I think you may have a possible solution. All the rads (except one) have
TRVs on them although I suspect this was something the previous owner added
and not a Redrow standard fitment. This probably means that there isn't any
special plumbing to handle such a situation. The only radiator not to have a
TRV is the small one in the hallway where the thermostat is. Since I keep
the lounge door closed, the thermostat is actually in the coldest part of
the house.

Is the following a realistic scenario ?

Themostat in hallway demands heat. TRVs say it's too hot and close down
although the hallway is still cooler so the boiler stays on. Since there is
now only one small radiator to take the heat away, the boiler overheats
because the heat cannot be taken away fast enough. When this happens, the
pump keeps running even though the boiler is not lit.

Is the solution therefore to set the TRVs to maximum and turn the hallway
thermostat down a touch to prevent the rooms getting too warm.

Thanks

Antony



"R P McMurphy" wrote in message
...

"Roger Mills" wrote in message
...

"Antony" wrote in message
.. .
I've just moved into a 2 year old house and have discovered that the
boiler
seems to be playing up. It's a Baxi Solo 3 40 PF.

The problem is that the overheat light keeps coming on. The boiler
thermostat is set to maximum but I'm sure I read that this is the
recommended setting.

Any recommendations for things to try?

Thanks.....



Is it actually tripping, such that you have to press the manual reset
button
to get it going again?

If so, it is overheating because the residual heat is not being carried
away
fast enough after the main stat has cut the flame.

The first thing to do is to turn the main stat DOWN - it should not be
on
max. This then means that when it goes off on the main stat, it can
afford
to get a bit hotter without tripping the over-heat device.

Then check that the pump is wired correctly. This should be connected to
the
boiler in such a way that the boiler keeps the pump running for a bit
after
the boiler has stopped firing, in order to carry the residual heat
away -
i.e. the boiler has terminals for pump connection, driven by its pump
over-run stat.

Then check that with all hot water and heating demands satisfied - but
with
the pump still operating to cool the boiler (as above), the water
actually
has somewhere to go. If the hot water and heating are each controlled by
separate 2-port zone valves, there MUST be a by-pass circuit to permit
circulation under pump over-run conditions. [If you have a mid-position
3-port valve, you probably don't need a by-pass UNLESS all your rads are
fitted with TRVs].

HTH,
Roger



this makes sence. my baxi solo mk1 used to have to be reset regularly
until
i turned the stat on the boiler down to about halfway...not had a problem
since. aamoi, my system has a 'short circut' between flow and return with
a
tap controling the flow....all rads have trv's....would it be of use to
fit
a auto bypass valve like what screwfix sell it the taps place? the tap
system seems a crude way of donig its job.

rpm