Indirect hwh piping banging

Peteys

I installed a WM aqua 80 and it's been working fine all summer but now winter is here and the boiler is making steam, the piping is banging like crazy unless I have the bypass valve open almost all the way. Then the temp gauge goes down to like 120 degrees. Would like it at 180. I've bled the system and I'm pretty sure I've piped the hwh to the specs of the WM .pdf file attached. Is it possible there is air in the system somewhere in the piping. Could there be another issue?

It's driving me crazy! Any ideas?

Much appreciated

EBEBRATT-Ed

Try throteling the ball valve on the discharge side of the pump (going into the water tank) a little bit. this wiil cause the pump to pump a little less water which may smooth things out. Looks like you have it hooked up correctly according to their drawing. Personally not a fan of flo-checks but that's the way they drew it.

If your boiler water is hot the pump suction may be causing it to flash into steam. Try playing with that valve and the bypass as well to smooth things out.

Paul48

The bypass to reduce the supply temp to the indirect is closed. Is there a reason?

Peteys

The bypass was closed in the summer which is when the picture was taken

Peteys

Thank Ed, I'll try that!

I also manually opened all Flo checks but it didn't seem to make a difference. It did reduce a little rattle in one of them but the banging was the same

Peteys

I tried throttling valve and that didn't work unfortunately. What causes knocking? Air in the piping? Might it be possible I have a loose solder joint somewhere that air is getting in? There are no water leaks in piping but it was difficult to solder 1" piping with one torch. 2 is always better with piping larger that 3/4" for me at least. The only thing I'm going to do next is try to resolder any fittings that don't look good. After that I'm out of ideas unless someone has any.

Am I asking for too much to not have water hammer? Has anyone been able to achieve 180 degree mixed water when the boiler in making steam and have it quiet with an indirect and a steam system?

EBEBRATT-Ed

Can't tell from the pictures what the elevation of the piping to and from the indirect is compared to the boiler water level. I would try and keep all the piping as low as possible until it gets to the indirect.

Is it possible some of the piping is at or above the water level before it gets to the indirect??

Just for the fun of it try raising the water level in the boiler (temporally) run the boiler sight glass at 3/4 full and see if anything changes.

It's not a solder joint problem if the joints are not leaking.

Paul48

Maybe the pros can help you prioritize heat or hot water. Delaying a heat call for a short time shouldn't be a huge issue.

Peteys

Ok, I'll try that Ed. All piping is below the water line by a few inches until it gets to the supply of the Indirect which is higher on the tank.

That's sounds like a good idea Paul. If anybody knows how to do that, please let me know.

If any pros are near the north Bronx and could take a stab at it, that would be great too.

Peteys

Hi Ed, I raised the level of the water on boiler and it still knocks. The knocking is coming at the elbow right before it meets the the bypass line. I'm going to resolder the joint and maybe repipe it so there's only one elbow and see if that helps. I called Weil Mclain and they didn't have any ideas except for opening the flo checks manually and checking for air leaks.

I do see a very very slow drip from the union after the bypass valve. I'll tighten that up and maybe add some tape to that joint. We'll see if that helps

EBEBRATT-Ed

I am pretty much out of things to try. I think lowering as much of the piping, in other words drop down as low as you can as soon as you enter and leave the boiler, (although Weil McLain shows it up high) throttle the ball valve on the discharge side of the pump to reduce the flow slightly.

I am sure you already checked this but is you pump pumping in the right direction?? What size pipe 1"?? What are you using for a pump??

The fact that you said that "it worked fine all summer" means it's banging because the water is hotter and the pump suction is causing an area of low pressure which is causing some of the water to flash into steam...hence banging. I would think slowing down the flow would help.

Peteys

Piping is all 1" except where it leaves boiler which is a 3/4 tapping. B&G 100, not the bronze. I'll check direction of pump. It is flashing.

Gonna lower everything to see if that works. Thanks for all the help Ed. Appreciate all the support!

Zman

Just a quick observation. You have a pretty large circulator and quite a bit of piping/resistance on the intake. The problem started when you raised the water temp for the winter. You are surely cavitating.
I am no steam guy but a smaller circ with the check valves and other resistance on the outlet would probably solve the problem.

EBEBRATT-Ed

I am leaning in the same direction as @Zman as I stated above, cavatation and flashing.

The other thing is where the 3/4" comes out of the boiler the aquastat well is in there which is restricting the flow.

Maybe you can take the 3/4" tapping, blow it up to say a 1 1/4" tee with the aquastat well in it then reduce to 1" to go to the pump

Peteys

Sounds like a good idea! So what your saying is 3/4 out of boiler, 3/4 by 1 1/4 by 1 1/4 tee, then reduce down to 3/4 for well and then use the bull side of tee to reduce 1 1/4 to 1" for supply to hwh?

I'm also going to see if there's another tapping on the boiler that would be lower. Boiler is a Weil McLain 968. Way oversized for the 500 sq ft of attached radiation

I called b &g today and they said even if the supply tapping is 3 inches below the water line the circulator could pull some steam through that line and cause cavitation with that circulator.

Zman

The water in the boiler is already right at the boiling point. Any minor pressure drop will make it cavitate/flash.

A generously sized intake and the smallest circ you can get away with will minimize the problem.

Circulators create a pressure differential while doing their job. You want to be sure yours is additive at the outlet, not subtractive on the intake.

Paul48

I understand your making steam to heat the house now, but why isn't the aquastat controlling the boiler for a DHW call? The 2 can be prioritized. If it worked all summer, it should work now.

Peteys

Ok, Zman, so as long as the supply tapping is below the water line, which it is, it shouldn't make a difference where the supply comes out of the boiler as far as flashing? So where I'm supplying the hwh at the aquastat tapping is ok. It just needs a large tee as Ed recommended?

Is the water temperature the same at the bottom and the top of the boiler and either could cause flashing as the water temp in the whole boiler is very close to steam? That's not the issue. It's that it's too restricted at the supply to the circulator?

Please bear with me as I'm not familiar with pressure drops and the such you and Ed have been talking about. So maybe using a large tee at the present aquastat tapping and possibly a smaller circulator could reduce or eliminate the flashing?

"You want to be sure yours is additive at the outlet, not subtractive on the intake." I'm not sure what that means? Lol. Could you possibly explain if you have the time?

Much appreciated

EBEBRATT-Ed

Assuming the water temp is the same top to bottom (it isn't the top is hotter) the reason for using a lower tapping if you have one is that you will put "inlet head pressure" on the pump. The weight of the water from the tapping wherever it is up to the water line in the boiler will put an inlet pressure on the pump. That pressure will be approximately 1/2 psi for every 14" of height. You may not be able to get that much but every bit helps.

When the pump runs it tries to lower the water pressure for instance: water boils at 212 deg at seal level. If you had a pan of water on a stove at 205 degrees at sea level it wouldn't boil. If you lowered the pressure on the water (by reducing atmospheric pressure) the water would boil in the pan.

That's what the pump is doing ...lowering the pressure...that's how it moves water. that's why you get banging

The fix:
1. smaller pump or reduce the flow by choking the valve on the pump discharge. (will reduce pressure drop in suction pipe to pump)
2. Use a lower tapping if available (will increase head pressure in pump)
3. Larger suction piping (will reduce pressure drop in piping and keep pump inlet pressure higher)
4. Minimum # of elbows and fittings and valves and pipe between boiler suction tapping and pump.


If you can understand this, make a few small changes first, remove aqustat well temporally, look for a lower tapping, choke the discharge down a little.

Visualize this: You looking to have the water suction from the boiler to get to the pump like water pouring over a waterfall freely without restriction as much as possible. Not the pump pulling a vacuum and trying to suck the water out of the boiler.

Of course you can't acheve this 100%, you just need to tip the scales in your favor.

Peteys

Ok, thanks Ed. You guys are alot smarter than me. I'll try those things this week and update

Peteys

I found an 1 1/4" tapping in the bottom front left of boiler. Am I better off using this as the supply tapping? Return is piped on the bottom back of boiler.

Peteys

Picture of 1 1/4 tapping on front and return tapping on back of boiler. Return is the one with the yellow handle ball valve.

kcopp

Good luck getting that out.... Did you see this article?

https://heatinghelp.com/systems-help-center/how-to-run-a-hot-water-zone-off-a-steam-boiler/

Peteys

Lol, I loosened it already. Took a medium sized wrench and a 5 foot pipe. Not that bad!

kcopp

a 5 Foot pipe wrench !?!!?!

Peteys

No, a 2 foot wrench with a five foot pipe for leverage

kcopp

mis-read that....

Peteys

Actually have a 4' aluminum one that is great, light and strong.

I'm gonna pipe it in that way and see how it works

Grallert

One thing I found could happen. Supplying and returning a loop at the bottom of the steam boiler could result in the water passing right on through and not picking up enough energy on its way to satisfy a demand for domestic hot water. This happened to me years ago. Just something to think about.
peace

Peteys

Yes, I've heard of that. Hope it doesn't happen to me. Gonna repipe it Monday or Tuesday. My return is piped to a tee off the mud leg so maybe I'll get lucky. Could use some with this job.

Peteys

Well, supplying from the 1 1/2 tapping at the bottom front of boiler didn't work. There wasn't enough heat transfer and the circulator wouldn't stop.

So as Ed recommended, I repiped the aquastat well with a 1 1/4 tee and this worked great except with a caveat. There was no banging at all except when the boiler was producing a few ounces of pressure and then the circulator came on. Even then it wasn't that bad but there is still some banging and flashing.

I'm going to repipe some of the supply piping next so it's lower and less elbows and see if that eliminates it. Finally, if that doesn't work, I will put a smaller circulator in. Only then, will I give up!

Does anybody know what my options would be in a smaller circulator?

Peteys

Well it worked! Lowered piping and reduced all the extra elbows. No banging and silent as a mouse. Just in time for Christmas.

Thank you everyone for your help. Couldn't have done it without you.