Determining water line in already installed Steam boiler

Fred Jordan

We have an account with a Utica 4 section oil fired steam boiler. The unit has been going through switches in the Mc Donnel Miller Low Water cut off. The water level seems to go above the normal operating level we think and is damaging the switch. We only can go by what the customer tells us. That said, the near boiler piping and Hartford loop are done in copper and done incorrectly. The Tee in the loop is too low and the eq tube is piped to a dry return from one steam main, instead of  an elbow for the return at the HartfordLoop there is a Tee going op to the main as another Eq tube. The remainder of the return piping is original and I want to replace it as I believe it may have some restriction slowing the return water flow. We replaced the McDonnell water feeder with a hydrolevel feeder with time delay. This helped but then the switch failed. We would like to correct the return piping but would like to determine where the water line should be so that we could pipe a false water line or raise the boiler. Any ideas?

Rod

Boiler Waterline

Hi - The boiler's designed waterline level is determined by boiler manufacturer and is normally stated somewhere in the I&O manual, either in a drawing or in the written text.  This is the water level the boiler water should be when the system is cold and not operating. (If you don't have the manual handy let us know the make (Utica) and

model number and we may be able to dig up a manual for you.)

  From your post I'm getting a fuzzy mental picture of a very screwed up system. It would help a lot if you could post some photos of the system. At what  pressure is the system operating? It should be no more than 2 PSI maximum and a lot of systems will operate at less than that. (Lower = better)

- Rod

Jamie Hall

If the equalizer

is going to a dry return, and is not a drip directly to the Hartford loop and the wet return of the boiler, I honestly don't see how you can hope to have a reasonably stable water level -- never mind the potential back pressure on the dry return, crippling part of the system.  Maybe I'm not seeing the mental image properly... been known to happen.



If all else fails, and there is a sight gauge on the boiler (there ought to be...), one can guesstimate the correct water level as being half way to two thirds of the way up the gauge.



Now determining what the water ought to be based on the rest of the system can be a little trickier, but if there are any wet returns at all a good general thought is that the bottom of any drip or vertical piped down to the wet return, either from a dry return or a steam main, should meet the wet return at least a few inches below the boiler water line.  Doesn't have to be all that far -- but it does have to be below.  But you are going to have to trace out all the lines to make sure you haven't missed something in a back corner.

Fred Jordan

water level

Perhaps I didn't state this clearly. The correct water level for the boiler is already a given , we know that. It is the water line of the heating system that we don't know. This boiler was put in place a while back by a ham and egger who didn't know steam. The boiler is obviously shorter than the original. Usually one would make note of the previous water line before replacing to boiler and either create a false water line with a piping arrangement or raise the boiler. This was not done and we believe this is part of the overfilling problem we have.  Imagine there is no boiler in place at all , just the steam piping, forget about the near boiler piping, we already know how to do that. What we need to know is how to ascertain the water line of the system so that we can either reposition the boiler or create a false water line, either way, we need to know how to figure this in the absence of the old boiler.

nicholas bonham-carter

Over-filling problem

Can you valve off the auto-feeder, and observe the waterline. How quickly will the waterline return to normal?

It sounds as though the improper piping is causing water to be thrown up into the steam main, from which it slowly drains through improperly configured/clogged returns.

In some cases, the original return lines can end up being higher than the waterline of the new boiler, and will hide water as pressure rises, and the level rises in those returns.--NBC

Jamie Hall

Probably can't be exact, but...

As I noted in my first reply, you can at least establish a range for the correct system water level, and it isn't hard.



First, it must be high enough so that no portion of any wet return is less than about 4 inches below the water line.  This will ensure that there will always be a water seal between all the various pipes connected to the wet return.  The trick here is to find all of those possible connections.  Be diligent.



Second, the water line must be low enough so that pressure in the boiler cannot back water up into any dry return or steam main when the boiler is steaming (why the steam mains?  Because until the steam mains are filled with live steam -- which will be at the end of a cycle -- the pressure at the far ends of the mains will be significantly lower than the boiler pressure, if not actually atmospheric).  That distance is roughly 28 inches for each pound of pressure in the boiler (note that in most houses this is a very good reason for keeping your pressure down -- at 2.5 psi that works out to about six feet.  Not too many residences have that much headroom...)



So... figure those two dimensions, and your boiler water level can be anywhere in between.

Charlie from wmass

The original water line

means nothing as you do not have that boiler anymore. You need the system to work with your current water line. That level you know.