RE: Ultimate Central Heating Th ermostat

[Williams Christopher C <CCWILLIAMS@xxxxxxx>]

I have a Honeywell AQ6000 that I installed several years ago, before
getting into HA.
This unit has temperature sensors outside, on the hot water tank (if I
had one :)) and on the central heating flow pipe coming out of the
boiler.
When first switched on it learns the heating response for the house (
takes 3 days apparently ). I guess it comes up with some figure for the
thermal resistance of the house in general. It is programmed to be a
certain temperature at a certain time and if it is colder outside it
comes on sooner.  Initially it comes on with the boiler running at full
tilt, but once up to temp. it reduces the temperature of the water in
the radiators, by switching the boiler off earlier than its own
thermostat, to maintain the temperature at the desired level.  This
means you never have to alter the boiler settings and the heating just
comes on in the spring and autumn to take the chill off.

I am very pleased with the system.  The main cpu box can be mounted near
the boiler and zone valves and the control box/thermostat  can be
mounted where convenient.  It is connected to the main unit with just
two wires.  ( Supplies power and bi-directional comms! Pre 1-Wire?? ).

The main problems with the unit are that it can only control 1 zone.  (
This is probably a consequence of the way it works.  Would be difficult
to learn the thermal resistance of different parts of the house and even
more difficult to control the water temp in the different zones? )
There are only three temperature settings that can be set, Comfort,
Activity and Night.  Each range can be set to whatever temp you like.
You can have up to six temp changes per day and days are either work
days or rest days.  One problem that occurs, if it is currently in say
Activity mode and someone is cold, the temptation is to increase the
temperature level of the mode instead of changing mode.  This setting is
then permanent, until I reset it :).

Additionally the unit runs the pump for a minutes at 12pm every day and
switches the system off in the summer ( automatic due to outside temp.
compensation ).  It also has build in frost protection.

I have got 5 zones in my house, Downstairs, Upstairs, Kitchen, Bathroom,
Shower Room.  I have fooled the controller into thinking that the
Bathroom and Shower Room radiators are in fact hot water tanks!  So far
I just have a simple arrangement with a relay so I can force the system
to heat up the bathroom radiator with the flick of a switch just outside
the door.  Eventually I will use a Tini processor to control the zoning
so that I can boost the Shower Room or the Bathroom or either.
Currently the Upstairs and Downstairs zones work in parallel.  I may add
an upstairs thermostat to reduce the temp during the day, this may upset
the controller however.

Cheers,

Chris Williams



> -----Original Message-----
> From:	REB.Barnett@xxxxxxx
> [SMTP:REB.Barnett@xxxxxxx]
> Sent:	Thursday, October 26, 2000 8:25 PM
> To:	ukha_d@xxxxxxx
> Cc:	ray@xxxxxxx
> Subject:	[ukha_d] Ultimate Central Heating Thermostat
>
> Winter is nearly here, and I have a spare 5 minutes, so I've started
> on the
> spec for the house thermostat I've always wanted (no commercial
> product I
> can afford does what I want). My requirements are moderately
> sophisticated,
> and there's a chance what I want won't work, so if anyone has any
> comments
> or experience to share I'd appreciate it.
>
> *Multi-zone via Dallas one wire temperature monitors
> *Predicts rate of rise and fall of house temp in order to anticipate
> when to
> run boiler
> *Specify house warm by time and warm until time
> Support for multiple programmes - week mode, weekend mode, alternate
> week
> mode
> Display to show current temp, set point, boiler on/off
> Buttons to override on/off, adjust set point
> RJ45 network connection to provide web interface to thermostat and
> Comfort
> Zone inputs from Comfort to permit occupancy/alarm/telephone control
> Zone outputs to allow 12v control of boiler (e.g. via Comfort)
> *Additional outputs to allow independant heating of other rooms as
> required
> Serial input from Comfort, to permit Comfort to use thermostat web
> interface
>
> I've asterisked a couple of the features I think I want, because I
> wondered
> if anyone on the list has any experience of getting these sorts of
> things to
> work. My current thermostat does a reasonable job of anticipating the
> rate
> at which the house heats and cools, yet often seems to let the
> temperature
> fall 1/2 degree too low before switching on. I'm thinking of
> implementing
> some sort of weighted average of temp increase rates held against
> ambient
> temperature, so the system will know that if the current temp is 18C,
> it
> will take x mins to reach 20C. That way I can set it to have the house
> at
> 20C by 7:30am, and on colder days the system will come on earlier to
> compensate.
>
> I'm keen on making it multizone simply because my current single zone
> system
> is easily fooled by heat from external sources - e.g. coal fire in
> lounge,
> oven in kitchen. I'm not sure how best to implement multi-zone. One
> plan
> would be to have one 'current' zone that the thermostat attempts to
> maintain
> at the set point. The trouble with that though might be that different
> rooms
> need different set points depending on where the temp probes are
> located.
> Also if the 'current' zone were to be switched based on monitoring
> zone
> activity from Comfort, it might make the 'rate of temp increase'
> algorithms
> a touch tricky.
>
> Another solution might be to have the system to keep an eye on all
> zones. If
> some start escalating out of control (e.g. lounge and kitchen temps
> soar),
> but other zones remain in keeping with established parameters for rate
> of
> heating and cooling, then perhaps the thermostat could selectively
> ignore
> zones once it determines it has lost control of their temperature.
> Some
> safeguard would be needed to ensure that once any zone reached a
> maximum
> safe set point the heating is shut down on the assumption that 'a
> fault has
> occurred'.
>
> Finally, the conservatory is on the main central heating system, but
> naturally cools more quickly in the winter when the heating is off,
> producing a draft into other warmer rooms. To combat this, we use a
> convector heater to supplement the central heating in that one room.
> If the
> thermostat were set to associate an X10 address with a particular
> zone, it
> could ensure that zone was maintained warm when the main system was
> off. Not
> sure if this makes it all too complicated though.
>
> Ray Barnett
> Systems Developer
>
>
>
>
>
>
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