Wiring a boiler controller

[Chrisknowlesuk]

I need to wire a controller for an electric boiler.


Boiler is currently supplied via a 45amp breaker and a suitably large cable.

Controller needs a 240v supply. Instructions suggest this can come from boiler supply via a 3a fused spur.

Is it acceptable for this cable to be 2.5mm sized and a very short run of about 12inches to the spur. Or should it be equal size as the cable running to the boiler. Not sure if two cables that size would fit so the other option would be taking the power direct from the ccu and a 6amp breaker.

Technically it would not be protected if it were 2.5 coming from the boiler. I think I may have answered my own question but wanted to see what everyone else thinks

Thanks

 

[robd]

Can't you change the 45a breaker or is it an old one?

 

[Spoon]

There are lots of was to do it. I would not recommend a new circuit purely for this, in your case.
Where is the boiler relative to the CU?
Is there a ring main near the boiler. (That sentence is going to get some peoples backs up... Try doing scuba diving and call a 'fin' a 'flipper' and just watch all the angry faces.. )

 

[Midwest]

I'm going out on the edge here. As the FCU is limited to 13A, the 2.5mm cable ccc supplying the would not be exceeded. What do the manufacturers instructions suggest? Some gas boilers do have an output supply terminals, but I've never done an electrical boiler of this type.

 

[buzzlightyear]

I need to wire a controller for an electric boiler.

pic would be nice .to what boiler you have .

 

[Chrisknowlesuk]

It’s very close to ccu. But an old one with no RCD so I’d rather not get involved in that.

Here’s the boiler pic

 

[robd]

Can't you put it through an RCD spur? A 47mm single surface box should give you enough room

 

[Chrisknowlesuk]

Thanks for the advice so far.

I’m more concern with having a short length of 2.5 coming from the boiler terminals to a fused spur as effectively this is being protected by the 45amp trip which would be no protection at all.

The way it’s wired at the moment is with no control or stat and botched.

I’ll see if I can find manufacturers guidelines for it.

 

[Midwest]

Thanks for the advice so far.

I’m more concern with having a short length of 2.5 coming from the boiler terminals to a fused spur as effectively this is being protected by the 45amp trip which would be no protection at all.

The way it’s wired at the moment is with no control or stat and botched.

I’ll see if I can find manufacturers guidelines for it.

I did make a comment on that, #4, wait for another member to agree or disagree. What is the 'controller', and what does that 3core & earth cable do, connected into the boilers pcb terminals?

 

[Leesparkykent]

The usual way with an electric boiler that doesn't provide an output for external controls....like the potterton gold electric boiler you have is to have the control wiring fed through a 3A SFCU. The SFCU doesn't have to be from the Boiler power circuit. I wouldn't come from the boiler terminals with a bit of 2.5mm as I would suggest the connection with the larger CSA cable will not be one that's electrically sound. If the CCU is near by, like you say, then why not just run a new circuit for the controls?

 

[Midwest]

Looking at your pic, fear an additional set of wires into the main terminal isn't going to be successful.

 

[Midwest]

Looking at your pics, looks as if someone's already done what your suggest OP?

 

[buzzlightyear]

looks to me a 6kw heater .

 

[Chrisknowlesuk]

The current set up is a redundant controller which accounts for that 3 core flex and the two singles coming straight from the large terminals to the block where the controller would normally be. So it’s wired as permanently on via an external switch.

Just thought of a possible solution. If I took the 6mm cables from ccu to a switched spur. Take another set of 6mm from the supply side of the spur to the boiler. Then 2.5mm from the load side of the spur to control circuits.

Provided I can fit 2 x 6mm cables into supply side of spur this means all cables are suitably protected??

Does that sound correct.

 

[buzzlightyear]

Gold Electric 6kW Boiler - Potterton Gold Electric boilers | TDL Online - https://www.tdlonline.co.uk/Heating/Boilers/Gold-Electric-Boiler-Range/6219-/Gold-Electric-6kW-Boiler

 

[buzzlightyear]

The current set up is a redundant controller which accounts for that 3 core flex and the two singles coming straight from the large terminals to the block where the controller would normally be. So it’s wired as permanently on via an external switch.

Just thought of a possible solution. If I took the 6mm cables from ccu to a switched spur. Take another set of 6mm from the supply side of the spur to the boiler. Then 2.5mm from the load side of the spur to control circuits.

Provided I can fit 2 x 6mm cables into supply side of spur this means all cables are suitably protected??

what is the k/watt?

 

[Leesparkykent]

The current set up is a redundant controller which accounts for that 3 core flex and the two singles coming straight from the large terminals to the block where the controller would normally be. So it’s wired as permanently on via an external switch.

Just thought of a possible solution. If I took the 6mm cables from ccu to a switched spur. Take another set of 6mm from the supply side of the spur to the boiler. Then 2.5mm from the load side of the spur to control circuits.

Provided I can fit 2 x 6mm cables into supply side of spur this means all cables are suitably protected??

Does that sound correct.

Erm no. I think you maybe a little out of your depth...prob best to get an electrician in.

 

[buzzlightyear]

POTTERTON GOLD INSTALLATION AND SERVICING INSTRUCTIONS Pdf Download. - https://www.manualslib.com/manual/812769/Potterton-Gold.html go on knock, self out !

 

[telectrix]

and did my eyes deceive me or is that a 3c/E with the cpc cut off? into the green terminal strip (that has more copper exposed than a capsized boat)

 

[SparkySy]

That is rougher than a hedgehogs back! Last one I did I bought the supply cable into a 2way con unit at the heater end with a 63a main switch for the heater and 6a mcb for the control side then they are both isolated by the mcb protecting the circuit at the main consumer unit.

 

[Chrisknowlesuk]

I agree coming out of the boiler supply terminals would be dodgey, not a secure fit and a 2.5mm cable essentially only protected by a 45amp breaker.

I'd rather not add a new circuit to the CCU as it is an old MK board and I think I would struggle to find an appropriate breaker?

I've just seen a 45amp dual appliance junction box from TLC. It seems to be designed to accept a 6mm 45amp supply cable and split to two 6mm output cables. One could go to the boiler and one to a 3a SFCU for the control power. That should keep all cables protected and through sufficiently rated connections.

 

[123]

Not quite on topic but I have used the Click Dual Cooker Connection Units and they are great. I am shocked at how much copper is on show from a product image, over sized earth sleeving on the supply, and it doesn't look like any CPC's are doubled over. Everything looks a little strained as well.

 

[Toneyz]

That is rougher than a hedgehogs back! Last one I did I bought the supply cable into a 2way con unit at the heater end with a 63a main switch for the heater and 6a mcb for the control side then they are both isolated by the mcb protecting the circuit at the main consumer unit.

You beat me to it I was going to suggest that idea and if it is next to the boiler you isolate all supplies into it (one isolator) you may still need to fuse down to say 3A from 6A mcb for the controller/programmer.

 

[Chrisknowlesuk]

Update on this job...

Couldn’t find any power to safely tap into. CCU has a last inspection date sticker showing 1998!!!

Looks like an HMO property too judging by the random people appearing. Should have realised all of this on first visit I suppose.

Left job and put in recommendation that they upgrade CCU, add emergency lighting, smoke detectors, CO2, Fire blanket etc etc

Given the job to return and do...

 

[Toneyz]

So what did you decide to do with the boiler controls then?

 

[davesparks]

You beat me to it I was going to suggest that idea and if it is next to the boiler you isolate all supplies into it (one isolator) you may still need to fuse down to say 3A from 6A mcb for the controller/programmer.

Or just fit a 3A mcb if that’s what you need.

 

[Toneyz]

Or just fit a 3A mcb if that’s what you need.

That would be the perfect solution, Dave but not all manufacturers do them and not often stocked by wholesalers.

 

[Chrisknowlesuk]

So what did you decide to do with the boiler controls then?

The original controls were defunct and someone had wired it as simply On/Off via a switch. I left it as I found it and contacted the person managing the property.

Think I may have the job of going back and doing the complete job to bring it all up to spec...

 

[davesparks]

That would be the perfect solution, Dave but not all manufacturers do them and not often stocked by wholesalers.

But in the modern world of next day delivery it’s easy enough to order, unless it’s an emergency job

 

[SparkySy]

What I can't understand with these water heaters is why they don't build in an output for the control circuit, they have a protected output for the pump built in so why not for the control it would save a lot of messing around!

 

[davesparks]

What I can't understand with these water heaters is why they don't build in an output for the control circuit, they have a protected output for the pump built in so why not for the control it would save a lot of messing around!

It’s cheaper for the manufacturer to not put it in.
the higher end units will have it included but in the lower end products these are the kind of corners that get cut to make them cheaper.

 

[Eliza Bennett]

Check your entire system for obviously loose connections, or failed circuits, and examine any fuses which may have popped out on your main board (if you have an older boiler, you may not have a main control board, and will need to check the fuses of all your devices). If you still cannot find a problem, you may need to call in an engineer.