Why water might leave a steam boiler

HeatingHelp

Why water might leave a steam boiler

When it comes to steam boilers, it's not so much about the amount of water that's in a boiler as it is about the space in which the steam has to form.

Read the full story here

OldSchoolHVAC

So if you don't mind me asking, how was this particular problem job solved? Did the boiler just need to be skimmed? Were the boiler sections just too narrow to function properly?
You have my curiosity piqued!

DanHolohan

OldSchoolHVAC said:

So if you don't mind me asking, how was this particular problem job solved? Did the boiler just need to be skimmed? Were the boiler sections just too narrow to function properly?
You have my curiosity piqued!

The sections were too narrow for the boiler to function on steam. It was a hot-water boiler that the manufacturer had fitted and sold for steam systems (this goes back some years). They eventually abandoned that model of boiler and replaced it with a new model that had much wider sections. That was the solution. In the meantime, all the contractors could do was down-fire the boiler, and that often led to other problems.

willie13

We always sell time delay water feeders now, too, because of the chance for flooding due to feeding water before it is really needed. Would a Vaporstat have helped by keeping the pressure down?

DanHolohan

No, this wasn’t a pressure issue. There just wasn’t enough space. 

retiredguy

Almost anytime an older boiler was removed and a newer, higher efficiency boiler was installed it almost always had water line problems. Unless the boiler manufacturer would eat the job, which was almost never, the only remedy was to reduce the boiler's input and to add an extremely large header and even sometimes a steam separator. We even had jobs where the manufacturers rep and/or the manufacturer would recommend reducing the boiler's input. When this happened you knew there was going to be problems. Since we rarely installed residential boilers or anything nearly that small this only happened occasionally. Most of our installations consisted of the an H B Smith 650, 450, 350, sectional boiler, or a larger tube boiler. These units never had water line problems as long as the water was clean and treated. So, give me an old boiler with a large steam space or steam chest and let someone else install the smaller units.

Carol0013

What does a good system cleaning consist of?

DanHolohan

Carol0013 said:

What does a good system cleaning consist of?

https://heatinghelp.com/systems-help-center/how-to-flush-the-return-lines-on-an-old-steam-system/

DanHolohan

And Carol, the start-up cleaning procedure for a steam boiler varies with manufacturers. They do have it in their installation manuals. 

dopey27177

What is left out here is a problem of condensate lag.

Even when the boiler manufacturers stopped making "hot water boilers for steam" and made the sections larger ""the new Steam boiler" These boilers were significantly smaller in size and held a lot less water in the boiler than the older boilers.

With these newer boilers a false water line did not help with the boilers running out of water mid heating cycle. Condensate lag can be alleviated by some creative alteration to the piping systems.

I learned this in a financially strapped church with a poor congregation running an after hour school for religious study and a tutoring service for children in Brooklyn, N.Y. where there was not sufficient money to re-pipe the heating system. After some careful study of this very long and large piping system with a dry return I reasoned that if I can intercept the flow of condensate from the un-insulated steam mains and large radiators nearest to the boiler and divert that condensate to a wet return (shorten the the time and flow of the condensate flow back to the boiler) the shutting down of the boiler mid cycle and activating the automatic feeder which eventually flooded the boiler not occur.

I decided that a charity event was going to occur because this was an untried evolution and an experiment.
I and the contractor of record decided to do a partial change to the piping system as this was November and boiler run time would not be as great as late December, January and February.

We installed eight condensate interceptor locations with a 2" wet return to allow for future connections. The deal was if this worked the contractor would install eight more condensate interceptor stations and the price was given. We would both get paid in monthly installments to keep the church from having to get loans and run fund drives to raise the needed money to pay for the corrective work.

See the enclosure which shows a one riser counter flow system and a two two pipe riser parallel steam system. On the counter flow system condensate did not return via the steam main. On the two pipe parallel flow system the steam riser was dripped to a wet return and the return side of the system also was dripped to the wet return, additionally, the condensate from the first floor radiator immediately returned followed by the second, third and forth floor radiators. In these examples the condensate lag was shortened by 5 to 8 minutes'

This same method can be applied to many smaller piping systems by dripping radiators and risers nearest the boiler and going outward to the end of the steam main.

Jake

retiredguy

I only ran into this problem a few times since we rarely did smaller steam but when I did, to save time I would change the condensate system to a demand type using a small feed tank and a pump/low water control on the boiler. Like magic, problem solved.

dopey27177

The condensate tank and pump will work well in smaller systems because the condensate tank (about 12 gallons of stored water is fine. In the job that I did the tank would have to store 100 gallons of water. The recommendation I gave is for jobs where mechanical equipment maintenance would not be done.

Jake

motoguy128

In my own house, the 375k HB Smith G300 (I think that was the model) ran smoother and at consistently lower indicated pressures than the 200k Hydrotherm I installed in its place.

The G300 wasn’t even piped correctly. Single supply and no equalizer. But its steam chest was so big it didn't matter. Overall thermal efficiency however is slightly better on the smaller boiler, probably mostly due to longer cycles reducing standby losses. Both have/had draft dampers installed.

The G300 was starting to leak a little between sections, probably from running too high pressures for years and minor steam leaks not being fixed. Also likely was fired low on water a few times since the auto feed was broken and the LWCO was stuck closed when I bought the house. Eek!