On Sun, 12 Sep 2004 19:58:03 +0000 (UTC), "John"
wrote:



I would agree with you but with reservations. There was very little point in
owning an analyser for the majority of domestic boiler work.


Technology was fairly simple and a manometer on the outlet of the gas
valve was good enough - right?



The situation
is changing now since premix and modulating burners are becoming common.
The emphasis previously has been to ensure that any products of combustion
were correctly evacuated with no spillage or leakage from flue into room
space, and that combustion was basically correct as viewed by flame picture
and gas rate relying on the manufacturer making appliances to an agreed
standard in the\first place.

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

For commercial appliance service the situation is somewhat different and
personally I'd never go near a blown gas burner without a full spec analyser
its not possible to be certain that one of these is burning correctly any
other way - too little air = CO due to incomplete combustion, too much air
=CO due to flame chilling

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.




Quite a lot of the boilers coming onto the market, especially those
with premix burners, seem to have use of a combustion analyser in the
setup procedure - typically that the emission composition should be
checked at low and high end and the gas rate adjusted to match the air
supply from the fan at the given burn rate.

BG seem to have them, although this seems to be mainly so that they
can just check the flue with the probe and pronounce the boiler OK
without taking it apart.

The BG analyser is often only a minimalistic job giving CO/CO2 ratio
readings and while satisfactory is not a full analyser

Possibly beyond the comprehension of the average operative. They just
seem to write down the number and that's it.


.
One day's visits and they've paid for the analyser comfortably.

Yup!



..andy

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