Sloshing in pipes after new boiler install

austin907

Recently had our old 1980 Weil-McClain standing pilot, gas-fired boiler replaced after mineral deposits caused irreparable damage to the heat exchanger with a new Weil McClain CGa-4 electronic ignition gas boiler. We have two zones (first and second floor) with finned tube and a hot loop to the garage with a unit heater. The zone valves are Honeywell's and the pumps is a Taco 007e. All the near boiler piping including the zone valves (first and second floor zones) and pump were replaced as a part of the installation. Now whenever the second floor zone calls for heat there is a very loud sloshing noise that lasts for a minute or two and slowly fades into a little trickling sound and eventually disappears completely. I already had the installer come back once to fix the issue and they purged the system and I used the coin vents on the baseboard to try and purge any remaining air but the sound did not go away. Because of the type of sound (sloshing) I would think it is air, but after having the system thoroughly purged I'm starting to wonder if the noise is from something else. Anyone have any ideas what this could be? I'm trying to have the installer come back out again since they gave me a one year parts/labor warranty on the install but wanted to see if there was anything I could do to narrow down the problem. I attached some pictures of the boiler and near boiler piping. The system is two zones (first and second floor) with finned tube. If any additional system specifics would help, please let me know.

GW

It’s air

Seems like somebody needs to purge the zone a little bit more.

you said coin events. How old is this house? I suspect it’s a continuous loop, but coin vents are a bit of a pain. kinda doubt you have one pipe, but it’s possible 

If you’re going to keep the coin events, just make sure the pressure doesn’t drop below 10 or 12 psi.

I don’t see the classic air eliminator. Maybe the pictures aren’t showing it.

austin907

Hey GW, thanks for the quick reply! The system doesn't have an air eliminator, should I have one installed?. Currently, its just an automatic air vent on top of the boiler (says it has an integral air scoop) and one on top of the unit heater in the garage. Just thought is was weird that we would only hear the sound for a minute or two once the zone kicked on. As the zone runs for a while, does the air that is in the system stop making noise?

EBEBRATT-Ed

I can't tell from the pics but see if the pump is pumping away from the expansion tank. I beleive the tank is connected to the return manifold but can't tell for sure.

It does sound like an air issue

austin907

Hey EB, the pump is pumping away from the expansion tank. They originally installed it the other way around and I had them re-pipe it to match the boiler IOM. The expansion tank and fill line connect to the same spot on the return line right before the pump.

austin907

Hey GW, to follow up on the coin vents and piping configuration, the house was built in 1980. The first floor and second floor are individual zones piped in series (i.e. continuous loop). I attached an image showing one of the finned tube coin vents. The pressure is currently at 12 psig on the fill line and the reading on the supply line coming out of the boiler varies from 12-12 psig depending on what zones are open.

GW

OK maybe it’s fine, I’m not familiar with that boiler nor the piping instructions.

The sound, generally what happens is all that air gets pushed to the end of the zone and just sits there, quietly. Then when the zone goes off, the big air bubble spreads its wings and gets to the piping all over again 

The installer people should have a good handle on the stuff, I hope. If they really start scratching their heads, get the system up to about 25 26 or 27 psi or so, and then open up the purge valve. 30 psi is when the puker blows. (Trade talk for relief valve)

austin907

Gotcha that makes a lot of sense, the boiler installation manual shows an air separator in the piping schematic and calls it out as "if used" which I take to mean it is optional.

Does increasing the system pressure help purge the air?

EBEBRATT-Ed

@austin907

Increasing the pressure to 25 psi or so will help with purging and venting air.

The Weil McLain boiler have an internal air separator built into the boiler itself.

If you look at the boiler near #10 you will see the larger supply pipe that feeds the system, Right near that is a smaller 1/2 or 3/4" pipe tapping. Some install and automatic air vent on that. That small tapping is the vent off the internal air separator. If you use a compression type expansion tank instead of a bladder tank it is connected to this tapping.

That's what they mean by the note at #10