Can you see any issue with this garage supply?

[Superspark23]

I've been asked to provide and install a garage supply which will have sockets and lighting to run off.

The house is on an TT System i'm getting an ze of around 9MOhms, all socket circuits are 16a all circuits have rcd protection. Getting back to the Consumer unit for a new supply is going to be a nightmare. So i'd like to avoid doing this as the owner doesn't want surface trunking in the house or her bedroom carpet lifted which is only 2 weeks old! add to this the upstairs floors are all different levels and i can see issues getting through parts.

I have 2 radial circuits i could use that are approx 2/3 meters away from the garage each have around 7/8 sockets on them.

Can you see any issue with upgrading the mcb for one of these radials to 20a providing all cables are run in a way to allow for an 20a breaker which i'm sure i'll be fine to do at this point.

and extend from the end of line to a DP Switch so all power can be isolated from within the house and from there go into an adaptable box in 2.5mm TE. and from the adaptable box run some 4mm 3 core swa into the garage into an 2gang garage consumer unit. Is it okay to rely on the exsisting stake or should i install a new one for the garage and finnishing the cpc at the garage end on the swa

The breaker sizes within the garage consumer unit will be 16a and 6a both covered by an 30ma rcd

 

[Rockingit]

A Ze of 9Meg? Did you mean to say that?!

 

[Superspark23]

no the actual highest reading i got was 9.17Ohms the M was a mistake woops. But thanks for pointing that out been a busy day.

 

[malcolmsanford]

I've been asked to provide and install a garage supply which will have sockets and lighting to run off.

The house is on an TT System i'm getting an ze of around 9MOhms, all socket circuits are 16a all circuits have rcd protection.Why if all circuits in the house already have 30mA RCD protection do you want to also put it in the garage? As by your design your going to use an existing radial final circuit

Getting back to the Consumer unit for a new supply is going to be a nightmare. So i'd like to avoid doing this as the owner doesn't want surface trunking in the house or her bedroom carpet lifted which is only 2 weeks old! add to this the upstairs floors are all different levels and i can see issues getting through parts.

I have 2 radial circuits i could use that are approx 2/3 meters away from the garage each have around 7/8 sockets on them.

Can you see any issue with upgrading the mcb for one of these radials to 20a providing all cables are run in a way to allow for an 20a breaker which i'm sure i'll be fine to do at this point.

and extend from the end of line to a DP Switch so all power can be isolated from within the house and from there go into an adaptable box in 2.5mm TE. and from the adaptable box run some 4mm 3 core swa ​Why the larger cable unless your thinking of future proofing and to be honest if that was the case then I would be thinking more of a 6/10mm

into the garage into an 2gang garage consumer unit.I personally would not want to feed a CU off of a radial circuit that already had 7/8 sockets on it. Not against any regs but just IMO poor design

Is it okay to rely on the exsisting stake or should i install a new one for the garage and finnishing the cpc at the garage end on the swa.If you getting an Ra of under 10ohms then that is a fantastic result. I have my doubts and would feel that unless the rod installation is superb your getting perhaps a PME parallel path here from another system, or parallel paths from pipes. Personally depending on the distance I would install another rod and tie them both together. As it is a TT system you can easily tie the rods via the SWA armour by connecting both ends of it.

The breaker sizes within the garage consumer unit will be 16a and 6a both covered by an 30ma rcd

Personally I would extend the 7/8 radial circuit into the garage making it, well as many as you wish really VD provided. Then spur off the nearest socket into a FCU and 3amp for the lights

 

[Superspark23]

Thanks for the advice

I was going to use 4mm swa for 2 reasons one because its rated up too 43Amps and secondly i have some left over from a previous job.

and i was going to do my way mainly as it would future proof incase another electrician would like to provide an dedicated circuit to the garage at an later time

How ever i do like your idea and i feel this is proberly the best way too go.

would you put an switch fused spur within the house with an 13 amp fuse?

in fact this installation already have 2 rods 1 giving an reading of around 40Ohms, the other 18ohms and when interlinked the reading reduces to 9 ohms. its clay type soil as well

 

[malcolmsanford]

Thanks for the advice

I was going to use 4mm swa for 2 reasons one because its rated up too 43Amps and secondly i have some left over from a previous job. Lol never knock the design criteria of Material left over from another job

and i was going to do my way mainly as it would future proof incase another electrician would like to provide an dedicated circuit to the garage at an later time

How ever i do like your idea and i feel this is proberly the best way too go.

would you put an switch fused spur within the house with an 13 amp fuse? To be honest I most likely would yes simpley for the reason if your not going to use the garage power for long periods you can simply isolate it. Also if you ever want to work on the garage install only you can without affecting the house sockets. So either a FCU or a double pole switch

in fact this installation already have 2 rods 1 giving an reading of around 40Ohms, the other 18ohms and when interlinked the reading reduces to 9 ohms. its clay type soil as well I have to admit that does not make much sense lol one at 400 the other at 18 and then an Ra of 9, I still think your picking up parallel paths but you Ze is 9 so happy days

..........................

 

[johnboy6083]

..........................

. It's 40 ohms he said Malcolm, not 400.

Agree with all points Malcolm has raised. I would take the opportunity to check the connections to the rods, that they're not loose, corroded ect.

 

[malcolmsanford]

. It's 40 ohms he said Malcolm, not 400.

Agree with all points Malcolm has raised. I would take the opportunity to check the connections to the rods, that they're not loose, corroded ect.

That bloomin' guide dog of mine i'll swing for it ....................cheers john how is it going mate in god's country?

 

[johnboy6083]

good mate, and the job im on will prob last till x-mas, so im a happy bunny. got next week off to do 2391-2, so my x-mas is gona be project time anyway.
You back for x-mas?

 

[malcolmsanford]

good mate, and the job im on will prob last till x-mas, so im a happy bunny. got next week off to do 2391-2, so my x-mas is gona be project time anyway.
You back for x-mas?

Tried to PM you mate but your box is full, popular lad lol and wish you luck with the course, yes home on the 15th mate.

 

[telectrix]

i readit as 400 as well malc., we must use the same optician. LOL.