supplying garden shed

[samson337]

I agree with the above to a point, but I would always go for separate supply to shed, garage, because people think great we have power out there lets bung the dryer, freezer, washer, well the washer won't always be put in there, but I've seen it and one is at my sisters shed apart from others, and how much more would it cost, an rcd fcu are not far off the price of a small cu, so my point is as long as the supply cable to the shed can handle future upgrades if needed then there will be no issues coz you can't up grade your fcu, and plus if there is a fault with the shed then the house will lose power, and if taken off down stairs sockets,if duel rcd then that means no up stairs lights on dark nights, may be a bit extreme but I like to work to minimise inconivence

 

[OnOff]

I think that a separated supply, with an isolator in the house and then supply to the shed with armoured to the mini CU.I just wondered what you guys think, the same situation but there is a free slot in the house CU, 4mm2 armoured to a mini CU in the shed with 3 RCBOs (I always use a supply cable that is a bit bigger than what is required at the time of installation because there is always someone who will add something on the load side.... The home CU does not have RCD (pre 16th) would anyone of you put in the home CU RCD to protect the supply cable (to the shed) or you think that it is not necessary and MCB will be enough?

Guess you mean you have a similar situation? Before doing the shed wouldn't it be a good time to look at the home CU? Lots of questions there come to mind. YOUR earth system? Are you going to export the house earth or do a TT at the shed end? If TT at the house are you going to RCD protect the supply itself?

 

[AK-UK]

TN-S, in the house, no RCD in the house

 

[PC Electrics]

.... I would always go for separate supply to shed, garage, because people think great we have power out there lets bung the dryer, freezer, washer.....

So, why can one not run a drier or a washer from an fcu?

....and how much more would it cost, an rcd fcu are not far off the price of a small cu...

Well, I'm guessing that since you're an electrician you must be very wealthy and can afford to default to the "rolls royce" solution. Not everyone else is so lucky. Most clients are looking for a cost effective solution that meets their needs.

.....future upgrades if needed.....

Fair enough to discuss with the client any future upgrade needs they may see a need for, but if the client says "no" would you still insist on offering the client to "rolls royce" solution only, because that's the way you think it should be done?

....and plus if there is a fault with the shed then the house will lose power, and if taken off down stairs sockets,if duel rcd then that means no up stairs lights on dark nights..

Seriously now, what is the risk? Just how often do you think the average household suffers RCD tripping faults? An all RCBO solution is appropriate in an industrial and some commercial applications where downtime on otherwise healthy circuits could cost considerable amounts of money (or in the case of a medical location could even be seriously dangerous), but in your average domestic??

A good tradesman should be assessing the clients needs and offering the client solutions that meet those needs. Offer the client several solutions and let them chose by all means, but don't just default to the "rolls royce" solution - you're liable to loose the job to someone more honest and upfront. True we don't have all the facts here regarding the clients needs, but that doesn't make the FCU solution non-valid.

 

[samson337]

Well first I didn't say you could'nt run a dryer off an fcu ,and why would you be happy with the shed that could possibly pull 20 amps as you say running off a 13 amp yes we no it could but why, just plan it right then it wont have to,O and I'm doing ok thanks on the work front, but in your post you did put well if it takes the power out in the house then it's only a slight inconivence, that's why I like to separate, shed, garage, from main house, end of I'm always up front and tell them the cost, I have happy customers and always straight with them I don't work on cheap an cheerful and if I lose the job then that's the name of the game, move on, my post was not aimed at you or anyone just my opinion on what I would do

 

[AK-UK]

PC Electrics - I think that in principle I agree with samson337, firstly to can not say that he is not honest enough... You don't know. The other thing is that I always offer and recommend my customers the Rolls Royce option, among other options, I explain the differences and let them decide. I will accommodate any request from a customer as long as it does not compromise the regulations requirements (and safety of course).

There is no question in my mind that the Rolls Royce option has advantages above the cheep options, in safety and practical points of view, therfore this is the way I go...

 

[Doc Hudson]

For a lot of domestic shed situations, where it is mostly power for a few garden tools & charging battery drills a metal clad 20A double pole switch at the house end, provides adequate functional isolation if needed in the even of a fault and a metal enclosure in which to terminate a SWA. Just feed this off a suitably rated MCB, 16A / 20A. The distribution circuit has no specific requirement for RCD protection. 32A MCB, 6,0mm SWA & second small CU at shed sounds overkill to me. Charging customer for a lot unnecessary work.

Doc H.

 

[batty]

All I will say on this you need to talk to customer as what they are going to use the shed for. I used to do a lot of shed type buildings that where used for offices now if I had run these of an existing 13 amp spur I think I would have lost a lot of future work. You need to talk to the customer and find what they are going to plug into there 3 x 13 amp sockets.

 

[kme]

Well first I didn't say you could'nt run a dryer off an fcu ,and why would you be happy with the shed that could possibly pull 20 amps as you say running off a 13 amp yes we no it could but why, just plan it right then it wont have to,O and I'm doing ok thanks on the work front, but in your post you did put well if it takes the power out in the house then it's only a slight inconivence, that's why I like to separate, shed, garage, from main house, end of I'm always up front and tell them the cost, I have happy customers and always straight with them I don't work on cheap an cheerful and if I lose the job then that's the name of the game, move on, my post was not aimed at you or anyone just my opinion on what I would do

Do me a favour - take a breath when you`re posting! I got partway through that, and gave up, due to carp spelling and grammar.

Dunno exactly what you were trying to say, so I`ll just give my thoughts on the OPs question.

I think Batty has alluded to the fact that the customers` intended use has to play a part - your knowledge and experience will tell you what overhead you need to allow in their supply.

If someone had spurred my shed from the ring, I`d be super peeved - I regularly use a chopsaw in the shed, which only uses 2KW - but it is connected to a "combivac", which starts at the same time as the saw, and is rated 1200W.

When I first installed the submain, it was on a B16. Starting the saw drops the breaker one time in three - which is a pain in the rear. Now it has a C20 - which is fine.

I couldn`t have done that from an FCU. But grandad,with his 4` florrie and a DSO for his drill will be fine - I`ve even seen (not fitted) em` as a spur from the ring, with no isolation at the house end.

What we`d have in an ideal world is one thing. What we HAVE to provide is another. The answer is somewhere in between.

Or, if it helps:

1) There is a "Best possible result"

2) There is a "Best result possible"

They can be wildly different; even though they`re the same three words.

KME

 

[AK-UK]

How many times you find that a garage/shed is supplied via 13A FCU, and then 6 months later the "only light and one double socket" became a source of supply to a 6 or 8 ways extension cable with appliances and tools connected to it... What seems to be an overkill, in many cases is "The best result possible"...

 

[unphased]

There is a 13A fuse in the extension lead plug. Plug as much as they want in to the extension lead. ]

 

[AK-UK]

There is something that called "overloading", was it cancelled or still needs to be considered as part of the design...? :innocent just asking...

 

[unphased]

13A fuse in the plug. This ensures overload will not happen. If the user does overload the socket it won't do any more than blow the fuse. That is what is "designed" for. Do you wish to continue?

 

[AK-UK]

Yes, the main idea is that the fuse will not blow, by making sure that the load is spread and not connected to one supply point, this is a good design...

 

[unphased]

So, why are 4-gang 6-gang or even 8-gang extension leads made? They only have a 13A fuse in the plug. Is this poor extension lead design?

 

[lselectrical]

if you install a cu for the shed you will have to break the earth and put it on a tt system,

 

[steptoe]

by the same token that you can buy an extension lead rated at 10A that is perfectly capable of accepting a 13A fuse for protection,

poor design. IMO

BTW, I do have some of those 4/6 gang leads, handy for plugging all the PC/TV stuff into so that 1 switch turns everything off at once.

---------- Post Auto-Merged at 15:39 ---------- Previous post was made at 15:39 ----------

if you install a cu for the shed you will have to break the earth and put it on a tt system,

not necessarily.

 

[lselectrical]

it clearly states in the regs about breaking the earth???

 

[rins]

cheers lads for all your advice this being my 1st shed job its been much appreciated.

i like the idea of spurring off to a dpsfcu then feeding the shed with swa then spurring off socket in shed to a 2nd dpsfcu with 3a fuse for the lights simple, cheaper and at end of day its safe. i probably wouldnt have got the job by suggesting 2 small cus at either end would of cost abit more and probably alot of hassle. i will be returning to the property tomorrow to price the job up so will ask exactly what the power will be feeding thanks everyone

---------- Post Auto-Merged at 16:06 ---------- Previous post was made at 15:59 ----------

ps how do i get my elecsa logo under my name to stop the whingers saying " are you part p" or "are you an electrician". its a forum people come on here to get advice, give advice and generally help each other but on alot of the posts right through the forum you always get the whingers. now i have been given some cracking advice about this shed job which now i wont ever need to ask about again its logged into my brain for future reference for which i am most greatful, am sure the whingers had questions when they started out RANT OVER

 

[PC Electrics]

13A fuse in the plug. This ensures overload will not happen. If the user does overload the socket it won't do any more than blow the fuse. That is what is "designed" for. Do you wish to continue?

NO, NOT AT ALL.

I take it you missed my point in my first reply:

# If you've read up on the ESCs concern regarding overloading of multi gang extensions and have looked at the current / time curve for a 13A 1362, you will know that a 13A 1362 will pass 20A indefinately. So you have effectively provided the client with a 20A supply. Because of this I recommend designing the supply as 20A and using a high quality FCU to be able to cope with this potential overload.

Search the back issues of Switched On magasine on the ESC website and you will find an article about this exact subject. These multi gang extensions are dangerous, for the simple reason that they can be continuously overloaded.

The simple reason for this is that the design requirements for the 'appliance' (the multiplug in this case) require that they are capable of passing 13A continuously. Most are rigorously designed and tested down to a cost to ensure they can meet this standard - JUST. They cannot handle any more than 13A or they overheat / melt / catch fire. However as I elluded to in my post, a 13A 1362 is capable of passing 20A continuously. So here we have a mismatch between the design requirements of the extension and the real world protection afforded by a 13A 1362. The extension can be overloaded to 1.6 times its design capability continuously. A typical MCB asked to pass 1.6 times its rating would trip out in around 12 - 14 minutes.

The big problem is that the layman does not know this, so when he loads up his extension with heaters, kettles, toasters etc etc he has no idea that he's overloading it. He thinks that if he did so the fuse would blow. WRONG (to a point).

It's why I suggested that one should be aware of this "property" of 13A 1362s so that one can guard against this type of overload in ones design (cable sizes, quality of fittings etc).

I'm not, however, suggesting one should exploit this property of 1362s to provide 20A supplies. If a shed or other device needs a 20A supply, then use a 20A MCB.

if you install a cu for the shed you will have to break the earth and put it on a tt system,

Not at all. Where is this in 7671?

---------- Post Auto-Merged at 16:28 ---------- Previous post was made at 16:26 ----------

not necessarily.

You feelin' okay?

Perhaps Patch should take your temperature?