UK Installing 50A Hot tub supply

[Janger92]

The earthing arrangement where the hot tub will be installed is formed in the TN-C-S system.
I want to install the sub-main distribution circuit from the main house consumer unit to the outside of the building to have a power source for the final circuits: hot tub, sockets and lights.
The supply cable is SWA going from the house consumer unit to the outside consumer unit, which will be installed in the TT system.
At the outdoor consumer unit, the SWA cable won't be terminated to the earth to provide separation between TNCS and TT.
SWA doesn't need to be protected by RCD, but I am confused about the situation when you transition from TNCS to TT.
- Do I need to install a fault protection delay time 100mA RCD at the installation's origin (house main consumer unit), or could it be only an MCB? The cable will be fixed to the outside walls.
The outside consumer unit will have 63A RCD type A and then some RCBOs for the final circuits.
If you have a different approach to installing this power supply, please let me know below
Thank you,

 

[westward10]

Keep the supply cable on TN-C-S, enclose the termination at an all insulated enclosure and then create TT at the outdoor consumer unit.

 

[Janger92]

Keep the supply cable on TN-C-S, enclose the termination at an all insulated enclosure and then create TT at the outdoor consumer unit.

That's the plan, but I wonder what kind of protection I need to use at the origin of the installation supplying the outdoor consumer unit. Is it MCB or S Type RCD 100mA? The outdoor consumer unit has 63A RCCB

 

[westward10]

Will an mcb provide fault protection alone.

 

[Janger92]

Will an mcb provide fault protection alone.

I believe an MCB will provide fault protection in this case scenario alone. What If the customer decides to run T&E through the ceiling to the outdoor WISKA box and then run the SWA cable to the consumer unit? T&E will need to be protected by RCD. In the outdoor consumer unit, there is already RCCB. To meet selectivity requirements, I will need to install 100mA delayed type RCD ?

 

[James]

Do not let the customer redesign the circuit arrangement
decide what is the right way to do it
quote them and wait.

if they come back and say xyz electrical will do it “this way” and it’s cheaper.
walk away, do not lower your standards to meet unreasonable expectations or other people’s quotes.

if xyz wants to do it for £123 and do it there way, go ahead and get them in would be what came out of my mouth as I was preparing to leave.

 

[westward10]

What you believe is not enough, whether T&E needs additional RCD protection is dependent on installation methods.
I see you are a trainee so what is your involvement in this?

 

[Janger92]

What you believe is not enough, whether T&E needs additional RCD protection is dependent on installation methods.
I see you are a trainee so what is your involvement in this?

That's correct, I am. I want to give it a go as a part of my learning curve. I want to improve my skills and gain knowledge. Quick summary : Sub main supply SWA cable protected by an MCB to outdoor consumer unit with main 63A RCCB and MCBs or 63A main switch and RCBO's . SWA earthed only at origin of the installation. Outdoor consumer unit converted to TT system.

 

[Janger92]

Do not let the customer redesign the circuit arrangement
decide what is the right way to do it
quote them and wait.

if they come back and say xyz electrical will do it “this way” and it’s cheaper.
walk away, do not lower your standards to meet unreasonable expectations or other people’s quotes.

if xyz wants to do it for £123 and do it there way, go ahead and get them in would be what came out of my mouth as I was preparing to leave.

Good advice thank you.

 

[westward10]

That's correct, I am. I want to give it a go as a part of my learning curve. I want to improve my skills and gain knowledge. Quick summary : Sub main supply SWA cable protected by an MCB to outdoor consumer unit with main 63A RCCB and MCBs or 63A main switch and RCBO's . SWA earthed only at origin of the installation. Outdoor consumer unit converted to TT system.

I would suggest this isn't something you should be giving a go. It is also notifiable works under Part P.

 

[Janger92]

I would suggest this isn't something you should be giving a go. It is also notifiable works under Part P.

Theoretically speaking, is my summary correct?

 

[westward10]

Theoretically speaking, is my summary correct?

Inappropriate to comment.

 

[Janger92]

Inappropriate to comment.

I understand you might find commenting inappropriate, and I truly respect your perspective. Your input would be greatly appreciated. I've invested significant time researching data for this installation, and I'm genuinely interested in knowing if I'm headed in the right direction.

 

[nicebutdim]

I understand you might find commenting inappropriate, and I truly respect your perspective. Your input would be greatly appreciated. I've invested significant time researching data for this installation, and I'm genuinely interested in knowing if I'm headed in the right direction.

I'm impressed by this response!

 

[westward10]

I understand you might find commenting inappropriate, and I truly respect your perspective. Your input would be greatly appreciated. I've invested significant time researching data for this installation, and I'm genuinely interested in knowing if I'm headed in the right direction.

Are you undertaking this installation.

 

[Janger92]

No, I am not undertaking this installation. I am just collecting design installation and testing information about this project.

 

[James]

Post #1 reads very much like you are doing this installation in real life, not a theoretical case study.

 

[Janger92]

Post #1 reads very much like you are doing this installation in real life, not a theoretical case study.

At some point, I will be installing and testing this installation anyway, but in accordance with someone else design. I want to prepare my own project and confront this with other people from my company.

 

[James]

Great idea, design it how you think it should be done and compare that with the spec that you are given. Then you can ask the designer to discuss the differences between the two designs.