New boiler, new water hammer problems

mattm

Hello all,

We had finally gotten our system into a good (and most importantly silent) working condition. It was a 1 pipe steam, vaporstat set low, with a gas conversion boiler that was probably over-sized by a factor of 2 or 3. There was also no mains venting, but it still was working kind of OK. However, that boiler died after about 50 years. Prior to the vaporstat, we had lots of banging.

So, new boiler: Weil-Mclain PEG-40, the plumbing looks good, it is correctly sized, we now have some mains venting as well, with a pressuretrol. However, it has gone from mostly silent with the old boiler, to an extremely loud water hammer with the new boiler! The water hammer is only heard in the central part of the building, and not at the front or back (it is a rectangularly shaped building). Because of this, I assume that the banging is not originating at the furnace, but somewhere else in the system. The radiators smelled a bit at first after the install, but it is dissipating.

Obviously, a lot of things have changed on the system - the boiler, the pressure control, the theromstat, the mains venting. Any idea what is causing this water hammer problem?

Thanks!

Steamhead

Something changed. Where are you located? We might know a Steam Guy near you if the original contractor is clueless........

Intplm.

Was any other work done in the building? In the "central part" of the building perhaps? Has a pipe dropped from a hanger causing it to sagg? I would check to see if any pipes have lost their pitch, allowing condensation to pool and cause the hammering.

I would also tell the installer that since the new boiler install, this noise has started. They might be able to find and correct the problem.

mattm

I'm just outside Boston. No other work was done in the building, although the building is 110 years old, and judging from the cracks in my plaster has settled a fair bit.

Nothing beyond the boiler has changed that I can tell. If there was a preexisting sag in one of the risers, would the lower pressure (from the vaporstat) on the old boiler mitigate that somehow? If the burn-off smell indicates that there are contaminants in the water, would that make a water hammer more likely?

Since it is warmer outside, the system cools down pretty completely between kicking on now.

Jamie Hall

Call @New England SteamWorks and get him in there to fix it. The question isn't what is causing the water hammer -- that's easy; condensate pooling somewhere it shouldn't. Question is what did the new install do to make it do that, and where.

And contaminants actually might make the problem worse, if no one bothered to properly skim the boiler after installation.

KC_Jones

Jamie Hall said:

And contaminants actually might make the problem worse, if no one bothered to properly skim the boiler after installation.

This would be my guess, to the OP did they skim the new boiler?

Dave0176

@mattm take some pictures of the boiler, we’d like to see the piping around the boiler.

EBEBRATT-Ed

We need pictures to look at the piping. The boiler also probably was not skimmed.

I would have saved the vaporstat for reuse

Jamie Hall

The contractor probably took the vapourstat to use on another job -- not a bad way to make a profit. At your expense, of course.

That may be part of the problem, too, if the pressuretrol is set so that the pressure can rise high enough to back water up to somewhere it doesn't belong.

Get a new vapourstat (sorry about that) and a good low pressure gauge (to calibrate it; the old ones didn't need calibration) and install it.

mattm

Hi all. First off, I appreciate all the help on this board. This has to be my favorite corner of the internet!

@EBEBRATT-Ed and @Jamie Hall I actually did ask the contractor to save the vaporstat. We still have it, but for some reason he insisted it was unnecessary to install it. So, it is just sitting here.

One thing to add is that when it is cold outside, the system comes on more frequently, stays hot, and doesn't steam hammer.

I have taken a bunch of pictures, as well as a diagram. My problem is that my basement was half-finished, and I'm in a three unit condo where I occupy the 3rd floor. I'm a bit confused about where the skim port would be on this for skimming.

Danny Scully

This is where the skim tapping is suppose to be...in other words, it was never skimmed. Have the contractor come back and install a skim tapping and skim the boiler. He should also confirm the operation of the pressuretrol with a gauge. You’d be amazed how often they need calibration, even right from the factory.

Alan (California Radiant) Forbes

I'd ask him to insulate his piping, too.

Dave0176

Are you sure the boiler has been sized correctly. I mean did he look at and measure every radiator then compare the specs with the radiation listed in the books to come up with what we call an EDR (equivalence of direct radiation) then multiplied by 240 to come up with the needed BTU??

Also as has been addressed the skim tapping had never been installed, which leads us to believe he’s not a very good steam heating man. Everything thing needs to be looked at when replacing a steam boiler, it should be treated as a system not just the boiler. Main vents, radiator vents, and proper sizing need to be taken into consideration, or you can end up with what your experiencing.

mattm

Weirdly, I could have sworn that there was something where the skim tap is supposed to be, but it looks like he took it out when he finished.

With respect to the sizing, I think it is pretty close. We had two quotes for this work, both of them gave us the same spec for the size: PEG 40. I also did the sizing calculation myself and got the same thing. The heating itself has been wonderful, only the noise coming from that rogue radiator is a problem.

Intplm.

"Rogue Radiator?" You might just need to pitch that rad toward its valve, That will allow condensate to drain. Might need only to do that.

Danny Scully

@mattm, the skim tapping hasn’t been touched. The insulation would be gone if it had. How exactly was the boiler sized? Was every radiator measured?

Jamie Hall

Well now... if you still have the vapourstat, you are fortunate! And congratulations for hanging on to it. It won't be that hard to put it back in line -- something you can do yourself, if you're handy. A short nipple where the pressurestat hooks in, then a T with the run horizontal, then two nipplies, one each way, then two 90s up, one on each side, then nipples -- and the pressurestat goes on one side and the vapourstat on the other. Wire them up in series, and your done. The pressurestat can be set to something reasonable, and the vapourstat left as it was.

If it is the old mercury vapourstat, be sure that the pigtail is oriented so that it sits exactly level.

mattm

Thanks for all the suggestions, much appreciate it!

With respect to sizing, every radiator was sized (I went through it with them). As to the rad, I wish it were so simple, but it is definitely tilted correctly, and the riser as well I believe.

Sounds like I should get the contractor to come back, put a skim tap on, and install the vaporstat in series with the pressurestat.

JUGHNE

There could be a horizontal pipe going to the noisy rad.
If you lift the entire rad a 1/2" on both ends and then add shim to the end opposite of the valve you might correct a minor sag in the pipe.
Lift the valve end slowly first, if possible.