"Dave Plowman (News)" wrote in message
...
In article ,
NY wrote:
We're thinking of getting a Hive remote-controlled central heating
controller/thermostat so we can set our heating to come on several hours
before we get home from holiday etc.

I'm trying to work out whether we need a single- or dual-channel
controller. Hive's customer support was di they wouldn't offer any
advice and just said "speak to a qualified central heating installer".
Imagine not being able to offer any pre-sales advice!

We have a combi boiler which currently has a dual-timer: one for the
central heating and one for the hot water. The hot water is pre-heated
in a reservoir in the boiler, hence the reason for being able to time
when that pre-heat comes on and off, so it's not wasting fuel keeping
the reservoir hot overnight.

Hive say "single-channel for combi; dual channel for conventional boiler
with hot water cylinder". Our system sounds as if it has some features
of both: it's mostly heat-on-demand but with timed pre-heat of a small
reservoir in the boiler.

So, single or dual?

If you have a combi, why would you want remote control of on/off for the
water? The tap does that.

Yes but we need to be able to control the hours that the boiler pre-heats
the water, so it doesn't heat it overnight. That's independent of the
on-demand heating of water. I imagine that when you turn on the tap, the
water that comes out of the tap (excluding what's in the pipe) initially
comes from the pre-heat reservoir, to give the boiler time to start heating
cold water - otherwise it would take a long time to run warm.

Also, are you sure your system doesn't already allow you to set it while
away on holiday? So it comes on the day or whatever you return? Even if a
day or two out, you're not going to use the gas cost of one of these.

As far as I know, the controller just has time-on, time-off settings - I'm
not aware that you can say "from dates d1 to d2 come on between these hours,
but otherwise come on between these hours".

Anyway, what we want is "between these dates, heat the house to a frost-free
temperature; otherwise heat to a normal temperature". Since the boiler is
outside, any frost stat in the boiler will just be to keep the boiler itself
from freezing, not to prevent the house (eg water pipes) from freezing.

My understanding of the Hive (as regards central heating) is that it
functions as a combination of timer controller and thermostat, so as to turn
on the boiler when some condition is met. And that condition is a function
both of room temperature and time of day, so you can tell it to set the
thermostat to frost setting overnight, maybe high temperature in the morning
and evening, and a medium temp during the day so the boiler doesn't have to
work as hard to re-heat the house ready for when we come home.