Grant 70 MkII Combi

[nick280]

Hello,

My first post and in need of help please so a big HELLO to all you lovely people 😀

I have a Grant Combi MkII 70 with a Riello 50 70 RDB burner.

The boiler has been giving poor performance recently by delivering little hot water.

I have serviced the boiler to a point and it has improved a lot but still not as good as it has been. I have fitted a new jet (previous jet was Danfoss .60 x 80deg H but I installed the standard Danfoss .60 x 60deg EH), adjusted the electrodes, cleaned the combustion chamber which was spotless, set the expansion vessel pressure to 1bar and recharged the water pressure to 1bar. I altered the air damper to 0.5 backed off from visible smoke on a still day which turned out to be number 5 on the damper indicator. The combustion smells like it is burning nice and clean.

I now have a good 5 minutes of nice hot water and then it drops on the cold side of tepid.

I haven't checked the oil pressure nor the flue gases with a meter as I don't have access to these tools although I am quite prepared to buy an oil pressure gauge.

I have changed the heat exchange last year due to it leaking from cold to hot side.

I have occasionally heard the flame go out and reignite itself without the fan stopping.

Can anybody help me please or point me in the direction of help.

I have had bad experiences with plumbers and I'm reluctant to continue the search for a reliable honest one.

Please do think I'm tarring people with the same brush with that comment, I've just been very unlucky.

Thanks in advance for any help.

Regards,
Nick.

 

[Billy Bob Bob]

nick your not a qualified oftec engineer,so stand a very high chance of killing yourself and loved ones by messing with your boiler my best advice to you is either post a ad in the need a engineer section on here or look at oftecs website for engineers in your area