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Thread: Idratek FAQ 3 - Installation

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    Moderator Gumby's Avatar
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    May 2004

    Default Idratek FAQ 3 - Installation

    3. Installation

    NB: Idratek have produced a series of guidance notes available here:-

    Note also that there are various restrictions and requirements related to wiring (including telecomms and control) that vary from country to country and may have statutory power. Nothing in this FAQ should be taken as definitive information and the reader remains responsible for confirming compliance with applicable standards themselves. Seek professional advice if necessary.

    3.1 What is a Node-I?
    By analogy with Node-0 in LAN cabling, Node-I is a name used to describe the point at which various Idranet spurs are brought together for connection to each other and typically to the Cortex platform.

    3.2 What network topology can I create ?
    Almost anything without loops. So you can have a long run from your MPD or IPS power supply unit to a convenient point and then branch out multiple times to reach individual modules. Or you might choose to have a main feed for each room and branch from that. Another popular topology is to daisy-chain each module.

    Practical considerations include the number of individual cables that can be joined in a single IdraNet connector (eyesight and dexterity dependant but probably 3), spreading the load reasonably evenly across the 4 MPD power outputs and retaining some isolation capability in case of servicing requirements. Perhaps a good initial starting point is to plan a loop for a set of modules, bringing both ends of the loop back to Node-I, but terminating only one. This gives a "spare end" which may help in case of trouble.

    3.3 Can I plug a module into my Ethernet ports?
    Not if it's connected to an Ethernet device - this is likely to damage either the module or the Ethernet device, or both. Idranet is NOT Ethernet.

    However, if you have structured cabling through your house then you can also use this cabling to support Idranet modules.

    3.4 What type of cable can I use ?
    The Idranet needs 6 cores for full functionality: power, data and audio. Typically a Cat-5 cable is used and the Idratek recommendation is screened cable (aka STP or FTP). Some people have found that using a mains-rated insulated Cat-5 (eg pink C-Bus cable) makes installation routing easier and it is possible to send Idranet over burglar alarm cable in favourable circumstances.

    3.5 What can I use the spare cores in a Cat-5 for ?
    One possible use is to double up on the power pairs to reduce voltage drop on longs runs, or if you have long runs to a highly populated distribution node (ie high current).

    3.6 Where do I put PIR modules?
    This depends on which module you are using, more than one module type can have a PIR function, and the other functions may require a certain placement. For example, MFP and DFPs have PIR functionality, but also need to be placed where a person can access them to press buttons and read displays etc.

    PIRs work by detecting heat changes across a grid of patches. Constant heat is not detected, the patch has to see a change. This grid can be considered to project in 3D from the PIR device, creating an array of "rays" from each patch. Basically you want to position the "rays" to maximise the chance that typical activity will causing crossing of as many rays as possible. The PIRs have an important role in presence detection, both to detect motion near doorways and also long-standing occupancy such as a desk, sofa or bed. It is also helpful to minimise detection through doorways into adjacent rooms. Also check whether doors being open will obscure occupants from the sensor, and don't forget that sensors can't see round corners.

    Cortex can support multiple PIR devices per room, and can also utilise 3rd-party devices connected to suitable modules digital I/O connections. Typically 3rd-party sensors are designed for alarm functions and may be less sensitive than the Idratek modules.

    3.7 Where do I put temperature sensing modules?
    If used (typically) for heating control then these would ideally be placed near to the most commonly occupied position, since air currents and draughts can lead to a significant variation of temperature readings in a room. A common recommendation for thermostats is shoulder height. However, other factors may lead to a compromise position. Cortex allows for temperature offsets to be including in a temperature reading to take some account of this (for example if you want to set a temperature to 20degrees). Alternatively you can take the approach of adjusting the thermostat temperature until the room is comfortable and not worry about the absolute reading.

    3.8 I've mounted my modules in the ceiling and they seem to read very low?
    And you thought hot air rises. It is possible that mounting the modules in a ceiling can allow cold air to fall through the back box and through the module vents. If this occurs you will need to block up the back-box openings (not the module vents).

    3.9 What else do I need to think about when ceiling mounting modules?
    Building regulations may apply for various reasons, including sound and fire isolation. Seek professional advice.

    3.10 Where should I put light level sensors?
    These are commonly used to detect room level lighting to allow for automatic decisions on whether lights should be turned on. They can be though of as "seeing" the surface opposite the sensor window. So ideally this surface should be a good representation of room illumination level, perhaps a wall opposite a window. Try to exclude artificial lights from the sensing area, since this can make the detection less effective. Shiny reflective surfaces can change significantly when room lights are turned on, so matte surfaces are probably better. It's also a good idea if the sensing area is not frequently obscured by people carrying objects which can change the sensed brightness level significantly.

    3.11 Can I use my existing light switches?
    You can potentially use them to switch mains in parallel to an Idratek relay to give a manual fallback control.

    In theory they could be used connected to digital inputs to feed into Cortex but this can cause confusion, retractive (push/momentary) switches are better.

    3.12 Can I use alternative light switches?
    You can connect alternative switches to digital inputs on Idratek modules and use them to control lights (and other things). You will lose the possibility of user feedback via LEDs and you should also take care on screening and routing of these wires.

    3.13 Can I re-use my mains lighting wiring to connect to digital inputs?
    In theory, if it's isolated from the mains then it could be used. However, it does create a potential danger if wiring is later modified and confused, so it is better practice not to do this.

    3.14 What wires do I run to each module?
    At a minimum every module requires an Idranet connection (eg Cat5 or min 6-core). For modules with digital inputs you might run in additional wires, such as PIRs or window contacts. For modules with relays you may run in mains connections to be switched, or use the relays for lower voltage functions (eg 24V).

    3.15 How many modules can I attach to each Idranet cable?
    This depends on the power consumption of the modules, the distance between them and the type of cable. For Cat-5, based on a cable rating per core of 1A and modules consuming as little as 10mA, then there could be as many as 100 modules on a single spur (more if spare cores are used). However, most installations have far fewer modules than this.

    3.16 How long can I make a spur?
    The answer is not known definitively, but the longest known Idranet spur is 350m. Yes, Three hundred and fifty. Spare cores were used to double up on power and ground connections.

    3.17 How many modules can I have in total before overloading the bus?
    This is difficult to state definitively due to the potentially random stimulus causing messages to be generated, the variable length of messages and other factors. The largest reported installation is 120 Idratek modules (many multifunction) equating to 752 network objects. It should also be noted that the Idranet bus design continues to transmit data even in a bit collision scenario (unlike Ethernet, for example) and various prioritisation and traffic randomisation features in Cortex are also implemented.

    3.18 Do I need MCBs to protect my DIN rail units?
    Firstly, any circuit protection devices come under Part P in the UK, so you may need to seek advice. Some other HA lighting control systems are often installed with MCBs (typically 1A rated) between the load and the module to protect the module under bulb failure (short circuit) conditions. So far there is no experience to show that Idratek dimmer or relay modules need this protection. However, it is necessary to provide a means of safely isolating loads for servicing (eg bulb replacement). It is more convenient if this is done at the individual circuit level rather than, say, whole floors and the difference in cost between MCBs and isolator switches is quite small.
    Last edited by Gumby; 5th May 2009 at 05:31 PM.

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