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Andrew Gabriel

In article ,
writes:
On Sunday, 13 November 2016 18:55:56 UTC, Andrew Gabriel wrote:
In article ,
David writes:

Brief background; visiting a friend with very old central heating -
reminds me of what was in our last house when we moved in in 1984.

An old Glow-worm 85 100 floor standing lump of iron. Kettles like a really
kettly kettle. Radiators of various vintages, some with suspiciously cool
bottoms.

It hasn't been serviced recently (then again, these are so simple that
there isn't much to service compared to modern boilers). This also
suggests it might do with a flush and some inhibitor.

If it's not room-sealed, then it really should be checked every
year, as it can suddenly build up soot through the heat exchanger
which causes incomplete combustion and emission of carbon monoxide.

Also, in such a system, a flush and inhibitor might clear out some
scale sealing leaks, particularly in the boiler itself.

Recently knocked up a Pi-based controller for a Kingfisher cast-iron
lump, to try and improve efficiency of an old system for a friend.
That has a pumped heating circuit, but a gravity hot water cylinder
coil. It didn't have a roomstat or cylinder stat originally - it does
now, and remote control/monitoring over the Internet.

In principle I suppose you could monitor flu gas temp and turn the flame on and off frequently to keep the exchanger just above condensing, and thus get a big improvement in efficiency.

Flue gas temp in a non-condensing boiler is normally 140C-200C anyway,
as the heat exchangers are nowhere near as efficient. The minimum
boiler temperature I allow to be set is 56C, although it needs to be
nearer 70C to get enough power out of the radiators to heat the house
at this time of year.

Key new features a
o Room stat.
o Setback temperature overnight.
o Frost stat protection.
o Hot water tank stat.
o Pump run-on to get back all the heat in the boiler tank when boiler
demand ceases (otherwise the stored energy just convects out the flue).
o Timeswitch settings different each day to match family requirements.
o Simple manual override with 3 buttons - toggle heating, boost heating
(switch on for an hour higher stat setting), hot water.
o All controls/monitoring available remotely over the Internet which
enables them to use them when out, and me to monitor remotely.

Also, everything is logged so I can see how the system behaves, and
I've used this data to tune system operation, e.g. how long it takes
to heat the water, and the house from any given starting point and
outside temperature.

The logging also reveals a gremlin, whereby around once a month, the
gravity circulation to the hot water cylinder coil fails to work for a
day or so, and then fixes itself. It's also interesting that it takes
10 mins or so before it kicks in anyway once the boiler is hot - I
guess until some hot water rises into the flow pipe, there is no
pressure differential to generate any flow, but when it gets started,
it picks up very quickly.

--
Andrew Gabriel
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