Missing NC wire for heating

chris_bushell

Hi,
I’m replaced a Danfoss wired controller with a Tado wireless one. It’s a combi system. The old unit did not have a wire connected at point 2 labelled HTG OFF. The new Tado one requires this wire at the CH NC connection.
I have been using it without. The hot water works perfectly. The heating works now and again, only when HW on but goes off when the temperature is a long way from being reached.
How can I solve the issue and get the CH working properly and independently of the HW?
FYI the WiFi connections are all ok and all units communicating with each other.
Thanks
Chris

wateroakley

@chris_bushell This sounds like a wiring and/or setup problem. What make/model controller and thermostat have you replaced? What is the boiler make/model? Did you need to fit a link L to COM on the receiver? Have you bridged the thermostat wires? Have you set the wireless receiver to combi?

Please post a photo of your wireless receiver with the wiring, and how you have bridged the old thermostat. Same if you have photos of the old controller/thermostat wiring?

chris_bushell

These are the images of the old controller.

chris_bushell

This is how the Tado unit is wired.

chris_bushell

Thank you @wateroakley for looking at this.

chris_bushell

I’m pretty sure I set it to combi when installed but not sure how to double check. The old thermostat was unbranded. This is what is left.

Mickyman

To me, I think your wiring looks correct. Stupid question but is the red, blue and yellow cable shown where you old thermostat was, is that the the red blue and yellow wiring shown on the controller? Because as far am I aware the the thermostat would be connected to heating on 4 connector in series with the boiler. I am obviously talking about you old controller.

wateroakley

@chris_bushell Check your thermostat wiring. On the thermostat box, the yellow wire doesn't appear to be properly inserted into the Wago connector? You should see the yellow down to the connector and copper on the other side, like the red wire. The yellow wire will probably be the CH from the NO connector on the wireless receiver. If there is no connection, the boiler won't fire up for CH, although the HW would be OK. If it's a bad or intermittent yellow connection, the boiler may not fire up or may be intermittent.

chris_bushell

Thank you @wateroakley I have put the yellow wire further into the connector box, there’s now copper visible the other side. So far it’s not kicked the heating on and the Tado thermometer is over 3.5 degrees lower than I’ve set it to.

chris_bushell

Hi @Mickyman thanks for having a look at my issue.
The yellow had been in point 4 on the old controller which was labelled HTG ON and the Tado install instructions implied that should be CH ON for the new receiver. Do you think it should be CH NC?

Mickyman

On the picture of the receiver, there is a a red, yellow and brown wires shown not connected . What are those wires?

chris_bushell

I don’t know what the other wires are. They weren’t in use before. There is some writing on the white casing.

Mickyman

I'm guessing that if you have a combi boiler them wires could be over from a hot water cylinder stat.

chris_bushell

So it seems the issue is with the mid position actuator that is not being switched from hot water only to mix or heating only as required. Do I need to replace the existing one or change the wiring somehow?

hugbilly

I would just double check that when the wireless receiver shows the heating to be on there is actually 240V on the CH NO terminal. If there is then the problem must be downstream of that. But if it's a combi boiler what function does the HW control perform because, presumably, there's no tank . . .

chris_bushell

I think I may have confused as there is a tank and I have followed the Y diagram when installing the Tado kit.