On 5 Jan, 20:50, "Roger Mills" wrote:
In an earlier contribution to this discussion,

wrote:

Unless you really want to replace it I'd fit a new battery and spend
the money on a programmable thermostat.

Hmm. I hadn't thought of that. It sounds like it might be a bit too
sophisticated for our requirements, though. I'll bear it in mind for
the future. At the moment, I'm looking to get something done for the
short term in case of the combined effects of a power cut, a cold snap
and us being out - so our pipes don't freeze and burst.

In that case, a programmable room stat would do some of that nicely. (Just
swap it for the current analog stat). As far as the main timer is concerned,
the CH is on constantly - with the actual timing being done by the
programmable stat. Typically these allow you to specify 6 temperature
changes per 24-hour period which - if you wish - can effectively be three
on/off periods. When you want the heating on, you specify the required room
temperature (which can be different at different times of the day if you
wish). When you want it off, you specify a temperature (say 5 degC) which
is low enough that the house will not normally fall to it between heating
periods. However, if the temperature *does* fall that low, the heating will
come on to prevent everything freezing up.

Some programmable stats have other gizzmos such as:
* Optimum start. You specify the time by which you want the house to be
warm, and the stat works out when to turn the heating on.
* Party mode. Allows you to override the settings for a specified number of
hours in order to, for example, keep the house warm longer when you're
having a party. Can also be used for saving energy by lowering the
temperature for a few hours when you go out shopping etc.
* Holiday mode. Turns the heating off for a specified number of days (mine
does up to 99) and then returns to the normal programme. Useful if you want
to come home to a warm house without leaving the heat on all the time when
you're away. Also acts as a frost stat while you're away, and will turn on
the heating to prevent freezing if necessary.

A programmable stat won't help in the event of a power cut of course -
except that its timer will be battery operated, so will continue to tell the
correct time. Are you considering a generator to power the CH's electrics?
That's quite do-able when you're there to plug it in and start it up - but
starts to get complicated (and expensive!) if you want it to be fully
automatic.

Heh - no! That is far more sophisticated than I want. Currently, a
power cut causes the timer not only to forget the time but the
heating/ hot water settings. Hence, just a short power cut will cause
the heating to shut down completely until someone resets it.

I've got a battery on order now. I'm hoping that once I've installed
it, the central heating will once again work as it used to and come
back on and work normally after a short(ish) power cut.

Thanks for the info about programmable thermostats. I'm not sure our
system is sophisticated enough to benefit from one, though. The one
place in the house which gets too hot is the kitchen and that is the
only room that doesn't have a radiator. Most of the other radiators
have thermostat valves. We don't have any wall thermostat.

Cheers,

Ben