LP522 - Nest

[Craig Inskip]

Hi All,

I know there are plenty of threads about this but I still can’t seem to hit this one on the head. I had an LP522 in place in my new house and am trying to hook up a new Nest to it
I have a swapped out the cables as per all instructions

LP522 L - Heatlink L
LP522 N - Heatlink N
LP522 1 - Heatlink 4 (hot water off)
LP522 2 no cable
LP522 3 - Heatlink 6 (hot water on)
LP522 4 - Heatlink 3 (Heating on)

The thermostat downstairs I have disconnected, added the nest (no neutral) and connected the T1 and T2 to the wiring nest on 3 and 4 (3 contains the link to the thermostat and what looks like a link back to the heatlink - possibly CH On - 4 contains both the links to the thermostat link and to the 3 way motorised valve)


I’ve also tried the stat not wired in and just wireless with the old one wired up and set to full.

what I can’t get to work is the hot water. No matter what I try the relay doesn’t seem to click over. It has in the past.
move even had a replacement from nest as previously I had it working but if you called for hot water whilst heat was on it caused the heatlink to flip out and keep disconnected and ticking the relay.

has anyone got any ideas as I am pulling my hair out with this one

cheers

 

[Craig Inskip]

Forgot to mention that 2 and 5 on the heatlink are looped into L on the heatlink too

 

[ianmcd]

edited

 

[ianmcd]

The thermostat downstairs I have disconnected, added the nest (no neutral) and connected the T1 and T2 to the wiring nest on 3 and 4 (3 contains the link to the thermostat and what looks like a link back to the heatlink - possibly CH On - 4 contains both the links to the thermostat link and to the 3 way motorised valve)

your post is so confusing , T1 and T2 are 12V connections to the nest thermostat to save you using a USB cable to power it, they dont control anything on the heat link they are simply a power supply ?

 

[Craig Inskip]

Sorry for the confusion.. I think I’ve got myself confused in the process!!

So am I right in thinking that T1 and T2 can just run to the thermostat just powering it from the heatlink?

If I take it out of the wiring nest there will be a white wire from the 3 port motorised valve that isn’t connected to anything.

At the moment that white wire is in the connector bloc with the ‘control’ wire to the thermostat downstairs



If we ignore that part (ive disconnected it at the moment the thermostat isn’t wired in just connected via usb and plug) it’s still the same results as above.

Thank you

 

[ianmcd]

So am I right in thinking that T1 and T2 can just run to the thermostat just powering it from the heatlink?

yes that is what those terminals are for

If I take it out of the wiring nest there will be a white wire from the 3 port motorised valve that isn’t connected to anything.

That is the CH on wire and must be connected to 3 on the heatlink

 

[Craig Inskip]

yes that is what those terminals are for


That is the CH on wire and must be connected to 3 on the heatlink

The other end is into the heatlink (the image of the old Drayton programmer)

the 2nd image of the wiring nest shows port 3 which I THINK is the CH on (which is connected to the heatlink which is what I’m confused about) and the link to the current stat.


if we strip it back and take the wired stat out of the equation my wiring looks low the below

LP522 L - Heatlink L
LP522 N - Heatlink N
LP522 1 - Heatlink 4 (hot water off)
LP522 2 no cable
LP522 3 - Heatlink 6 (hot water on)
LP522 4 - Heatlink 3 (Heating on)

Plus the 2 & 5 live loops

but still no hot water relay ticking over

Have I got that wiring right from the Drayton?

 

[ianmcd]

Post pics of what you have done as you are not making any sense whatsoever

 

[stem]

LP522 L - Heatlink L
LP522 N - Heatlink N
LP522 1 - Heatlink 4 (hot water off)
LP522 2 no cable
LP522 3 - Heatlink 6 (hot water on)
LP522 4 - Heatlink 3 (Heating on)

Plus the 2 & 5 live loops

That sounds right to me.

The thermostat downstairs I have disconnected,

If you mean this:

It can't just be disconnected, the grey neutral should be isolated, but the two live wires [brown and black/brown sleeve] should be connected together to complete the circuit, it can be done at this end of the cable, or at their origin in which case the cable can be completely disconnected. Having said that, this wouldn't effect the operation of the hot water, only the central heating.

and connected the T1 and T2 to the wiring nest on 3 and 4

This worries me more. If I understand correctly what you are saying here, you have connected the T1 & T2 12v terminals to terminals connected to 230V. If so, the Heat link could well be toast

T1 & T2 as per @ianmcd is provided to power the thermostat.

 

[Craig Inskip]

This worries me more. If I understand correctly what you are saying here, you have connected the T1 & T2 12v terminals to terminals connected to 230V. If so, the Heat link could well be toast
View attachment 212320

T1 & T2 as per @ianmcd is provided to power the thermostat.

View attachment 212321

Thats correct. It went into 3+4 in the wiring nest.
I was afraid that you were going to say that. Soon as I did it I thought that.
Surely if it was fried though it would just be dead and not display the odd behaviour of no water hot water?

Thanks again

 

[Craig Inskip]

The other thing that im not too sure on is this.. In the diagram

wiring nest2.jpg

If I remove the Thermostat Live and Thermostat Control (3 and 4 which go downstairs to the stat) and connect them into the T1 and T2 of the heatlink, that leaves the CH on and 3 port valve wire (white) not connected to anything?

 

[stem]

From your photo, you have identified the two thermostat live wires as going to wiring centre terminals 3 and 4. So these two thermostat wires are removed from terminals 3 & 4 and a link inserted to join terminal 3 and 4 together to complete the circuit. [or instead simply put the remaining two wires 'CH On' and the Motorised valve white wire into the same terminal either 3 or 4] You are bridging the thermostat at the origin of the cable.

Which is what I was said earler...

the two live wires [brown and black/brown sleeve] should be connected together to complete the circuit, it can be done at this end of the cable, or at their origin

The end result will be that the wire from Heat link terminal 3 (Heating call for heat) will be connected to the white wire of the motorised valve.

The neutral wire contained in the same cable can just be disconnected. You will now have a cable that is completely disconnected from any of the mains wiring and can be used to connect T1 at the Heat link to T1 of the thermostat, and T2 at the Heat link to T2 of the thermostat.

 

[Craig Inskip]

Excellent that’s what I thought cheers Stem.

Does it sound like I have bricked the heatlink with the water issue in your opinion?

 

[stem]

Sorry I can't comment really on the Heat link, I would have though it more likely that it would have damaged the 12v power supply, but I don't know how it works internally. And it would depend upon whether the mains terminals you linked to the 12v were actually made live or not at any point.

I suppose that there is actually a requirement for hot water? By that I mean that the hot water cylinder isn't already full of hot water and so doesn't need any extra heating.

 

[Craig Inskip]

I’ve just solved it. Stupid problem!!!

The live loop for the hot water wasn’t actually seated correctly so no power was going to the relay! (What a wang!)

tested all working correctly! That’s everyone for all your help. I’ve still got a small amount of hair left so that’s a win in my eyes!! Thanks again!