No hot water

Set up is a Potterton Open Vented holier on open vented system. 12rads with Tado TRVs on, one megaflo, 3 port valve plus one two port connected to the cyl stat and a hallway thermostat. All working fine controlled by a Honeywell ST6400C which I replaced with an Extension kit. Rewired the Neutral, Live and 1, 3 and 4wires to the same place. Moved the jumper to position 2. All rebooted fine until the morning when there was no hot water. The new kit doesn't seem to divert the flow to the megaflo...

Any ideas?


  • Did you get the wiring instructions from Tado? To get HW from the cylinder the 3 port valve needs to be in the correct position and the 2 port valve opened. The 2 port valve is there as a fail safe and is a mandated safety feature for all unvented cylinders. It’s really important that the control valves are wired correctly.

  • Wired exactly as the instructions from Tado. Each of the 5 sets of wires went to the L, N, 1, 3 and 4, exactly as they were when on the Honeywell. I've not put a smart thermostat on but having looked at the wiring it's operating as a switch so not sure what putting a wired thermostat would do. I think as it worked when wired to the honeywell, with the same wiring configuration with the extension kit it must be a software glitch.

  • The wiring instructions provided by Tado are likely correct. It could be that they have not enabled HW control in the system configuration. The relays in the EK make a definite sound. If you cannot hear them switching it point towards an incorrect software configuration.

  • I don't believe I've got a unique set up so I agree something likely wrong with the system/ software. I've emailed tado support so I'll see what they suggest. Before we moved I set the system up in the last house, slightly different config there, but installed and ran like a dream. I hope I can get it resolved.

  • Final update on thread in case any one comes across similar problems. Re-installed the system in the following order: Wired Smart Thermostat, Smart radiator valves, Extension kit. Everything now works including the hot water controls. It seems as thought the smart thermostat was the missing link. Doesn't logically make sense as the extension kit and radiator valves should be sufficient but all now seems OK.