Alpha InTek 40GS with multizone Nest

[MattSmith]

Hi Guys
Sparky here but I'm really scratching my head on this one. Alpha boiler which currently has both a wired Alpha stat (connected to BUS on the boiler) and a second RF Alpha thermostat connected to a relay board. The boiler also has a Honeywell 3 port valve actuator also connected to the relay board and x2 Honeywell 2 port valves controlled by the switched live from the relay board (permanent lives on the valves have been left disconnected).

My thinking was that terminal 2 from the boiler should go to both nest thermostats in terminal 2. Then terminal 3 from the Nest should switch the Honeywell 2 port for that zone and return to terminal 1 in the boiler. Unfortunately this didn't work and I suspect the original boiler wiring has been modified (I noticed terminal 1 in the boiler has no wires connected to it).

If anyone could help i'd really appreciate it. Thanks

 

[muggles]

What control do you have now? Can you post a photo of your motorised valve arrangement? Do you have a hot water cylinder or is it just heating zones?

 

[picasso]

If the relay board is just opening the 2 ports but not firing the boiler unless the low voltage controls are calling you wont be able to fit the nests unless yo contert all to 240v controls, ie get rid of the other two low voltage controls, It looks like you have a mishmash of low and high voltage controls (not really allowed according to alpha) do you know whats controlling the 2 x 2 ports at the moment?

 

[MattSmith]

Hi guys. Thanks for the replies. Yes there is a hot water cylinder with a temperature probe connected to the boiler. The 3 port is a Honeywell VC6013 and the x2 2 ports are Honeywell V4043H1056

I tested the voltage from the wireless stat and got 24v so I think its all low voltage at the moment. It connects to the relay board. The x2 ports are also currently controlled by the relay board. (Sends power to the brown wire in the 2 ports)

I've was looking at the flow diagram which shows x3 4 to x3 3 inside the boiler. However x3 3 has no cable to it inside the boiler

Should I try connecting this to terminal 1 in the boiler? (currently empty)

Much appreciated guys

 

[picasso]

No don't connect anything to 1, its simple you cannot connect the nest stats unless you get rid of the ow voltage controls, at the moment when a call for heat is made the 3 port and both the two ports open, there is no control over them all operating together, if you want to install the nest/s you have to convert the controls to a standard s plan, the 3 port is controlled by the boiler so is not part of the s plan.

 

[picasso]

Sorry not quite right , I assume the relay board is opening the 2 port valves on demand from the two stats, same outcome you cant fit the nest .

 

[MattSmith]

Thanks for your help picasso. You've confirmed my suspicion. If I change to a s plan 3 port valve then it wouldn't prioritise the hot water over the central heating as the current 3 port does. Sounds like a choice between a smart valve or a smart thermostat.

Very interesting. Think it might have to stay how it is. Thanks again

 

[picasso]

The 3 port stays and is controlled by the boiler software, you then have a choice of either alphas own low. voltage controls or s or y plan where you can use nest hive or whatever stat you want.

 

[MattSmith]

If the 3 port isn’t the problem then I’m confused. The idea was to remove the low voltage thermostats, replace with the nest and control the x2 2 ports valves with separate nest thermostats. If I could connect these up like an s/y plan would the 3 port controlled by the boiler still function correctly?

 

[picasso]

Remove the low voltage stats, leave the 3 port wiring as is, rewire the 2 port valves as a standard s plan with the nest stats controlling the valves and put the orange switched lives in 2 (where the red link was on the wiring diagram)

 

[MattSmith]

That’s exactly what I have tried but the central heating wouldn’t come on

 

[picasso]

Link live and 2 in the heat links, oranges from 2 port to 2 in the boiler.

 

[MattSmith]

When I tested terminal 2 on the boiler it had 240v on it even with the thermostats off. This shouldn’t be should it?

 

[picasso]

yes sorry looking at wrong diagram, connect to 1 as you said.

 

[MattSmith]

Thanks for all your help picasso. That brings me back to my earlier problem that terminal 1 has no wires connected to it, so connecting to it won't do anything? Do I need to connect terminal 1 to somewhere inside the boiler to make it work?