"Nigel Percy" wrote in message
om...
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.

Obviously this is the boiler stat turning the boiler
off but I wouldn't of thought this would happen as the
flow temp from the boiler is 74 degree C and the return
about 62 degree C.

Is the problem the amount of time it takes to heat the
house up in the morning?

Is it a problem or am I concerning myself about something
that isn't a problem

If it's a problem is there a solution?

Cheers

Nige

I suspect that the boiler is a bit too powerful for the job it's doing - and
is simply cycling on its own stat to maintain the set flow temperature. If
this is a problem, you could try de-rating it a bit by reducing the gas
pressure. [If you look at the installation handbook it will probably have a
table showing heat output vs gas pressure].

If you do this, of course, it will be a bit slower to heat up on really cold
days.

As others have said, a modulating boiler would vary its output
automatically - but it's a bit drastic to throw away an otherwise perfectly
good boiler!

Roger