What's 'normal' travel on a Worcester Bosch 28CDi diverter?

[garyo]

With central heating switched off, when I try to use demand hot water, my boiler ramps up the flame to full burn, but then quickly reduces it to half burn, resulting in luke warm water.

I replaced the water-to-water exchanger last year, so I don't think that's the problem. I also changed the diverter value diaphram. The valve is moving out enough to engage the microswitch, and when I look in to the valve (i've just taken the exchager off to have a look at it) there are no obvious signs of blockage.

How far should the valve be moving? It looks to me like it's moving 5mm - is that enough?

Gary

 

[onlyfitidealboilers]

may be NTC problem, get a eon or bg on a fix price repair to come an sort it for you

 

[garyo]

Cheers. I've tested the DHW sensor and it seems to be within range (13k at ambient, then down to around 3k when heating)

Strangely, if I leave the hot water taps running for a few minutes in 'luke warm' state, then whenever I move the water temperature selector, the burner seems to run on full gas pressure for around 20 seconds, and then returns to 'luke warm'

Sometimes it'll do this by itself too - maybe once in every three minutes. It's almost as if the potentiometer behind the knob is failing, or some element of the PCB.

Gary

 

[Andygasman2010]

The pin travel determines wether the burner is on or off, not modulation, so don't worry about that.

Sounds like a gas valve set-up issue which you will need an RGI to do.

 

[petit_pablo]

Is the heating flow getting hot when you run hw?

For what reason did you change the hw heat exchanger? Id bet on it being blocked.

 

[nickso]

Is the heating flow getting hot when you run hw?

For what reason did you change the hw heat exchanger? Id bet on it being blocked.

i'd start there.

 

[garyo]

Thanks for the replies.

The central heating pipes aren't getting warm when I run the hot water.

I changed the heat exchanger last time because it was blocked up - we're in a hard water area.

I've taken the heat exchanger out - it didn't seem to be blocked up but I've descaled it over night anyway and given it a good flush. This has made the problem marginally less worse, in that it's slightly warmer than luke warm!

Does it help if I say this problem happened fairly suddenly - one day the system worked, the next it performed very poorly?

Cheers

Gary