Installing an AD10U
X10 Din Rail Appliance Module

How it was !
How it was This article documents the removal the old mechanical timeswitch controlling my Immersion Heater and its replacement with an AD10 DIN Rail Appliance Module from X10. Although the timeswitch has been reliable for the last 10 years or so, it does have some serious shortcomings.
  • No visible indication of the ON/OFF status.
  • Limited to two ON/OFF operations per day.
  • The time has to be altered twice yearly as the clocks change.
  • Manual override remains active until the next ON/OFF.
  • Impossible to override within 30 minutes of an ON/OFF
If you tried to override the timeswitch just as it was about to perform one of its switching operations, the knob would be difficult to turn. If sufficient force was applied then the timeswitch could be overriden but in doing so the mechanical stops inside the timeswitch would move slightly. The result of this was that the switching times were then permanently altered. This then added 15-30 minutes to the ON time leading to much increased electricity bills.
The modern replacement.
AD10 The AD10 overcomes all these shortcomings and allows much more control of the Immersion Heater. The AD10 can be controlled by a variety of methods.
  • X10 signals. Address set by codewheels on the front of the module.
  • Manual Override. Blue switch on the front of the module.
  • External Latching switch connected to terminal 1. (Normal OFF/ON switch)
  • External Momentary switch connected to terminal 2. (Press button)
The output status of the AD10 is indicated by the LED on the front panel.
With my newly installed AD10U controlled by HomeVision I now have unlimited ON/OFF settings and as HomeVision can automatically adjust the time for daylight saving I dont need to worry about changing the time. I can also now implement some new features.

At holiday times the hot water can be turned OFF for the duration of the holiday but switch on a couple of hours before our anticipated time of return ensuring a full tank of hot water when we get home.

If it is a time when we wouldn't normally have a full tank of hot water but I decide to take a bath I can turn the immersion heater on from my remote control. This sends an X10 command which Homevision uses to trigger a Macro to turn the heater on for 90 minutes. Likewise I can also turn it off from my remote if the plans suddenly change.

One future enhancement will be a temperature sensor on the hot water tank which will indicate to Homevision that there is no hot water or the temperature is too low to be useable and trigger the macro to heat the water thus ensuring that we never run out but at the same time don't run the heater un-neccessarily.

Before you start !

There are a some important points to note about the way the AD10 operates which must be considered BEFORE you decide if it is suitable for your needs.

  • X10 Control
    If you only intend to control the module by X10 then you do not need to make any connections to terminals 1 or 2. Manual override is possible with the blue switch on the front panel. All that is required is setting the address of the module.
  • Manual Override
    Moving the switch to the 1 position causes the module to switch ON permanently. Likewise, setting the switch to 0 will cause the module to remain OFF. When the switch is restored to the Auto position the state of the module will remain unchanged until X10 or switch control signals are received.
  • External Latching Switch Control
    When the switch connected to terminal 1 is closed the module will be permanently ON.
    It will NOT RESPOND TO ANY X10 SIGNALS whilst the switch is closed !!
  • External Momentary Switch Control
    Pressing the switch will cause the module to toggle its OFF/ON state. The module will still respond to X10 signals.
Note that when using any of the local control methods NO X10 signals are sent and your Home Automation controller will be unaware of any change of state.

Down to the nitty gritty !
Remember to turn the power OFF before starting work!
Empty box From the previous picture of the AD10 it can be seen that some form of enclosure is required to safely house the module. I chose to adopt the self contained approach for my timeswitch replacement as I wanted to place it in the same location as the existing timeswitch. Had I been rewiring the house I would have installed it into a consumer unit.

The box I chose was from my local electrical retailer and cost under £4. It is manufactured by a company called Gewiss and the model number is GW40022. The two pictures show the empty box and the DIN rail which is supplied pre-mounted.

It is worth noting that the DIN rail and cutout in the lid are not in the centre of the box. This means that the wiring space is smaller at one end of the box than the other. It is worth installing the module to check which orientation of the box will suit your wiring layout prior to breaking out the cable entry blank.

DIN Rail
Ready for connection Mounting the box and preparing the cables.

The AD10 module doesnt have any earth terminal and neither does the GW40022 enclosure. This meant that it was neccessary to use a terminal block connector to join the incoming earth wire to the outgoing earth wire. Also, as this was a replacement for an existing timeswitch the wiring already existed and was previously cut to the length required for the timeswitch. As a result the outgoing live to the Immersion Heater wasn't long enough to reach to the top of the box. This was extended with suitably rated cable. I chose to use flexible cable as it is much easier to wire in a confined space than a solid conductor.

There is insufficent space at the side of the installed module to allow any wiring to pass from the top to the bottom of the box, but there is a gap of around 6mm beneath the DIN rail so I passed the wiring under the rail.

The connector block sits neatly at the bottom of the box and the wiring protruding from the front will easily fit within the lid of the box.

Any bare earth wiring MUST be insulated with earth sleeving.

Installing the module.
Almost done With the box mounted and the cables prepared, the final step is to install the AD10 module. This is simply snapped onto the DIN rail. Once fixed securely in place the wiring can be connected. I am not using any local switches but if used they connect between the incoming LIVE and either terminal 1 or 2 for latching or momentary switches.

The incoming live is wired to the live terminal at the bottom of the module. The outgoing live is connected to the live terminal at the top of the module. The neutral wires from both cables are connected to the N terminal at the bottom of the unit.

Having checked the connections , set the required address code, fit the cover and reconnect the power.

You should now have a fully functional DIN module.

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This page last updated : 5th October 2000