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Kitchen appliance isolator
My mythical kitchen is slowly creeping towards installation - I bought
the hob last week! Now planning the wiring and am mindful of the need to be able to isolate the power to washing machine, dishwasher, hob ignition and extractor hood. I _really_ do not want to fit fused spur isolators above the worksurface so I was going to fit all three (running hob and extractor from the same isolator) in the space under the sink. However, this is going to make for quite lengthy, parallel, cable runs and I was wondering if I could incorporate a single isolator for the whole of the ring on the appliance side of the kitchen. Is it possible? And could it be done discretely - I don't want something that looks as though it could have designed for use by the CEGB. Alternatively (and probably simpler) would a cooker isolator (switch only), spurred off a socket on the kitchen ring, feeding the four under surface sockets for the appliances be acceptable? And could I wire those sockets in series with a suitable weight of T+E? I'm thinking that the sequence would be: ====SKT====Ring======= | Switch ------ W/M --------- D/W----------Hob--------Extractor TIA Richard |
#2
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Richard Savage wrote:
My mythical kitchen is slowly creeping towards installation - I bought the hob last week! Now planning the wiring and am mindful of the need to be able to isolate the power to washing machine, dishwasher, hob ignition and extractor hood. I _really_ do not want to fit fused spur isolators above the worksurface so I was going to fit all three (running hob and extractor from the same isolator) in the space under the sink. However, this is going to make for quite lengthy, parallel, cable runs and I was wondering if I could incorporate a single isolator for the whole of the ring on the appliance side of the kitchen. Is it possible? And could it be done discretely - I don't want something that looks as though it could have designed for use by the CEGB. Alternatively (and probably simpler) would a cooker isolator (switch only), spurred off a socket on the kitchen ring, feeding the four under surface sockets for the appliances be acceptable? And could I wire those sockets in series with a suitable weight of T+E? I'm thinking that the sequence would be: ====SKT====Ring======= | Switch ------ W/M --------- D/W----------Hob--------Extractor I was in a similar situation, and decided to solve it by placing sockets (surfacemount metalclad) inside the base units adjacent to appliances. A hole at the back of the base unit is used for passing the plug through. Works well, as long as you don't mind sockets in your base units. -- Grunff |
#3
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Dave Plowman (News) wrote:
I'm curious about why you feel the need for any of this? All the appliances - with the possible exception of the cooker hood - could surely be unplugged for isolation? And if you needed to isolate the entire ring, what's wrong with the MCB in the consumer unit? If it is necessary to isolate an appliance quickly, sockets behind the appliance could be hard to reach with the appliance in place. Chris -- Chris J Dixon Nottingham UK Have dancing shoes, will ceilidh. |
#4
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In article ,
Chris J Dixon wrote: I'm curious about why you feel the need for any of this? All the appliances - with the possible exception of the cooker hood - could surely be unplugged for isolation? And if you needed to isolate the entire ring, what's wrong with the MCB in the consumer unit? If it is necessary to isolate an appliance quickly, sockets behind the appliance could be hard to reach with the appliance in place. Every appliance I've seen has got an on/off switch. But if you're going to the effort of re-wiring to include isolator switches, why not simply situate the sockets where they are accessible without removing the appliance? -- *Plagiarism saves time * Dave Plowman London SW To e-mail, change noise into sound. |
#5
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Alternatively (and probably simpler) would a cooker isolator (switch
only), spurred off a socket on the kitchen ring, feeding the four under surface sockets for the appliances be acceptable? And could I wire those sockets in series with a suitable weight of T+E? I'm thinking that the sequence would be: Put in whatever switches you like. Provided that the appliance is connected via either an FCU or a plug and socket, then there is no requirement for switching. Just ensure that on a 32A ring, the switch must be double pole and rated at: one single socket = 13A (20A more likely to be found) one double socket = 20A more than one socket = 32A (45A more likely to be found) Alternatively, a 13A FCU may be used to switch for any number of sockets, provided the expected appliance load is below this, which it isn't. Personally, I used a 3 x 20A DP grid switch to switch my tumble dryer/washing machine and dishwasher independently, all fed off a dedicated 32A radial circuit. I used a junction box to drop the 6mm incoming to 3 x 2.5mm that would fit the switch terminals. As each switch only controls one single socket which will be fused in the plug, this is permissible for both short circuit and overloading. Finally, the cable run mustn't be done in 2.5mm cable after the switch if the third option (more than one socket not limited to 13A) is used. You must use at least 4mm, probably 6mm cable, which will be a pig to install, as getting 2 x 6mm into a wiring accessory will not be easy/possible. You may have to drop to 2.5mm in a large junction box just outside the socket (which is permissible as you are allowed to assume 20A max from a double socket or 13A max from a single). Christian. |
#6
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Thanks to all (i.e. the usual helpful few!)
To try and answer some of your questions: The units will all be built in and spread around an 'L' shaped area of worksurface interspersed with drawer units. I think that the drawer units really make access to sockets behind unreasonably fiddly and I'm not prepared to have FCUs or appliance sockets above the worksurface. There is only one 'cupboard' providing the possible option of locating 3 FCUs and then running radials to sockets close to each appliance. This under the sink which is approx 2/3 from the top of the upright in the L. This is why I said something about lengthy cables in the original post. If it was my choice I would not provide any isolation, but just put single, possibly switched, sockets close to each unit and use the MCB in the CU as an isolator. It is only the installers who said that each appliance must be supplied by an FCU/socket pair and cannot simply be plugged into the kitchen ring. I understand what you say (Christian) about using 6mm cable - I had feared as much! The CU is some distance from the kitchen and, needless to say, hidden in an under-stairs cupboard. In any case is it acceptible to have the MCB as the only way of isolating the kitchen appliances, especially the hood? If it is it might be easier to show SWMBO how to test the RCD which is separate from the CU and thus more accessible! A big red emergency off button has a certain appeal - is that feasible (only half joking)? Some sort of remote test switch for the RCD would have the desired result. Have I heard/read about kitchen over-heat sensors that can trip the power supply to the kitchen? Presumably they trip a suitably rated contactor? The ones supplying the last mainframe room that I worked in used to stick on!! Cheers guys Richard |
#7
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In article ,
Richard Savage wrote: It is only the installers who said that each appliance must be supplied by an FCU/socket pair and cannot simply be plugged into the kitchen ring. Who are they? I'd say they're talking ********. I'd certainly want reasonable access to the sockets, though. -- *If PROGRESS is for advancement, what does that make CONGRESS mean? Dave Plowman London SW To e-mail, change noise into sound. |
#8
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Every appliance I've seen has got an on/off switch. This is not allways double pole and what about repairs to said appliance ? Peter |
#9
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"Christian McArdle" wrote in message . net... Alternatively (and probably simpler) would a cooker isolator (switch only), spurred off a socket on the kitchen ring, feeding the four under surface sockets for the appliances be acceptable? And could I wire those sockets in series with a suitable weight of T+E? I'm thinking that the sequence would be: Put in whatever switches you like. Provided that the appliance is connected via either an FCU or a plug and socket, then there is no requirement for switching. Just ensure that on a 32A ring, the switch must be double pole and rated at: one single socket = 13A (20A more likely to be found) one double socket = 20A more than one socket = 32A (45A more likely to be found) Alternatively, a 13A FCU may be used to switch for any number of sockets, provided the expected appliance load is below this, which it isn't. Personally, I used a 3 x 20A DP grid switch to switch my tumble dryer/washing machine and dishwasher independently, all fed off a dedicated 32A radial circuit. I used a junction box to drop the 6mm incoming to 3 x 2.5mm that would fit the switch terminals. As each switch only controls one single socket which will be fused in the plug, this is permissible for both short circuit and overloading. Finally, the cable run mustn't be done in 2.5mm cable after the switch if the third option (more than one socket not limited to 13A) is used. You must use at least 4mm, probably 6mm cable, which will be a pig to install, as getting 2 x 6mm into a wiring accessory will not be easy/possible. You may have to drop to 2.5mm in a large junction box just outside the socket (which is permissible as you are allowed to assume 20A max from a double socket or 13A max from a single). Christian. Sorry you cant do this 2.5mm is limited to a 16a mcb ! Wire the appliances on the ring using 20A dp switches above each appliance with a socket below, the Hood should be on a switched fused spur (3Amp fuse) and the cooker in 6mm with a 45A DP switch within 2mtrs of Hob Peter |
#10
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Peter wrote:
Regs require that the means of isolation be double pole and readily accessible, if the socket is behind the washer then it is not. I think the strict requirement you mention applies only to electric motors - and I don't think washing machines count! For domestic appliances, functional switching as provided by the front panel is accessible, while isolation and switching-for-mechanical-maintenance are (I claim) adequately provided for by removing a plug from a socket. I'm sure we could argue the toss about corner cases where two faults (a live-to-casing *and* an earth continuity fault) make it dangerous to move a washing machine or similar to get at a socket hidden behind it; but domestic installs are typically designed under a single-fault assumption. Better practice is indeed to have either an FCU in an accessible position, mayhap as part of a gridswitch, or at least have the socket in a next-door base unit so that isolation doesn't require movement of the appliance; but I'm not convinced that the letter of the Regs is violated by the common arrangement with the socket at the back of a gap between applianceses... Stefek |
#11
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The CU is some distance from the kitchen and, needless to say, hidden in an under-stairs cupboard. In any case is it acceptible to have the MCB as the only way of isolating the kitchen appliances, especially the hood? If it is it might be easier to show SWMBO how to test the RCD which is separate from the CU and thus more accessible! No ! it is not and the Hood will need to be fused down via a 3AMP switched fused spur, now that you have said that the appliances will be built in they are classed as fixed for the regs and MUST have a means of isolation next to the appliance that is double pole. Peter |
#12
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So, does your sense of aesthetics rule out using grid-switch FCUs in the
relatively-distant cupboard? That'd take up only one double mounting box; and with FCUs controlling the spurs to each dedicated socket, providing closer protection for the cables, the runs from there to each socket can be in 2.5mmsq. The "Big Red Switch" does have appeal, but isn't feasible with a ring (not without bizarre contact arrangements to switch both sides of the ring *and* preserve continuity of the rest of ring when you bypass the relevant section). Unless, that is, you have a truly dedicated kitchen ring, and can replace the twin 2.5mmsqs running back to the CU with a single 4mmsq or 6mmsq (6mmsq is safe bet, 4mmsq needs calcs on permitted length), and you put a 45A cooker-style isolator at the point where the thicker incomer fed out into two arms of the kitchen ring... |
#13
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Stefek Zaba wrote: So, does your sense of aesthetics rule out using grid-switch FCUs in the relatively-distant cupboard? That'd take up only one double mounting box; and with FCUs controlling the spurs to each dedicated socket, providing closer protection for the cables, the runs from there to each socket can be in 2.5mmsq. The "Big Red Switch" does have appeal, but isn't feasible with a ring (not without bizarre contact arrangements to switch both sides of the ring *and* preserve continuity of the rest of ring when you bypass the relevant section). Unless, that is, you have a truly dedicated kitchen ring, and can replace the twin 2.5mmsqs running back to the CU with a single 4mmsq or 6mmsq (6mmsq is safe bet, 4mmsq needs calcs on permitted length), and you put a 45A cooker-style isolator at the point where the thicker incomer fed out into two arms of the kitchen ring... 'Tis indeed a dedicated kitchen ring. But I don't think that a Big Red switch will meet the aesthetic requirements of SWMBO. She has already vetoed red with aluminium edging as the colour scheme for the units ;-) Richard |
#14
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In article ,
Peter wrote: Every appliance I've seen has got an on/off switch. This is not allways double pole and what about repairs to said appliance ? Then make sure the one you buy has got a double pole switch. And when the appliance is moved for servicing, you unplug it. -- *Why don't you ever see the headline "Psychic Wins Lottery"? Dave Plowman London SW To e-mail, change noise into sound. |
#15
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Peter wrote: Sorry you cant do this 2.5mm is limited to a 16a mcb ! Wire the appliances on the ring using 20A dp switches above each appliance with a socket below, the Hood should be on a switched fused spur (3Amp fuse) and the cooker in 6mm with a 45A DP switch within 2mtrs of Hob Peter Similarly sorry. Come what may there will be no switches above the surface! In one instance (the W/M) that is for aesthetic reasons, in the other it is because the hob and sink are either above or below the units (the D/W and hood). Oh, and it is a gas hob (as mentioned in the initial thread) so we're only worrying about ignition power. The ovens are on the other side of the room with their own feed. Please keep the comments coming, being able to argue the toss with bods who understand the problem is sooo much more satisfying than trying to discuss it with SWMBO. Rgds Richard |
#16
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In article ,
Peter wrote: No ! it is not and the Hood will need to be fused down via a 3AMP switched fused spur, Bollox. It can be on a 3 amp fuse plug. Or run off the lighting circuit with no additional fusing. -- *Frankly, scallop, I don't give a clam Dave Plowman London SW To e-mail, change noise into sound. |
#17
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"Stefek Zaba" wrote in message ... Peter wrote: Regs require that the means of isolation be double pole and readily accessible, if the socket is behind the washer then it is not. I think the strict requirement you mention applies only to electric motors - and I don't think washing machines count! For domestic appliances, functional switching as provided by the front panel is accessible, while isolation and switching-for-mechanical-maintenance are (I claim) adequately provided for by removing a plug from a socket. I'm sure we could argue the toss about corner cases where two faults (a live-to-casing *and* an earth continuity fault) make it dangerous to move a washing machine or similar to get at a socket hidden behind it; but domestic installs are typically designed under a single-fault assumption. Better practice is indeed to have either an FCU in an accessible position, mayhap as part of a gridswitch, or at least have the socket in a next-door base unit so that isolation doesn't require movement of the appliance; but I'm not convinced that the letter of the Regs is violated by the common arrangement with the socket at the back of a gap between applianceses... Fixed appliances must be earthed when you remove a plugtop from a socket outlet you remove the earth therefore a double pole switch should be provided maintaining the earth bonding. Peter |
#18
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Peter wrote: Fixed appliances must be earthed when you remove a plugtop from a socket outlet you remove the earth therefore a double pole switch should be provided maintaining the earth bonding. Peter Well, FWIW the installation notes for both units (W/M and D/W) make no mention or distiction between free standing and building-in with regard to permanent earth connections. The only mention of permanent earthing is where the 13A plug is removed and the unit hard-wired into a permanent connection. In that instance, as you say above, the switch must be double poled with a min 3mm gap between poles and must not 'break the yellow and green cable at any point'. No mention of permanent earth when using a 13A plug. Richard |
#19
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"Richard Savage" wrote in message .. . Peter wrote: Fixed appliances must be earthed when you remove a plugtop from a socket outlet you remove the earth therefore a double pole switch should be provided maintaining the earth bonding. Peter Well, FWIW the installation notes for both units (W/M and D/W) make no mention or distiction between free standing and building-in with regard to permanent earth connections. The only mention of permanent earthing is where the 13A plug is removed and the unit hard-wired into a permanent connection. In that instance, as you say above, the switch must be double poled with a min 3mm gap between poles and must not 'break the yellow and green cable at any point'. No mention of permanent earth when using a 13A plug. The IEE Wiring regs do, that is why you dont plug in an immersion heater or storage heater etc etc Peter |
#20
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Peter wrote: No ! it is not and the Hood will need to be fused down via a 3AMP switched fused spur, now that you have said that the appliances will be built in they are classed as fixed for the regs and MUST have a means of isolation next to the appliance that is double pole. Peter My previous reply to your point above seems to have dissapeared into the ether. Copied he Sorry, didn't mean to omit that vital element from the equation.. What exactly is meant by 'next to' the appliance? I suspect that my '3 FCUs under the sink' solution will be chosen whether or not it qualifies. Ta Richard |
#21
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Peter wrote:
Fixed appliances must be earthed when you remove a plugtop from a socket outlet you remove the earth therefore a double pole switch should be provided maintaining the earth bonding. Piffle (in the domestic situation). You're seriously suggesting that the Regs somehow forbid having a washing machine, built-in microwave, wall-mounted convector heater, yada yada, sitting in a room, disconnected from the mains by virtue of being unplugged!? That they're supposed to have the Magic Green-n-Yellow Wire continuously attached from the moment they cross the threshold? Ye cannae be serious, jimmee... |
#22
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Peter wrote:
Sorry you cant do this 2.5mm is limited to a 16a mcb ! Sigh. So unfused spurs don't exist, right? Nor is it permissible to design a circuit where the nature of the load means an overload will not arise using circuit protection only for short-circuit conditions, but not for overloads? And I'm hallucinating when I see a 20A MCB 2.5mmsq entry in the Conventional Cricuits table (7.1) of the OSG? Hint - those are "rhetorical questions". Meaning, their factual answer stands in stark contradiction to your simplistic, and plain wrong, claim that "2.5mm is limited to a 16a mcb"). Yes, to use 2.5mm on circuits with protective devices rated over 16A needs a bit of thought, sometimes (gasp) some calculation of earth loop impedance in the cases where there isn't a precomputed Table in the OSG for us. And your advice at least errs on the side of caution. But accurate and complete it surely ain't... Stefek |
#23
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"Stefek Zaba" wrote in message ... Peter wrote: Fixed appliances must be earthed when you remove a plugtop from a socket outlet you remove the earth therefore a double pole switch should be provided maintaining the earth bonding. Piffle (in the domestic situation). You're seriously suggesting that the Regs somehow forbid having a washing machine, built-in microwave, wall-mounted convector heater, yada yada, sitting in a room, disconnected from the mains by virtue of being unplugged!? That they're supposed to have the Magic Green-n-Yellow Wire continuously attached from the moment they cross the threshold? Ye cannae be serious, jimmee... Well regs say so sockets are for portable appliances if said appliance is fixed then it should be wired via a switched isolator one exceptionn given is a clock. Peter |
#24
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"Richard Savage" wrote in message .. . Peter wrote: No ! it is not and the Hood will need to be fused down via a 3AMP switched fused spur, now that you have said that the appliances will be built in they are classed as fixed for the regs and MUST have a means of isolation next to the appliance that is double pole. Peter My previous reply to your point above seems to have dissapeared into the ether. Copied he Sorry, didn't mean to omit that vital element from the equation.. What exactly is meant by 'next to' the appliance? I suspect that my '3 FCUs under the sink' solution will be chosen whether or not it qualifies. Yes that is ok it just means adjacent to and accessible Peter |
#25
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"Stefek Zaba" wrote in message ... Peter wrote: Sorry you cant do this 2.5mm is limited to a 16a mcb ! Sigh. So unfused spurs don't exist, right? Nor is it permissible to design a circuit where the nature of the load means an overload will not arise using circuit protection only for short-circuit conditions, but not for overloads? And I'm hallucinating when I see a 20A MCB 2.5mmsq entry in the Conventional Cricuits table (7.1) of the OSG? Hint - those are "rhetorical questions". Meaning, their factual answer stands in stark contradiction to your simplistic, and plain wrong, claim that "2.5mm is limited to a 16a mcb"). Yes, to use 2.5mm on circuits with protective devices rated over 16A needs a bit of thought, sometimes (gasp) some calculation of earth loop impedance in the cases where there isn't a precomputed Table in the OSG for us. And your advice at least errs on the side of caution. But accurate and complete it surely ain't... The context in which the reply was given was reduction of cable size from 6mm to 2.5mm this has to be fused down, there is a limit to the amount of sockets on an unfused spur you cannot spur all the kitchen appliances onto a single 2.5mm cable sorry if this was not clear. Peter |
#26
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In article ,
Peter wrote: Fixed appliances must be earthed when you remove a plugtop from a socket outlet you remove the earth therefore a double pole switch should be provided maintaining the earth bonding. Please explain how you'd achieve this on a normal kitchen appliance supplied with a mains lead with 13 amp plug? -- *Who are these kids and why are they calling me Mom? Dave Plowman London SW To e-mail, change noise into sound. |
#27
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In article ,
Stefek Zaba wrote: Fixed appliances must be earthed when you remove a plugtop from a socket outlet you remove the earth therefore a double pole switch should be provided maintaining the earth bonding. Piffle (in the domestic situation). You're seriously suggesting that the Regs somehow forbid having a washing machine, built-in microwave, wall-mounted convector heater, yada yada, sitting in a room, disconnected from the mains by virtue of being unplugged!? That they're supposed to have the Magic Green-n-Yellow Wire continuously attached from the moment they cross the threshold? Ye cannae be serious, jimmee... Sounds like someone is trying to write their own regs. Most would say the only fixed appliance you'll commonly get in a kitchen is a large cooker that can't run off a 13 amp plug. What possible reason could there be for requiring earth continuity with the appliance unplugged? All the water connectors are non conducting, for gawd's sake. -- *It doesn't take a genius to spot a goat in a flock of sheep * Dave Plowman London SW To e-mail, change noise into sound. |
#28
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On 11 Oct 2004 "Peter" wrote:
Sorry you cant do this 2.5mm is limited to a 16a mcb ! Wire the appliances on the ring using 20A dp switches above each appliance with a socket below, the Hood should be on a switched fused spur (3Amp fuse) and the cooker in 6mm with a 45A DP switch within 2mtrs of Hob I think if you re-read the OP you'll find it doesn't mention a cooker at all. It mentions a hob, presumably gas, which has a mains ignition circuit so a 3amp fused plug or spur is adequate. -- Richard Porter Mail to username ricp at domain minijem.plus.com "You can't have Windows without pains." |
#29
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The context in which the reply was given was reduction of cable size from 6mm to 2.5mm this has to be fused down, there is a limit to the amount of sockets on an unfused spur you cannot spur all the kitchen appliances onto a single 2.5mm cable sorry if this was not clear. Agreed - a single 2.5mmsq feeding many sockets, not-fused-down, where the protective device is (say) a 32A MCB, is indeed a Bad Thing and should Not Happen. But a 6mmsq "backbone", with short 2.5mmsq feeds (unfused, connected via junction boxes say) to individual single or even (though it's sillier) double sockets, would be compliant, though not a Conventional Final Circuit. Each such single appliance-feeding socket (a) would be protected against fault current by the upstream 32A MCB - here the "short" feed is important to keep the earth loop imedance low, so that operation of the MCB in the required 0.5s can be guaranteed, and the temperature rise in this faulting cable can be kept within limits; (b) would be incapable of producing an overload for the rating of the short length of 2.5mmsq cable, since you can't pull a sustained 27A out of a single socket (RefMeth1 rating of 2.5mmsq), hard to do so even out of a double, and the actual connected load - single white-goods appliance - will in fact pull no more than rating plate says, prolly 2kW = 8A at peak water-heating time for a "modern" dishwash, possibly the full 3kW = 12A for an older/fancier/faster water-heating appliance; (c) closer-rated fault-current protection will be provided by the plug in't fuse. It's actually a completely direct analogue of the "normal" unfused spur in 2.5mmsq taken off a 32A 2.5mmsq-both-ways ring: the ring is fused at higher than the rating of the spur cable, but the combination of plugfuse and circuit-MCB provide fault protection for the spur cable, while overload is "designed out" by fitting only one power take-off point, either single or double socket. Having said all that, and certain as I am that design calcs would sanction such a layout in the right circs, I'd still shy away from installing a circuit like that in an ordinary domestic setup: it's simply too unintuitive for a subsequent householder or inspecting/minor-worksing electrician to feel comfortable with. Having had, in the previous house, a period of enthusiasm for FCUs with directly-wired-in appliances, and then been inconvenienced when repairers have needed to reliably disconnect the appliance or wheel in a spare, I've come to appreciate the wisdom of the standard arrangement with FCU to act as control switch for easy-to-operate isolation, feeding a conventional 13A socket (unswitched for preference) at the back of the appliance. Stefek |
#30
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Peter wrote:
"Stefek Zaba" wrote in message ... Peter wrote: Fixed appliances must be earthed when you remove a plugtop from a socket outlet you remove the earth therefore a double pole switch should be provided maintaining the earth bonding. Piffle (in the domestic situation). You're seriously suggesting that the Regs somehow forbid having a washing machine, built-in microwave, wall-mounted convector heater, yada yada, sitting in a room, disconnected from the mains by virtue of being unplugged!? That they're supposed to have the Magic Green-n-Yellow Wire continuously attached from the moment they cross the threshold? Ye cannae be serious, jimmee... Well regs say so sockets are for portable appliances if said appliance is fixed then it should be wired via a switched isolator one exceptionn given is a clock. Peter I bet all of those built in kitchen appliances are supplied with moulded on plugs!! Peter D |
#31
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In article ,
Stefek Zaba wrote: I've come to appreciate the wisdom of the standard arrangement with FCU to act as control switch for easy-to-operate isolation, feeding a conventional 13A socket (unswitched for preference) at the back of the appliance. Why use an FCU if there's a conventional plug? Wouldn't a simple 20 amp DP switch be neater and less confusing? -- *A cubicle is just a padded cell without a door. Dave Plowman London SW To e-mail, change noise into sound. |
#32
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"Dave Plowman (News)" wrote in message ... In article , Peter wrote: Fixed appliances must be earthed when you remove a plugtop from a socket outlet you remove the earth therefore a double pole switch should be provided maintaining the earth bonding. Please explain how you'd achieve this on a normal kitchen appliance supplied with a mains lead with 13 amp plug? you dont its classed as portable Peter |
#33
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Sounds like someone is trying to write their own regs.
Most would say the only fixed appliance you'll commonly get in a kitchen is a large cooker that can't run off a 13 amp plug. Most people are not qualified to know different What possible reason could there be for requiring earth continuity with the appliance unplugged? All the water connectors are non conducting, for gawd's sake. the same reason the metal sink is earthed its called bonding Peter |
#34
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"Stefek Zaba" wrote in message ... The context in which the reply was given was reduction of cable size from 6mm to 2.5mm this has to be fused down, there is a limit to the amount of sockets on an unfused spur you cannot spur all the kitchen appliances onto a single 2.5mm cable sorry if this was not clear. Agreed - a single 2.5mmsq feeding many sockets, not-fused-down, where the protective device is (say) a 32A MCB, is indeed a Bad Thing and should Not Happen. But a 6mmsq "backbone", with short 2.5mmsq feeds (unfused, connected via junction boxes say) to individual single or even (though it's sillier) double sockets, would be compliant, though not a Conventional Final Circuit. Each such single appliance-feeding socket (a) would be protected against fault current by the upstream 32A MCB - here the "short" feed is important to keep the earth loop imedance low, so that operation of the MCB in the required 0.5s can be guaranteed, and the temperature rise in this faulting cable can be kept within limits; (b) would be incapable of producing an overload for the rating of the short length of 2.5mmsq cable, since you can't pull a sustained 27A out of a single socket (RefMeth1 rating of 2.5mmsq), hard to do so even out of a double, and the actual connected load - single white-goods appliance - will in fact pull no more than rating plate says, prolly 2kW = 8A at peak water-heating time for a "modern" dishwash, possibly the full 3kW = 12A for an older/fancier/faster water-heating appliance; (c) closer-rated fault-current protection will be provided by the plug in't fuse. It's actually a completely direct analogue of the "normal" unfused spur in 2.5mmsq taken off a 32A 2.5mmsq-both-ways ring: the ring is fused at higher than the rating of the spur cable, but the combination of plugfuse and circuit-MCB provide fault protection for the spur cable, while overload is "designed out" by fitting only one power take-off point, either single or double socket. I agree here sorry if I misunderstood what you saiid before Having said all that, and certain as I am that design calcs would sanction such a layout in the right circs, I'd still shy away from installing a circuit like that in an ordinary domestic setup: it's simply too unintuitive for a subsequent householder or inspecting/minor-worksing electrician to feel comfortable with. Having had, in the previous house, a period of enthusiasm for FCUs with directly-wired-in appliances, and then been inconvenienced when repairers have needed to reliably disconnect the appliance or wheel in a spare, I've come to appreciate the wisdom of the standard arrangement with FCU to act as control switch for easy-to-operate isolation, feeding a conventional 13A socket (unswitched for preference) at the back of the appliance. Well then we agree Peter |
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"Dave Plowman (News)" wrote in message ... In article , Stefek Zaba wrote: I've come to appreciate the wisdom of the standard arrangement with FCU to act as control switch for easy-to-operate isolation, feeding a conventional 13A socket (unswitched for preference) at the back of the appliance. Why use an FCU if there's a conventional plug? Wouldn't a simple 20 amp DP switch be neater and less confusing? Yes I did suggest this too Peter |
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Dave Plowman (News) wrote:
Why use an FCU if there's a conventional plug? Wouldn't a simple 20 amp DP switch be neater and less confusing? Yes, it would - better all round, saving the hassle of the "wrong" fuse blowing. Only justifications for an FCU would be if you were feeding multiple socket locations, or "can't find a 20A DP sw in old-georgian scroll-effect brass, but can get an FCU in same this rainy Sunday" (or whatever weirdo decorative demand has been laid down by the domestic authorities ;-). But you're quite right, the 20A DP switch wins in practically all respects. Stefek |
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the same reason the metal sink is earthed its called bonding
You really need to do some more reading. There is no requirement to bond a metal sink. Indeed it may be increasing risk to do so. We're talking about kitchens here. Christian. |
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On 12 Oct 2004 Peter wrote:
Peter wrote: Well regs say so sockets are for portable appliances if said appliance is fixed then it should be wired via a switched isolator one exceptionn given is a clock. I bet all of those built in kitchen appliances are supplied with moulded on plugs!! They may look "built-in" but I bet the appliances we are talking about (a washing machine and a dishwasher) are in fact free-standing, probably on castors, and just slide into purpose-made slots in the kitchen units. In that case they are not "fixed" and can have normal flexes and plugs. -- Richard Porter Mail to username ricp at domain minijem.plus.com "You can't have Windows without pains." |
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In article ,
Peter wrote: Please explain how you'd achieve this on a normal kitchen appliance supplied with a mains lead with 13 amp plug? you dont its classed as portable Indeed. Could you give some examples of domestic kitchen appliances - apart from some large cookers - which aren't? -- *Red meat is not bad for you. Fuzzy green meat is bad for you. Dave Plowman London SW To e-mail, change noise into sound. |
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On 12 Oct 2004 "Peter" wrote:
Sounds like someone is trying to write their own regs. Most would say the only fixed appliance you'll commonly get in a kitchen is a large cooker that can't run off a 13 amp plug. Most people are not qualified to know different If you don't know the relationship between volts, amps, watts and ohms and can't read a rating plate on an appliance then you shouldn't be playing around with the electrical installation at all. On the other hand if you do understand the underlying science and know a few basic principles you'll probably do a safe job even if it doesn't comply with the last detail of the 16th edition. Some cookers can run off 13amps e.g. a single built-in oven or a small electric hob or a dual-fuel cooker. -- Richard Porter Mail to username ricp at domain minijem.plus.com "You can't have Windows without pains." |
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