Worcester 24, 28CDI Nest Thermostat

[Badger1966]

Any existing room thermostat should be set to maximum and the Nest will take over. If you wanted to disconnect that we can guide you through that too

Hi and thanks. If I set the nest to a lower temp than ambient, turn the existing stat up, the heating still comes on.

 

[Badger1966]

Can you press the 'On' button on the "Room Stat' panel, and see if that provides an override? - I'm guessing the LED above the button should illuminate.

Think its in the on position, if I set the nest to a lower temp than ambient, turn the existing stat up, the heating still comes on.

 

[Badger1966]

Well that has worked to a certain extent, fuse isn't blowing. But, heating is not coming on. Should I be setting the installed room stat on the boiler to something specific? Or disconect it? It's in the "on" mode at the moment

And I connected 2 from nest "common" to ST8 LS and 3 from nest "call for heat" to St8 LR

 

[Badger1966]

Any existing room thermostat should be set to maximum and the Nest will take over. If you wanted to disconnect that we can guide you through that too

If I set the nest to a lower temp than ambient, and set the old stat higher, the heating comes on. Oh, I didn't see it post so I replied again

 

[CBW]

Something isn’t right then obviously, something is signalling the boiler to come on. Left any links or added any?

 

[Badger1966]

Something isn’t right then obviously, something is signalling the boiler to come on. Left any links or added any?

I took the link out at ST8, Ls and Lr when I put the Nest wires in. Otherwise everything is as it was.

 

[RandomGrinch]

Something isn’t right then obviously, something is signalling the boiler to come on. Left any links or added any?

Because the controller has a built-in wireless receiver, it is difficult to know how to bypass it.

I haven't been able to find any technical information on the receiver itself, other than it being a:
WORCESTER 87161561170 PROGRAMMABLE RECEIVER

There appear to be only three wires on the back, so it's possible that it is simply +V, gnd and switch, but I wouldn't like to bet on that without testing.

@Badger1966 , can you remove the module, and pull out the plug and see if the Nest then has control?

 

[Badger1966]

Because the controller has a built-in wireless receiver, it is difficult to know how to bypass it.

I haven't been able to find any technical information on the receiver itself, other than it being a:
WORCESTER 87161561170 PROGRAMMABLE RECEIVER

View attachment 325539

There appear to be only three wires on the back, so it's possible that it is simply +V, gnd and switch, but I wouldn't like to bet on that without testing.

@Badger1966 , can you remove the module, and pull out the plug and see if the Nest then has control?

So, with the old stat and nest under ambient temp, as soon as I disconnect the module, the heating fires up. I tried with the old stat set above ambient temp and nest below, pulled module and it fired up the heating.

As for testing, black and red 23.7v (black is negative) nothing on green. Heating on, black and green 4.5v

 

[RandomGrinch]

So, with the old stat and nest under ambient temp, as soon as I disconnect the module, the heating fires up. I tried with the old stat set above ambient temp and nest below, pulled module and it fired up the heating.

So it fires up the heating when the module is disconnected? - good!
Can you leave the module disconnected, then disconnect the Lr and Ls connections at the boiler and see what happens?

I'm sorry this isn't straightforward - I can't see any information in the boiler manuals about how these modules connect.

 

[Badger1966]

So it fires up the heating when the module is disconnected? - good!
Can you leave the module disconnected, then disconnect the Lr and Ls connections at the boiler and see what happens?

I'm sorry this isn't straightforward - I can't see any information in the boiler manuals about how these modules connect.

Thanks, will give it a go when I get home this evening

So it fires up the heating when the module is disconnected? - good!
Can you leave the module disconnected, then disconnect the Lr and Ls connections at the boiler and see what happens?

I'm sorry this isn't straightforward - I can't see any information in the boiler manuals about how these modules connect.

Hi, so module unplugged, Lr & Ls disconnected, nothing happens. Plug module in with Lr,Ls disconnected, nothing happens even with old stat above ambient temp. Tried Nest wires other way round in Ls,Rs and same as before. Old stat above ambient, nest below, heat comes on. Tried old stat below ambient and turn up nest, nothing. I also presume nest is OK as I can here the base at boiler click when you go above and back below ambient.

 

[CBW]

Can you post a photo of the wiring and existing thermostat?

 

[RandomGrinch]

Hi, so module unplugged, Lr & Ls disconnected, nothing happens

Nothing happens, as in boiler doesn't come on? - great!
With module unplugged, and a link wire between Lr and Ls, does boiler come on?

 

[Badger1966]

Nothing happens, as in boiler doesn't come on? - great!
With module unplugged, and a link wire between Lr and Ls, does boiler come on?

Well we have truly entered the twilight zone. Got home from work yesterday evening and my wife says the heating isn't coming on. Of course, like the previous evening the old stat is working. so I try turning it up and down, nothing. left it on a higher setting. Turned the nest up, still nothing. Look at the boiler and power is on, everything as usual. So with both stats higher than ambient, I press the red reset button on the boiler, nothing, pressed it for longer and boom, the heating fires up, phew! Go down stairs, turn the nest down below ambient and I hear something up stairs, go and have a look and the boiler is off! I leave the door open and go back down to the Nest stat, turn it up and the boiler fires up! I'm like what the hell is going on. Nothing has changed, wires, everything as it was. But here we are, somehow the nest is now in control and has been working since. Crazy.