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Around a year ago, my parents got a new drying machine installed. The dryer didn't come with any cables, and the when my parents called the company, they told them that it was the customer's responsibility to supply wiring and connect the machine. I thought that was crazy, but my parents got an electrician to set up the machine.

Over the year, the machine's electric switch got fried over 5 times. Every couple of months, either the switch shorts, or the cables melt in the switch, and just yesterday, I woke up to find that the wall outlet's hot and neutral wire have turned into charcoal, even though the switch is perfectly fine.

We've tried a lot of switches, we changed the cables, we switched electricians, but nothing is working. What the hell is going on?

The dryer's hot and neutral wires are connected to the wall's through the switch. The dryer is rated at 25 amps. The tripper is rated at 30 amps. We have tried switches from 30 up to 45 amps. Nothing seems to work.

Any help is greatly appreciated.

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  • does the panel breaker ever trip off? does the dryer actually work right at any time? when i tried to imagine how it could be miswired i came up with dozens of ways, – Skaperen Jun 20 '15 at 9:19
  • The tripper only trips when I turn on both the dryer and air conditioning. The air conditioner has a tripper of its own (30 amps), but it seems to me that the dryer and the conditioner share the tripper (the two trippers are controlled by only one switch). It also trips only when I turn on both the dryer and the conditioner at about the same time - if I turn on the dryer for a little while, then turn on the conditioner, breaker doesn't trip off. I believe that's because the dryer draws the max amount of current as it starts working (ie heats up). – Malfunction Jun 20 '15 at 9:39
  • And the dryer does work correctly - it's just the wiring that's the problem. After changing the cables or the switch, everything works fine for about a couple of weeks, but that's about it. – Malfunction Jun 20 '15 at 9:40
  • Where on the planet are you? – ThreePhaseEel Jun 20 '15 at 17:01
  • The middle east, Saudi Arabia to be exact. – Malfunction Jun 21 '15 at 9:52
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In the first place, having two pieces of equipment (the dryer and the aircon) that both need quite a bit of power, both on the same circuit is probably not a good idea. You have already noticed there is interference between them. So the first step would be to get one or the other onto a second circuit. I don't know how electrical codes are in your country (which you haven't specified - it may be significant due to different voltage levels), but in most of Europe we tend to put:

  • lighting on one phase
  • the kitchen plaque (a high power consumer) on a second phase
  • power outlets on a third phase.

The name of the game is to spread consumption equally across all three AC phases.

In the second place, you say the dryer is rated at 25A. It would be nice to verify that it is really drawing that much current but no more, for example with a clamp ammeter (e.g.: http://en-us.fluke.com/products/clamp-meters/ ). Perhaps somebody in the trade could lend you one.

If it really draws that much current (or almost as much), this is indeed a piece of equipment with a high power requirement, that I feel should go on its own circuit all by itself.

Additional note: there are two kinds of electrical "tripper". One is the classical circuit breaker, that breaks the circuit when excessive current draw takes place. This is what happens when you have a short-circuit within the apparatus.

The second type is a differential breaker, that actuates when a large difference in current takes places between the phase and neutral wires. The idea is that the difference in current must be going somewhere - possibly directly to the machine chassis and then to earth. This is quite dangerous for the human operator, since if he/she has wet hands and a good connexion to earth, the excess current could very well short to earth through the operator.

It is standard practice (at least in Europe) for several circuit breakers to be protected by a single differential breaker. If any of the circuits develop a short to earth, the differential will trip leaving all circuits open.

The OP would need to have the dryer checked, that it has no internal short circuits. This can be done by connecting the apparatus to another circuit.

He should further check it has been correctly wired to AC. Swapping the neutral wire with the earth is a relatively easy mistake to make if non-standard color wires have been used. Hint: the earth wire and connexion should be green/yellow and have a slightly larger section than neutral and live.

HTH

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  • I'm not entirely familiar with how breakers are designed, but the dryer is the only thing running off the 30 Amps tripper. The air conditioner runs on another tripper, 30 amps, again by itself. It's just that both these trippers are controlled by the same switch (ie when one trips, so does the other). – Malfunction Jun 21 '15 at 9:56
  • The problem is that we don't run both the air conditioner and the dryer at the same time - all the problems with the dryer happened when it was running by itself. – Malfunction Jun 21 '15 at 9:57
  • OK, I think I can finally see what is happening. Am editing my answer to take into account your latest remarks. – ALAN WARD Jun 21 '15 at 17:22

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