The programmer is fitted with a non-rechargeable, non-serviceable long life battery, which will maintain the programmed time settings with the mains supply disconnected. Look at the wiring diagram for your make/mode of room thermostat that you are removing. If you don't have the instructions for it, a diagram is usually printed inside the lid. This will show which are the two switching wires, and which is the neutral wire. (If there is a neutral present. Not all thermostats need or have one fitted) unfortunately you can't rely on the wire colours.

Once the secondary circulation is out of the picture, the Zone 1* connections would be wired to the Central heating terminals of the Heatlink and Zone 2* connections to the Hot Water terminals. You should identify what each of the wires connected to the Horstmann does from the diagram you have posted, and then move them to the terminal that has the same function at the Heatlink. If this is indeed the case, I don't think I can use the Nest unless I use some sort of relay, or change the valve. I'm wondering this due to the wiring indication that came with the valve, and also the number of wires in the connecting box.

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Finally at least one radiator in the room where the Nest Thermostat is located should not be fitted with a TRV, otherwise it could interfere with the operation of the Nest and prevent it working properly.

All ChannelPlus XL controls are fitted with battery reserve which maintains programmed times in the event of a mains power failure. REAR VIEW OF CHANNELPLUS XL PROGRAMMER Then, once the common at the Heatlink is connected, both devices will function identically to each other. The Secure Meters Horstmann CHANNELPLUS H37XL is a white 3 channel 7 day electronic digital programmer with independent timing of heating and hot water. User friendly, it is designed for domestic use, providing advanced, easily programmed features. I am assuming here that you are referring to a 'Secondary Hot Water Circulator' that circulates the domestic hot water around a ring main so that hot water is available instantly at each outlet, then the answer is yes you will need to move that to another timer. This is the first time I have come across this in a domestic property, but can understand why if you have an unusually long pipe run.

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Lower the front flap of the unit. On third Channel press the ADVANCE(Enter) and SELECT(Blue) buttons together then release the buttons and the programmer will return to the preset factory settings. TIME AND DATE - The programmer has been pre-set with the current time and date during manufacture. No alteration should be required to the time and date, however if any modifiaction is required please refer to the 'Adjusting Time and Date' section of the user guide. I'm not sure I understand what you mean by the above, because the switching elements of the Channelplus 37xl and the Heatlink work in exactly the same manner. In reality, the blue wire may not be actually doing anything, but only the original installer would know. However as I said earlier, you are simply exchanging one electrical switch for another and the corresponding terminal at the Heatlink would be (1) Heating Satisfied.