Y-plan from scratch with Nest

[PeakyPaul]

Hello all and thank you for taking the time to look at my thread and indeed 1st post!

Now before I get shot down in flames I have looked at the many,many other threads on Y-plans and Nest 3rd gen and there is some great info but in all honesty I just ended up more confused than when I first started!

My central heating/hot water wiring is a right mess and the hot water is way to hot in our house and adjusting the hot water tank and or boiler temperature has no effect so I have got a new HWT stat. to fit. I am also wanting to fit a Nest thermostat 3rd gen with heat link whilst I am at it.

Normally I'd be happy with a bit of trial and error with getting everything wired up however as we are talking about the heating and hot water my wife will seriously injure me if I mess this up and leave us with out any HW or CH !!

Please can you knowledgeable people take a look at the below wiring diagram and tell me if I have got it correct? if not I have supplied a blank layout for the lines to be drawn so to speak.

Thank you in advance
Paul.

Current mess!

 

[ianmcd]

I bet you have an immersion heater backup in your HW cyl and it has been left switched on

 

[PeakyPaul]

I bet you have an immersion heater backup in your HW cyl and it has been left switched on

First thing I checked lol.

Its been like it since we had our boiler replaced so I think when they wired that in they somehow wired the tank thermostat out....or its broken one or the other.

 

[ianmcd]

hot water is way to hot in our house and adjusting the hot water tank and or boiler temperature has no effect

The HW temp in the cylinder can never be hotter than the temp selected on the boiler thermostat , unless it is being heated by another source i.e. Immersion heater

 

[flameport]

I have got it correct?

Cylinder thermostat 2 isn't connected to anything - the wire is shown as going to 16, which connects to nothing else.
Needs to be connected to valve grey, so 7 or 8.

Diagram also shows no pump overrun, which was common with old boilers but far less likely with a new one.

 

[PeakyPaul]

Cylinder thermostat 2 isn't connected to anything - the wire is shown as going to 16, which connects to nothing else.
Needs to be connected to valve grey, so 7 or 8.

Diagram also shows no pump overrun, which was common with old boilers but far less likely with a new one.

Ahh great spot, thanks for that!

I meant to put an extra line up from 8 to 16 as it passed by on its way to the nest but missed it.

Other than that does the wiring look right?

I did use your webpage below for inspiration,
Flameport Y-Plan

Thanks

 

[PeakyPaul]

The HW temp in the cylinder can never be hotter than the temp selected on the boiler thermostat , unless it is being heated by another source i.e. Immersion heater

Interesting, well the Immersion is for sure turned of at the wall unless that wall spur is wired wrong, The red light goes on and off when switch is operated.

I'll check it with the multi-meter when I do the rewire.

 

[ianmcd]

Interesting, well the Immersion is for sure turned of at the wall unless that wall spur is wired wrong, The red light goes on and off when switch is operated.

I'll check it with the multi-meter when I do the rewire.

many systems have 2 immersion heaters with individual switches one high and one lower in the cylinder, something is adding heat to the cylinder

 

[PeakyPaul]

many systems have 2 immersion heaters with individual switches one high and one lower in the cylinder, something is adding heat to the cylinder

However the water is cold if the boiler is off so don't think it can be immersion heater.

Anyway its more the wiring question I'm interested in an answer on, Thanks

 

[ericmark]

Default with Y Plan is DHW, once CH starts to stop DHW you need a supply from the tank thermostat to stop the DHW heating.

I suspect that wire is missing?