In an earlier contribution to this discussion,
Wngstr wrote:

I have a normal boiler (non-combi) that is 2 years old in a fully
pumped open vented system, with a programmer and a thermostat in the
hall. The pump is 1 year old.



I switched off the heating for a week to go on holiday and since
switching it back on I have had difficulty getting the heating to
come on. The hot water is fine (comes on regularly) and the boiler
fires up for that, but the heating has only come on once or twice in
the last few weeks. The pump is very hot and I can hear it
fizzing/gurgling but no central heating.



The system has been flushed recently and I recently rebalanced the
radiators as the living room radiator (the one furthest from the
pump) was only luke warm with the one nearest was scorching.



Any ideas?

If it's a fully pumped system, it will almost certainly have either 2
motorised zone valves - one for CH and one for HW - (S-Plan) or a single
3-port mid-position valve (Y-Plan)
See http://content.honeywell.com/uk/homes/systems.htm for more details.

If HW is ok, the pump must be working - to some extent, at any rate. The
likely culprit is the CH zone valve or mid-position valve (depending on
which you've got). It *just* could be the room stat, or a wiring fault - but
these are less likely.

I presume it *has* worked since you flushed and balanced it? If not, you
could have a massive air lock somewhere.
--
Cheers,
Set Square
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