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Is Replacing Central Heating Timer Controller Difficult?

Postby miketurner201 » Wed Aug 07, 2019 7:54 am

HiI have a Glow Worm Flexicom 24hx Condensing boiler and I would like to move my existing Towerchron QE2 timer / controller which is currently in an airing cupboard on the first floor, moving it down next to the boiler on the ground floor.

Would it be difficult to move the timer controller QE2 downstairs next to the boiler ?

I can see 2 cables coming out of the bottom of the boiler and one goes to the pump and the other into the wall, there is also an electric switch on the wall near the boiler (but out of the boiler cupboard) which if turned off then turns off the electrics to the boiler.

Any help with what would be involved would be much appreciated.
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Postby ericmark » Wed Aug 07, 2019 8:59 pm

First read the instructions. https://www.glow-worm.co.uk/glow-worm/f ... 157170.pdf I note on page 24 it gives the connections, I can see an ebus connection but nothing about using it with a thermostat, so it would seem this boiler uses a mark/space ratio (it turns it off/on) so it would seem easy to add, or move the controls.

However much depends on what cables are already installed, and how the boiler needs controlling? In the main we use a series of plans, with a combi very easy. But where it heats the domestic hot water (DHW) we have a number of options.
1) Thermo syphon
2) Pumped
3) Time only control
4) Thermostatic control
5) 2 port valves
6) 3 port valves
Since you say airing cupboard I would assume it does DHW as well as central heating, the normal method is to use wiring centres to reduce the number of wires between the cylinder thermostat, motorised valves, room thermostats and pumps.

When I came to alter the controls on my central heating it was the cables or more lack of them, which forced me to adopt a way of controlling it. Some times wireless can be used, however consider if they fail safe, if when batteries go flat or some thing blocks signal it can continue heating 24/7 that is not good, some wall thermostats look for signal every 1/2 hour and if no signal shut down (fail safe) others don't.

So basic method is, a thermostat is powered from a programmer, then thermostats often one wall and one tank then power the motorised valves, the valves then power the boiler and if required pump.

Central heating nearly always has a pump, but DHW can be thermo-syphon.[attachment=0]C_Plan_My_HouseC.jpg[/attachment] This is the plan for my house, the two wiring centres the boiler, pumps, valves in fact all but the wall thermostat was in the flat below the main house, only 2 wires link main house and flat below, so selected Nest as it allowed me full control from main house with only 2 wires.

That is what you need to work out, how many wires do you need, how many have you got, and if not enough how easy is it to add extras.
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C_Plan_My_HouseC.jpg
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Postby miketurner201 » Thu Aug 08, 2019 8:43 am

Hi Eric

Many thanks for that very comprehensive reply.
Ultimately I'm aiming to add the Tado wireless controller and thermostat to my central heating/hot water system. I though perhaps first I would move the controller downstairs and then swap it with the Tado one.

The Tado system is self installed (or can pay a fee for them to do it) and they talk you through the straight swaps. I may just leave the controller in the upstairs cupboard and just swap it over with the Tado one, as I don't want to add to any problems I may have.

So thanks again for the very comprehensive reply, I'm not doing it for a few months so I will continue to consider what to do.

Thanks again.
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Postby ericmark » Fri Aug 09, 2019 12:25 am

Not used Tado, however I think similar to EvoHome? From what I have read the TRV head controls each room, in turn it tells the thermostat if the boiler needs to run, the thermostat is more like a hub than a thermostat.

So it does not matter so much where the thermostat is located.
ericmark
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