leaking hoffman 60 vacuum breaker

boiled

I have two pipe steam heat with a Weil-McLain model E-7 series 2 boiler. I recently had to replace a McDonnell Miller Series 67 LWCO attached to the boiler. The previous LWCO had a pressure gauge, pressuretrol, and vacuum breaker connected to the top of it. Those same controls have been attached to the new (identical) LWCO in the same manner. Since the LWCO replacement I've noticed the following issues:



- vacuum breaker (Hoffman 60) is dripping water when burner starts heating the water. water dripping out is warm, but not hot.



- when burner shuts off, the pressure decreases and goes in to a vacuum. during this time, the sound of air/water gurgling is coming from the vacuum breaker. and at around 4 Hg on the pressure gauge, the vacuum breaker makes a louder sucking sound, at which point the needle on the pressure gauge shakes and the water in the gauge glass bounces up and down. when this starts happening, the pressure in boiler increases (goes closer to 0 on pressure gauge). and inside the gauge glass, there appears to be water dripping down from the top inside.



-pressuretrol does not seem to cut off burner at high cut off. I have it set to 0.5 psi and 1.5 lb additive differential. previously it was cutting the boiler off at about 3 psi on the pressure gauge, but currently I have let it go up to 6 psi without observing the burners turning off.



is the drip/leak on the vacuum breaker something that needs immediate attention? is the possible mal-functioning of the pressuretrol related to the leak on the vacuum breaker? are there any suggestions on how to diagnose the problem further?

Pumpguy

I can't comment about...

your system operation, but I can shed a little light on the vacuum breaker.  My Hoffman contact says they never heard of a #60, however I am very familiar with the #62, 3/4" vacuum breaker.  These spring loaded adjustable and have an O ring seal.  If that O ring has perished, the breaker will leak when at pressure.  The O ring is renewable.  I would suggest using a Viton O ring which is good for 400 degrees F.  If you have any Amine chemicals in your condensate, then I would suggest an EPR O ring which is good for 300 degrees F and is resistant to Amine based water treatment chemicals. 



Good luck with the rest of it.

boiled

will try to replace vacuum breaker

Thanks for the suggestion. The Hoffman 62 looks identical to what is on my boiler. My best guess is the Hoffman 60 is a previous obsolete model (I see pictures of it on the ebay: http://www.ebay.com/itm/NEW-HOFFMAN-NO-60-3-4IN-NPT-VACUUM-BREAKER-D294045-/301028932375).



I think the leak in it is likely preventing the pressuretrol from detecting the correct high pressure cut off point. and the warm water leaking out is from the pigtail under the pressure gauge.



Is replacing this vacuum breaker and/or o-ring easy enough for a non-professional to accomplish? seems like just requires a wrench to loosen existing one and tighten new one on.

Jamie Hall

It's possible

that a leak in that vacuum breaker could be causing the pressuretrol to sense incorrectly -- but it isn't very likely.  Are you sure that all the piping is really clear, and the the opening in the base of the pressuretrol is clear?



Point is that the pressure gauge is showing pressure in that line -- which suggests that the pigtail is clear -- and the vacuum breaker is leaking a bit, but holding enough of a vacuum to make that sucking sound when it opens, which suggests that that bit of pipe is clear... but the pressuretrol isn't sensing it.  Something is not right about that. 



Seems to me that either the pressuretrol can't sense the pressure, or it is flat busted (unlikely; they are pretty bomb-proof) or that it got miswired when the LWCO was replaced -- somehow got wired in parallel with the LWCO, instead of in series as it should be.

boiled

replaced vacuum breaker & pressuretrol

I had a heating & plumbing service stop by to check the vacuum breaker and pressuretrol issues I described previously. They confirmed that the existing pressuretrol was wired in-series with the new LWCO.



They replaced the old Hoffman 60 vacuum breaker with a new Hoffman 62. However the old pressuretrol still did not cut out.



They then replaced the old Honeywell Pressuretrol PA404A 1009 with a new Honeywell PA404A 1033.



The new pressuretrol is set to cut-in at 0.5 psi and cut-out at 1.5 psi. According to the existing pressure gauge, the boiler cuts in at 3.5 psi and cuts out at 4.5 psi.



The new vacuum breaker also is dripping water, but much much less than before. And, now when the boiler goes into vacuum, the gauge starts shaking at about 2 Hg and the breaker starts making a quiet sucking sound - this seems to be the factory setting of the vacuum breaker.



are the drips from the vacuum breaker expected - just due to normal condensation inside the piping above the pigtail? or is it piped poorly - i.e. vacuum breaker needs to be higher than where it is currently, and this condensation would roll back farther in to the pipe and never be able to make it out of the breaker? do I require a vacuum breaker at all?



should I be concerned with the discrepancy between the pressuretrol cut-in/out settings of 0.5/1.5 and the actual readings of 3.5/4.5? since the pressure gauge seems to be accurate for the vacuum side for the breaker, does that mean it is also accurate for the psi side?

nicholas bonham-carter

Where to put the vacuum breaker?

Maybe in the trash for the moment, in order to let the system run in a vacuum, just to see what changes might be seen.

If you want a vacuum breaker to do its job, after that experiment, then it should be mounted high up with the main vents. Mounted on the top of the M-M LWCO, it will have to let the air back in through a sort of water seal, which is resisting any air flow.--NBC

boiled

good point about the air thru the water

Ok. thank you. I'll try some different configurations then. (and I have some reading to do about steam heat in a vacuum...)