control heating valve

[domoticom]

Hi,

I am going to update an existing heating system in an office building.
The radiator groups are controlled by a 3-way valve with a motor that only has 2 230v control inputs. One is drive open, one is drive-close.
Details here: http://cn.siemens.com/cms/cn/English...QL_EN_4505.pdf

Nouw I want to control it proportional. One way to do it is to use an actor than can drive the motor based on drive time. I.e. valve 50% open is drive 1/2 of the total driving time. Is there a KNX actor that is build for this purpose ? Or can I use a shutter actor with this time function to drive the valve to an absolute value.

Another option, that I like better, is to replace the motor with a 0-10v controlled motor, and then simply use an analog KNX actor with 0-10v outputs.

Any thoughts on this ?

Thnx,

Mike

[multimedia]

Hi Mike,

I think there is no KNX actuator where you may direktly connect and control this valve.
I have done a similar project with a Siemens LOGO! with KNX extension.
There are 4 relais built in and you may either use an inernal PI controlblock or any other external KNX PI temperature controller to create the one byte control value.

However, if you only have to control this single valve it may be more efficient to use a common HW regulator (which is really cheap) and send only the temperature values to the bus.

Cheers from France

[domoticom]

ok thnx. There are only 2 radiator groups, so 2 controllers.

How do you connect HW controllers to the bus ?

Any example HW controller ?

[multimedia]

Hi Mike,

a simple HW-controller would be something like this:
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Well, of course it is a "closed sytem" - but the advantage is, that you have a outside-temperature based regulator with several control curves that may be adapted exactly to your installation and in 98% of all cases this may fit to your demand. If really necessary (IMHO it is not) you may then use additional KNX temperature sensors like http://www.elsner-elektronik.de/uplo...heet_EN_01.pdf or Arcus-EDS: SK08-T8 <br>Temperatur 8-fach <br>8 Channel Temperature to send the temperature to the bus.

The disadvantage of such a closed system is, that it is not possible to influence the installed timer functionality from KNX. Here again the question if this is necessary, as mainly these timers are adjusted once in a life of a heating system.

[domoticom]

it is nessesairy that all parameters, timers, values etc. are accesible from KNX. So it should be one system, not more autonoumous systems