Removing a Hoffman differential loop

Ren_Man

Leaking Hoffman differential loop (the homeowner put the duct tape over the pinhole, he said it lasted over a year). The system is 2-pipe and each radiator has 20+ year old thermostatic traps. Boiler was replaced about 10 years ago and of course it’s oversized but when they replaced it they added an equalizer & Hartford loop and the operator is a standard .5-1.5 not a vapor. There is ample B dimension and if I take a few burners out of the boiler and add a vaporstat with 8-12 oz operating range I’m thinking the differential loop is unnecessary. However I’d love to hear any feedback/suggestions. Especially curious about your thoughts on how best to deal with the end of main— remove crossover traps and put main vents? Or leave the main traps. Or leave it all and just patch the diffy loop holes. Open to any constructive criticism. Thank you very much for your time and help!

Ren_Man

Hm, seems my pics didn’t post, I’ll keep trying 

mattmia2

You can make one with pipe, it is just a water seal that equalizes the main and the return if the differential gets too high.

Get the pressure down, keep but make sure the crossover traps are working.

Ren_Man

Ren_Man

Ren_Man

Ren_Man

Ren_Man

Ren_Man

Ren_Man

Ren_Man

Jamie Hall

Keep it, or build yourself a new one. Not at all difficult, and the patent ran out years ago. All it is, fundamentally, is a calibrated water seal loop, with the vents on the dry return where they join and go into the top of the loop on the return side.

I would venture that the reason it developed leaks is the (for it) extremely high pressure. If you get a vapoustat and a good low pressure gauge, and set the cutout to no more than 7 ounces, it will never operate anyway.

Also keep the crossover traps, but do make sure they are working. And also make sure that there are no other vents whatsoever on the system other than the one or group at the Differential Loop.

Jamie Hall

I might add that having an operating loop will protect all of your traps from excess differential pressure (which is what kills them) and may save you a bundle in trap replacements down the line.