CM67 Optimum Start algorithm

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Set Square wrote on 08/02/2004 :-

20 years ago I designed one of these controllers and the next stage in its development was to include the facility which you mention. The whole idea was well ahead of the market at that time, so I was struggling on new ground.
I got as far as working out a rough algorithm. It went something like...
Starting with a basic programmed in setting, then incrementing or decrementing preheat time value, based on whether it attained the temperature before or after the set time. Which equates roughly with your last suggested method.
It was all very experimental. There was a theory going around, that in order to achieve this function, that an outside temperature sensor would be needed to enable the calculation to be done satisfactorily. I wonder if your unit includes an outdoor temperature sensor?
--
Regards,
Harry (M1BYT)...
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On Sun, 08 Feb 2004 13:26:54 GMT, Harry Bloomfield

I've done some work on this as well. Working purely on an internal reading and time, you can make a first approximation assumption that heat loss and thermal inertia effects are linear with time. That is roughly true and better than doing nothing. It becomes better if the controller can gather data and average over several heating sessions.
The CM67 type of controller doesn't use outside temperature sensing but some of the sophisticated boiler controllers have outside sensors.
On mine, there is an outside sensor which goes on a north facing wall out of the sun and gives the boiler a temperature signal based on resistance. There is an inside controller which senses temperature and hooks up to the boiler with a pulse width modulated digital code, in effect providing an analogue temperature value.
It is possible to set the proportional bandwidth and the relative sensitivities to each of these terms, with data being accumulated over several days. The boiler output is then linearly modulated from 3kW to full power by controlling the fan speed (influences gas input rate) and pump power level. The slope and end points of the boiler temperature vs the environment temperatures can be varied as well.
The controller behaviour can be logged to a PC so I can look at the temperatures and power levels over a period of time.
I've tried running with the outside sensing turned off and it does make some difference, although principally when there are fast moving changes in outside temperature.
.andy
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Is this a system sold with the boiler or something bought or developed separately?
Just curious!
Michael Chare
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On Sun, 8 Feb 2004 22:15:04 +0000 (UTC), "Michael Chare"

Integrated in as part of it.
http://www.man-heiztechnik.de/_html_e/produkte/micromat.php

.andy
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So, in a nutshell, the project failed? Why doesn't this surprise me?
Fuck off, Harry, you useless goat penis.
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Sore losers
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Self adaptive optimum start, and optimum stop, controllers have been around on the commercial field for over 20 years. Microprocessor based too.

It is far better with an outside temperature sensor, But using just one inside temp sensor, a decent optimised start performance can be achieved.
The DCD controller has a number of user set time zones during the day. Each one is optimised on and off (I believe). The CM67 is only optimised on, in the morning period, so I believe. Subsequently the DCD controller saves a lot on energy.
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In an earlier contribution to this discussion,

This does not stack up with my experience! My CM67 is programmed to provide a lunchtime boost of 21 degC from 12:30 to 13:30 having been set back to 18 degC for the morning period. The boiler usually fires up just before 12 in order to achieve the target temperature by 12:30. If you monitor the target temperature on the stat, it changes this from 18 to 21 at the point when it decides to fire up, rather than at the programmed time.
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Set Square
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wrote:

As some will remember, with the groups useful advice I fitted a CM67RF to my existing system a few weeks back. It's transformed the level of control and refinement compared to before (a TRV only system) but if like me you are new to these types of stat it does take a bit of mind set change to get the best out of programming the device e.g. one error I made was to set the target temp time too early because I was thinking along the lines of giving the house a chance to warm up before getting up. The CM67 started the system up in the middle of the night. A bit of tweaking sorted that.out.
I've not changed the factory settings but like most tuning (bikes, cars, IT systems etc.) I'm going along the path of changing one user setting at a time and checking the results over the next or so. I may move on the factory settings but I doubt it.
Jules
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wrote:

And I fitted one just after Jules (after tapping you lot up for info). It has totally transformed our house. It feels comfortable ALL the time now!
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Are these things ever advertised? I only learnt about the existance of programmer/thermostats where you can vary the temperature during the day from earlier posts in this ng. I have always wanted such a device so when I learnt that they existed I ordered one from plumbworld.
Installing and using the device has made me realise how slowly my house responds to temperature changes. Maybe 1C /hour either up or down.
Michael Chare
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Likewise. Plus work commitments means the house is empty for a few days during the week ATM. Previously I'd frig around with the old timer to get the house warm on my return but it didn't really do the job i.e. the air was warm but the house still felt cold, much better now even without fine tuning the programs or factory settings. I'll be interested to see in the gas bill next time mind.
Thanks again to old CH hands in this group. Why on earth installers put the Mickey Mouse stats or in my case none at all can only be put down to cost, but for the sake of less than 90 quid it's false economy in my book.
Jules
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And ignorance. Most installers know sweet nothing of control.

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wrote:

Because people understand basic thermostats. I think the CM67 is a brilliant piece of work (especially being able to use the party button to kill the heating for a few hours if you go out) but you need to understand the concept of time/temperature variations rather than on/off and then how to override it when required.
It's not difficult but I put one in at my mum's place and she really does not like. With a 10 stat when the rads went cold she could just turn it up a bit more <g>. Expensive controls that people cannot/will not master are a waste of money.
--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
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The Lord alerted my mind to the presence of this EVIL article by Harry Bloomfield, and I thusly replied:

You do like to sing your own praises, don't you?
--
The Reverend Parson Peter Parsnip
Smiting Sinful Usenet Users Since 1874
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On Sun, 08 Feb 2004 13:26:54 GMT, Harry Bloomfield wrote:

Good, you must be nearly dead now then.

Modesty, Harry.

Christ that was boring.
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Phil Kyle - Usenet Legend.

http://philkyle2003.reachme.at /
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Does anyone have any views on the relative merits of the Honeywell and ACL Drayton programmable stats? Much of a muchness?
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