Drayton wiser wiring woe

Hi,

I bought a Drayton wiser kit (one, heating only) to try and keep the temperature in our toddlers bedroom more constant.

However... My current thermostat is a digistat 3. It has two wires going into it. One is a constant live. I guess the other completes the circuit when the relay in the digistat flips turning the heat on. The digistat has two batteries powering it.

my question... Can I swap my digistat 3 for the wiser hub? My feeling is not because I have no "com" wire? I.e. I can't power it. I cant really follow the wiring diagram though and I don't understand the instructions where it says it is voltage free????

thanks for any help!

Hi
the term volt free simply means the item will only switch the voltage it is supplied with, the item will not produce a voltage, ie if you put 10v in you get 10v out, 240v in 240v out.
Why dont you just pay someone who knows what their doing to put it in for you.

Thanks for your response, that's interesting to know.

I did consider paying for installation, but money is a bit tight for us at the moment, toddlers seem to cost a fortune

after doing some further reading, I think I would need to channel out the wall and add a second cable in to power it, or move it closer to the boiler and use some trunking. Both aren't really practical (because our toddler seems to take up every spare second).

so I think the most sensible thing is to send the wiser kit back.

Hiya
to be honest it is easier than you think, but i could not guide you any further for fear of you hurting yourself or others, perhaps contact the manufacturer direct but i suspect their answer would be the same. Sorry i know it's not the answer you are after.

I have tried to find a wiring diagram however failed but it refers to standard wall plate so it would seem like Nest and Hive the hard wired bit replaces the programmer not the thermostat, and the existing thermostat is set to max or by-passed.

However not sure you really need a new wall thermostat to do what you want, in the main bedrooms are warmer than living rooms so a TRV head that can be set to a required program and temperature is likely enough, as yet not done a winter with the cheap electronic TRV heads, I have used expensive wifi models (£40 each) in old house and they worked well, but the cheap (£15 each) bluetooth units are now fitted upstairs and the expensive down stairs but not run a winter, so how good can't say.

There seems to be two cheap electronic heads the Terrier i30 and the EQ-3 the latter £10 for non bluetooth and £15 with bluetooth these are what I have used. When to website I got them from and no longer listed but the non bluetooth done by screwfix.

Thanks both for the replies.

I've spent some time looking into the details of the wiser hub, my current thermostat (digistat 3) and my boiler (valiant ecotech 824 R1). For anyone else following in my tracks (for clarity)...

Drayton wiring diagram can be found here: https://images-eu.ssl-images-amazon.com/images/I/C1FSY99jQPS.pdf

Valiant manual here: https://www.vaillant.co.uk/downloads/z/ecotec/ecotec-installation-servicing-2-2005-261445.pdf

I replaced the old (bimetalic strip) room thermostat with the digistat 3 when I moved into the house. The old room thermostat simply acted as a switch, completing a circuit back to the boiler when the room dropped below a certain temperature (calling for heat). This is why it only had two wires going into it. It needed no power.

The digistat 3 is programmable and (importantly) battery operated. So when the temperature drops below the set value, it uses battery power to switch the relay, again completing the circuit and calling for heat. So fine with my two wire set up.

The wiser home hub acts in the same way. When told to, it completes the circuit and calls for heat. The difference is that is has some intelligence built in and remote temperature sensors, but still, flicks a relay and so turns the heating circuit on.
However it needs power to run. You must have a power supply going to the home hub. You can use the common live from the boiler as power, but with the two wire set up (that I have) their is no neutral to connect the home hub to. If you use the other wire going back to the boiler (the live return), this effectively completes the circuit, calling for heat, and leaves the heating running constantly. There are connection charts in the above PDF that make this clear.

So I'm now 99% sure that what I say above is correct - I would either need to run another wire to the home hub so I have a neutral, or abandon the current wiring and rewire from the boiler (supplying at least three wires, a live supply, a live return and a neutral to the unit, all outlined in the boiler documentation above).

Thanks again ericmark and macc for help

You seem to be suggesting to replace your thermostat with a programmer -- that's a bit odd.

I don't know about the Wiser, but Nests retrofit nicely as they call for heat using a wireless connection (as distinct from Wifi) back to the switching ("heat link") unit (which you can install next to the wiring for the zone valves). This means you can re-purpose the existing thermostat wiring to provide power to the Nest instead.

I expect (guess) a Wiser installs using the same idea -- the heat hub would be installed next to your "control system" -- i.e. in your airing cupboard or maybe next to your boiler. Basically wherever your current hot water programmer is. Your room thermostat would be replaced with a Drayton thermostat.

Sorry - I wasn't clear.

The hot water is controlled from the valiant combi boiler. so nothing external to the combi, it is all built into the front of it (the timing for the heat can be controlled from there too).

The digistat +3 allows you to set times for heating (programmer) and then temperatures at those times (thermostat). So I guess its a combined device.

To turn the heat on and off there are two wires going into the back of the digistat +3, one is the live supply from the boiler, the other the live return. A battery powered relay connects them when the room is below temperature (for the given programmed time).

Hope that makes more sense

I can see how if you had a separate programmer and thermostat things would be easier. Thanks for your reply.

I would personally use Nest e, as the Nest e is a two wire connection it is powered by batteries, it also has option to use OpenTherm I see the boiler does have ebus option not sure if that is OpenTherm.

Nest e works with MiHome Energenie TRV heads with a follow command, not sure how good, I have Nest Gen 3 linked to Energenie TRV heads but not done a winter yet so can't say how good.

So as I see it, either return Drayton and fit Nest e or rewire with a neutral, there may be other thermostats that don't need a mains supply to the base unit, but I don't know of any.