Installing Controller - Missing Connection to Terminal 3
I've just bought a Wireless Smart Controller V3 Starter Kit (Heating plus Hot Water) and have gone through the installation right up to dismounting the old wired controller (Honeywell ST9400A), only to discover that the only terminals in use are: Earth, L, N and 4. Nothing on Terminal 3!
If I understand these things, Terminal 3 is involved in controlling the Hot Water. This may explain why I've always thought the water in the cylinder gets too hot.
The image below shows the back plate with Terminal 4 disconnected and labelled. It looks as if wires go to 3, but, in fact, they go under the back plate which is mounted right on top of the cable, coming out of the wall, from the gas boiler and the power switch. No idea what the cables joined up with plastic connectors are for!
The question is: what can I do about it? Will the Tado work without a Terminal 3 connection, albeit on a manual programmed schedule (as currently, I guess)?
Answers
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If you want hot water control then you need to get the wiring sorted out. I would recommend getting it checked by a heating engineer if you're not confident with the wiring.
Apart from anything, even without Tado, you'll be wasting lots of gas by having the hot water tank constantly re-heating. I experimented with leaving my HW on 24/7 but found that I was using much more gas compared with having it scheduled a couple of times a day
I wonder if the terminal 3 was bypassed at some point due to a faulty controller and then never reinstated?
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Thanks for the comments. I agree totally that I need to sort out the problem with lack of feed back from the hot water cylinder to the controller, but that's going to take some time to organise, probably going back to the gas boiler installation company to try and find out why.
In the meantime, I need to know whether I should return everything or install the Tado controller anyway. Before doing this latter option, I need to know that the Tado controller will activate the gas boiler to heat the hot water on a basic time schedule basis or not, whilst running the central heating as required. I've been exchanging e-mails with Tado Support but they have stopped answering (and I've not been pestering them) without confirming (or otherwise) what I need to know.
Update: Had e-mail from Tado Support tis afternoon:
The cable in 3 is supposed to control the hot water. So If it's not wired, you are not controlling the hot water.
Please follow the instructions in the app and do not use any cable in 3 as you did not have one. Just stick to N, L, 4. You will be able to control the heating only.
So, I guess that answers my question, so will install the wireless controller.
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