Water hammer from central heating valve???

[Dave Fawthrop]

I have just had a new Combi fitted to the old *single pipe* radiator system. Two zones upstairs and downstairs controlled with valves. It worked fine.

The downstairs valve was in the wrong place so I drained the system and moved it. Crossed a thread and had to replace it with a different make. Refilled, bled radiators, and adjusted CH pressure to 1-2 bar.

Now the problem! The system gives a *single* bang a few times a day, at random. Random events are a pig to fault find. It sounds to me as if it

*could* be water hammer caused by the valve closing. It really does not sound like a gas explosion, just the pipes reverberating.

What do people think? What is a good method of fault finding?

Google gives

US site says that air chambers are no longer recommended. High temperature sealed are filled bladders?

[Awesometoday]

recommended.http://www.builderswebsource.com/techbriefs/waterhammer.htm

Gutenberg

Free to any

Are The valves motorised? If so do you have a two seperate thermostats, one for upstairs and one for downstairs? Does your new combination boiler have in integral bypass if not then there is your problem. As both the valves close the water has no where to go hense the banging. You will need to fit an AUTOMATIC bypass between the flow and return pipes. Usually in 22mm and a certain distance from the boiler depending on the size of your system this will be explained in your installation manual. You will need to set the bypass so it gives a minimum flow rate when both valves are closed which will aslo be in the installation manual.

Hope this helps

[cynic]

recommended.http://www.builderswebsource.com/techbriefs/waterhammer.htm

Gutenberg

Free to any

Ignore US sites. The problem will be due to the new valve shutting more suddenly then the old one. Some makes are more prone to this than others. The Honeywell rubber ball type "usually" are least prone to it but YMMV A shock arrester might be useful but no guarantees

[Awesometoday]

recommended.http://www.builderswebsource.com/techbriefs/waterhammer.htm

Gutenberg

Free to any

Do a basic check before anything else................. make sure you have fitted the replacement valve correctly. On the brass body on the underside you will see the letter A on one port and B on the other port. Make sure water is flowing in the direction of A to B.

[Roger Mills]

It shouldn't be too difficult to check that it *is* the valves doing it. Use the relevant room stats to cause each valve in turn to close and see whether you then get the noise. You should be able to isolate which valve it is, and also whether it only happens when the *second* valve closes but not when one valve remains open.

Even if it is a valve, it's only annoying - not serious. But also see someone else's post about a by-pass valve.

[Dave Fawthrop]

|!On Mar 18, 7:26 am, Dave Fawthrop |! wrote: |!> I have just had a new Combi fitted to the old *single pipe* radiator |!> system. Two zones upstairs and downstairs controlled with valves. It |!> worked fine. |!>

|!> The downstairs valve was in the wrong place so I drained the system and |!> moved it. Crossed a thread and had to replace it with a different make. |!> Refilled, bled radiators, and adjusted CH pressure to 1-2 bar. |!>

|!> Now the problem! The system gives a *single* bang a few times a day, at |!> random. Random events are a pig to fault find. It sounds to me as if it |!> *could* be water hammer caused by the valve closing. It really does not |!> sound like a gas explosion, just the pipes reverberating. |!>

|!> What do people think? What is a good method of fault finding? |!>

|!> Google gives

|!>|!> A US site says that air chambers are no longer recommended.http://www.builderswebsource.com/techbriefs/waterhammer.htm |!> High temperature sealed are filled bladders?

|!Are The valves motorised? If so do you have a two seperate |!thermostats, one for upstairs and one for downstairs?

Yes! I have now shown that the problem is with the new downstairs valve by fiddling the controls

|!Does your new |!combination boiler have in integral bypass if not then there is your |!problem. As both the valves close the water has no where to go hense |!the banging. You will need to fit an AUTOMATIC bypass between the flow |!and return pipes. Usually in 22mm and a certain distance from the |!boiler depending on the size of your system this will be explained in |!your installation manual. You will need to set the bypass so it gives |!a minimum flow rate when both valves are closed which will aslo be in |!the installation manual.

The boiler is a Baxi 105 instant, which is grossly overpowered the radiators fitted. Is it possible to turn down the output of the boiler pump?

They did not leave me the installation manual, I will try to find it on the Web

I was thinking of draining a bit a bit of CH water and adding some more, so that the air would boil out and form a de facto shock arrestor.

[Frank Erskine]

I have the installation mnanual in front of me at the mo.

According to the manual the pump (a Grundfos 15-60) MUST be set to '3' (maximum speed).

If you wish I could scan you the relevant bits of the manual...

[Dave Fawthrop]

|!On Wed, 21 Mar 2007 08:20:45 +0000, Dave Fawthrop |! wrote: |! |! |!>The boiler is a Baxi 105 instant, which is grossly overpowered the |!>radiators fitted. Is it possible to turn down the output of the boiler |!>pump? |!>

|!>They did not leave me the installation manual, I will try to find it on the |!>Web |!>

|! |! |!I have the installation mnanual in front of me at the mo. |! |!According to the manual the pump (a Grundfos 15-60) MUST be set to '3' |!(maximum speed). |! |!If you wish I could scan you the relevant bits of the manual...

Thanks but I will believe you.

[<me9]

That is wahat is says in mine (a system boiler). It also says to reduce flow to suit the load by using an in line valve on the output of the boiler, thus diverting some flow through the internal bypass. I also fitted an external bypass set to minimum, near the zone valves, for when the TRVs reduce the load even further.

[Andrew Gabriel]

Ask the fitter for the installation/servicing manual. They are required to leave it with you.