Cable missing in central heating wiring

[naylorpd]

I had a problem a couple of days ago with my boiler shutting down due to too high temperature difference between the input and output, which transpired to be because the boiler had been wrongly wired.

I have two zones in my heating system, so as I understand it there should be 5 wires between the controller and the boiler - L, N & E plus two switched live. But there was only a 4-core cable so the boiler had been wired in a slightly different way to accommodate this. Interesting to speculate whether the cable would have been fitted by the plumbing or electrical contractor in a new-build house! Anyway, it is what it is - but practically impossible to rectify as the two ends are on different floors and not directly one above the other.

The gas engineer who came to check it out rewired in a different way but acknowledged that it's still not optimal. He speculated that I may be able to do something with a wireless connection between the boiler and controller. Any ideas about how to do that, and what I would need to buy?

Thanks

 

[mainline]

I'm beginning to think you are selling these Avo

I reckon it's his desktop wallpaper pic.

 

[brianmoooore]

As Lucien and davesparks say, it's not really important how long the pump runs after the boiler shuts down as long as it runs for long enough to remove the heat soak. A simple delay off timer would be an effective solution.

 

[naylorpd]

The Mainslink is exactly the solution that was described to me and I thought I was looking for.

But relocating the pump also seems to be a simple and elegant solution.

Thanks guys

 

[Avo Mk8]

I'm beginning to think you are selling these Avo

If only!

 

[Avo Mk8]

I reckon it's his desktop wallpaper pic.

Good idea But not better than an old Avo!

 

[baldelectrician]

You could do away with the timer and install a hive reciever in the area where the zone valves are.
A 2 channel hive (or similar) would work and leave you an extra core if needed as the hive only needs a 230V supply
You would still be able to connect things to this such as remote thermostats etc.

 

[davesparks]

You could do away with the timer and install a hive reciever in the area where the zone valves are.
A 2 channel hive (or similar) would work and leave you an extra core if needed as the hive only needs a 230V supply
You would still be able to connect things to this such as remote thermostats etc.

How would that solve the problem?

 

[baldelectrician]

How would that solve the problem?

Unless I am reading it wrong there is one core short at the junction box (where the zone valves / cylinder are)

The Hive (or similar) only needs a L,N,E so the reciever can be located adjacent to the joint box. As the reciever will give you seperate switched lives for HW (on), CH (on) and even HW (off) if you need it in the cylinder cupboard you will have a supply and switch wires needed at that location.

Am I missing something?

 

[davesparks]

Unless I am reading it wrong there is one core short at the junction box (where the zone valves / cylinder are)

The Hive (or similar) only needs a L,N,E so the reciever can be located adjacent to the joint box. As the reciever will give you seperate switched lives for HW (on), CH (on) and even HW (off) if you need it in the cylinder cupboard you will have a supply and switch wires needed at that location.

Am I missing something?

Yes there are 4 cores between the joint box and the boiler when it requires 5, so the pump cannot currently be connected to the pump terminal of the boiler.

The controls, whether they are wired or wireless have no bearing on this part of the circuit.

 

[baldelectrician]

Yes there are 4 cores between the joint box and the boiler when it requires 5, so the pump cannot currently be connected to the pump terminal of the boiler.

The controls, whether they are wired or wireless have no bearing on this part of the circuit.

I would have the 4 cores as
L,N,E - supply to JB (install hive reciever at joint box)
4th core pump over run

The hive adjacent to the zone valves stops the need for the s/l for the CH and HW as it can now be derived from the new hive reciever (in the cylinder cupboard)

 

[Lucien Nunes]

But if the receiver is in the cupboard, the problem is getting its output to the boiler.

 

[baldelectrician]

But if the receiver is in the cupboard, the problem is getting its output to the boiler.

I was assuming the 5 cores went from the boiler (FCU) to the cyliner cupboard.
By moving the reciever for the programmer you now have s/l for CH and HW adjacent to the pump and motorised valves, the 4 cores you have will do L/N/E/SL - boiler.
The existing programmer would now be redundant

 

[Lucien Nunes]

Operating the valves from the programmer is not the problem. It is getting SL from the valves in the cupboard to the (remote) boiler, and the boiler's pump output back to the pump in the cupboard. For these two functions there is only one core. Previously, the core was used as SL to the boiler and the pump was operated directly in parallel, but the lack of overrun caused boiler overtemp. Hence the present offering of solutions: Move the pump adjacent to the boiler, leave the pump in the cupboard and control it with a wireless link from the boiler, or ignore the boiler pump output and provide a timer in the cupboard to create the overrun.

 

[davesparks]

I would have the 4 cores as
L,N,E - supply to JB (install hive reciever at joint box)
4th core pump over run

That gives you no switched live to the boiler, so it will never work!

 

[brianmoooore]

What are the four wires going to the boiler at the moment? Earth, neutral ,switched live to boiler, and perm. live?