Worchester Bosch 28CDi

[craigs6124]

Hello all
My Worchester Bosch 28CDi is not getting as hot as it used to on the central heating side. A month ago, if the thermostat was set to maximum, you couldn't hold your hand on some radiators for more than a few seconds, but now, although they are still pretty warm, they are not getting as hot. I am checking radiators that have the thermostatic valves set to maximum, or the radiator in the bathroom that has not got a thermostatic valve on. I have even checked the 'Feed' outlet pipe on the boiler and that is only getting as warm as the radiators. The domestic hot water (that is the tap water isn't it?) still gets VERY hot with the thermostat on maximum. I have tried to bleed the radiators, but there is no air in them. The pressure gauge on the boiler is reading about 0.5 bar when the system is cold, but this rises to about 2.0 bar when the heating is on. What should this be reading when the system is hot/cold?
I assume it must be a temperature sensor/thermostat issue, but where do I find these on the boiler, and can I check which is faulty without buying each part in turn until I find the correct one?
Thanks for reading.
Craig

 

[LUNAT]

HI

pressure when cold 1-1.5 bar
when hot 1.5-2 bar.if the system is not treated chemically then try adding sludge remover then inhibitor.

 

[craigs6124]

Thanks Lunat

Upped the pressure to 1.5 bar, when cold, and the temperature in the radiators came back. Pressure has dropped back down again though. It's losing it out of the PRV, so I've just ordered a new one.

Thanks again for your help.

 

[kitch0978]

if your prv is passing ir is possible that youe expansion vessel needs recharging or replacing........r

 

[craigs6124]

Is there any way I can tell if the expansion vessel is at fault, or will I just have to see if the new PRV passes too? What does recharging the vessel involve? What is it filled with?

 

[kitch0978]

it is the big red vessel that is visible behind the boiler pump, gas valve plate heat exchanger etc......there will be a valve on it at the front( bike/car type schrader valve) take cap off and press pin in......if water comes out then you need a new expansion vessel, if air comes out then still worth recharging, if nothing comes out the needs recharging. to recharge you need to drain boiler ............then attach a foot pump or equivelent to valve and pump up to approx 1 bar pressure , refill boiler and off you go

 

[craigs6124]

Thanks for that kitch0978
Just tried it now, and no water or air came out of the valve. Isolated the F & R valves and drained the boiler to empty, and then closed the drains. Pumped up to 1 bar, but the gauge on the boiler was going up too. I wasn't sure what to do at this point, so I hope I did the right thing....I opened the drains again, and kept pumping the footpump until the water finished draining (probably about 10LTRS in total) AND I had 1 bar reading on the footpump, which seemed to be holding. Then I closed the drains, and refilled the boiler to 1.0 bar on its gauge, then opened the F & R valves.

Have I done this correctly?

Does this mean I didn't need to replace the PRV valve?

I'll have to see if the pressure drops off again.

 

[kitch0978]

sounds like you managed the job except ypu may now find that the valves leak!! but maybe not.....turn you heating on and find out, i suspect that the prv will still leak but you have probably fixed the problem that caused it to leak in the first place( expansion vessel pressure loss).

 

[craigs6124]

You are right, water is coming out of the PRV already.

Will I need to repressurise the expansion chamber when I drain the boiler to replace the PRV?

 

[kitch0978]

you shoildn`t have to re pressurise it again but while its drained to replace prv you might as well check and see if its held its charge ...... if it has then with a new prv you will be up and running...good luck