RE: Boiler control update and query

["Dave McLaughlin" <dave@xxxxxxx>]

Hi Kevin,

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-----Original Message-----
From: Kevin Hawkins [mailto:lists@xxxxxxx]
Sent: 17 December 2003 00:16
To: ukha_d@xxxxxxx
Subject: RE: [ukha_d] Boiler control update and query

>      Do you have any internal thermostats that are on any zoned areas
or
>radiators that have a time clock on them ? I have some Digistats where
I
can
>set 3 differ rent temps for 3 time periods in one day. This effectively
>changes the dynamics of my whole system. I have some rooms that aren't
>heated in the morning for example. The clue has to be in something that
is
>timed I feel or something that is 'open' or 'closed' but only in the
>evenings.
>
>      I wonder if this is something that happens once your thermostat
has
>actually become satisfied. Have you anyway of noting if this happens in
the
>morning ? Maybe the oscillation of the temp in the morning and
lunchtime is
>just the boiler actually kicking ON and OFF based on the water temp
inside
>itself, whereas in the evening the room thermostat is actually turning
the
>boiler ON and OFF. I am guessing it is not a modulating boiler from the
>graph.

There is no room thermostats on the system. There are thermostatic valves
on the radiators. The boiler is a combi made by Worcester Bosch.

The oscillation in the morning and afternoon is as you state, the boiler
switching on and off to maintain the set temperature within its own
thermostat.

All rooms are heated all the time.

>      Lastly maybe you have thermostatic radiator valves - and as some
of
>these kick in and close down radiators then they will cut off large
volumes
>of water or reintroduce large volumes of colder water back to the flow.
This
>could cause sudden dips in the temperature as they open and a reduction
in
>circulating water volume as they shut off,  this could create higher
>peaks...

All radiators are on all the time so it seems strange, but you could be
right and with a bit more temperature sensing in the rest of the house
I might be able to track it down.

>      The graph is very interesting and I shall have to have a go
myself.
>Where have you tapped the water temp on the boiler.

I simply located a DS18S20 between the boiler wall and the cladding
and this seems to work reasonably well. It may be a few degrees
below the actual water temp, but good enough for me.

Regards
Dave...
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UKHA 2004: 15th and 16th May 2004

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