ~3 inches during heating cycle

jlt83

I have a Weil-McLain EGH-95 (1,000 sq ft of steam) connected to convectors and radiators with about 1,500 of EDR. Last season the system worked fine -- cut off (high pressure) is about 12 oz.

Over the Summer I replaced the condensate take feed pump (and flushed the feed tank).

Now the system is short cycling -- in a very strange way. The system starts cold at the correct water level. As the water heats and starts to boil, the water level rises ~3 inches and the pressure rapidly reaches 12 oz (and the pressuretrol shuts the burners off). The water level then falls ~3 inches (or more) and then the burners restart. The (short) cycle continues. Eventually the water level falls enough at shutoff to prompt the feed tank pump to add condensate.

What is / could be going on here??

neilc

pictures ?
of the sightglass attached to the boiler?
is the top valve open? not blocked?
is the top gasket leaking?
is the bottom valve blocking up, needs cleaning?
and you're getting carry over from the pipe and tank work this summer?
did you skim ?
is it a steady or bouncy 3 inches ?

Mad Dog_2

Dirty . MAD DOG 🐕 

EBEBRATT-Ed

Does you boiler have a control like a MM 3150 that controls the feed pumps (boiler feed tank) or does a float in the tank operate the pump (condensation tank)?

Do you have a hartford loop at the correct height? Do you have check valves between the feed tank and the boiler that could be hanging up? Water could be traveling back and forth between the boiler and the tank if you have bad check valves. You are supposed to have 2 check valves one at the pump discharge and one where the water enters the boiler.

next time you start the boiler valve off the boiler feed pump (you should have a valve between the pump and the boiler) and make sure the pump is shut off electrically. Run the boiler and see if the water line stays steady and gradually goes down as it steams.

Don't run the boiler out of water just do this as a test

jlt83

Thank you for all the ideas. The link shows a video of the waterline starting just after the burners restarted and ending just after the burners shutdown due to pressure.

https://share.icloud.com/photos/0ccZnJ2GBh61Tq5NxBpzRqEmQ

To answer other questions asked: Water is feed into the boiler from a condensate tank controlled by McDonnell & Miller float switch. The pump does not run (most of the time) while short cycling (until enough water has steamed). I did close the isolation valve between the boiler and the feed tank -- no change.

From the comments it seems like I need to skim the boiler. Is there a good link and/or how to? (Do I get the water in the boiler hot, but not steaming, and then open the highest drain valve I have (which is about 1 inch above the normal waterline)?)

Dan_NJ

My Peerless 63-04 used to have an apparent water level rise in the glass as the boil was heating up, and before it started really steaming. It was a good 1/2 inch or so of apparent water level rise in the glass, maybe a bit more that I always attributed that to the volume of the water vapor being created in the boiler and not yet flowing out to the system. Once the full boil was underway and steaming along that water level would go down, and continue going down an inch or so as steam went out through the mains. Wondering how much if any of this rise you are seeing is expected? the 63-04 was 147 MBH and about 11 gallon capacity.

EBEBRATT-Ed

@jlt83

I have my own method which is @DanHolohan method using TSP. Some don't like that method but it works every time.

I have attached the manual for your boiler you can follow the Weil McLain instructions

jlt83

All thank you. I did skim the boiler for 2 hours this evening and this reduced the problem by 80% (I will skim again tomorrow evening). As of now the boiler is no longer short cycling. Thank you.

BobC

If the water still has oils in it, the problem will come back. Just keep skimming it every few days or follow Ed's advice above.

Bob

pedmec

TSP works the best.

STEAM DOCTOR

The wand. I am a fully converted believer. 

EBEBRATT-Ed

All the ones I skimmed I would run the boiler 5-7 days as is before skimming. They I would do it once with TSP using Dans method and that fixed it every time