I remember reading a while back about a gadget that could be wired into the
boiler & that when the temperature fell below a certain level, then the
apparatus would fire up the boiler for a short time to protect it from
freezing. I am moving my boiler to a cold outhouse & would like to fit
something to protect the boiler from freezing temperatures. Anyone know what
would fit the bill.

In article ,
"jamesy" writes:
I remember reading a while back about a gadget that could be wired into the
boiler & that when the temperature fell below a certain level, then the
apparatus would fire up the boiler for a short time to protect it from
freezing. I am moving my boiler to a cold outhouse & would like to fit
something to protect the boiler from freezing temperatures. Anyone know what
would fit the bill.

First thing - you need protect the whole system from freezing, not
just the boiler. It may be that your boiler is the most vulnerable
point in this case, but think for a moment if there are any others
too.

I'm presuming this is a condensing boiler (as you wouldn't be allowed
to move it otherwise). What I would do is install a frost stat in the
outhouse, which brings the heating on. Ideally you want to do this at
the lowest boiler temperature setting, but your boiler probably won't
have any provision for doing so. What you could do it to wire the frost
stat in series with a pipe stat on the return pipe, set to switch off
at 30C or similar. That would fire up the boiler for long enough to
get some warm water through the system, without wasting much energy.
Ideally you want a pipe stat with large hysteresis, so it switches
off at, say, 30C, but won't switch back on until it drops to, say, 15C,
to prevent unnecessarily frequent boiler cycling.

Assuming you are not intending to heat the outhouse, make sure all the
pipework in the outhouse is well insulated (hot and cold), except
perhaps around the pipe stat. Might need some provision to prevent the
condensate drain and cold water pipes freezing too, such as running
them in close proximity to the heating pipework. You may get enough
heat from the boiler casing to take the chill off the outhouse, but
many modern boilers don't actually lose much heat through the boiler
casing anymore.

Some boilers which are intended to be installed in unheated areas have
a built-in frost stat, although that usually only switches on the pump,
and doesn't necessarily cause the boiler to fire up.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]