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| Thread ID: 69082 | 2006-05-21 06:58:00 | Another question for the forum sparky types | personthingy (1670) | PC World Chat |
| Post ID | Timestamp | Content | User | ||
| 456599 | 2006-05-22 16:15:00 | OK I'll stick my neck out!! No legal reason not to come off the H/W circuit, as long as the feed to the towel rail is the same size cable as the H/W feed . Then the circuit itself is still protected by the fuse, which is there to protect the cable . It would be better to come off the light circuit if you can . And a permanently wired appliance doesn't have to be on an RCD . I've actually had some towel rails trip an RCD, so had to feed them off a heater circuit in the bathroom . As to the home owner doing any wiring, no one is allowed into a switch board . And all home owner work has to be checked and certified by a registered inspector, not electrician . I can't certify any one elses work, only my own . And if you don't get it checked and certified, the insurance company mightn't pay out in case of fire . I don't feel using the hot water heater feed as service for the towel heater is a good idea . Just for giggles, assume that each leg of the heater is fused at 30 amps, then the towel heater will also work with that value too . . . . and a 30 amps fuse for a device that pulls maybe 1 or 2 amps is not going to be a good idea . Do you understand how bad of a short the towel heater would have to have to trip a 30 amp fuse? Does thermonuclear meltdown ring a bell? Not safe at all . . . . . in fact very dangerous . :( And as far as the idea that the fuse is just to protect the in-wall wiring, although it's a good idea to not be able to see the wires glowing thru the walls, is to protect the consummable (human) who uses a device that is on the terminal end . Houses can be replaced, humans on the other hand require lots of paperwork by the coroner, police and courts when they expire, especially from bad wiring and do-it-yourself'er installations . :annoyed: |
SurferJoe46 (51) | ||
| 456600 | 2006-05-22 21:17:00 | Just for giggles, assume that each leg of the heater is fused at 30 amps, then the towel heater will also work with that value too....and a 30 amps fuse for a device that pulls maybe 1 or 2 amps is not going to be a good idea.Do you understand how bad of a short the towel heater would have to have to trip a 30 amp fuse? Does thermonuclear meltdown ring a bell? Not safe at all.....in fact very dangerous. Ok, another way to look at it.Our stove circuits are fused/circuit breakered at 30 amps, and a lot of stoves now on the market don't have any fuses in them, relying on the main fuse.You can plug your shaver into the ppt on the stove.........Powerpoint circuits are fused at 20 amps, my phone charger doesn't take that.And most home hot water circuits are 16 amp here. So we fuse according to the current ratings of cable, not what is going to be plugged in. And all new light/powerpoint circuits from a switchboard have to have an RCD fitted.It doesn't stop you getting a belt ,but is safer!! |
Neil McC (178) | ||
| 456601 | 2006-05-22 21:22:00 | Not safe at all . . . . . in fact very dangerous . :( And as far as the idea that the fuse is just to protect the in-wall wiring, although it's a good idea to not be able to see the wires glowing thru the walls, is to protect the consummable (human) who uses a device that is on the terminal end . The lack of an RCD (or GFCI) would be a valid concern . As I mentioned before currents of 1mA can be fatal in some circumstances . A typical human could draw 230mA from a 230v contact . A typical RCD will trip on 30mA, RCDs in medical use trip at 10mA but Fuse values start around 5 Amps . Fusing can only be for the cables . |
PaulD (232) | ||
| 456602 | 2006-05-22 21:48:00 | Well . . . NO! . . . Not really! The wire is designed to carry the current to the device at hand, and the fuse/breaker is set at approximately 105-110% PEP of the device in question for surge capacity . The draw of the device must be calculated into the equation . . . I run wiring for a living and on a typical electric stove run, I am allowed to use 8ga copper, 4-conductor + ground for distances under 75 feet . Over that distance, I have to increase the size of the wire . . . in this case to 6ga or better, the same number of conductors . Now, if you have a duplex receptical on the stove front to plug in a mixer or some other tool, it HAS TO BE seperately fused to the max allowable current that 99% of such devices should attain . Most draw an amp or two (we use 110v AC for our stuff here, 220v or 208v for our heavier equiptment) . So, we typically use a 15 amp/110v receptical, although 20amp/110v units are available . The GFCI (required on installations after a certain date) must protect the auxillary device, not the stove . So, here I have a stove on 220v AC that draws 50 amps per leg thru #8ga copper multi-strand cable, 4-conductor (2 legs of 110v, 2 matching ground legs, and 1 aux ground wire . . . all of the same gauge), for a distance of less than 75 feet . If I have a duplex receptical on the stove front (actually unheard of here in the US nowadays because of the differential draw on the legs from the 220v side), it should be seperately fused for the anticipated draw . I was wondering why you had so many thoughts on the feasability/advisability of the installation you want . . . now I see . It ain't a good idea to break a 220v circuit and saddle it also with a 110v tap on one leg or the other . It will unbalance the whole circuit . But that's US law . . we don't typically use 220v as our primary current . Feeling that you should not put the towel heater on the same circuit as the water heater is still my thought for various reasons . . . the rule youse guys have about night current or whatever that is; the fact that you have a very minimal draw from that towel heater on a circuit designed to trip off at much higher rates; the possibility that I may misunderstand that you do or don't have GFCIs on your water heaters . If you have a device that draws 50 amps and you are rated at 30 amps in the wiring, and the breaker is set at 50 amps, them there's a serious mis-balance . Protection must consider all the parts of the system . You can over-rate the wire by using larger diameter, the fuse/breaker is not there to protect the wire . . . but the device on the end of the wire . Wiring protection is secondary . . . the wire itself must be up to the draw of the stove or water heater plus a fudge factor of about 10% in this case . I am not trying to quote NZ electrical codes, just some common sense . . . electricity is still electricity even if you are upside down in NZ and drive on the wrong side of the road . |
SurferJoe46 (51) | ||
| 456603 | 2006-05-22 22:07:00 | SurferJoe, NZ systems are a tad different to American systems in so much as almost all domestic installations use a single phase 230volt supply for the whole house . Phase, the hot wire is fused in some way . Nuetral, the return wire is not fused, and is grounded at various points as well . We therefore do not usually have fuses on each leg of the supply for a stove or HWC . There are some houses with a 2 or 3 phase supply, but this is more usually found in industrial installations . It's a little different from your 110 - 0 - 110 volt system where one has 2 opposing hot wires allowing 220volts supplies for heavy draw appliances such as water heating, ovens, aircon, etc, and 110v supplies for your lighter domestic lights and appliances Hot water supplies are usually set up with a 20amp circuit breaker, or less, which is the same as how our plug circuits are set up, apart from the HWC being controlled externally by the power companys to keep peak demand slightly under control . Back to the towel rail . . . . . Its going to be added to the underloaded lighting circuit, and share a few lights with a 10 amp breaker . Hopefully it doesn't trip the house RCD, if it does it's gone . |
personthingy (1670) | ||
| 456604 | 2006-05-23 02:26:00 | . . . Protection must consider all the parts of the system . You can over-rate the wire by using larger diameter, the fuse/breaker is not there to protect the wire . . . but the device on the end of the wire . Wiring protection is secondary . . . the wire itself must be up to the draw of the stove or water heater plus a fudge factor of about 10% in this case . Taurine excreta, Joe . The fuse or breaker is there to protect the fixed wiring (and thus the whole house from fire) . It can't protect the "device on the end of the wire" . If the protection device is needed, it's all over for the device; that's why the excess current has happened . . . . Firstly, are you planning on connecting the heater rail in series or in parallel . I'm worried about the current draw on the connection, switch and wiring . Reckon at the very least you will blow the fuse . The peak current when the water heater switches on will blow your lights out!! . . . Words (almost) fail me . Connecting a towel rail (about 60W) in series with a WHC element(2-3 KW) would not produce any surges, let alone huge ones . (Their turn on current would be just about the same as the running current: they don't get hot enough for their resistance to vary significantly . The total current would be just under 60W . Connecting in parallel, as is normal in electrical wiring, the total load would change from 2-3 KW to (2-3 KW + 60 W) . Not enough difference to bother fuses or circuit breakers which would require 2X the rated current to operate immediately . Again, there would be no surges . |
Graham L (2) | ||
| 456605 | 2006-05-23 02:53:00 | Absolutely correct, Graham L. Unfortunately this sentence did not convey what I was thinking. What I was worried about if someone, maybe himself was to get electrocuted by faulty wiring in a damp atmosphere then the HWC fuse would not protect him. The reference to series or parallel wiring was to see if he knew the difference. If he doesn't, do you still think he should do the wiring himself? The reference to "blowing your lights out" had nothing to do with the lighting circuit, rather I meant it could possibly kill him. Hope this clarifies the issue. BURNZEE |
Burnzee (6950) | ||
| 456606 | 2006-05-23 03:03:00 | If a fuse has a rating of about 5mA, then it may offer some protection. | Terry Porritt (14) | ||
| 456607 | 2006-05-23 04:06:00 | The reference to series or parallel wiring was to see if he knew the difference. If he doesn't, do you still think he should do the wiring himself?The reference to wiring a towel rail in series with the HWC was so of the wall that "he" didn't consider it worth humoring with acknowledgment. | personthingy (1670) | ||
| 456608 | 2006-05-23 14:36:00 | Talkin' to a Building Technology Consultant today, (how's that for a BS title!!) and I put your question to him. As I recall, your question was if you could LEGALLY wire in your towel rail. Anyway, he put me onto the relevant law and website where it can be viewed. Thought it might be handy so here they are: The Law is New Zealand Electrical Code Of Practice 51 (2004), it can be viewed here (http:) They also have a short brochure called DOING YOUR OWN ELECTRICAL WORK SAFELY AND LEGALLY (2004) which can be viewed here (www.ess.govt.nz) NZECP 50 may also be relevant. Hope this helps. BURNZEE |
Burnzee (6950) | ||
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