Water hammer sound when pump shuts off

Sweet_Lew

OK...I stumped the Pro...



My Taco 007-F5 seized on me today and had it replaced with the same model. I noticed when the heating cycle completed and the pump stopped, I heard what sounded like water hammer or a metallic "CLANK". I called the company that installed it and they said they would send the tech back. He confirmed that was not normal and swapped the pump with another new one. Same issue. He checked the pressure in the boiler and it was 5 lbs off from the boiler gauge and the expansion tank read 16 lbs. He doesn't know what it could be. I bled the radiators after he installed the second pump and the clanking was still happening. He called his office and they were stumped. The only idea the tech had was maybe something with the expansion tank. They are going research and call me Monday. When the original pump was working, I never had this issue.



Any ideas? The only thing I could think of was that I don't have an air separator and that air was still stuck in the system causing the hammering noise.

Gravyfries

Thanks

I'd be interested in knowing what your contractor says since we both have the same problem.  I'll let you know what mine says but it will be a little while before I get them out there.  Thanks!

Sweet_Lew

Anyone?

I was supposed to have the owner of the heating company out yesterday to troubleshoot, but we got snowed in. Hopefully he'll be out next week.

EricAune

Clank

Does your system have electronic zone valves? If so, do you know if there is a pressure differential bypass valve installed and working properly? What tells the circulator to turn on and off?  Is there a weighted flow check valve, could that be the cause of the noise?  



Of course I have no knowledge of your particular system but there are a few things that can cause noise.

Sweet_Lew

Setup

Thanks for the reply. No zone valves. I believe I have an converted gravity system.

Bryant legacy BW2 CI boiler, Taco 007-F5 circ, B&G pressure reducing\auto-fill valve, Watts #30 expansion tank, Honeywell aquastat (can't remember the model, but it's a fairly common one). That's my system. Very basic. It all resides in the basement and heats two floors via CI radiators. I did contact Taco support to see if they could assist. Here was their response:

"I've never heard a circulator make a banging sound unless there is air in the system. I have heard zone vlaves make a banging sound. Make sure each zone is purged individually & purged from supply out to return. "

I have bled the radiators twice already and I've had air come out each time.. I'm wondering if there is air still in the system somewhere.

Pics:

Gravyfries

pump

I'm having my contractor come out Monday morning.  I'll post when I find something out.

Sweet_Lew

Thanks!

Much appreciated. I just bled the radiators a 3rd time this week and got air coming out of all upstairs rads and one on the first floor.



Also, I just saw what Mark posted in your thread. I'm going to try that later today. Also, my contractor is coming out Tuesday.

Sweet_Lew

Figured it out

Contractor came out. I never listened to the system shutting off in the basement. It was always upstairs where the radiators are. So when I went down there and had the guy turn off the system, I didn't hear anything. When I went upstairs I heard the bang again. It ended up being the relay in the aquastat making the noise. It would send it through the pipes. So now, I'm going to live with it. 

NRT_Rob

wow

that's pretty random. thanks for posting.

Sweet_Lew

No problem..

It's the least I can do. Everyone on here is always super helpful. Hopefully that IS the problem...LOL. I still have constant air in my radiators since the pump replacement and it's been over a week. Need to figure that out now.

Nanuk

Air in system

It can take a long time to get all the air out of your system if it was drained down completely.



The fresh water used to refill your system contains a lot of dissolved air and with no separator in the system that air will release in the boiler and bump and bang its way to the high points. Also some of it will dissolve back into the system as it goes up and the temperature drops slightly only to pop out again in the boiler heat exchanger.



There is a really good technical paper from Caleffi on this and I'm sure Spirovent has information on how this happens as well.

Sweet_Lew

Thanks!

I'll check it out.