Tado x thermostat required?

shay223

Hi all!

Wondering whether i can have Tado x without a wall thermostat, i.e. just the rad valves, a receiver next to the boiler and a bridge to control online/via app?

Thanks

policywonk

Does your system have a motorised valve controlling access to central heating in place? It is normally plumbed in somewhere between the pump and the first radiator, and usually not far from the boiler.

What specific boiler do you have?

shay223

Thanks, yes it does. It’s a Worcester Greenstar CDI 30 system boiler (approx 10 yrs old).
-Ground floor is underfloor heating with zoned manifold wired to heatmiser uh4. Planning to do straight swap of wired stats with Tado x wired stats.

-First floor and loft room rads all off one zone valve and controlled by one room stat in first floor hallway, hence wondering if i can do away with a tado stat here and just use the tado rad valves to communicate with the wireless receiver to open the zone valve and turn the pump on? Since i posted i’m wondering whether it’s wise to have a tado wired stat in hallway in case app goes down so can at least get it on and off.

policywonk

The wired wall thermostat on the first floor plays a crucial role in opening the motorised zone valve for the first floor and loft. You can remove its role in the mechanism, in two ways:

1. Temporarily. Bridge the valve that handles your radiators so that it is opened directly by the call for heat from the Tado wireless receiver. The figure below presents the wiring needed for a CH zone valve and a HW zone valve. The zone valve on the left is the one for central heating. It is powered by two wires (i) a blue Neutral wire and a brown Live wire. If you move the brown live wire so that it is connected directly to a place that goes Live when central heating is on (in this drawing thats PIN 4), it will open when there is a call for heat from one of the Smart TRV Tado heads.

2. Permanently - replace the motorised zone valve with an automatic bypass valve, calibrated to shut off flow when all the radiators have shut down, ie their TRVs wont let heat through. It saves money by removing unnecessary flow in the CH circuit.

Dont forget to ensure that the UFH thermostats are Tado wired thermostats. If you have a problem with wiring it is possible to marry a Tado wireless sensor to a Tado wired thermostat in the app, in a way that allows you to place a wireless sensor in a location you prefer; it then instructs its wired counterpart to open and shut the call for heat as needed.

Does this make sense? Need any more help?

shay223

Thank you. Photo attached of existing: 3 zone valves for megaflow tank, ufh and first floor/loft rads. On far right you’ll see there’s an auto bypass valve.

Looked into it a bit and i get the benefit of the auto bypass where it currently is to open flow when zone valves are closed. However, what you’ve said is to replace the radiator zone valve with a bypass and set it to close flow when tado heads are closed, which seems to me to be the opposite of their general purpose. If tado heads are closed, there’d be no call for heat so existing zone valve would close anyway so i’m not clear how the bypass is any better? Cheers

policywonk

You have a constant pressure pump implemented in this property.

In a zone, when all TRVs are open, the bypass valve doesnt register resistance, ie asback pressure. Your plumber in fitting the valve will calibrate the valve to register when all rads are open, and then again when all rads are closed. It can then reliably when all rads are closed.

Remember that when any of your smart TRVs, or even mechanical TRVs opens up, the bypass valve releases heat back into the circuit.

This has the same impact as a zone valve in reducing waste, but much, much more reliable.

Does that help? Your plumber should immediately get this.

shay223

@policywonk Hi again. I have bought some kit and had a plumber in but wasn't playing nicely so will make some adjustments to wiring so set up as S Plan Plus. What I have now:

-Worcester Greenstar CDI 30 conventional heat only boiler
-UFH manifold (inc pump)
-Honeywell STC 2 channel programmer set to always on for HW and Heating
-Heatmiser UH4 wiring centre
-Megaflow Tank
-External pump leading to 3 motorised zone valves (hot water, UFH and 1st/2nd floor heating). Also has an auto bypass valve at the end. Photo below:

Current Ground floor (underfloor heating): 5 zones controlled by 4 wired room stats plus one in the hall that controls the 5th zone, but it also carries switched live to the Heatmiser UH4 wiring centre. So, this stat needs to be on before any of the other 4 room stats/zones get any heat.

Objective:
Replace with 5 wired Tado wall stats to control all 5 zones individually. The "master" stat in the hallway is obv a problem so plumber will run a new cable between the Heatmiser UH4 wiring centre and zone valve so it activates upon call from any of the 5 Tado stats. Will also run another cable to the hallway stat so it only acts as a regular stat.

Will replace Honeywell controller with a Tado wireless receiver connected to the boiler so bridge allows online control. As Tado receiver is 2 channel only, will not make it a zone controller for ground floor and instead have the call to boiler go from UH4.

Current First and second floor (radiators):
6 Rads
5 bathroom towel rads
Wired hallway stat on first floor controls all

Objective:
Replace with 6 Tado radiator thermostats
Leave 5 towel rads as bypass
As mentioned in my first post, no hallway stat so will make Tado wireless receiver the zone controller so Tado heads call it directly.

As per your temporary solution, would have a cable from Tado receiver to zone valve so it opens when Tado heads call.

I think that could all work but if not please let know.

For a set up without a first floor hall stat, your permanent solution was to replace the zone valve with a bypass. Will that still work with my set up? Won't it conflict with the existing bypass and will it still work given I have 5 towel rads without Tado heads? Also, what then sends the signal to the pump?

Greatly appreciate any guidance or tips on getting this right!