SWA 16mm 3 core cable for garden office

[Berty]

Sorry if this is not the correct wat to post my query, I am new to the site. I am not a spark but would like to tap into the skills and experise on here before I set off on the wrong course with my current spark. I am having a garden office built, it has had its own CU installed but my ex spark neighbour came round to look and has caused a row with my spark by saying he was incompetent and had done it wrong. I'm confused and don't know who to believe.

The new cu is fed from house via a henley block with its own 100amp isolator. The CU in house is on a mains fuse of 100 amp with 25 mm tails.
The issue is the cable used to the garage, it is free to air, 15 m long and swa 16mm 3 core cable. 1 of the cores has been used as earth, so my spark says its 2 core single phase system which can carry 115 amp.

The room will sometimes draw 70 to 80 amps as has an electric 9.5 kw shower, sockets and lights.

My neighbour ex spark has disagreed and says 'in his day' it would be on 25mm cable. Is my house in danger or is my spark complying with current regs?

 

[Darkwood]

Hi Berty, Welcome to the forum

Can you just clarify for us if you are an Electrician or not, you say you are but your post comes across that you are not but actually employing a spark to do your work.

If you are not a spark it will help us to know so we can relocate the thread to the appropriate section thankyou.

 

[Simonslimline]

Sorry if this is not the correct wat to post my query, I am new to the site. I am a spark but would like to tap into the skills and experise on here before I set off on the wrong course with my current spark. I am having a garden office built, it has had its own CU installed but my ex spark neighbour came round to look and has caused a row with my spark by saying he was incompetent and had done it wrong. I'm confused and don't know who to believe.

The new cu is fed from house via a henley block with its own 100amp isolator. The CU in house is on a mains fuse of 100 amp with 25 mm tails.
The issue is the cable used to the garage, it is free to air, 15 m long and swa 16mm 3 core cable. 1 of the cores has been used as earth, so my spark says its 2 core single phase system which can carry 115 amp.

The room will sometimes draw 70 to 80 amps as has an electric 9.5 kw shower, sockets and lights.

My neighbour ex spark has disagreed and says 'in his day' it would be on 25mm cable. Is my house in danger or is my spark complying with current regs?

I very much doubt that really.

 

[Octopus]

Sorry if this is not the correct wat to post my query, I am new to the site. I am a spark but would like to tap into the skills and experise on here before I set off on the wrong course with my current spark. I am having a garden office built, it has had its own CU installed but my ex spark neighbour came round to look and has caused a row with my spark by saying he was incompetent and had done it wrong. I'm confused and don't know who to believe.

The new cu is fed from house via a henley block with its own 100amp isolator. The CU in house is on a mains fuse of 100 amp with 25 mm tails.
The issue is the cable used to the garage, it is free to air, 15 m long and swa 16mm 3 core cable. 1 of the cores has been used as earth, so my spark says its 2 core single phase system which can carry 115 amp.

The room will sometimes draw 70 to 80 amps as has an electric 9.5 kw shower, sockets and lights.

My neighbour ex spark has disagreed and says 'in his day' it would be on 25mm cable. Is my house in danger or is my spark complying with current regs?

So there is no over current protection for the sub main except the DNO fuse?

Think you should talk to the spark doing the work about the design load of the distribution circuit.

 

[Berty]

Sorry, no I'm not an electrician. I have limited knowledge at best and would never attempt to install anything, thats what I pay you guys for as saftey is everything. My question in short is can a 16mm swa 3 core cable (1 core used as earth) carry the 100 amp load to the second consumer unit? My interferring ex-spark neighbour says it cannot and has got me doubting my spark.

 

[Midwest]

Sorry if this is not the correct wat to post my query, I am new to the site. I am a spark but would like to tap into the skills and experise on here before I set off on the wrong course with my current spark. I am having a garden office built, it has had its own CU installed but my ex spark neighbour came round to look and has caused a row with my spark by saying he was incompetent and had done it wrong. I'm confused and don't know who to believe.

Think you should clarify the situation, its seems like another shaggy dog story to me. :thinking:

Edit: posted before reading #5.

 

[Darkwood]

Sorry, no I'm not an electrician. I have limited knowledge at best and would never attempt to install anything, thats what I pay you guys for as saftey is everything. My question in short is can a 16mm swa 3 core cable (1 core used as earth) carry the 100 amp load to the second consumer unit? My interferring ex-spark neighbour says it cannot and has got me doubting my spark.

Thanks for the reply, I will edit your opening post and correct it, when admin is next online you may be given DIY access and the thread relocated, this will not effect any postings already made.

 

[Andy78]

Sorry, no I'm not an electrician. I have limited knowledge at best and would never attempt to install anything, thats what I pay you guys for as saftey is everything. My question in short is can a 16mm swa 3 core cable (1 core used as earth) carry the 100 amp load to the second consumer unit? My interferring ex-spark neighbour says it cannot and has got me doubting my spark.

Simply tell your neighbour to keep his nose out.
If you have misgivings about the design, ask your installing electrician to back up up his design choices with reference to the regulations. Any decent guy will be easily able and happy to do this. Ask your neighbour to do the same.

I would say that Murdoch's post is relevant here and I doubt that the reference method is free air, more likely clipped direct.

 

[Midwest]

OP you will need to provide some details about the type of swa used (pvc or XLPE) and how the cable has been installed. You say 'free air' which is a reference method in BS7671, not a term a layperson would use?

 

[ruston]

OP you will need to provide some details about the type of swa used (pvc or XLPE) and how the cable has been installed. You say 'free air' which is a reference method in BS7671, not a term a layman would use?

Methinks you are getting warm.

 

[uksparks]

All smells a bit fishy to me....

 

[Risteard]

OP you will need to provide some details about the type of swa used (pvc or XLPE)

I consider it extremely unlikely that any of the terminations are suitable for 90 degree operation.

 

[davesparks]

Can you post a picture of the isolator which has been installed at the supply end?

 

[PEG]

OP you will need to provide some details about the type of swa used (pvc or XLPE) and how the cable has been installed. You say 'free air' which is a reference method in BS7671, not a term a layperson would use?

...It could be suspended between two clothes props... not as unlikely as you think,was at a pals' fathers farm,and welder went off,supply came from house,via SWA suspended from a catenary made from 16mm G/Y...

...stupid spell-check...catenary catenary catenary ...have a bit o' that...:stooge_curly:

 

[HappyHippyDad]

I think you just listen to the Spark that you are paying to do the job. 16mm may well be absolutely fine as it's highly unlikely you'll be pulling 100A through the cable. However it would be impossible and a little reckless to say "Yes, 16mm is fine for you to use, go ahead and do it".

It depends on a number of factors that you haven't mentioned Bertie (and wouldn't be expected to being a non-spark), max demand (including diversity), Ze, a 'confirmed' cut out fuse size (how does he know it's definitely 100A?), is the 100A isolater just an isolater or is it a switch fuse and I expect theres other questions that I have missed. All of these your Spark will (should have) have taken into account to decide upon 16mm SWA.

The one other point, just to make it more complicated is that all the electrics fed from the cutout should have a single point of isolation, it sounds as though you are going to have 2! The 100A isolator for the office CU and the main switch in the house CU.

 

[Richard Burns]

The 115A rating for single phase armoured cable is for 90°C cable and means the cable must be installed in such a way that the conductors can reach 90°C; it is not likely that this is practical to do, therefore even if the cable is rated at 90°C the limit on conductor temperature is 70°C therefore the cable can only carry 97A.
Too many other factors to cover to be able to say if the installation is safe.

 

[NDG Elecs]

Sorry if this is not the correct wat to post my query, I am new to the site. I am not a spark but would like to tap into the skills and experise on here before I set off on the wrong course with my current spark. I am having a garden office built, it has had its own CU installed but my ex spark neighbour came round to look and has caused a row with my spark by saying he was incompetent and had done it wrong. I'm confused and don't know who to believe.

The new cu is fed from house via a henley block with its own 100amp isolator. The CU in house is on a mains fuse of 100 amp with 25 mm tails.
The issue is the cable used to the garage, it is free to air, 15 m long and swa 16mm 3 core cable. 1 of the cores has been used as earth, so my spark says its 2 core single phase system which can carry 115 amp.

The room will sometimes draw 70 to 80 amps as has an electric 9.5 kw shower, sockets and lights.

My neighbour ex spark has disagreed and says 'in his day' it would be on 25mm cable. Is my house in danger or is my spark complying with current regs?

Change the iso for a switch fuse and have a 63/80A fuse in it. Likely to be fine then (without further info (TT supply maybe, etc, etc)). As mentioned it is highly unlikely to be drawing 70-80A unless the police helicopter has spotted something on their thermal imaging cams!

 

[telectrix]

was just thinking the same. a KMF fused at 80A. just doing a similar but with 10mm SWA fused at 60A. however, i hate the wylex KMF. it's designed for incomer at bottom, and there's no way to have incoming cable into top feeding the bottom of the isolator. next option up from the GC MSF

won't even fit in the meterbox using a crowbar and sledgehammer.