DIY Doctor UK DIY Forums

Hi,
I've had a new system fitted last year and to this day is not working right.
The first problem is, is the loud knocking noises when the boiler fires up. I have tried tracing it and it sounds like it is coming from the front of the house pipes. It sounds like its the pipes, but it never made this noise with the old system.
Secondly, the radiators have never felt really hot when the CH and HW is both on. I have moved the wireless thermostat tp upstairs and this has helped a little. All rads have trv's except the bathroom and the one in the hallway (it did, but I took if off). The one thing I have noticed though, is that when the HW is off and the CH is on the rads get really hot, which they should do at 20 degrees. I tried this tonight, switched the HW off and the rads got hot straight away.
Please could someone help me on this, as it is driving me mad. I keep asking different plumbers but no one seems to give me a real answer.
Thank you

Hi Ben

Need more info to advise,but if you now have a combi? I would suspect diverter valve and or controls

Hi,
Thank yor your reply.
It is not a combi. Standard condensing boiler.
The old boiler was in the kitchen, but had the new one fitted in the loft.
The radiator in the bathroom is fed by the hot water.
All rads did have TRV's on, but I have sinced found out that 1 should be let off. So I have taken this off (hallway).
I called the heating guy back a couple of months after the install (last Oct) as the rads up stairs were not getting that hot. He said it was because the water needed diveting, so installed a divertor (red knob).
This made a bit of difference, but not much. This is when I noticed that when the HW is off and the CH is on (at weekends we are at home), the rads get much much hotter. This is how I think it should be as I could then set the TRV's to 4 instead of 6 at present.

As for the knocking noise, it's doing my head in! It made a bit of noise last year, but never as bad as this. It's literally when the boiler fires up. I have bled all rads, some air but not much.

Hope this is more information for you. Please ask as many questions as you like and I will try my best to answer them.

Many thanks
Ben

Hi,

Is your pump working,have you bled it ?

Hi,
Would this be the pump attached to the hot water tank or the one in the boiler? How would I know if it wasn't working? The one in the boiler was is new. How can I bleed them?
Thank you
Ben

Hi mate, there should be a lockshield gate valve on the coil coming out of your cylinder usually at the bottom. This should only be opened about a quarter. Sounds like yours may be fully open because when you have both CH and HW on the water will be taking the quickest route back to the boiler therefore not circulating round the radiators effectively. Not sure about the noise though, hope this helps.

My guess is there is problem in boiler which is making noise or els the boiler is loose fitted.

Ben,

Pump on the boiler, take the large screw out in the middle of pump, some water will come out -- rags, you should be able to see spindle rotating. Also does your boiler have an auto air vent?

Hi Steve,
Sorry for the delay.
Where would the auto air vent be?
Thanks
Ben

On the boiler near pump resembles a bicyle valve - unscrew it/ should be loose fitting.