On 26 Nov 2003 01:42:27 -0800, (Nigel Percy) wrote:

All CH Experts...

Background

Conventional Ideal FF380 80,000btu Boiler
13 Rads (No TRV's) and Programmable Thermostat
System just balanced - temp drop of 11/12 degree C
across all rads and boiler. Pump speed on minimum.

Problem:-
The boiler will fire continously while the house is
warming up from cold in the morning but for a short
period just before the room stat is satisfied the
boiler will short cycle, Fire for 2 mins off for about
the same duration. This will happen until the room
stat switches the boiler off.

It only tends to happen in the morning when warming
the system up from cold. When demand is triggered
during the day/evening to top up the temp it seems
to fire continuously until the room stat is satisfied.

During the morning warm-up, the flow temperature will probably be at its
highest after the longest "burn" - I assume from what you say about later
demand that the periods are much shorter ? 2 mins on/2 mins off is not
really a great problem in terms of lost efficiency.

However, I note you say you have a fairly powerful boiler and a lot of
radiators. I have a similar configuration, but my boiler pump is set on
max. Anything less and the boiler will "trip" more often. The rads on my
system vary from about 1/2 turn open to almost fully open to achieve an
acceptable balance. (They all have TRVs too, however, although I did the
balancing when they were all demanding heat.) Anyone care to comment on
whether boosting the pump a little might help the OP ?

--
Insanity is hereditary - you get it from your children.

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