On 12 Sep 2004 21:52:19 GMT, (Andrew
Gabriel) wrote:

In article ,
Andy Hall writes:

Largely similar to one another, and one could also time the meter,
although I have never seen an installer do that.

Oh really? That's what I ended up doing with my Keston.

That's 'cos you read the instructions.... :-)


It was supposed to be factory set, but it was miles out.
At the top end, it was (IIRC) 10% too low -- they only allow
+-5%. At the bottom end (which the instructions didn't even
suggest checking), it was about 4kW instead of 7.5kW, which
explained why the gas ignition was travelling back up into
the premix area and making a sound like a 32 foot organ pipe.
There is only one mixture adjustment, but fortunately it
seems to have a much more dramatic effect at the bottom end
than the top end, so it was possible to bring them both in
much nearer to the rated values, although the top hit the
correct value whilst the bottom was still a bit under.

That was my experience as well. The bottom end was more critical
than the top and there was a certain amount of iteration.



Of the two boilers that I shortlisted, the Keston Celsius could be set
up by checking the gas rate - the gas valve being preset. The
manufacturer does give combustion gas figures for later checks.

On the MAN Micromat, that I eventually installed, an analyser is
required for set up. Gas rate is checked and then top and bottom
combustion gas composition is measured - there being gas valve
adjustments for each. In practice, little change was needed, but at
the extremities of the settings, CO does rise.
There is no question of doing pressure tests at the gas valve. The
nipple is there, but the pressure is negative.

That is one of the checks on the Keston. I says something like
it should be at least -1.25" -- it's not at all clear which side
of the -1.25" is the 'OK' side, and it was off (can't recall which
way). Having adjusted the power input via meter timing, fortunately
it ended up being exactly -1.25" so I didn't need to worry which
way was 'OK'.


Hmm curious.... Presumably that is at full burn rate?


..andy

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