Hot water baseboard water hammer

zhenying

My home's heating system uses hot water baseboard. We had an old oil boiler running for many years. The system was getting old and started to have small problem and I decided to convert it to gas combi boiler.

However, right after the conversion, it sometimes makes single big bang noise when zone valves turn on. It happens randomly, and around 2~6 times a day. My plumber who install the new Bosch Greenstar 151 Combi boiler system couldn't figure out the reason.

The bigger problem is, I believe, this water hammer has lead to two failures on the boiler's pressure relief valve and leaked a lot of water in my basement.

Here is the diagram of my heating system:


I also capture a video showing the banging noise when the zone valve turns on. My in camera microphone may not do a good job capturing the big noise, but it is loud.

Can you help?


https://www.youtube.com/watch?v=VDqcaVgA_Dg

Jamie Hall

First problem I see is that the circulator is in very much the wrong place. It should be between the Spirovent and the T to the two zone valves (pumping away from the expansion tank). That one change may eliminate the problem... but needs to be done anyway, for the health of the circulator.

woodrow

2nd problem they did not follow the piping diagram primary secondary or low loss header

Zman

Have your installer come over and repipe the boiler as directed in the installation manual and you should be good to go. They way you are piped, you will have no warrantee.
You likely have a check valve installed in the circulator which is making the noise worse.

SuperTech

Yup. Piped all wrong setting you up for multiple problems.

If the installer didn't pipe it right are you sure it's vented properly and the gas pipe installed correctly? Has a combustion test been performed?

Installers that don't follow the instructions on the most basic parts of the installation scare me, if they don't care about the basics then I'm sure all the important details have been overlooked.

zhenying

Jamie Hall said:

First problem I see is that the circulator is in very much the wrong place. It should be between the Spirovent and the T to the two zone valves (pumping away from the expansion tank). That one change may eliminate the problem... but needs to be done anyway, for the health of the circulator.

Thanks for your comment, I am not a plumber, can you elaborate ?

zhenying

woodrow said:

2nd problem they did not follow the piping diagram primary secondary or low loss header

Can you elaborate? thanks a lot for your help.

Jamie Hall

Compare your diagram, @zhenying , with the one @Zman posted, item by item. There are numerous differences. @Zman 's is correct; except that you don't need items 6 and 7 on his diagram. Everything else you need, and it must be piped and linked together in the way shown on that diagram.

Since you are not a plumber, you probably need your installer -- who should have known how to do it properly in the first place -- to come back and redo the whole thing properly.

zhenying

Hello my friends, I am so glad that somebody replied my post. I took a picture of my heating system and put some labels there. Below is the original image with high resolution. Please take a look and see if that matches my diagram drawing. Thanks a lot.

zhenying

Jamie Hall said:

Compare your diagram, @zhenying , with the one @Zman posted, item by item. There are numerous differences. @Zman 's is correct; except that you don't need items 6 and 7 on his diagram. Everything else you need, and it must be piped and linked together in the way shown on that diagram.

Since you are not a plumber, you probably need your installer -- who should have known how to do it properly in the first place -- to come back and redo the whole thing properly.

Hi Jamie, thanks a lot, I am planning to talk/complain to my plumber "again", but I need to educate myself more so that they will take me seriously. The boiler pressure relief valve failed twice, they came back and only fixed the valve.

Can you or anyone explain how the current pipping can cause water hammer bang when the zone valves turns on? and why that happens randomly?

zhenying

Zman said:

Have your installer come over and repipe the boiler as directed in the installation manual and you should be good to go. They way you are piped, you will have no warrantee.
You likely have a check valve installed in the circulator which is making the noise worse.

Hi @Zman , can you explain why "You likely have a check valve installed in the circulator which is making the noise worse" ? Thanks

zhenying

A few more pictures.

zhenying

Zman

If your system is set up so that water is isolated from the expansion tank, the water in that loop will become over or under pressured compared to the water exposed to the expansion tank. You will get a noise like yours when the valve opens and the pressure equalizes.

You have a zone valve on one side of the heating loop. If you have a check valve on the circulator, you will have isolated that loop.

All that aside, your boiler is piped completely wrong and needs to be fixed.

SuperTech

Basically, all the piping on the boiler needs to be cut out and completely re-done. It's not a matter of one or two small changes. Google primary secondary piping and familiarise yourself with the concept, that's what a low loss header accomplishes. Your boiler should be piped in this manner. The circulator needs to be installed after the expansion tank and air separator on the supply pipe. Zone valves should also be on the supply.

What about combustion analysis? Was it performed? This is critical to safe and reliable operation. I would strongly suggest considering finding someone else to repipe the boiler and perform the necessary work done during commissioning, the original installer obviously doesn't care about following the manufacturer specifications and instructions.

zhenying

> @SuperTech said:
> Basically, all the piping on the boiler needs to be cut out and completely re-done. It's not a matter of one or two small changes. Google primary secondary piping and familiarise yourself with the concept, that's what a low loss header accomplishes. Your boiler should be piped in this manner. The circulator needs to be installed after the expansion tank and air separator on the supply pipe. Zone valves should also be on the supply.
>
> What about combustion analysis? Was it performed? This is critical to safe and reliable operation. I would strongly suggest considering finding someone else to repipe the boiler and perform the necessary work done during commissioning, the original installer obviously doesn't care about following the manufacturer specifications and instructions.

Hi @SuperTech, can you tell me a little more about combustion analysis? or do you have a link to a literature? Thanks

R Mannino

Gentlemen, the floorstanding Greenstar has a low loss header built into it. My money is on a check valve installed on the Grundfos.

GBart

R Mannino said:

Gentlemen, the floorstanding Greenstar has a low loss header built into it. My money is on a check valve installed on the Grundfos.

He is correct, please as I have stated 1200 times, refer to the factory manuals. Page 26

your unit is piped correctly to a degree, the circ should be pump away and the expansion tank behind it

https://www.bosch-climate.us/files/6720810590_GreenstarFS_Installation_Instructions_en_02.2017_US.pdf

SuperTech

Combustion analysis is performed by drilling a hole in the flue pipe (unless the unit has one) and sampling the flue gas using a digital combustion analyzer. It measures the air fuel ratio and carbon monoxide output. The manufacturer specifications in the installation guide will state what the levels should be. This is critical when commissioning a new installation of equipment that burns fuel. Any system creating more than 100 PPM of CO is not safe to operate. No appliance is good to go out of the box.

The installer is responsible for the safety reliability and efficiency of the equipment. This can only be assured by proper combustion analysis. A print out from the analyzer should be left with the equipment or written on the invoice.

EBEBRATT-Ed

That is a hefty looking pump for a couple of small zones. The zone valve may have trouble operating with that pump. Did it come with the boiler or did the plumper line size the pump?

could have too much head for the zone valves