Boiler water content question??

Robert O'Connor_7

I've currently been asked to provide a quote for the install of an oil fired steam boiler. The original is an OLD Thatcher (about the size of a minivan), upon calculating the EDR and getting supplier quotes I was asked if a receiver tank was necessary. The new boiler obviously has about 1/5th (a guess) water content than the old one has. I couldn't possibly fire up the existing boiler and wait for the condensate to return to acuratly determine this just for a proposal. It's an old vapor vacuum system firing @ 5.75 gph @175psi/ 2 pipe direct return. Any thoughts short of valving off the returns and measuring the condensate? The boiler IS in its own pit aprox 4' below the basm't level and is no longer being used to provide domestic water...Robert O'Connor/NJ

Unknown

Returns hold the answer

If the system has high (dry) returns, it would be different than if the returns all dropped vertically into a wet return.

Steam pressure (on a gravity/no pump tank) pushes the return water 28 inches up the vertical pipes that connect high return piping to wet returns, per PSI steam pressure. The more risers there are, and the higher the steam pressure, the more water you "raise" from the boiler water level.

Dry returns that are empty during the off cycle will contain what they are carrying, especially at start-up, in addition to what the wet risers hold. This wont be much, unless, 1) you are making wet steam,and the equalizer isn't taking all of the water from the header, and 2) the piping has crud in it that holds back the return flow.

If the wet returns are holding back water, a pump tank won't help. The tank and/or the boiler will flood.

There aren't many residential vapor systems that are gravity that I would change to a pumped return. I'd need to have a good reason, such as a wide, single story building with miles of dry returns that are perhaps cruddy inside, or something along those lines.

Noel

George_10

Robert

I talked to Dwight about your problem. Here is a very simple way to get an answer. Measure the length, width and height (of boiler) and multiply to get the cubic feet.

Estimate what percentage of this would be water. Multiply this by 7.48 gals. You will have eliminated the innards of the boiler like tubes, burner area etc.

It is not elegant, but it will give you some sort of answer
as to volume. Maybe the water line could give you a clue as
the active water level.

The percentage estimate is the key.

Robert O'Connor_7

Tank??

First off let me thank you for the responds. The boiler is not what I would consider residential, its for a 20 family apartment building w/2 stores below. The returns are extensive, and are a combination of wet and dry. I was puzzeled about the receiver tank because if it never had one then why would it now need it. I typically charge/include in my estimates for flushing the wet returns out and was confused because installing either a condensate receiver (float type) or a boiler feed unit was not only adding to the cost (and possibly making me too high priced) but was also adding more devices and controls thus making it more complicated, more labor intensive, and frankly adding another piece to the system that I don't feel would be necessary. The original boiler size is apox. 8' long x 6' wide x 6' high (not counting the chamber) the buildings EDR/BTU is only 749,708 net btu. I just was unsure if the obvious lack of water content (from the new to old) automatically made it necessary to install such devices. I personally don't feel its required but from gathering prices from various vendors, they ALL asked me the same question? I quess with old age comes uncertainty...Robert O'Connor/NJ