Combi boiler volt free, heating off boiler and ufh zone

sparkyork

Hi everyone,
Just been to look at a job, customer has a tado starter pack.

Combi boiler feeding radiators and a seperate zone for some ufh

Combi (biasi s) only accepts volt free

Customer had purchased an electric ufh stat which I advised isn't really suitable.

Currently heating is controlled at the boiler.

I've suggested buying another tado for the ufh and having that talk to the other one and fire the boiler when necessary.
I may have to get him to cancel the order as I was looking at connections using a much larger box ( extension box? )

I need to utilise a volt free setup, will the original tado thermostat and bridge accept another thermostat?
The bridge us just the thin white box linking router to stats?

I believe I've potentially got 2 tado wired thermostats, if the one I said to order gets ordered !

If I had an extension box I'd break out the low voltage from the boiler into the box and it all happens from there ??

Do I need am extension box or another stat going to work ?!

Sorry a bit confused

johnnyp78

You can only wire either one Tado extension kit (now known as a wireless receiver) or one wired thermostat to the boiler. Both can be connected by voltage free relay (The wired thermo can also be connected digitally).

Is the UFH electric or hydronic?

There are two versions of the starter kit, one wired and one wireless. Which version does the customer have? Sounds like the wired.

If it’s hydronic UFH it’s simple (ish). there’s a guide here - https://support.tado.com/en/articles/3487152-how-does-tado-control-multiroom-heating-setups-with-a-combination-of-radiators-and-water-based-underfloor-heating

Tado recommends connecting the wired thermostat to the ufh zone valve and then getting a wireless receiver wired to the boiler and smart trvs on the rads to call for heat.

If it’s electric UFH, you could wire it to the existing Tado wired thermostat provided it can be switched with a low current (max 3 amps). Tado can’t switch high current UFH directly. Set that as zone controller for the room with UFH.

You could then get either another tado wired thermostat or the wireless starter kit, and wire to the boiler. Set either the new wired thermostat or wireless receiver as zone controller for the rooms with rads.

Can also use smart trvs on the rads with the wireless receiver instead of a wireless temperature sensor if you want to control rooms individually.

https://support.tado.com/en/articles/3557820-is-tado-compatible-with-electric-heating-systems

sparkyork

Thanks for your detailed reply, the customer has just 2 wired thermostats, I thought he had the extension box but not the case.

If I use a relay at the boiler can I just use the 2 stats as normal stats and trigger the relay via both stats?

I could ask the customer to cancel the order and get a wireless stat maybe ?

johnnyp78

If you look at the Tado guide to installing mixed ufh / rad systems they recommend getting a wireless receiver (not a wireless thermostat) and trvs for the radiators and wiring the wired thermostat to the ufh zone valve, so you could go with that if it’s hydronic ufh.

I think you could use a wireless receiver to the boiler on relay and the two thermostats connected wirelessly if the ufh is plumbed in like a hot water cylinder on s/y plan, but I’m not an expert, though the control for the Ufh would then be called ‘hot water’ on the app.

sparkyork

Thanks, so I need the extension box or a wireless receiver? Same thing ? And one of the stats maybe made wireless if getting a cable to the household rads is difficult.
Ufh is standard plumbing

johnnyp78

Extension kit is the old version of the wireless receiver. Both fine. Like I said, you can only have one direct connection to the boiler so it depends on the ufh plumbing and wiring. I think the problem you’ll have if you wire it to the hot water relay is the client asking where the room control for it is and why it comes under hot water.

sparkyork

Turns out there is a zone valve for the house rads and some sort of actuator for the ufh.

So no way of wiring these 2 stats in traditionally and having them show up on an app?

The boiler is going to need a relay to use the volt free contacts.

Customer tried to cancel the order for the second wired stat but it got delivered instead.

Will do some reading and studying and maybe end up getting a wireless stat but tbh I'm thinking now it's not really upto the job.
It's a second heating zone and not hot water.

If a wired stat shows on the app why won't two ?