On 18 Mar 2007 03:37:45 -0700, "Awesometoday"
wrote:

|!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 giveshttp://www.water-hammer.com/
|!
|! A US site says that air chambers are no longer recommended.http://www.builderswebsource.com/tec...aterhammer.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.
--
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