Hot water but no heating (Tado Wireless Starter Kit)

Discussion in 'Electrics UK' started by peggleg, 10 Nov 2021.

  1. peggleg

    peggleg

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    I installed a Wireless starter kit last night however, we only have hot water and no central heating

    I followed the instructions from the Tado app for the install. I bridged the connections where the old thermostat was removed. The only way I could get the heating to work was to reinstall the old thermostat.

    Old System:

    Honeywell ST6400C programmer


    Honeywell T6360b wired thermostat


    Hot water tank in airing cupboard

    I am now waiting for a Tado wired thermostat to be delivered. Will this make the install easier? I can always re-use the wireless one in a room with Tado radiator control?
     
    Last edited by a moderator: 10 Nov 2021
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  3. stem

    stem

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    If the heating wasn't working with the 'bridge' in place, but then it worked when you only removed the bridge and put the old thermostat back, you did something wrong with the 'bridge'.

    The old thermostat is simply an on/off switch. When it's removed the bridge makes the same connections that the thermostat would when it was 'on' and calling for heat.

    The wires in the Honeywell T6360b terminals 1 & 3 are the wires that should be 'bridged'. You can simply replace the old thermostat with a junction box and connect the wires that were in terminals 1 & 3 together in there and isolate any other wires individually.

    Or, if you don't want a junction box on show, trace the cable from the Honeywell T6360b back to its origin, when you find it, note where the wires are connected and then disconnect them all and remove the cable. Then insert the bridge between the terminals that you have just removed the wires that went to 1 & 3 from, so that the terminals are electrically connected.
    A wired Tado thermostat should be easier to install, however you will have to leave the heating set to be permanently 'on' at the Honeywell ST6400C otherwise it will interfere with the operation of the new thermostat. Also, control of the hot water will still be from the Honeywell ST6400C.

    It would be unusual two have a Tado wired thermostat and a Tado wireless receiver on a heating system with only one heating zone. Normally this set up would be where there are two heating zones (eg upstairs and downstairs) each with their own room thermostat with the wired thermostat controlling one zone, and the wireless receiver the other one and the hot water. Whether two Tado devices can control a single zone successfully or not I don't know.
     
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  4. peggleg

    peggleg

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    @stem

    Thanks very much for the detailed reply.

    I have made some progress.

    Installed the wired thermostat to replace the T6360B. This works and fires up the boiler when heat is needed without starting up HW

    My next question is, I have installed smart radiator valves (also Tado). Is there a way to only switch one of them on without the need for the wired thermostat to be on (entrance area with radiator without valve that can be opened or closed)

    When I enable heating on the smart valve the app shows its heating, but its not doing anything.

    Hope that all makes sense :)
    I am very new to all this

    Thanks again
     
  5. ericmark

    ericmark

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    I steered clear of Tado as so hard to find out what it does and how to wire. Does seem to be a big secret, I found this upload_2021-11-12_10-7-36.png and this upload_2021-11-12_10-8-10.png which seem to show a reasonably standard set of connections, the first seems to be what they called wired and does not include DHW but does have the OpenTherm option, the second they called wireless and seems to be a simple pair of relays, the same as many old programmers.

    Nest instructions actually show S, Y, Combi wiring.

    It is easy to see from diagram how it all works, but once you open your wiring centre it rarely seems to follow the diagram terminal numbers, or wire colours, so job one is work out what terminal is what.

    I normally start with the motorised valve since at least those colours are standard, and in the main 2 x 2 port valves = S Plan and a 3 port valve = Y plan and no valve = C Plan, there are exceptions, I have C Plan and two pumps and 2 x 2 port valves and two relays, but in the main you can from the motorised valve work out what you have.

    It is unlikely with a Honeywell ST6400C programmer and Honeywell T6360b wired thermostat that your boiler is opentherm enabled. However it seems there are very few systems that can work OpenTherm with domestic hot water as well. Maybe EPH?

    It seems you have miss identified some wire, but best option are photos, we may with some luck see your error. I know when I came to do mine I just identified cables and wired from scratch.

    Sorry was writing at same time as you.
     
  6. ericmark

    ericmark

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    I should hope you can do each room independently, most can, but trying to follow Tado is not easy. In the main (except silly Nest) the TRV tells the wall thermostat I want heat at same time as opening, but each make slightly different. Hive for example will not switch on if room where thermostat is has exceeded 22°C, EvoHome has the TRV heads displayed on the wall thermostat etc.

    However I found with electronic heads on my TRV's the lock shield valve needed to be set spot on, when I started the lock shield valves were open too much, the valves I have take around 3 minutes to close, so unless the lock shield set, the radiator is stinking hot in 3 minutes so over heats the room.

    What I did was look at the target and current and if current exceeded target I closed the lock shield a tad.
     
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  8. peggleg

    peggleg

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    Ill take some pics of the Tado install and share as I did with the original Honeywell and upload in a bit
     
  9. stem

    stem

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    If your current set up is that all of the radiators are plumbed together on a single heating circuit then no. The set up is similar to your cold mains water supply, if you turn off the main stop tap where the pipe enters your house then all of the taps supplied with cold mains water will all go off. In the same way, when your thermostat turns off the heating it all goes off.

    It can be replumbed into separate zones, hence my earlier comment:
     
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  10. peggleg

    peggleg

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    Ah... Thanks for clarifying. We only have a single zone in the house as far as I can tell (single thermostat in the entrance). By the looks of it I will need to have main radiator on with the room valves on / off where we want heating.
     
  11. ericmark

    ericmark

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    In the main radiators are in parallel with a by-pass valve so each radiator can be controlled individually, and as hot water returns to the boiler it will auto turn boiler first down, then it will cycle off/on once at minimum output, the wall thermostat is only required so on warm days the boiler will not cycle on/off all day, as without pumping the water around it does not know if any TRV has opened or not. But to set the TRV, lock shield and wall thermostat to work in harmony is not easy, so the idea of a hub which collects info off each TRV and tells boiler what to do is far easier to set up.

    Most wall thermostats explain how they work, but Tado is rather poor at telling you how it works, with Hive it tells you exactly how it works, Nest does not any longer work with TRV heads, Honeywell EvoHome has the wall thermostat control I think 6 TRV heads, and Drayton Wiser the TRV head tells the wall thermostat when to fire the boiler, some like EPL work only with motorised valves.

    Main difference between a motorised valve and a TRV is the motorised valves are hard wired and have micro switches inside them, they both do the same job, personally I want to have the ability to select each room, rather than a group of rooms so use TRV with electronic heads in main house, but in the flat under house use a motorised valve so whole flat can be turned off on a single control.

    With a thermostat in the hall it also needs a TRV, as when you open the door to outside the hall will cool rapid, and so it needs to reheat rapid, but before it reaches the temperature to switch off the wall thermostat the TRV needs to throttle back or it will switch off boiler before rest of house is warm. It can be done, I did it with mothers house, with non smart stuff, but with smart stuff it depends how it can be set.

    When I tried with Nest and Energenie I found it auto set both at same temperature (until google withdrew support) but since the TRV in lower than the wall thermostat and closer to front door, it needs setting around 2°C cooler to the wall thermostat, and this was not available, so my TRV and Wall thermostat have the same times when program changes temperature but different temperatures set.

    It seems in USA they have released satellite Nest thermostats which tell the main thermostat to keep boiler running if room with satellite in is still cold, but not released here yet.

    But at least one can read how Nest works, Tado is so hard to read instructions I rejected it.
     
    Last edited: 12 Nov 2021
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