Banging Radiators on new Main Eco 30 HE Combi Boiler?!?

[Indi]

Hi guys,

I was wondering if someone could help with this one... Just had fitted a new Main 30 HE Eco combi boiler on existing radiator and pipework system. The system was flushed and cleaned and all was well... Until a 48 hours later when four of the radiators have started banging?! They are all getting hot but the banging persists on 4 out of the odd 10 of so in the house? They all have Honywell TRV's fitted and the system is plumbed using microbore. Apparently when the TRV's are adjusted the pace of the banging increses and decreases... Is it just a case of faulty / sticking TRV's or maybe something else I haven't thought off...?

Thanks in advance, any sugestions would be welcomed!

 

[buryboy]

Some TRV's have to be fitted on the flow side of the radiator.
When system cold turn on boiler then check which side of the radiator the pipe gets hot first.
If the TRV is fitted on the pipe that doesn't get hot first and its one of the radiators that's banging then I would suspect that it could be that the body of the TRV wants to be turned around or moved to the other side of the radiator. Check the instructions that came with the Honeywell TRV valve.
That's why I always fit Danfoss RAS 2c TRV. No drain down needed to turn the valve around.

 

[Indi]

Thanks buryboy. So why does that in itself make the radiators bang then? Ie: If the TRV's are on the wrong side? Also note that the TRV's are existing from the origional boiler system and I haven't changed, or moved these when the new boiler was fitted.

 

[buryboy]

When the banging occurs put your hand on the TRV and see if you can feel if the banging is occuring inside the valve.

When you say it was flushed, how long was it cleansed and with what chemical and when it was drained - was it whilst CH system water still hot?

The pump on the new boiler will be stronger than the old pump, which could cause hammer when the TRV is almost closing.
Also is it known how old the Honeywell TRV's are?

When the boiler was changed presume the new flow was connected the same as previous.

You could remove the TRV's sensor head completely and see what happens. If that stops the banging, then problem solved. Unless that is, the little pin it pushes down is stuck. You should be able to push the little pin down with the head removed and it should come back up unaided.

 

[Indi]

Thanks Buryboy!

The cleanser was left in the system for a week before being drained. I understand it was Furnox? I understand that the water was still hot.

The honywell TRV's are as old as the house from what I can see - around 15 years old. I also understand that the flows were indeed conected the right way around.

I'll try removing the TRV heads and see the state of the pins... Thanks for all your advice!

Ohh, one thing, why does it mater if the water was hot or cold when it was drained? Just for my reference really?