On 13/01/2004 Danny opined:-
My theory is that because the water (in the system) is actually
already at temperature and the house never goes below 20 degrees and
that this is a more efficient way to heat my house and keep the bills
down. When the room thermostat is not calling for heat the boiler
only comes on every now and then for approx 30 seconds, I assume just
to keep the water which flows through the HW cylinder at the required
temp.

It is never more efficient to leave the heating on for a period than to
turn it off. Having said that, we do leave our heating on, but set to
retain a low temperature. Even when the house will not be occupied for
several days, we leave the heating on set at 5 deg C to protect against
frost.

If your boiler cycling on and off for 30 seconds at a time, when there
is no obvious call for room or water heating, then there would appear
to be something wrong with it.

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Regards,
Harry (M1BYT) (Lap)
http://www.ukradioamateur.org