MEM Gridwwitch 8000

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On Sat, 06 Dec 2003 12:09:00 +0000 (GMT), Dave Plowman wrote:

OK and when you want to get the mains plug back out again with all the plumbing in place... B-)
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This could run and run...
I'm assuming you're not stupid enough to have the stopcock behind the machine, so the filling hose will come into an adjacent cupboard - as will probably the waste. My machine hasn't room for them behind it anyway. So put the socket near them, but away from any possibility of getting soaked. The mains cable is always longer than the hoses.
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On Sat, 06 Dec 2003 00:51:12 +0000 (GMT), Dave Plowman wrote:

Only under the sink. B-)
And you don't need the hole for those to be any more tha clearance for the pipe. It's the gert big 13A plug on the end of an appliance cable that makes the hole so much bigger.
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Hoses usually have fittings which are larger than the hose itself, so will never be a perfect fit. If you really want this you'd have to make some form of split plinth to fit round them after inserting. So you might as well make the hole big enough for a 13 amp plug...
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On Fri, 5 Dec 2003 09:09:20 -0000, Christian McArdle wrote:

And 6mm from the gridswitch to the sockets? If you've dropped to 2.5mm from the gridswitch to socket that section is not properly protected by the 32A breaker...
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Yes it is. It is protected from short circuit within the cable by having sufficiently low earth loop impedence. It is protected from overload by the 13A plug top fuse. It is no different from having unfused 2.5mm spurs from a ring main. You are permitted to assume that a single socket will only draw 13A and a double socket 20A, apparently, but must still provide short circuit protection, which is easy enough with a B32A MCB if the 2.5mm section is short.
Christian.
P.S. the 2.5mm actually runs from before the grid switch, as there is no way you can get two 6mm cables in one terminal.
2.5mm 2.5mm 6mm #--------SW-----SKT =======###-------SW-----SKT #--------SW-----SKT
## = junction box SW = 20A DP switch SKT = unswitched 13A single socket
The 2.5mm sections are kept short to reduce earth loop impedence at SKT to ensure that 160A can be reliably drawn on an earth fault at the furthest point.
Christian.
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Does the MEM Gridswitch 8000 have trips or just rocker switches?
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"Dave Liquorice" wrote in message

Wrong. 2.5mm^2 will usually be fine for the socket runs. Overload protection is provided by the plug-top fuses, s/c fault protection by the fuse or MCB in the consumer unit. Strictly speaking the designer should check that disconnection time and cable thermal protection requirements are met, but, with MCB protection and normal circuit lengths of a few metres from the split, there won't be a problem. This combination of device rating and cable size is no different to that of the unfused spur taken from a 32 A ring circuit.
In fact 1.5mm^2 would probably be OK for the socket runs in most cases, but would certainly need to be checked by calculation. Sticking to the conventional 2.5mm^2 gives a degree of belt'n'braces safety.
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On Sun, 7 Dec 2003 10:31:29 -0000, Andy Wade wrote:

And if the overload is pre the plug?

True enough, just doesn't "feel" right. Like I said I haven't thought that hard about the practical requirements of installation only the I want this feature.
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"Dave Liquorice" wrote in message

That can't happen - the branch is feeding one socket only. (Unless you connect three 3 kW fires through an ancient unfused 3-way adaptor...)

Consider the fact that for all sizes of T&E cable except 1.0 mm^2, the earth conductor can be 'undersized' relative to the fuse rating. This is OK and it is known, by design, that in the event of an earth fault the fuse will blow before the earth wire in the cable overheats. The situation is the same with an 'undersized cable' where overload protection is either not required, or is provided downstream.
It's important to distinguish between 'faults' - i.e short-circuits caused by someone cutting through a cable, or whatever - and 'overloads' where the design load is exceeded - too much equipment connected, relative to the design expectations.
Fault and earth fault protection is always required. Overload protection is required in general, but can be omitted where the characteristics of the load are such that overloading just can't happen. For example, a circuit feeding a single heating appliance is designed for the maximum loading of the appliance and doesn't need overload protection. Overload protection can also be separate from the fault protection and can be downstream, as in this case. The industrial motor circuit is another common example. The fuses in the dis-board only provide fault protection for the wiring; overload protection comes from an 'overload relay' in the motor starter.
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If you must mount it on the back, then a batten on to the wall wouldn't be too difficult?

Do you at the minute switch off *at the socket* (or unplug) all these appliances that you're going to provide this grid switch arrangement for? And have fuses blowing regularly enough to make it worthwhile?
If not, it seems like a lot of effort for something that is unlikely to be used - or needed.
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Not the fuses. However, I've often used isolating switches when funny things happen. Even simple events, like the washing machine making a funny noise the switches can be useful, particularly with modern appliances with software controlled switches that just ignore you, as they know "best".
I particularly hate those time delay door opening switches. I simply can't see the point of them. OK, so being locked when turned on, maybe. But having to wait 3 minutes for no discernable purpose, I cannot fathom. I frequently disconnect the lock when the machine gets well past warrantee.
Christian.
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<snip>

It's called forced thinking time for dossey house wives, all very un PC though... !
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On Fri, 05 Dec 2003 13:04:03 +0000 (GMT), Dave Plowman wrote:

But you also need a fing big hole to get the plug through into the cupboard. OK you can cut the supplied, moulded on jobbie off (invalidating any guarantee?) and thread the cable througha small hole. But if you need to move the machine out further than the length of cable you have to take the plug off...

Yes, young children, they fiddle. Even though ours know not to fiddle they occasionally forget. The washing machine is always switched off at the (above worktop) socket when not in use.
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Well, you've presumably already got holes for the hoses?

Right. So you do have a good reason for them. But be quick in fitting them or the kids will be big enough to reach over the worktop...
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Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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wrote:

What hoses ? My fridge & freezer doesn't need a water supply, nor are they gas appliances !.... :~)
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On Fri, 5 Dec 2003 21:17:36 -0000, Jerry. wrote:

Ah but they won't be on the gridswitch supply or kitchen ring but a separate radial from another CU with a transfer switch on it's input... Well in the really big scheme of things they would be, in the shorter term it is more likely to be a radial pre the main CUs RCD with a transfer switch on it's input.
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You regularly switch off your fridge and freezer? How quaint.
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Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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wrote:

Yes, when they need defrosting ! OK it's not regularly I'll grant you, but not having to empty a cupboard to unplug is worth a little more work when installing new wiring when refitting a kitchen IMO.
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What's wrong with simply turning down the thermostat on the fridge?
I've not got a built in freezer, so I don't know if they can be defrosted like this.

You could fit the socket at the top of the cupboard - away from possible water leaks?
It's just that separate switches and fuses - especially if brought together on a central panel of what - four minimum - would not be any closer for some than opening the cupboard alongside and unplugging the appliance.
And would serve no purpose for most.
Sorry to go on, but I remember doing just this on one installation years ago using something like an 18 gang panel for switches fuses and neons. And on going back some years later for a few modifications because of a couple of replacement appliances, it was obvious the switches were never, in fact used.
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Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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