Replacing Mechanical Programmer Switch with Thermostat

22 Jul 2014
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United Kingdom

I would like to know if i can replace an old and now broken Randall (Danfoss) 102 mechanical programmer with a new digital wireless roomstat with my current configuration. At least a wireless programmer would be useful.

I know i can replace the unit with a 102E5 electronic mini-programmer but this is wired so relocation to the living room would mean additional wiring.

Current configuration is below.

Boiler: Glow worm Fireblaze BTU Back Boiler 56F
Programmer: Randall 102 mechanical programmer

The wiring as per the current programmer is as below

1 2 3 EARTH 5 6

I would like to know if a system like this can have separate hot water and heating controls or whether it just heats them both when it's on. Also i would like to know if it's possible to add a wireless room thermostat to this system or if it has to stay as the thermostat on the boiler with programming via the programmer.

Thanks for any help with this. I'm good with wiring, just not so good with boilers and plumbing.

I am happy to provide any additional information or images if needed.
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Thanks for replying. Sorry about the delayed reply i was away from the house.

I have had a look and taken some photos.

Link here

There appears to be one pump that is wired into the current programmer via some white 3-core

There doesn't appear to be a thermostat on the side of the tank or a motorised valve anywhere.

One 3 core is wired into an isolator switch.

And there is the remaining black cable which is wired into the boiler.

Thanks for your help.
If there is no stat on the side of the cylinder and no motorized valve you have a "gravity HW, pumped heating" system.

With this type of system the heating and hot water times are always the same, but you can turn the CH off in the summer. This why the pump ia wired to the timer.

If you want separate times for HW and CH you will have to convert it to a fully pumped system and install a motorized valve and a cylinder thermostat.

Am I right in thinking that you do not have a roomstat? If that's the case, you would also need a 2-channel programmer and room stat. Wireless ones are available

Here are the layout and wiring diagrams.

View media item 69 View media item 70
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