No hot water after installation

Ayres

Hi,

I currently have a Baxi duo-tec combi boiler with a wired Drayton thermostat called CombiStat, as well as a Drayton programmer on the wall. The programmer has options for the heating and hot water, these are off, timed, once, and on. The programmer does not control our hot water and this setting is always off.

I replaced the thermostat with the Tado X thermostat following the guide from the app, I’ve attached a photo of my old thermostat wiring. I left the wall programmer active, but on the always on setting for both hot water and heating. However, I have no hot water.

The problem seems to be that the boiler switches off when nothing is calling for heat and since the boiler is off it means no hot water, and turning on a hot tap does not power on the boiler.

Does anyone know how to resolve this?

Thanks in advance.

Boiler - https://www.jtatkinson.co.uk/pr/hbax052/baxi-duo-tec-combi-boiler-28kw-7219414

policywonk

Hi @Ayres. Welcome to the community. Have looked up your boiler's details and it seems from this Installation guide (see page 44-45 figures 36 - 37) that it can operate more effectively and efficiently in Opentherm mode, not dumb on-off mode as your Drayton controls are presently wired to it.

Your boiler can be controlled in dumb-on-off mode or in digital mode.

• If you elect to run it in Opentherm mode (which saves money), then you have to move everything (clock and thermostat) to digital mode.
• From the manuals published, it looks like the programmer does not support digital mode controls, neither does your thermostat. This means that if you elect to run in digital mode, your programmer must be taken out of the loop because your boiler will misbehave if the programmer is on the switched live side of it (as it was), and the Opentherm connection to be active at the same time (as the Tado device should be).

If you want to fully migrate to Opentherm, which your Tado X supports really well, these are the steps.As you take these steps, take photos, and label wires as you remove them. Keep a list of the labelled wires so that if you get lost, you can reset your brain. It also helps if this process fails to put everything back to where it was safely.

1. Decommission the programmer and existing thermostat. To complete that:
   1. Kill the power to the boiler, the programmer and the thermostat.
   2. Go to the boiler and locate Block G (identified in page 44), then identify PINs 1 and 2 on that block. Now, carefully identify the wires at Pins 1 and 2 which specifically go to the thermostat and the programmer. Note those wires. You'll be coming back to this.
   3. Go to the programmer and check the power is down. Then check that the thermostat also has no power.
   4. Go to the thermostat and check that the power is down.
   5. Use a mains testing screwdriver or electricity proximity tester to confirm.
2. Go back to the programmer and decommission it. You wont need it, as the Tado app controls your schedule. Remove the wires and label them as you do. You should find:
   1. Permanent Live (should be pure brown without a sleeve).
   2. Switched live (based upon your other photo, it should be black with a brown sleeve)- but you need to confirm this.
   3. Neutral (should be pure blue).
   4. Come back here and check if something is odd.
   5. If all is as expected, insulate the ends where the programmer is placed. Remove the programmer.
   6. Now, carefully. Trace back those wires to their origin - they should be found on the G Block, (probably on PIN 1, 2, N and L).
   7. Remove the wires. Insulate them. Label them. Double check that you've properly traced them. This is crucial.
3. Go to the thermostat.
   1. Identify the wires going into the thermostat by tracing, wire for wire, where they came from the boiler.
      1. The pure brown one which wired into the PIN 'L' should be permanent live -so be careful. Label it as Thermostat Opentherm +'. Label both ends of this wire, the one at the boiler, the one at the thermostat.
      2. The pure blue one wired into PIN 'N' should be permanent neutral. Label it as Thermostat P1. Label both ends and insulate both ends.
      3. The black one with a brown sleeve is a Switched Live (ie it turns on the boiler when there is a call for heat). Label it 'Thermostat Opentherm -'. Label both ends.
      4. Two of them, I suspect the one should have come from Block G (pins 1 & 2). Very important to be certain which pair of wires directly go from the boiler to the thermostat and are truly going to serve as Thermostat Opentherm + and -.
4. Go back to Block G. You should find that one side of PINS 1 & 2 are not connected now. To take this boiler out of dumb mode, you need install a bridging wire between PIN 1 and PIN 2 on block G and fit the wire. Look at the drawing on page 44.
5. Remember those wires which went to the thermostat (Step 3 above)? Now wire them to the Opentherm connecting point.
   1. Locate Block H, it has ten pairs. See page 44 on the installation guide
   2. Locate Pins 1 and 2
   3. Connect 'Thermostat Opentherm +' to PIN 1
   4. Connect 'Thermostat Opentherm -' to PIN 2.
6. Assuming that the Tado X is being fitted where the Drayton thermostat was originally, take these steps:
   1. Connect the Tado thermostat as described in the guide, using the wires previously labelled as 'Opentherm-' and 'Opentherm+'.
   2. Place the P1 wire in a parked position.
7. Double check. Make sure the APP is properly informed that it should be controlling the boiler in Opentherm mode, NOT relay mode. Note, a Tado thermostat, properly wired into your boiler doesnt have any right to control hot water, and with the correct wiring it should not happen.
8. Power it on.
   1. Does it work correctly?
   2. If not, there could be some mismatch between the boiler's installation guide and what was actually wired in place.

Come back if you have problems. Remember to reverse the process if you hit a glitch. We'll help reflect on the obstacles.