Hoffman Differential loop

clammy

Look in the lost art of steam book and take a glance at a false water line this way you can use you new lower water level boiler and still maintain the old water it is not very hard and would keep all your existing wet returns wet also look at drop header info and proper near boiler piping for the boiler that is going to be installed .Your heating contractor should have a good handle on this other wise goto the find a pro section peace clammy

Rob K

Hoffman Differential Loop

I have a job changing out a million btu steam boiler and found that there is a hoffman differential loop in the boiler room, and four traps with what seems to be a piping loop(made on job) that functions with the differential on the farthest end of the two loops (u shaped building with boiler in the bottom of the "u").

The water line in the basement was at 70" off the floor. The water line of proposed boiler is 27 1/2". Is there any way I can get away from raising the boiler to maintain the water level? -- I understand with this differential loop there are water seals. Can I lower the Diff loop? Any info on the Hoffman diff loop would help greatly.

Thanks -- Rob

Unknown

The Hoffman Differential loop is for solid fuel systems

It would, in the event of high steam pressure, pressureize the AIR in the returns so that the return water would drop into the boiler with the equalized pressure. This was because pressuretrols wouldn't shut off a coal fire.

A vaporstat does the job on a modern boiler. It keeps the supply and return pressures very close to each other. The Hoffman loop doesn't aid anything, any more.

If you run the system at a higher pressure than it was designed for, the same problems of water level control will occur; Hoffman loop or not.

Vent the whole system at the location of the Differential loop, on the high return.

Make sure that steam isn't blowing into the high return through the loop when the vaporstat satisfies, and you'll be OK. If it is, the pressure is set too high for the system.

The thing could be removed on a modern system, the check valves aren't needed, the steam feed to it can be capped. Don't put any money into the loop, it wouldn't be worth it.

Just make sure the vent works.

Fix any blowing steam traps.

Noel