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

 

[buzzlightyear]

What system is it, S, Y or other.

 

[buzzlightyear]

Two zone values would rewire 5 core.

 

[naylorpd]

What system is it, S, Y or other.

Sorry, I don't understand S, Y ?

 

[naylorpd]

Two zone values would rewire 5 core.

With a permanent live at both ends but nothing in between for the 5th core, I'm hoping there's a way to use a wireless device to provide the connection. It's a bit of a lash-up but may be possible these days.

 

[davesparks]

What is missing here? Is it the pump connection?

 

[davesparks]

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.

The number of zones is irrelevant, boilers will require either 4 core or 5 core depending on where the pump is located.

For a system boiler, or if the pump is located adjacent to the boiler, 4 core to the rest of the controls is sufficient.
If the pump is located with the valves etc then a 5 core is required to allow the boiler to control the pump.

 

[naylorpd]

The pump is near the valves - so 5 cores needed

 

[davesparks]

The pump is near the valves - so 5 cores needed

Can the pump be moved?

 

[Lucien Nunes]

So as I understand it, you have L, N, E and only one other core going to the boiler, but you need two because you have two control functions: demand signal from valves to boiler and the pump control from boiler to pump. The latter has been missing until now, and the lack of pump overrun has caused the flow temperature to go over limit. Your suggestion is to transmit one of those functions with a wireless link, and @davesparks suggestion is to relocate the pump adjacent to the boiler so that the pump can be wired directly to it.

If it were mine, I would make some kind of simple multiplexer device to enable both the demand and the pump control to be transmitted in opposite directions over the one available cable core. It would be an hour's work with a couple of relays, diodes and transistors, but I wonder whether such a thing exists commercially in an easy-to-integrate form, that would avoid having to rely on wireless?

 

[davesparks]

If it were mine, I would make some kind of simple multiplexer device to enable both the demand and the pump control to be transmitted in opposite directions over the one available cable core. It would be an hour's work with a couple of relays, diodes and transistors, but I wonder whether such a thing exists commercially in an easy-to-integrate form, that would avoid having to rely on wireless?

If it were mine I'd probably use a delay-off timer to keep the pump going for the required time.

As far as I know the pump overrun on boilers is a simple time based thing and not actually based on temperature.

 

[Avo Mk8]

Assuming you have a permanent mains supply at the end remote from the boiler, you could use this:

MAINSLINK 5KM WIRELESS MAINS TO MAINS 230VAC LINK

MAINSLINK is a plug and play solution to replace a switched live cable. When 230Vac “LIVE” is input to the transmitter; the receiver provides a 230Vac “LIVE” switched output at its screw terminals. When a cable run is awkward or expensive to achieve, the MAINSLINK can be used, saving time and...

www.rfsolutions.co.uk

 

[Lucien Nunes]

If it were mine I'd probably use a delay-off timer to keep the pump going for the required time. As far as I know the pump overrun on boilers is a simple time based thing and not actually based on temperature.

That sounds like a simple and practical solution. In the past there have definitely been boilers with thermostatic control of pump overrun, via separate contacts on the stat. I've never had cause to investigate how it works on modern boilers, but perhaps it doesn't really matter, so long as the pump doesn't just stop the moment the burner goes out.

The Mainslink remote control solution looks like a neat, practical device too. If it can do 1km indoors (?!) it ought to be pretty reliable from one floor to the next unless your building is a mass of rebar.

 

[MJPD29]

Assuming you have a permanent mains supply at the end remote from the boiler, you could use this:

MAINSLINK 5KM WIRELESS MAINS TO MAINS 230VAC LINK

MAINSLINK is a plug and play solution to replace a switched live cable. When 230Vac “LIVE” is input to the transmitter; the receiver provides a 230Vac “LIVE” switched output at its screw terminals. When a cable run is awkward or expensive to achieve, the MAINSLINK can be used, saving time and...

www.rfsolutions.co.uk

Are you selling these or something?

 

[DPG]

Assuming you have a permanent mains supply at the end remote from the boiler, you could use this:

MAINSLINK 5KM WIRELESS MAINS TO MAINS 230VAC LINK

MAINSLINK is a plug and play solution to replace a switched live cable. When 230Vac “LIVE” is input to the transmitter; the receiver provides a 230Vac “LIVE” switched output at its screw terminals. When a cable run is awkward or expensive to achieve, the MAINSLINK can be used, saving time and...

www.rfsolutions.co.uk

I'm beginning to think you are selling these Avo

 

[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!