Gravity Return with a Boiler Feed Unit

Dougo

Anybody ever hear of using a boiler feed tank on a gravity return system before?

nicholas bonham-carter

Some systems may benefit from a reservoir tank, mounted high enough so that its horizontal midpoint is at the same level as the boiler water line.
It would be piped down to the wet return, and above to the dry return, in order to expose it to the system pressure.
Are you having some waterline problems which you think might be solved by one of those?--NBC

EBEBRATT-Ed

If the boiler feed tank can be set at a level that the condensate will return to it by gravity, then yes you can use one. If not I have seen plenty of jobs that use remote condensate pump(s) to pump to the boiler feed tank.

What NBC mentions is a tank to use with smaller boilers to increase the water content of the boiler......it's not a boiler feed tank IMHO

ch4man

i know of many. usually because the new boiler did not have the water capacity as the old one. what once was a balanced system is now unbalanced. that was how Mcdonnell Miller describes the issue in there main catalog

JUGHNE

They took no chances of running out of water with this install.
The boiler is +/- 525,000 input.
200+' of 3" main.
It takes 95 gallons to fill boiler and tank.
Both boiler returns are connected with two 2" from the tank.
The return enters the back of the tank as in a Hartford Loop.
Equalizer of 2" connected into the top.
No drip equalizer of header, apparently enough height of 2 4" risers keep steam dry.
Not piped correctly but works like a dream, never over 8 ounces needed.
10 G2 vents on the 200+' of 2" returns were added.

It took a long time for me to figure out what this amounted to.
Finally just thought of it as a parallel boiler without a fire under it.

The original boiler, (1915 or so) was a coal then oil fired steel fire tube that might have stood just 6" under the 2 4" flanges with the asbestos insulation above them.

nicholas bonham-carter

I would not believe that lack of capacity, given that steam occupies 1700 times the volume of water. The old boilers had a larger steam chest above the water, and could tolerate non-standard piping, by our present day designs. Modern boilers have been designed, (we hope), to have enough flame surface, and water volume, to make an adequate amount of steam for the EDR requirements. Gravity return should work perfectly.
Any imbalance I would put down to bad main venting, or supply piping, which is throwing large amounts of water up into the supplies.—NBC