Replacing 2-zone +DWH Danfoss controls with smart system like Wiser or Tado

[Sammy21]

With the help of some kind people on this forum (you can read the thread here: https://www.diynot.com/diy/threads/upgrading-danfoss-controls-to-something-smarter.603716/), I managed to completely work out how my current home setup of a TP9000+TS2 and a TP5000 upstairs all works:

And here is the wiring box:

Assuming I'm going to keep the 2 heating zones, it looks like a Wiser installation might be simpler to install and cheaper. But I'd be interested to hear anyone's thoughts on Wiser v's Tado. Several people on this forum have has successful Tado installations, but only with direct help and intervention from Tado, which seems clunky to me. The Wiser 3ch hub plus a couple of wireless thermostat controllers looks simple enough. I could wire the hub where the existing T9k sits, though I would have to repurpose one of the earth wires in the 5-core cable between the T9k and the wiring box. Do you think this would be OK?

I have an alternative wiring system where I could move the hub next to the HW tank:

This would leave me with a couple of spare cables in the 5-core between the T9k and the wiring box, which might come in handy at some point, but I could always start out with the hub in the t9k location, and move it later if necessary.

I haven't worked out what the Tado wiring would be yet.

Any thoughts?

 

[oldbutnotdead]

First thought - if by 'repurposing' an earth flex core you mean connecting it to live or neutral- don't. It was always a rubbish trick and I believe it has been definitively banned in current wiring regs.
Second thought- I can't speak for Tado, the Wiser 2 ch + dhw works fine as a conventional controller but the Opentherm implementation on it is flaky (to be fair to Drayton they do state upfront that the 2ch + dhw control doesn't support Opentherm).
If you were to splash out and have a full set of WiFi TRVs you can ditch the heating zone valves entirely ( would change your cable spec).
The Wiser dhw channel is merely an on/off relay - you can program times for it or not, up to you. At the moment there are no smart toys you can put on that channel (can't see why you'd want to but it does mean you can't cheat and use a WiFi TRV as the motorised valve for dhw).
If you do go Opentherm you'd have to do something about the heating zone valves- Opentherm only responds to heating demand from channel 1 (ch) .

 

[Sammy21]

My boiler is an Ideal Logic 15 (10 years old) and it doesn't support Opentherm, so that's not an issue. Yes, I had hoped to use and earth core for the zone 2 heating cable. I get that it's not ideal, but the Froststat already uses an earth core as it's live in, so at least it wouldn't be the only off-code example in my heating system! Moving the hub upstairs near the boiler may in any case be the better solution, and that doesn't need any dodgy repurposing of earth cables.

I must admit that I'm unsure whether or not to get rid of the 2 heating zones and put TRV's in all the rooms. Even if I did that, if an upstairs radiator called for heat, the boiler would pump hot water around the upstairs and the downstairs circuits. Even if all the other radiators were totally off, I'd be warming up the downstairs loop for no reason. Wouldn't be a lot of energy lost that way, but it feels ugly, especially as I already have to the 3 switching vales...thoughts?

 

[ianmcd]

My boiler is an Ideal Logic 15 (10 years old) and it doesn't support Opentherm, so that's not an issue. Yes, I had hoped to use and earth core for the zone 2 heating cable. I get that it's not ideal, but the Froststat already uses an earth core as it's live in, so at least it wouldn't be the only off-code example in my heating system! Moving the hub upstairs near the boiler may in any case be the better solution, and that doesn't need any dodgy repurposing of earth cables.

I must admit that I'm unsure whether or not to get rid of the 2 heating zones and put TRV's in all the rooms. Even if I did that, if an upstairs radiator called for heat, the boiler would pump hot water around the upstairs and the downstairs circuits. Even if all the other radiators were totally off, I'd be warming up the downstairs loop for no reason. Wouldn't be a lot of energy lost that way, but it feels ugly, especially as I already have to the 3 switching vales...thoughts?

not if all the other TRVs are closed it wont, , honeywell evo home is my choice

 

[oldbutnotdead]

If there's no external bypass on the system you'll only be heating the loop as far as the rad that's on.
EDIT The WiFi valves are great for variably used rooms. EG watching a late film, sitting room gets chilly- no probs, extend that radiator for a hour. And extend the bedroom while you're at it.
If you're not using Opentherm then the zone valves will do no harm.

 

[ianmcd]

extend the bedroom while you're at it.

Or turn it down while you are at it stops you sweating too much

 

[Sammy21]

Well, just found the 3ch Wiser kit on Amazon for under £150, so bought this with 3 TRVs to test. I'll start with the non-PC wiring version so I can easily go back to my original Danfoss system after a couple of weeks if I don't like it, but I'll move the hub near the cylinder if I start to get connectivity issues. I'll post my findings here...

 

[oldbutnotdead]

Have fun. Extra valves are £40 at Wickes at the moment (so £5 cheaper than Jeff's shop) .

 

[Sammy21]

that's good to know. I bought from Jeff so that i didn't need to do a separate car trip for 3 trvs, but if I end up buying another...3 or 4, it'll from Wickes or SF. wish me luck

 

[Sammy21]

Can I ask you guys a quick Q? DOn't know if you've had a look at the other thread, but in order to put the Wiser hub where the TP9k goes now (least destructive installation in case I decide to go back) I'll need to repurpose the live wire in the 5-core cable between the wiring box and the tp9k back plate as the zone-3 switched live:

One of the replies was that this is a bit no-no. I get that it might be a little ugly, but is there any real risk or downside, as long as I label the cable clearly?

 

[oldbutnotdead]

This is 5 core flex yes? As a temporary lash-up, colour on that core completely hidden by brown pvc tape, only you will be working on it etc etc then it is still shoddy but I can see the appeal as a proof of concept bodge.
Since it's a temporary bodge and you are the only person working on it you can risk-assess your way round it (this is in your house isn't it)- yes go for it but do not let it become one of those temporary jobs that is still there in 10 years time.
To protect others, label both ends up (warning-all cores of this flex may be live) - yes you know that but you could drop dead tomorrow, next person needs to know.
To be absolutely safe (this is temporary after all), can you run a length of 2 core or 3 core flex between the devices?

 

[Sammy21]

Unfortunately, it doesn't look like it. In other countries like Italy electricians run flexible corrugated hoses in between two points so that you can change the wire contents at a later stage. But here in the UK it looks like all the cables are buried in the plaster, ceilings and floors. I can't see any easy way to replace the 5 core cable with a 5 core plus 3 core. Unless you have any clever suggestions? My wiring experience is all in Italy where things a lot easier!

 

[oldbutnotdead]

Ah boo. No magic tricks, I was thinking (it being temporary) about flex surface clipped from a to b. Might be impractical, depends how many walls and ceilings there are in the way.

 

[Sammy21]

Ah boo. No magic tricks, I was thinking (it being temporary) about flex surface clipped from a to b. Might be impractical, depends how many walls and ceilings there are in the way.

approx. 3 walls and i floor separates them, so that's a no-go on the extra cable. Don't worry, I'll make sure the earthlive is properly labelled!

 

[Sammy21]

So, yesterday I installed Wiser 3ch (2 ht zones +hw) plus 2 room stats and 3 trv's. Everything went according to plan, and no issues whatsoever. I'll test the system thoroughly over the next 2 weeks, then buy 3 more TRVs to increase the control. Unfortunately, in my bedroom, where there was a tp5000, there is no TRV valve, so I can't put a Wiser TRV there without calling in a plumber to put in a new valve*. This means I could end up unnecessarily heating my bedroom when one of the other upstairs TRVs call for heat. But apart from that, I'm pretty happy so far.

I will say that the Smart Room Thermostats seem to be a waste of space. You get 2 of them with the 3ch hub, but honestly, it's hard to see the point in them. Better to have TRVs in every room and control the zone valves that way. Unfortunately, it doesn't look like you can buy a 3ch hub without the 2 Smart Room Thermostats (not in stock on the Wiser shop, nor anywhere else) but if you could, I think you would be better off buying the hub and a bunch of TRVs instead, and skip the Smart Room Thermostats altogether. You'll end up doing all the control via the app anyway.

So far, so good.


[* Looked at a few YouTube videos, and draining the whole system seems like a job for a pro]