Home steam system filling too much

Bob S

My home heating one-pipe steam system has just recently begun over-filling to the point where the sight glass is full. The only recent change to the system was relacing the corroded Hartford Loop. That is, from the junction of the 2 condensate return lines at the ends of the basement loop and the boiler. This includes the lowest section of black pipe burried just below the basement floor level. In addition, the blow-down line of the McDonnell type 67 low water cut-off switch was clogged at the ball valve, so I gently poked through the clog to successfully clear it and allow occasional flushing throughout the heating season. A few days later I noticed the overfill problem beginning to occur.

Speculating that I may have damaged the float in the cut-off, I replaced it(not knowing that the float itself was replacable- Oh well...). It was coated inside with 9 years of sludge(the length of time since the new boiler has been installed). This did not help.
The system acts as if it is functioning properly with one exception. Once the water begins to violently boil, the sight glass level shows only about one inch. Either just before or after the thermostat stops calling for heat the water auto-feed kicks on and adds a small amount. I expect this is due to the float also being lowered and calling for water. Over the course of a day or 2, this cycle continues until I notice that the sight glass is 7/8ths full at which point I close off the feed line and remove water to about half the sight glass. Now I manually watch the level.

Does anyone know where the problem lies?

Long Beach Ed

Common Problem

Obviously, the water is leavingthe boiler, causing the feeder to feed water. When the water returns, the boiler floods.

There can be several causes. First of all, and most commonly, is the low water cutoff properly installed? It should not feed water until the level reaches the "minimum safe water level" of the boiler. Many are installed too high causing exactly the problem you describe. You may never have seen this problem beacuse the old feeder float was gooped up with mung.

Remember that a feeder is a safety device, not a convienence device. If installed to feed at the operating level, it will flood the boiler whenever steam leaves. It is not intended to maintain the normal water level.

If the feeder is installed at the proper level, then too much water is exiting the boiler when steaming. This can happen if the water is dirty or if the boiler is piped incorrectly.

Or the water is not returning to the boiler quick enough or being pushed out into the returns when pressure builds. When the Hartford loop was repaired was a properly sized and piped equilizer installed? Check the manufacturer's intallation diagram. If the piping doesn't match the instructions, you found your problem.

Lastly, the returns can be clogged, causing a delay to the returning condensate. Another common problem.

Of course the feeder valve may be leaking or the fill valve may be leaking. They were installed with unions under them, just as the instructions call for, right? Those unions are there so you can check to see if the manual or automatic fill valve is leaking water into the boiler.

And let's not forget a leaking tankless coil. If you have one and it leaks, the boiler water will get higher and higher.

Go fix this problem, as fresh water continually added to a cast iron boiler will eat it up, make it rust and leak.

It's all so simple -- but it can drive a guy nuts!

Good luck.

Long Beach Ed

Daniel_3

I would say check the boiler feed stopcock or whatever valve is feeding the water. It may be that the gasket is worn or you thought it closed all the way when you used it last. A stopcock to my boiler was a very hard turn and it had to be very tightly shut to prevent an overfilling that also happened to me.

Bob S

lots of possibilities

Thanks Ed. I'll go check some of those things you suggest.

A few notes: 1)The system hadn't been altered since it's installation, and has been extremely trouble free. 2)The feeder (same brand as low water cutoff) is installed correctly. I checked that it is wired as suggested by the manufacturer where the feeder is hooked to the alarm switch of the 2 switch cutoff, so I didn't screw that up during replacement. I assume this will trigger at a low level and not normal level. I also used the same fittings/pipes (cleaned if required) as before to make the job quick-thus, the height is the same. 3)The replaced Hartford loop is identical as before, but I will double-check the boiler install instructions and also if (maybe) the return condensate is backing up due to a change in pitch of the return lines. Is that possible?

Bob S

Thanks Dan. Same as Ed has suggested. I will check, but my feeder setup uses a washered valve only for the incoming water. The rest are ball valves and it incorporates a manual bypass in case the feeder craps out. But, I don't think there are unions installed, as Ed suggested, to check for leaks. I see an upgrade coming.....

bob young

believe it or not

BALL valves can seep. TEST IT.