ravenheat combi

[rona]

Hi just wanted someones opinion about my 7 year old boiler. The problem started a couple of weeks ago with the shower, which started to go cold but would return to temperature, then it ran cold and stayed cold so we guessed it was the boiler. We have called in a plumber who checked it and said it was either the thermostat or the gas pressure, either way 7 years is about the limit for a ravenheat apparently! So we need a new boiler.
One thing which concerns me is that when we try to run a bath we find black oily specks coming out of the hot tap which stick to the bath and need a degreaser to remove. Is there any connection with these black specks and the condition of my boiler?

 

[DP]

>>>We have called in a plumber who checked it and said it was either the thermostat or the gas pressure, either way 7 years is about the limit for a ravenheat apparently! <<<<

I am not surprised he said you need a new boiler. While I am no fan of the Ravenheat, I wopuld hope the boiler to last a lot longer than that. The chances are you plumber is not a heating engineer, therefore has no idea of what the cause may be. A faulty thermostat would not give you partcles you speak of. Gas pressure would effect CH as well- this I assume is functioning correctly. I cannot comprehend why some people are so keen to suggest a boiler change when existing is perfectly serviceable. I hardly ever push for a replacement boiler. Many a good boiler gets taken out to be replaced with a modern sneeze-on-me-and-I-catch-a-cold boiler.

If you stand in front of the boiler and get someone else to run a hot tap, does the boiler ignite and stays on or does it cycle (on, off, on etc intermittently)?

Black specks more than like are bits of perished rubber. Fresh water enters the boiler and is heated (indirectly) with dirty water. Diverter diaphragm is the only component that is in this flow stream.

 

[rona]

The boiler, when it sees fit, lights and stays on and will usually stay on 'til the tap is turned off. Unfortunately once it has run for a time it refuses to come on again at all, sometimes for 24 hours! The central heating does not seem to be affected.
If the black particles are perished rubber, could this be due to us changing a worn tap washer (though this was a couple of weeks ago and surely the bits would have been flushed out by now)?

 

[DP]

Bits of rubber are from inside of the diverter valve. When you run a hot tap, the boiler recognises this and runs to heat the water. I can safely assume that the boiler is not recognising demand for hot water.

If you run boiler for central heating, water demand will be seen but water will not get as hot. If this works, it will be for a short period of time only Days if not weeks)

 

[rona]

Thanks for that. It has given us a bit of breathing space til we can figure out whether the boiler will be replaced or repaired.
Now if the weather were just a bit cooler it wouldnt be so bad having the heating on! Oh well I'll just have to have it on first thing in the morning and last thing at night. The shower is just about usable now as well!
Glad I asked.