Loud Intermittent Bang!

Derv

Bought a house this August and now that the heat is on we keep getting a periodic bang that sounds like a car hit the house, usually comes from the basement, where the boiler is. The problem seems to be more frequent when the outside temp is below 20 deg.

System is a Utica hot water boiler with three zones. The circulator is just below the zone valves, which are at the tail end of the lines. Circ. pumps into the boiler. Approximately 1 1/4" copper pipe comes out of the boiler on the other side and through an air scoop. Pressure tank is mounted to the bottom of the scoop. House is 2 stories plus basement, probably 20-25 feet from boiler to highest zone. All of the lines are copper. The gauge on the boiler reads just under 30 PSI, and high shut off is at 190 Deg.

I have a hard time believing that the pressure is accurate. I tried to purge wire form the lines; any lower pressure and it sounds like running water through the lines. The Relief Valve seems to be working fine, but doesn't blow until gauge reads above 30 psi. Pressure tank Schrader valve reads 25 psi, for what that's worth. Also, when the burners are firing the boiler bumps, which I assume is kettling, since purging the lines didn't seem to help.

Any suggestions? I've probably spent 2 hours total sitting in the basement trying to figure out where it's coming from and when. Tonight it happened right as I heard one of the zone valves close. Tried to replicate it without success.

kcopp

it sounds like Hydraulic jump. It happens when you have a quick closing zone valve (Honeywell) and a flat curve circulator next to each other. Usually it happens when you have multiple zones calling and just one decides to close....you get a pressure jump.
To fix it you can do a few things. The simplest is to use a Delta P circulator like a Grundfos Alpha. Furthermore it sounds like your expansion tank it pretty much waterlogged. I would also change that to a new tank.

Derv

kcopp, I think you nailed it. I can't replicate the condition by manually opening the zone valves, but if multiple zones are open and I shut one zone with the thermostat . . .bang!

Since the manual override (which I assume closes slower) won't cause the noise, it seems like slower closing zone valves would solve the issue. A variable circulator looks cheaper, though.

hot_rod

Usually a flat curve circ doesn't cause valve bang. I guess never say never.

Another fix is a PAB pressure activated bypass valve. It allow flow to bypass as valves shut down, so one valve never tries to shut off against full circ output.

Pages 20- 23 in this journal
- http://www.caleffi.com/sites/default/files/coll_attach_file/idronics_5.pdf-

Better yet for a bit more $$, consider a delta P circ, also explained in the above journal. In addition to adjusting output to the required flow, it also consumes less electrical energy. Near magic

rick in Alaska

I would also check to make sure the zone valves are not in backwards. With the pump still running when the valve closes, it will slam the valve closed , and make a real loud bang. Seen it before.
Rick

wmtandson

rick in Alaska said:

I would also check to make sure the zone valves are not in backwards. With the pump still running when the valve closes, it will slam the valve closed , and make a real loud bang. Seen it before.
Rick

I had that exact thing happening with a new Traingle tube boiler i installed 2 years ago.Zone valve was being slammed shut by the circulator pressure.
Quick fix for me was turning there pump around .it was a temporary fix because it was driving the homeowners crazy!! it always happened in the dead of night and woke everyone up.
this spring we repiped all the stuff and installed slower closing Taco valves'Problem has not resurfaced and now the pump is in the right way again

icesailor

The description of "a loud bang that sounds like someone hitting the house" doesn't sound to me like some circulator or hydraulic problem. That description sounds more like pipe expansion where some pipe is pressed hard against some wood and is moving from expansion.

I'd be scouting around looking at the end of some main that extends far from the boiler and is rubbing on the bottom of a floor joist. Or going through a drilled hole in a beam. When and if you find something, put a piece of sheet metal between the pipe and the wood. Put some grease on it if you like. Hopefully, it isn't in a wall somewhere.

If you find such a thing, if you drop the pipe hanger, you might notice that the wood is worn smooth from rubbing. Its probably been there since the house was built or the heating system was installed or modified.

I'd be looking for simple and stupid things before I sprang for expensive attempts at solutions that might not be the problem.

The colder outside the OAT is, the cooler the basement will be and the greater the expansion.

IMO.

Derv

I'll look for any possible expansion conflicts. That was my original thought.

I can make any one of the zones clang though by turning all three thermostats up and then shutting one down. The zone valves are at the end of the loop.

Derv

Pic attached

RobG

Has it always done this or is it a new problem?

Derv

I don't know if the problem is new. We just bought the house and this is our first heating season. Problem seems to happen more frequently when it's colder, which would make sense under the theory that the quick-closing valves are causing a sudden pressure spike, since the colder weather means more zones open at a time.

BTW the zone valves are Erie and Honeywell.

Derv

Rick in Alaska and wmtandson: I'm not sure how to tell if the ZVs are in backwards. There are no arrows. But, on the casting, I can see an "A" and a "B." "A" is on the top. I.e., the water is flowing from a to b.

mars_6

A picture would help matters. Thanks Mars

mars_6

Sorry just saw pix. Mars

rick in Alaska

looks like the valves are going in the correct direction, so I would rule that out. That would have been too easy anyway.
If you manually open a valve, you say it doesn't make the bang when it shuts. Do you just release the lever, or do you use your finger to hold it back when it is closing? If you open it fully and then release it, it will act just the same as if a thermostat was doing the job, and it should bang the same. Does it?
Rick

hot_rod

I don't think either of those brands of ZV "make" the end switch when you manually lever them open, so you need to get the circ pump to run to check for noise in manual operation.

The expansion tank could be connected to a better location, looks like you are pumping against the tank from what I can see?

Derv

The zone valve for the basement zone seems to be the biggest, and probably only, offender. To test, I turned up the thermostat on the first or second floor so the circulator would keep running. If the basement zone is also open and I turn down the basement thermostat - Bang! Every time. If I do the same thing but open the basement zone valve manually and then release the lever, I get nothing. I haven't "made" the first or second floor do the same thing, but have been woken up by it at 4am while on the second floor.

One thing that comes to mind is that the basement zone has only 10-12 feet of fin tube. First floor has about 30 feet. And second floor has more like 50 feet. Each zone valve has a set screw that controls the flow rate through it. I wonder if I need to adjust the flow at each zone valve to compensate for the variation in length of each zone? I assume that this was down when the system was installed....

I'm nervous about draining the system and attempting to install a new zone valve while it's only 10 degrees outside.

Derv

Hot rod: what do you mean by better location for expansion tank? The water flows out the top of the boiler and through the air separator that expansion tank is connected to.

TomS

Since you have a Honneywell zone valve there is usually a simple fix for your problem. The Honneywell valves have two springs which cause a fast close. Take the top cover off and with needle nose pliers unhook one of the springs. One spring is easily assessable and that is the one to unhook. You can leave the other end of the spring connected and if for some reason you do not like the results you can easily rehook it. The valve with only one spring will slow close and the entire job should only take a minute.

Derv

Got to hand it to my buddy for the fix. I just turned the thermostat in the basement all the way down and left the basement zone valve in the manual open position. Temperature in the basement is fine, since the zone flows anytime the rest of the house does, and no more bang.

Also, buddy lent me his copy of Dan's "Classic Hydronics." If I ever replace/move the boiler, I'll change the plumbing according to Dan's plans, so the circulator and zone valves are on the other side of the boiler and expansion tank.

TomS: Erie valve is the problem and it has a torsion spring.

hot_rod

You are on the right path with some re-piping and component re-locating, when time and money allows. Keep reading the teachings of Dan.

You have a temporary solution, but a time may come this spring when you don't want or need a "wild" zone in the basement. Remember adding heat energy takes fuel dollars. It is nice to have thermostat control on the various levels of your home.

It's not the valves fault that you have a hammer noise:) regardless of the brand.

Le John

@TomS I was all set to install a bypass but saw your suggestion and after removing one of the springs the zone banging stopped.

Thank you @toms and @DanHolohan and @Erin Holohan Haskell for hosting the site.

Erin Holohan Haskell

Le John said:

Thank you @toms and @DanHolohan and @Erin Holohan Haskell for hosting the site.

Thanks!