New boiler bangs

Tjs2010

I had a new boiler installed a few weeks back and the system bangs like crazy. It's keeping us up at night. It's a laars mini-therm. Set to 180 at 19psi. When cold no bangs up to 120. Once passing 120 it bangs from the unit and psi jumps. The system has been bled many times and it was a complete repipe. The system is setup as boiler - outflow - taco recirculator - low water shutoff - air scoop with new expansion - split to two zones. I notice there is no bypass as required by this unit I believe. Would that cause the issue? Other thought is my circulator should be on the inflow side. System is being ran closed from main.

Tjs2010

Picture attached. Also the scoop is catching a good amount of air.

lchmb

The circulator should be after the air scoop not before.. The air scoop is to close to the elbow (manufacturer specs) the boiler supply should be tee'd in at the top of the expansion tank. if you still have air a couple weeks after install the system was not properly purged.. or you have leaks.. and yes..if you have room on your return you could move the circ there..not the best way to do it but it will be better than it is..

Leon82

Perhaps they didn't secure some piping and you are getting a hammer from a zone valve shutting

Ironman

Well, it's not piped correctly. The circulator should be after the expansion tank, "pumping away" from it.

But I don't believe that's the cause of the banging. It's probably one of two things from your description:
1. The water in the heat exchanger could be flashing to steam due to a lack of flow.
2. The zone valve(s) could be closing against flow while the pump is running. Make sure the arrow on the side is pointing the correct way. Also, the pump should stop before the valve completely closes. Putting them on the supply near the pump is not the best practice.
3. One more thing: was the check valve removed from the pump? Check valves and zone valves don't go together.

Ironman

Was the cold pressure on the boiler?

Tjs2010

Thank you for the quick response. Cold pressure is into the boiler, but the system line is closed. Does that matter? Would not having a bypass cause lack of flow? I am no plumber, but when the water kicks on you can hear the flow in so lack of flow seems like a suspect. Would circulator position cause this?

Tjs2010

Also, you ask if the check valve is removed from the pump. Where would this be? Again, I am no plumber.

Ironman

Tjs2010 said:

Thank you for the quick response. Cold pressure is into the boiler, but the system line is closed. Does that matter? Would not having a bypass cause lack of flow? I am no plumber, but when the water kicks on you can hear the flow in so lack of flow seems like a suspect. Would circulator position cause this?

No, what I mean is what is the pressure on the boiler when it's cold?

Tjs2010

Pressure is at 17 when cold.

Ironman

Tjs2010 said:

Also, you ask if the check valve is removed from the pump. Where would this be? Again, I am no plumber.

In the discharge side of the pump.

EBEBRATT-Ed

Primary/secondary and constant flow trough the HX would be much better

Tjs2010

Sorry needing it dumbed down, but where would I find that? I have a 30 psi pressure relief valve on it. Would the lack of bypass cause low pressure? The flow of the zone valves are correct. Arrows toward flow.

Tjs2010

> @EBEBRATT-Ed said:
> Primary/secondary and constant flow trough the HX would be much better

Sorry, no idea what this means. Will be having a different plumber come by tomorrow to quote. Since I have all the parts, what is average cost?

EBEBRATT-Ed

Check the installation manual and see what they recommend.

In addition to the poor pump location that others have mentioned I would be concerned with restricted flow through the boiler especially with only one zone calling for heat (looks like you have 2 zones)

Basically I am concerned with full input in the boiler (gas firing) and only a small flow through the boiler.

Primary secondary uses an additional pump to pump the boiler from supply to return which ensures the boiler gets full flow.

Then the zone pump and zone valves pick off this newly created loop.

Can't talk price on this forum...it's one of the rules but it certainly won't break the bank.

I would go primary secondary, bleed the system well and you should be ok

Tjs2010

Just cracked open the book and I get what your saying. Thank you for the help. Time to call a plumber to repipe. Anyone here on long island should I manually open both valves for the time being?

Zman

Copper fin boilers like that one are very sensitive to low flow. That is why every piping diagram in the manual shows a loop providing constant flow. If flow is inadequate, the boiler has micro flashes of steam in the exchanger. That is the noise you are hearing. By not "pumping away" the pressure at the boiler is lowered, making the flashes worse.

Tjs2010

Makes sense. I opened both zones and kicked the unite on for a heat call - no more noise. Ita definitely a low flow issue.

Tjs2010

Well my problem was solved. Had another plumber come in and look over the system. The lack of a bypass valve was causing poor flow to the unit. Once piped the problem is gone. Now o have a new issue - when the unit cycles I am getting a vibration noise in the room right above. I don't hear it much actually in the boiler room. Sounds like an electrical buzz almost or a vibration travelling through the pipes. Any thoughts?

EBEBRATT-Ed

Possibly some air left in the system from the repipe