On 28 Dec 2004 04:07:45 -0800, (PFO) wrote:

Had this boiler as a relacement for a few months now with some
interesting experiences, but generally good impressions.

My question is that with the old Stelrad (20 yrs old) we always ran it
at minimum heat output on a time switch/controller. It was the
smallest model and still to big for our 6 rad system, but it worked
faultlessly.

The 29HE looks good - is almost silent - but the instructions say to
set it to 'E' setting which outputs at 75 - 80 degC, way above the
pevious boiler.

OK, the rads are all hot, but are the instructions correct in
recommending this high setting? Is this a feature of condensing
boilers? Would I waste gas by setting back to a low output?

Basically you turned down the previous boiler because it was producing
too much output. For non-condensing boilers it is better to run them
at their design temperature of 82 degrees to avoid condensation and
corrosion which can occur at lower temperatures.

On condensing boilers, the lower the temperature the better - it is
more efficient to run at a lower temperature. However, when the unit
is installed as a replacement for a non-condensiong boiler, usually
the radiators will have been sized for that and on the basis of 82
degree flow and 70 degree return.

The condensing boiler modulates its output and increases or reduces
temperature as required to match the heat load. The thermostat sets
the top limit. I suspect that the reason that the manufacturers
suggest a high setting is so that output will be adequate when the
application is a replacement and the boiler output maximum output not
much more than the heating requires in cold weather.

You probably could reduce the setting, but there is no real point
since the boiler output should reduce automatically anyway.



--

..andy

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