Nest wiring

[fergusfog]

Folks,
I'm close to working out how to replace my Danfoss CP15 with the Nest Heat Link, but the terminology I'm just not familiar with (layman).

Hopefully 2 images show up in this post.

Wiring

• fergusfog
• 27 Feb 2015
• 1

Boiler

• fergusfog
• 27 Feb 2015
• 1

http://support-assets.nest.com/images/tpzimages/comp-system-wiring-diagram.png
http://support-assets.nest.com/images/tpzimages/comp-system-wiring-diagram.png

The wiring diagram probably doesn't really matter, all I need to do is rewire the 4 wires in the Danfoss into the Heat Link instead.

- N and L are easy enough.
- 4 on the CP15 refers to "HTG On" (heating on, I guess), so this wire should go to "Call for Heat" on the Nest?
- 3 on the CP15 is "DHW On", but this seems to refer to domestic hot water, whereas the boiler is for central heating only (Greenstar 15Ri). Where should I put this wire in the Nest, if anywhere?
- Do I need to use either Common or Satisfied on the Nest? I think maybe Common should be wired into mains live.

As you can tell, I'm a bit confused, having little idea about boilers or wiring, so any help will be gratefully received!

F.
P.S. I expected the wires into the thermostat to come straight from the boiler, but they come from the wall! Is my wiring just screwed up?

 

[Dean744PiN5]

your not even looking in the right area by the sound of it.
The nest can't do your hot water so your programmer has to stay to give you programmed hot water, you need to get into your wiring center which will most likely be next to your hot water cylinder.

As it stands your no way near close to understanding the wiring.

Get it wrong and you can blow up the nest.

Take a phot of the area around the hot water cylinder and should be able to advise better then.

 

[Phill Peck]

Calm down go on the nest approved installer site and find someone to do it for u. It's not worth the hassle for what it costs

Most will have a fixed price install mine is £85+vat but I'm not in your area.

As dean points out get in wrong and it's cost more than that.

 

[Rob]

Look me up if you're in the SW london area

 

[fergusfog]

Thanks for the replies.

I'm in SE9 and the only reply I got through Nest was £170. For that I might as well take a shot.

The boiler doesn't do hot water - for some reason there's a big immersion tank upstairs for that. This does the rads only.

Rob, do you go to SE?

Dean, I appreciate the response, but your post doesn't tell me why I'm nowhere near or looking in the wrong area.

 

[Rob]

The tank upstairs is heated by the boiler aswell.

With your setup wiring the heatlink from a switching point of view is fairly straightforward but getting the existing thermostat cable to go directly into it also to provide the 12vdc is where it gets a bit complicated.

are you replacing an existing hard wired thermostat? If so you need to identify that cable.

Lewisham is little out my area for this time of year!

 

[Dean744PiN5]

Thanks for the replies.


Dean, I appreciate the response, but your post doesn't tell me why I'm nowhere near or looking in the wrong area.

thats why i asked for a photo of the cylinder area, haven't got a crystal ball i'm afraid,
your boiler does the hot water as well otherwise hw on wouldn't be wired into the programmer.

 

[Dean744PiN5]

 

[fergusfog]

Guys, I know I'm not an expert and presumably you are, but believe me when I say the upstairs hot water tank is NOT served by the boiler.
Presumably the wiring is still there from when it was, but that up there is an electric heater. No fewer than 3 plumbers/sparks have looked at that and said "WTF?".

In fact, here is the Megaflo in all its glory, with 2 x 3KW heating elements

Untitled

• fergusfog
• 27 Feb 2015
• 1

So the question is, with the hot water out of the way, is this simple enough or is there still some work to do that a spark will have to be involved?

Cheers,
F.

 

[Dean744PiN5]

is that a cylinder stat lying on the floor what a hash up, i would go for the nest certified install if i were you foggy.

you need to work out what the redundant hot water wiring is doing first and eliminate it from the system.

is there a zone valve like in my diagram?

looks like someone ordered the wrong type of tank and fitted it anyway.

 

[Dean744PiN5]

where does that pipe in bottom right hand corner with the red handle valve go to?

 

[fergusfog]

Well spotted.
The red valve is where it stops, so I guess that was where the feed from the boiler went into the old (boiler-fed) tank. The same pipe goes into the pump for the central heating.
They just cut that pipe and installed this daft electric jobby.

The last guy in the house kinda did a lot of cruddy work tbh. Well, you can see that!

If the zone valve is the blue thing, no I guess there isn't. Unless that red tap is the zone valve.

Am I right in thinking the DHW On wire in the controller is doing nothing? Would appear to be the case.

 

[Dean744PiN5]

it would appear so, zone valves also look like this

is there a wiring center in the airing cupboard?

 

[Dean744PiN5]

i would get that plastic on the safety discharge sorted too if i were you ot not rated for the high temperatures that could potentially run through it.

 

[Dean744PiN5]

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