Water level problems

Paul S_3

Hey everyone, hope all is well.

We replaced a steam boiler last year, and I’m looking for some guidance on a recurring low-water issue. The original boiler was oversized by approximately 80 square feet EDR. The replacement is closely matched to the connected load of 938 square feet EDR, possibly slightly undersized. All the basement steam piping is insulated, and the system heats the home extremely well.

After approximately 20–30 minutes of continuous firing, the water level drops enough to trip the low-water cutoff. The default VXT feeder’s time delay allows the condensate to return before it adds water. After about five minutes, the water level recovers and the boiler resumes firing. The boiler heats the home extremely well even though it trips on low water.

I’ve skimmed the boiler multiple times and also cleaned it with a wand, but the issue persists. The wet returns were replaced approximately four years ago. I’m starting to wonder whether the replacement boiler needs a reservoir tank to provide additional water volume while waiting for condensate to return.

Some background on the system and installation

Two-pipe vapor system originally equipped with Haines Vento radiator traps and graduated radiator supply valves.

Radiators on the first and second floors. All radiator traps were replaced when the wet returns were replaced a few years ago.

Six ducted indirect heaters in the basement also serve the first floor. These sit approximately 2–3 feet above the boiler’s normal waterline.

Each indirect has a steam supply and an untrapped condensate drip into the wet return. The indirects are vented through crossover traps connected to a dry return above the heaters.

Vaporstat set to 10 ounces. The 0–3 psi gauge rarely shows any pressure.

Boiler piped with a 4-inch drop header.

Boiler water pH approximately 7.

How do i determine whether the boiler needs a reservoir tank or whether additional skimming and cleaning are necessary? Could the indirect heaters’ piping arrangement contribute to delayed condensate return?

Thanks for any guidance.

Paul

JohnNY

You may already know this but problems that require some significant run time in the cycle to show up are generally pressure related or there is an oversizing issue that overwhelms the system as vents start to close. You seem confident in your EDR numbers though. An expensive way to (probably) fix this is to install a second vaporstat and a step-fired gas valve (it's probably already there in a boiler at that output) to create a 2-stage burner. Another quick experiment might be to plug off the two outer burner tubes and see how that affects system behavior.

109A_5

Does the water just slowly steam away or is the water line violent? Maybe this will give you some help.

JohnNY

Has anyone ever successfully created that reservoir pipe that Weil-McLain has so casually included in their EG(H) piping diagrams for decades?

109A_5

https://forum.heatinghelp.com/discussion/comment/1908908#Comment_1908908

There has been at least one post with a pipe type reservoir with welded on end-caps, not sure if it is actually pipe or some sort of steel tubing and I believe it was added to a peerless boiler.

Paul S_3

@109A_5 it looks like it slowly steams away but the boiler is very wide. I hear the pressure controls shaking when I listen closely.

109A_5

@JohnNY, @JUGHNE posted this in another thread.

STEAM DOCTOR

Why not just leave things the way that they are? Building is heating properly. You effectively have a variation of the hydro level cycle guard

STEAM DOCTOR

Did you check the gas pressure? Very often, the gas controls themselves are not set properly. Maybe it's over firing?

Paul S_3

@STEAM DOCTOR customer understands short cycling and system wear and we just installed it not even a year ago. I never caught this after we originally installed it. And I feel if i used a different water feeder like the McDonnell Miller. I would've got a flooded boiler service call because of the default time delay

109A_5

Assuming the old boiler did not have the same issue I wonder if the water capacity was similar between the old and the new boilers.

Paul S_3

@109A_5 the old boiler was a Utica about 25 years old. It was a lot taller than the weil mclain egh 105 that's there now but no where as wide