Thanks Simon I will look into that.

Richard

"Simon Stroud" wrote in message
...

Tricky Dicky wrote in message
...
I am going to install a thermostat for frost protection of my CH system
mainly because the boiler has now been sited in the garage.

I think putting it in the garage will not do as in the winter the
temperature of the garage will not rise significantly and the result
will
be
it will over-ride the room stat settings causing the boiler to
short-cycle.

I thought of the hallway particularly on an outside wall so it should
detect
the as near as damn it the same temp that the garage should experience
yet
it should switch off once the temp in the hall has risen. My main
concern
is
that the temp inside will drop off much slower when the heating is off
compared to the garage and the stat will not not fire up the system
quick
enough.

Richard


I have an Eco Hometec badged (MAN Micromat) combi boiler in the garage.
This
has built-in frost protection based on the outside temperature (it has a
sensor for this) and the return water temperature.

I originally planned to add an external frost thermostat for additional
protection, and got the bits. However I haven't connected them up yet,
mainly because the boiler doesn't actually have a direct "CH demand" input
that I can see - their engineer said I could short out the outside
temperature sensor and this would make the boiler think it was minus XX
degrees and would force it into firing mode.

Anyway, you need two parts - the actual frost stat and a clip-on pipe
thermostat - I think it's called something like a "low limit" stat. When
wired together correctly this combination means that the boiler is forced
into CH demand mode when BOTH of the following are true :

1) ambient temperature is less than the frost stat setting (about 5 deg C
ISTR but probably adjustable in the frost stat)

AND

2) the return temperature (measured by the clip-on pipe thermostat) is
below
its preset temperature (I'm really guessing now - maybe something like 15
deg C).

So your problem would not happen - the room temperature in the garage
doesn't need to rise - it just makes the boiler fire until the water in
the
pipes/radiators is coming back at a reasonable temperature.

If you get a Honeywell frost stat, the instruction sheet explains all this
and the part number of the other pipe stat. Our local PM kept both in
stock,
so seems like a pipular combination.

Regards,

Simon.