The Landis & Staefa RVP will give proportional control by driving a servo on top of a mixing valve, measuring the flow, return, inside and outside temperatures, deriving the setting from a pre learnt heating curve for your house. Assuming your boiler already has a RVP the extra cost is about 200 quid for the valve and servo. With a rad based system I would recommend fitting this type of control as the temperature swings are eliminated by matching the heat input to the heat loss. But with UFH time constant you would really gain much from these controls.
They may not yet be into the supply chain. PHAM magazine came today and has a write-up on them as a new product with launch presentations from Feb 17th
Have a word with Richard at RKM Heating Controls (01954 261855). I can't see the HR80 or CM67z on their website, but they can probably get a price for you - and will sell you the kit for DIY installation!
This controller has a contact which makes and breaks with a duty cycle as described - e.g. 1 minute on, 4 off out of a total of 5. When this is controlling a supply to a device, it is pulse controlling it in this case with a long duty cycle.
That's the source of power to the controlled device. The controller is turning on and off.
I very much doubt it. An actuator should run from end to end reasonably quickly - certainly less than a minute.
You can't have an arrangement as you describe. This would require a controller which could stop and start the motor and another to reverse it and something to report back to the controller what the position is.
That is not a simple actuator and it requires a more complex controller than a CM67.
It is possible to have pulse width controlled actuators in other applications where the control to it is effectively open loop, but the pulse cycle time is vry much less and the switchover time in the cycle used to determine the stopping position - not the same thing and it also requires some electronics at the actuator to do the motor control. This is how model control servos work, for example.
I don't think so.
So please suggest a make and model that will work in a modulated fashion with a CM67.
OK, so now you are changing your tune.
OK. Please supply the part number of the L&S controller that will do this and a suitable modulating valve to go with it
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.
It's a better solution than letting them become extinct. There's some chance that their natural habitat can be stabilised at some point.
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.
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.
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.
Nope. You need either two signals driving a motor one way or the other, or a short cycle time pulse controlling some electronics hooked up to the motor.
In a form that could be controlled by a single output pulse switch controller like a CM67 they don't exist......
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