Nest, 2 port zone valve and hot water tank

[Ffiona70]

Installation of Nest seems to have led to the destruction of my heating system.
- Plumbers did some interesting wiring, connecting the power wires of the Nest thermostat to anything but T1 and T2 in the Heatlink, resulting in Nest H72 error.
- Got plumbers back and they wired the thermostat into a base (so just wireless), they connected the old thermostat power wires together, and made a big loop back to connector 6 on the Heatlink. Central heating was working at this point, not sure about the hot water because we also have solar water heating.
- I thought I could do a better job using the S and Y-plan diagrams in the Nest booklet (figured it didn't matter which it was because I just needed to connect the wire from the zone valve directly to terminal 6 in the Heatlink and connect the T1 and T2 wires properly to the Nest thermostat.) Success with the Nest remaining powered up, and terminals 3 and 6 switching appropriately when heating or hot water requested. I think the radiators were still heating up on demand at this point.

However, soon discovered that the boiler was not actually firing to heat the water when just hot water was requested.
- Saw another thread on this forum about how switching the 3 and 6 wires in the Heatlink could solve this, so I thought I'd try that. We then got hot water when requested but the pump was running when it shouldn't have been. I could hear the port valve triggering (slightly) when heating and hot water requested.
- Switched the 3 and 6 wires back again and the pump was powering up but not running when heating was requested.
- Then discovered the wire to terminal 6 was not connected properly - but when it was then properly connected I basically shorted out the boiler completely. No idea why but it seems what I thought should be the input wire to the zone valve was sitting at Neutral. As far as I'm aware the plumbers did not touch the wiring at the zone valve end, this arrangement had worked when we had a normal controller.
- Disconnected the wire at terminal 6 on the Heatlink which brought the boiler back to life, but now there are no lights on the pump and the boiler won't fire up even for a central heating request.

I've got a feeling the zone valve and possibly the pump are now defunct, and I'm running out of ideas. The zone valve seems to have the orange and grey wires connected to each other and nothing else, which is completely different to the wiring instructions. However, I don't think the plumbers have altered what was originally working with the old controller. Any advice appreciated. I am hoping to get professionals in but my confidence that they know what they are doing has been knocked by the initial experience.

 

[muggles]

That's a lot of words but you've not actually said much about your own system. Is it an S-Plan, a Y-Plan, or something else? What boiler do you have? What's your hot water arrangement? Post photos if you aren't sure. It might well be easier to disconnect all the wiring in the wiring centre and start again but it's impossible to say what's happened or suggest a fix without being able to see it.

 

[Ffiona70]

I have a Glow-worm Flexicon 30Hx boiler with a hot water tank. (The tank also has an immersion heater connected to a Solar i-Boost). I believe it is S-plan? The 2-port zone valve and pump are in the cellar below the boiler in the kitchen so I just see two cables running between the boiler and the cellar. Photos from cellar attached.

 

[Johntheo5]

The Immersion & I boost have/should have nothing to do with the S system, the immersion has its own thermostat. Don't know how the Nest works but would think that the basic S plan would still apply.
Your boiler must also have a permanent live, the boiler may then control the pump for overrun etc.

 

[Ffiona70]

The Immersion & I boost have/should have nothing to do with the S system, the immersion has its own thermostat. Don't know how the Nest works but would think that the basic S plan would still apply.
Your boiler must also have a permanent live, the boiler may then control the pump for overrun etc.

Thanks, I was hoping the iBoost was unrelated, the only issue is in testing the hot water heating when it is already at temperature from the solar. I believe the permanent live to the boiler is in place.

 

[Johntheo5]

To test the cylinder coil zone vale just turn the cylinder stat setting knob fully clockwise or until you hear a click, when check/test complete, return the stat to its original setting, normally 60C.