Another Hot tub install

[Gazthesparky]

I have my tin hat on because I know this has been done to death and have read through a lot of the old posts.

I just wanted to run my proposal past a few of you and see if there is anything I have missed as its always good to get someone else's view.

Customer is needing a 32amp supply and hot tub company has said they require a 6mm supply with an isolator and flex left for them to connect.

My plan is to run a 10mm 3 core swa to a 40amp isolator from a new 2 way consumer unit Henley blocked from the tails. There is a Isolator on the current tails so will keep this and it will mean that there is one form of complete isolation. I have done the calculations and a 6mm will suffice with a volt drop of 11.2v so its on the borderline so hence going a larger size cable. It also allows for future proofing.

Now this is where it gets a bit messy. The supply to the property is PME. I intend to use the PME for the hot tub supply supplying it from a 32amp RCBO in the house. I am also intending to install an earth rod am I right in thinking that this gets installed at the hot tub end of the SWA? the idea is that should there be a PEN failure there is an earth path and the potential between the floating PEN earth and true earth is reduced as far as possible.

am I right in thinking that the rod does go at the hot tub end and not by the intake position of the property?

I am going to mount the isolator onto some uni strut installed into the ground. There is a fence panel 1 meter from the hot tub so too close to the tub. Also the fence doesn't seem too safe so I want to install my own support.

Finally they have also asked for a double socket by the tub again, I'm going to keep this 2 meters away from the tub. I am thinking of running a separate cable back to the house so this can be isolated as the customer is wanting to plug fairy lights in so the customer can switch them from the house. Im just wondering if i'm over complicating it though and should I just spur off the hot tub supply and install a fused spur and double socket

Thanks to any replys

 

[stevethesparks]

These are double pole switching: Electrical Wholesaler - Hager RCBO 2P(1P+N) 6kA B-40A 30mA A Class AD940J - https://www.electricalwholesaler.ie/products/switchgearfuses/switchgeardistribution/rcboresidualcurrentbreakers/hagerrcdrccb2p40a30maaclassad940j. All the double pole switching units that are definitely double pole are two module wide, all those that say they are and are only one module wide on investigation are not.

What about the Wylex NHX miniature rcbo's, it's a switched neutral.

 

[SJD]

Just checked, the Fusebox RCBO are not DP switching so would be unsuitable for a TT style of supply isolation for an open PEN risk.

The older Fusebox RCBOs are not DP, but the new compact ones are DP, for example RTAMB32.

 

[pc1966]

The older Fusebox RCBOs are not DP, but the new compact ones are DP, for example RTAMB32.

I found that later, once the OP linked to the newer model!

 

[Mike Johnson]

I am surprised that Wylex have been able to produce a switched neutral RCBO in a single module, what surprise's me mostly is that if and I emphasise the if they are able to achieve a 3mm air gap (unverified) on both the phase and neutral in that space I would like to see how they do it, because that is what is required under EU specifications.

 

[nicebutdim]

I am surprised that Wylex have been able to produce a switched neutral RCBO in a single module, what surprise's me mostly is that if and I emphasise the if they are able to achieve a 3mm air gap (unverified) on both the phase and neutral in that space I would like to see how they do it, because that is what is required under EU specifications.

Can't find a single module DP RCBO tear down, but here's one of the Crabtree/Wylex single module RCBO/AFDD which crams even more into the same space.

View: https://www.youtube.com/watch?v=gdVntVfP6Q8

 

[Mike Johnson]

Thanks for digging that out, to me it only shows the phase being coil controlled by the large coil on the back of the unit, the smaller wire coil and toroidal unit controlling the arc disconnection, by my estimation to be a truly dual pole breaker there would have to be two large coils controlling the phase and neutral independently, supposition on my part, but that's where I was coming from in my previous post when I posted that the unit needing to be two module in width, there have been lots of claims of dual RCBO's prior to this point, but as I posted above they need to separate the contacts by 3mm to conform to the EU standard, I certainly look forward to someone finding one, as I have run out of room in my CU.
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Difficult to see the circuit diagram on the side of the FuseBox RTAMB, but it does look as though it is double switched, by one coil, would be interested in the separation gap of the contacts, I will try to contact them tomorrow.

 

[nicebutdim]

I've attached the data sheet for that Fusebox RCBO, which shows its circuit diagram.

It's interesting that Crabtree, Wylex & Fusebox label these RCBOs as 1P+N, but they're often advertised by wholesalers (who should know better) as DP.

My initial interest in this type of breaker stemmed from trying to find something that would offer additional fault protection on a TT system and settled on Crabtree, due to Starbreaker's main switch being on the left side. I was happy that these switched both poles in an overcurrent situation, but hadn't thought much beyond that. Combined with a time delayed upstream RCD, they're certainly better than what was replaced.

 

[Mike Johnson]

I've attached the data sheet for that Fusebox RCBO, which shows its circuit diagram.

Well that one certainly only shows the phase being switched and is denoted as 1P+N will assume it's not the new compact RTAMB type except that is the only Fusebox RCBO data sheet I can find also.

Even the Crabtree Starbreaker is denoted as 1P+N on it's data sheet, it makes me wonder if the N is electronically disconnected and not a physical 3mm separation.

https://www.tlc-direct.co.uk/Technical/DataSheets/Crabtree/Crabtree_Compact_RCBO.pdf

 

[stevethesparks]

I think an electronic disconnection would surely not be allowed? Wylex state no need for disconnection when testing so to me indicates proper isolation. Regarding a 3mm gap I couldn’t say but again would assume they would have to comply?

 

[Mike Johnson]

Agreed, but on the circuit diagram/s they only show one physical disconnection.

I just looked at the Hager two module RCBO data sheet and that says 1P+N, but N switched concurrently, could only find it on an African site, will look for a EU data sheet to see if it's different: https://www.africa.hager.com/bs/files/download/0/78809_1/0/AD906J_Data_Sheet.pdf

Found an Irish site with the data sheet on, but that shows even less information: https://www.hager.ie/files/download/0/559125_1/0/AD906J_Data_Sheet.pdf

 

[pc1966]

but as I posted above they need to separate the contacts by 3mm to conform to the EU standard

At around 8:30 in that video you can see the neutral contacts is open by at least 3mm (more or less central to the picture). Only later in the video when they flip it over you see the thermal-magnetic trip side that opens the line and has the arc chamber.

Most likely it is based on the typical "switched neutral" style of switch where N makes first/breaks last compared to the line contact(s) so does not have to switch the majority of current (hence no arc chute).

 

[Mike Johnson]

Got hold of a Hagar AD906J an it shows a physical disconnection of both poles on the diagram on the front of the unit whereas most single module units show a pass through of the N.

 

[pc1966]

Got hold of a Hagar AD906J an it shows a physical disconnection of both poles on the diagram on the front of the unit.

It also shows the thermal/magnetic in only the left (line) path, so basically the same.

 

[Mike Johnson]

Sorry don't understand your post, same as what?

 

[pc1966]

Sorry don't understand your post, same as what?

Same as the Wylex/Crabtree/Fusebox units that are 1P + switched N.
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Though without opening the Hager one there is no indication if the N path really has an arc chute, etc, as for L.