noisy newly installed Main 30HE

[Nomag]

Can anyone help diagnose this problem which my plumber (a friend of a friend....) seems unable to solve after 2 return visits?
I had a new combi installed to replace an ageing conventional boiler, HW storage tank removed, location of boiler moved. New rad installed in bedroom where airing cupboard prev. located which now houses boiler
The problem...
Whenever CH running boiler very noisy when rad in this room is OFF. When this rad is ON, boiler noise stops. Like a rattly, noisy whine, sounds like it could be the pump but no vibration from pump when cover off boiler.
All air "bled" from system.
Like I say, when the TRV on the new rad in the room where boiler located is ON< there is no noise!
Help please!

 

[Phil]

Nomag

How many radiators have TRV's on them?, it sounds like a bypass issue.

 

[Kings]

If you have moved the boiler (and pump) then you should need to re-balance all of the rad valves.
I'm guessing that with the rad in question open it is happily flowing through it but when closed it is struggling against the rest of the system, this also suggests that you may have a blockage or scale build up.

Also - what speeds are there on the pump?

I would start by opening all of the rad valves fully then balancing them.

 

[Nomag]

Thanks for the help so far.
I spoke to the plumber today who has now suggested removing the TRV and replacing with a lockshield. i'm not sure this is a PROPER solution though. He has also suggested as he will have to drain the system to do this he will do another "flush" to get rid of any sediment. We do get a lot of scale here - the water in Hartlepool is very hard indeed, and the plumber has fitted a scalemaster on the incoming mains CW supply to the boiler.
There are total 11 rads over 3 floors. There are 3 without TRVs - two bathroom towel rails and also an old rad in the dining room which is v close to the floor so the plumber couldn't get a TRV on it. All rads get nice and hot.
I'm afraid I'm not technical so don't quite understand what is meant by a "bypass issue" - does this mean that when the rad circuit closest the boiler is open, it "eases" the flow? I guess if he fits a non-TRV to the rad that currently when open stops the noise, the noise will stop if this valve is left open all the time, but it's not really a good solution as that is my daughter's nursery and we need to be able to control the tmep in there.
The pump is within the boiler, and it has no speed settings which can be changed I'm afraid.

 

[Kings]

A bypass is just a pipe and valve connecting flow and return, if all of the rads close down on their TRV's then you will still get a flow via this valve and the pump will be able to pump water round.
It can be a manual valve just open or an auto valve.
It does sound like it needs more investigation, I would start by opening all valves, checking all TRV's and then balancing the system.

If there is any scale or sediment coming out when draining then it's possible it has scaled up and will need descaling and flushing several times.

 

[Phil]

If you have 3 rads without TRV's then its unlikely to be a bypass issue.

 

[Nomag]

Just to update, our plumber fitted the same boiler at another address and it had the same problem, so he arranged for HeatTeam to come out who do Baxi Group maintenance.
The guy walked in the house with a new diverter valve in his hand - apparently a known fault - and it now works...silently!
Thanks for the advice