CM67 Optimum Start algorithm

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wrote:

I know your limits. Good enough for you.

That is not pulse. A pulse is a rapid on-off, probably 100s of time/sec.

There are modulating actuators around. I must have about 4 of tem in boxes.

You know very little of HVAC control.

It is vague.

Try their web site. It is not bad.

They don't belong here.
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You don't, you know :-)

It can be any cycle time. The technical definition does not put any time limitations on it.

So please give the makes and models so that it can be seen how they work.

Stop trying to evade the point.
You have asserted that the CM67 can control a modulating valve. You have further asserted that you have four such valves in boxes. You have been asked three times to provide the makes and model numbers of such valves. You have tried to divert the subject onto a different make of controller. You continue to duck the clear and direct question that is asked., When provided with a bit more information that might lead you to explain what you mean and how servos work you continue to evade and suggest that I know little about HVAC control.
This is your classic modus operandi and doesn't fool anybody.
Why don't you either come up with a modulating valve type for the CM67 or simply admint that you made a mistake?

I agree, and you certainly can't deduce what you have from it

I'm sure, but I'm asking the expert who claims to know all about this.

There's some chance that their natural habitat can be stabilised at some point.
.andy
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wrote:

Andy, I "know".

having a signal on for 6 minutes is not a pulse.

They are 230v electic actuators have a look: http://www.landisstaefa.com/opc_e/catalog/cat_content.asp ?

It is spot on.

It looked that way from the brief spec.

I have.

There are some valve, not the ones I have, in the URL I provided.

Which appears better.

I don't .

You know little about it that is clear fro all HVAC aficionados to see.

I don't fools anyone. Obviously confuse the hard of thing though.

Honeywell tech dept are the peopel to ask.

Who cares if all snakes go.
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Or try this: http://tinyurl.com/ypjw7
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The Landis & Staefa REV 300, this will modulate a valve. This is a class act...

CE1N2213
- Mains-independent, electronic PI controller with 3-position output, battery-powered - Self-explanatory touch screen - Choice of 3 different 24-hour operating modes and one 7-day mode including individually adjustable 24-hour modes - Remote operation, override button - Sensor calibration and reset function - Locking of display buttons for cleaning or as a protection against tampering - Frost protection function and minimum limitation of setpoint - Color: signal-white RAL 9003 - Holiday mode -Optimum start control for the first heating period -Adjustment of integral action time (volume adaptation) -Adjustment of control gain (adaptation of heating output) -For control of 3-position electromotoric actuators with a running time of 120...150 seconds (suitable for stroke or rotary actuators)
Operating modes: - 24-hour mode with 1 heating period - 24-hour mode with 2 heating periods - 24-hour mode with 3 heating periods - Continuously comfort temperature - Continuously economy temperature - Standby with frost protection setpoint (fixed: 5 C) - 7-day mode including individually adjustable 24-hour modes
Power supply DC 3 V batteries 2 x 1.5 V AA alkaline Battery life approx. 2 years Setpoint setting range 3...29 C
Switching capacity of relay Voltage AC 24...250 V <<<
This also modulates a valve too

- Mains-independent, battery-powered electronic PI controller with 3-positio n output - With digital 7-day time switch for 24-hour, working day, weekend or 7-day operation with up to 3 heating periods per day - Straightforward, self-explanatory menu selection via roller selector - Optimum start control for the first heating period - One temperature setpoint for each heating period - Remote operation - Override button - Sensor calibration and reset function - Limitation of the minimum setpoint - Holiday mode - Color: signal-white RAL9003 - Adjustment of integral action time (volume adaptation) - Adjustment of control gain (adaptation of heating output) - For control of 3-position electromotoric actuators with a running time of 120...150 seconds (suitable for stroke or rotary actuators)
Operating modes: - Automatic mode with 7-day switching program - Continuously comfort temperature - Continuously economy temperature - Frost protection setpoint - One 24-hour operating mode with one heating period
Voltage DC 3 V batteries 2 x 1.5 V AA alkaline Battery life approx. 2 years Setpoint setting range 5...29 C
Switching capacity of relay Voltage AC 24...250 V Current0.1...6 (2.5) A <<<<<
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In an earlier contribution to this discussion,

This thread has rather lost its way - and has unfortunately degenerated into a another slanging match between IMM and Andy - even including the merits or otherwise of keeping snakes!
I thought that this part of the discussion was whether the CM67 could drive a modulating type of mixing valve in order to control the output temperature of the mixed water. Since the CM67's only interface to the outside world is an on/off switch, it quite clearly can't provide closed-loop control of anything which needs to be driven to any one of a virtually infinite number of positions. From my experience, controlling mixed temperature with such a valve actually requires two control loops - one inside the other. The outer one monitors temperature, and outputs a position demand to the inner one. The inner one monitors position, and drives the valve to the position demanded by the outer loop.
Some of the kit cited by IMM can probably do this - but only by virtue of it's own controllers - so it is not relevant in the context of the CM67 discussion.
--
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wrote:

That was an illustration of proportional and switched control systems (at the start at least).

It was.

Not with that cycle time at least. It is possible to control things in a pseudo-analogue fashion with a much shorter cycle time - e.g. model control servos.

The L&S switched stuff is still largely open loop and will require regular resets by the controller so that the controller's idea of position will match the real one. Crude but effective to a point.
.andy
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No open loop. You are on about simulated proportional feedback, but it was obvious you knew that.
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is no direct feedback of the valve position to the controller. The only feedback is the outer control loop which is the temperature of the controlled environment. That has a much longer time constant than the operating time of the actuator
.andy
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A 0-10v simulated proportional feedback conbtroller has to guess to some degree. The word simulated gives it away.
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the result is more accurate and the system loop behaviour much more predictable.
.andy
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A decent "well adjusted" controller on a 3 position valve gives the same accuracy.
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driving the thing periodically to the end stop and timing from there.
DC controlled actuators have servo electronics in the head with position detection based on a stepper motor. That is inherently a lot more accurate than something run end to end with on/off control.
.andy
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wrote:

Doesn't need it.

It doesn't time it. The proportional side is in control until it is inside the proportional band and when it settles inside the band the Integral pulses it to set point. I have had "highly accurate " control with simple controllers and actuators.

Not necessarily, but generally I prefer this method.
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Then it won't be as accurate.

Glad you put that in double quotes.

.andy
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wrote:

Well I recommend 5 years in the control industry then you will.
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"Andy Hall" wrote in message

3-port (mixing) valves are very commonly used in commercial HVAC controls for things like weather compensation, so I'm surprised at the difficulty being had in identifying products;-) Drayton certainly used to make 3-port valves with a potentiometer to provide positional feedback - 'Theta YB' series' valves (just found an old data sheet). As this isn't my field I don't know whether these still exist, or whether they've given way to geared stepper motor drives (which should work OK open-loop) or something else. You could also sense the temperature (error) of the mixed water and use that to control the valve position.
Interesting thread this, although it's reminding me slightly too much of Ted Horrocks's lectures...
--
Andy



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Very true! The 0-10 or 0-20v simulated proportional feedback control supersede these. The pot on the valve acuautor was one of the points in a whetstone bridge. I'm not sure if they are still around, Satchwell made them, and were about the last company to get out of the 1950s (British of course). Billman (Quality Swedish stuff bought out by L&G) made them and parts were available, but probably not by now. You probably can still get them. Most just replace the actuator and controller if either one fails. The controller had to be mated to dedicated valves/actuators. You could not mix and match.

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On Thu, 12 Feb 2004 00:04:41 -0000, "Andy Wade"

Mmm. Exactly. You attended some of those?
.andy
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This is *precisely* the point that I made in earlier posts in this thread.
The SSB31... and SSB81.. valves are 3 position types which can be controlled with an on/off signal.
You apply a voltage (24 or 240v depending on model) between Y1 or Y2 and neutral and it will drive the actuator towards one end of travel or the other.
The controller to use this (e.g. REV300) relies on the end to end travel time being 150 seconds and the controller times the length of the on signal to adjust the valve. This is actually a really poor method of control because the controller has no absolute way of knowing the valve position and has to periodically drive it to and end point to calibrate it.
The CM67 type of controller, just doesn't have the two signals required to do the job or the logic either.
There is a third type, of actuator, SSB 61. This is a 0-10v control type and is able to achieve much greater accuracy because there is electronics in the valve head able to monitor the valve position. I'm using a Sauter equivalent of this product in place of TRV heads.
.andy
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