I am saying that there is no way that the feed to the shed is going to pull 56 amps !
External Supply
- Thread starter dans77
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In shed 2 all I require is 2 lights and a couple of sockets, one of the sockets I will have a running machine plugged into, the others will be spare as options.
In shed 1 I only require 1 light and a couple of sockets for lawnmower, charging batteries, jigsaw etc obviously these would not all be running at the same time!
The pond pump is on a 300W connection on the blagdon box and the filter on another and the pond lights on another with the 1x1000W and 1x300W unused.
Why would the sockets in shed 1 not be run as a radial rather than a ring?
In shed 1 I only require 1 light and a couple of sockets for lawnmower, charging batteries, jigsaw etc obviously these would not all be running at the same time!
The pond pump is on a 300W connection on the blagdon box and the filter on another and the pond lights on another with the 1x1000W and 1x300W unused.
Why would the sockets in shed 1 not be run as a radial rather than a ring?
Why not?
Summerhouse on maximum demand and shed on maximum demand!
It's not a good set up!
20A radial is all you need.
If RFC 32A but I guess the shed does not require a that.
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You are obviously not experienced in predicting dynamic loads.
Are you seriously suggesting that one should estimate 'maximum demand' by adding up the ratings of all the OPDs, without considering actual 'likely loading' and diversity? If you did that, what proportion of installations do you think would have a 'maximum demand' which was less that the rating of the cutout fuse, or of the main main switch (and perhaps also the CCC of the meter tails)?
Kind Regards, John.
No I am suggesting what the potential is on maximum demand. taking in to consideration we only have one circuit in each situation that can be offered diversity.
This is not typical of a domestic installation, where you could quite possibly have 8-10 circuits that can be offered diversity.
I do except that maybe the summerhouse and shed may not be in full operation at the same time, but I also consider they could quite possibly be.
This is not typical of a domestic installation, where you could quite possibly have 8-10 circuits that can be offered diversity.
I do except that maybe the summerhouse and shed may not be in full operation at the same time, but I also consider they could quite possibly be.
Unlikely, but does need to be thought about.
If the op ends up with a max demand at shed 1 cu there won't be any problem. How likely is it that a potential 10 kw load will be used in the garden at the same time?
If the op ends up with a max demand at shed 1 cu there won't be any problem. How likely is it that a potential 10 kw load will be used in the garden at the same time?
The worst case maximum I will draw would be;
Shed 2 -
Running machine which has a 2hp motor approx. 1500W = 6.5A
2kW heater = 8.7A
Lights – 2 at 60W = 1A
Shed 1 -
Circular Saw = 1800W = 7.8A
Pond Pump – 3A blagdon powersafe box
Pond Filter –3A on blagdon powersafe box
Lights – 4no at 60W = 1.1A
Total 31.1A
Shed 2 -
Running machine which has a 2hp motor approx. 1500W = 6.5A
2kW heater = 8.7A
Lights – 2 at 60W = 1A
Shed 1 -
Circular Saw = 1800W = 7.8A
Pond Pump – 3A blagdon powersafe box
Pond Filter –3A on blagdon powersafe box
Lights – 4no at 60W = 1.1A
Total 31.1A
Quite - and what are the chances that you would be using the running machine, heater and circular saw all simultaneously for any appreciable period of time? (I would imagine very low - in particular, a circular saw is generally a very short-term load). Also, do the pond pump and filter really take 3A each, or is that just the fuse rating of their supplies? I really think that the maximum likely load on all this is going to be pretty modest.
Kind Regards, John.
Thanks John.
I would say to use all at once wouldn't happen.
I mean if the good wife was on the running machine and me using the circular saw outside (I'm a fair weather worker!) then the weather would be as such we wouldn't have the heater on so reducing the load more.
The pump and filter, I used the fuse rating. In reality they are both around 70watts.
So back to my original plan I am ok in what I want to achieve.
Thank you to everyone so far, it has been educational.
I would say to use all at once wouldn't happen.
I mean if the good wife was on the running machine and me using the circular saw outside (I'm a fair weather worker!) then the weather would be as such we wouldn't have the heater on so reducing the load more.
The pump and filter, I used the fuse rating. In reality they are both around 70watts.
So back to my original plan I am ok in what I want to achieve.
Thank you to everyone so far, it has been educational.
So what if one day we decided it was a bit cold and decided to plug in one or two 3kW heaters?
That wouldn't happen. The only reason there is a heater in there is to keep the frost off my paint!
It's a summer house with a running machine in, naturally you get warm by running so it wouldn't be on during that time.
If its that cold that I need 2 3kw heaters then I think I would be tucked up indoors with the central heating on and fire blazing rather than sat in the summer house. You could say the same for the main house CU, the main fuse is 100A and I have 208A in mcb's. All done under 17th edition and passed off.
I understand and appreciate your point though, as long as I understand and know what the system can take would it be a problem? When I get it installed by a qualified electrician, part p etc then as far as I and for the purposes of insurance is concerned I have a safe system.
It's a summer house with a running machine in, naturally you get warm by running so it wouldn't be on during that time.
If its that cold that I need 2 3kw heaters then I think I would be tucked up indoors with the central heating on and fire blazing rather than sat in the summer house. You could say the same for the main house CU, the main fuse is 100A and I have 208A in mcb's. All done under 17th edition and passed off.
I understand and appreciate your point though, as long as I understand and know what the system can take would it be a problem? When I get it installed by a qualified electrician, part p etc then as far as I and for the purposes of insurance is concerned I have a safe system.
if it was a bit cold and 2 x 3kw heaters were used, the running machine, a circular saw intermittantly , the pond pump, filter and the lights. plus a radio.I bet his 32 Amp fuse would not disconnect.
However what i dont like is the 32A mcb, protecting the 2.5mm2 conductors in the distibution circuit. 30 Amps could be drawn which is too much for the operating temperature of the conductors
You can only design a circuit corectly based on intended use, and an assessment of demand. You could build in some future potential, which would be wise.
Where the 6mm2 cable exits the house. Could you not leave the existing swa in situ and use a new swa cable glanded of this point to the other building.?
This will prevent the problem of overloading the conductors in those to parts of the circuit
However what i dont like is the 32A mcb, protecting the 2.5mm2 conductors in the distibution circuit. 30 Amps could be drawn which is too much for the operating temperature of the conductors
You can only design a circuit corectly based on intended use, and an assessment of demand. You could build in some future potential, which would be wise.
Where the 6mm2 cable exits the house. Could you not leave the existing swa in situ and use a new swa cable glanded of this point to the other building.?
This will prevent the problem of overloading the conductors in those to parts of the circuit
Quite, and if anyone was tempted to use the heater and running machine simultaneously, they wouldn't be running fast enough!
As I suspected - so there's another 5A or so you can take off the total. In terms of what you've said, I suspect that a realistic maximum design current (maximum current likely to be drawn for appreciable periods of time) is probably not going to be even 20A, certainly not a lot more.
Also remember that, even if some of the scenarios PBoD is postulating ever did occur, provided all of the circuits were protected by MCBs of ratings appropriate for the cables involved, the very worst that happens if you 'overloaded' the circuit is that the MCB will trip and thereby protect the cable from any damage - that's precisely what they are there for. No different from what would happen if someone were, say, to plug four 3Kw heaters into sockets on the same 32A ring final circuit in your house.
Kind Regards, John
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