Biasi boiler problem

[1st.Choyce]

my boiler has been playing up. it is a Biasi Riva Advance HE. 6 years old. About 3 times a week when the thermostat calls for CE the rads don't get hot the boiler sounds as though it's working but with high temp on the gauge about 90c. the boiler sounds like a washing machine. other times every thing works ok. Biasi recommended a local heating engineer who has been out 3 times. each time he comes it is working ok. he has changed a diverter then a motorised valve but has not made any difference. I've found a temp fix. I give the boiler a big smack on the side. the sound changes the temp drops and the flow gets hot and starts working. the engineer seems reluctant to come again. hot water works fine. something else that may or may not be relivent. to fix a leaking rad valve I opened the drain tap but no water came out even with bleed valves open. I am stuffed

 

[jordand]

Is there pressure in the heating?

 

[1st.Choyce]

Yes, seems to be up and down through between 1 and 2 bar

 

[1st.Choyce]

as an aside to the above Biasi web site says "account closed" and I cannot find a phone no for them. I thought they were in Wolverhampton. have they gone bust?

 

[dancinplumba]

sounds like pump to me

 

[stevetheplumber]

there in walsal and still there

 

[1st.Choyce]

Thanks Steve
have found them now and their web site is working now

 

[1st.Choyce]

OK dancinplumba can this be tested or do I have to fit a new pump
also any ideas re. no water at the drain tap

 

[jordand]

I agree sounds like pump
Is this the drain valve that you get on some radiator valves or the drain for entire system?
Radiator may have been isolated and drained already

 

[bennygas]

i was thinking the same as dancin till you said the hw was fine. i think the "no water at drain tap" is a clue as to the problem which needs to be investigated before you start getting involved in swapping bits.

 

[1st.Choyce]

Hi Jordand it's the main drain tap under the boiler on the flow pipe
I think this is something to do with the problem. could the system be sludged up. when I've taken off rads before the water was very black

 

[1st.Choyce]

Hi guys
I've found the problem with the drain tap. the washer is stuck
so that was a red herring
back to my main problem. to get the boiler to deliver hot water to the rads I have to give the side of the boiler a hard bang. some time back I did speak to tech help at Biasi who, reading from a script sugested it might be the fan. has this boiler got a fan?