Two-pipe vapor system issues

svdesist · January 1

Happy new year to all!

This is my first post after lurking on the forum for a bit searching for solutions to some problems I have with my steam heat in an two story 4 unit apartment building. From what I have learned on here, I know that I have a two-pipe vapor system with a Hoffman Differential Loop. The boiler is a Burnham that was installed in 2021.

My issues are as follows:

Pressure gauge on boiler shows no pressure even after I swapped in a Oz. pressure gauge. (attached picture was taken as boiler was firing)
My dry returns don't get hot in a certain section of the system, whereas the dry returns in the rest of the system are piping hot to the touch.
The boiler is short cycling intermittently. I'm wondering if its not an ignition/exhaust issue as the exhaust is only 4" duct pipe with a power vent.

I am going to order a Gorton #2 and swap that in for those other vents on the Hoffman Diff. Loop. Currently, no tenants are complaining of a lack of heat which is a win for me. I still want the heat system to run optimally. Other than that I am curious what else I should look into. Thank you for your assistance.

Steamhead · January 1

One of those vents is actually a vacuum breaker. It doesn't vent anything. And that Hoffman #75H is way too small.

In a building that big, you will probably need two Gorton #2 vents on top of the Loop. It also pays to replace the crossover traps at the ends of the steam mains with Barnes & Jones Big Mouths.

The dry return should NOT be steam-hot. The traps should keep the steam out. Find the bad one and fix it.

Jamie Hall · January 1

I almost never disagree with @Steamhead — he's forgotten more about steam than I will ever know!

HOWEVER in this situation I do diagree. If you want to keep the function of the Hoffman Differential Loop, and you should, you need the crossover traps — not the vents. Just make sure they are functioning (the mains should be hot up to the crossover — but the dry return beyond the crossover should be at most warm).

I do agree that replacing the 75H, which is the wrong vent anyway, with a pair of Gorton #2s is the way to go.

The hot dry returns indicate failed traps. Warm returns are OK — but not returns are not.

And last… that pressuretrol is not usable on a Hoffman Equipped system, even if it weren't set way too high. You need a 0 to 16 ounce vapourstat, and if the Differential Loop is still in service (I hope it is) it needs to be set at 7 ounces per square inch cutout with a 4 ounce differential.

All that said, you may not see that much pressure any time — but check to make sure the pigtail is clear.

Steamhead · January 1

@Jamie Hall , the Big Mouths I recommended are direct replacements for the Hoffman #8 or #18 crossover traps on these systems, and they'll vent into the dry returns just like the originals. Might need to change the lengths of some pipe nipples but that's it. The effect is to vent the mains more quickly, evening out the heat and saving fuel.

svdesist · January 1

Excellent, two Gorton #2 s are on their way. Next, is to diagnose those crossover traps. Thank you!

mattmia2 · January 1

is the lwco a cyclegaurd? is that the source of the cycling?

Jamie Hall · January 1

https://forum.heatinghelp.com/discussion/comment/1880309#Comment_1880309

Sorry! I was confusing them with Big Mouth vents…

svdesist · January 1

https://forum.heatinghelp.com/discussion/comment/1880316#Comment_1880316

It is a cyclegaurd.

mattmia2 · January 1

those shut down every x minutes to measure the water level

Two-pipe vapor system issues

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