Loud bang and shaking pipe from heating boiler

[musicman53]

After having a new boiler fitted(ideal icos HE15)because the original one(Baxi)cracked, when the three port valve is at the mixed position there is no loud banging and shaking of the pipe to the radiators.
When the three port valve changes over to just H(heating)then when the boiler fires up and hot water goes thru(from the 3 port vave) the pipe to feed the radiators there is a big bang and the pipe shakes.

All radiators apart from the one in the bathroom are fitted with TRV's.
Radiators in main bedroom(same room size as living room)and living room are different sizes, the bedroom one was replaced by a very short double that seems not to be able to put out enough heat.
Hallway one is a very small double and this time of the year even if set full on cannot even put out enough heat to make any difference.
If the(only)control on the boiler is set to the lowest, or any setting right up to the last but one this time of year then the rooms take ages to warm up.

Heating engineers have said there is nothing wrong with the system.
Two valves were fitted to the top of the pipe into the hot water tank and on top of the pipe that feeds the radiators(the valves are supposed to auto let out air(?).
Anyone have any thoughts?

 

[Slugbabydotcom]

When thermostatic radiator valves are used, the space heating
temperature control over a living area having a heating
requirement of at least 0.9kW (3000Btu/h) of the boiler heat
output should be achieved using a room thermostat whilst other
rooms are individually controlled by thermostatic radiator
valves. A higher proportion of TRVs may be used, provided that
a bypass between the boiler flow and return is fitted, to ensure
adequate flow when all TRVs are closed.

Well theres a lot of things written about TRV's and that excerpt from the MI's seems to imply that with your current set up there should be a room stat in your bathroom and that the rad in there should be over 0.9Kw.
Whatever, heres some advice
If you dont have an automatic by-pass then get one fitted. If you do have one it could be set too high. I'm told they should be set about 0.3bar or usually about mid range if you just have numbers. See if adjustment makes any difference.

 

[Goldspoon]

Are the TRV's one way or two way flow?

If the boiler fitter switched flow and return and the TRV's are only one way then you will get pipe hammer (happened to me once and I had to either switch flow and return or change the TRV's - I switched flow and return).

 

[musicman53]

Are the TRV's one way or two way flow?

If the boiler fitter switched flow and return and the TRV's are only one way then you will get pipe hammer (happened to me once and I had to either switch flow and return or change the TRV's - I switched flow and return).

I questioned more than a few "engineers"who have been out to look at it if there was a chance that the person who installed the boiler got the flow and return pipes round the wrong way.
When he came to connecting the flow and return pipes on top of the boiler he said he could not see any markings to say what pipe was what.
He took a guess at the way they should be connected.
On the old boiler the two connections were round the other way to what they are on the new one.
I still do not know if they were connected right or not.
The TRV's are reversable(you turn something on the valve to change flow direction).
Have tried it but makes no difference.
The banging and shaking does not happen all the time.
It happens only when the three port valve is at the H position and after the hot water and heating have been on.
It's not what I would call hammer.
It makes the loud banging at least three times and does not happen until the water hots up again to go to the radiators.
If the CH temp control on the boiler is turned right down then it does not happen.