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Author Topic: Interesting electrical problem I thought I would share..  (Read 110 times)

Offline Wedgeman55

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Interesting electrical problem I thought I would share..
« on: June 27, 2013, 03:21:29 AM »
Ran into an electric dryer,   wouldn't run.   Pulled pigtail out a little,  checked voltage - 248.    Checked everything,   no bad wires,  nothing.    Then,  for the hell of it,  clamped meter leads on pigtail leads near terminal block.    Meter read 248.   When I pressed start button,   voltage went to zero.   
 
Turned out, the wire connections in a junction box leading to the 30 amp fuse box near dryer was heavily corroded.    I repaired all of wiring,  and then it worked fine.     
 
Something to think about incase you run into the same thing.     I have run into stuff like this before,  but it makes you aware that you have to make sure you are checking voltage under a load to find something like this.   Or it will just drive you crazy.   
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Offline RAH52

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Re: Interesting electrical problem I thought I would share..
« Reply #1 on: June 27, 2013, 05:47:11 AM »
Good post ,lots of times you check for voltage get the reading you want and assume all is ok .Don't assume anything .

Offline LowSL2

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Re: Interesting electrical problem I thought I would share..
« Reply #2 on: June 27, 2013, 09:17:17 AM »
That's a good tech tip. I've run into this a few times over the years on dryers and electric ranges. Its always good practice to check voltage at the outlet. At the same time I visually inspect it, and the plug on the cord. If I see anything out of the norm, like burnt/corroded terminals, I inform the customer they need to have an electrician replace the outlet.

This happens a lot when people replace an old dryer or range. I always get into an argument that the old machine worked fine and that this dryer caused the problem, blah, blah, blah.

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LowSL2
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Offline hesterappliance

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Re: Interesting electrical problem I thought I would share..
« Reply #3 on: June 27, 2013, 09:28:04 AM »
Bad ground wire. I see that about four times a year.I sometimes meet maintenance men at the house because they don't no about amperage drop.

Offline theoldstoveguy

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Re: Interesting electrical problem I thought I would share..
« Reply #4 on: June 27, 2013, 07:35:10 PM »
I have seen 4 times in the last 6 months where I have to pull a wall oven for burned wiring to elements. Opening the electrical box to disconnect wires as the box is above the oven? They have 3 wires only in the box. 1 leg is line 1 the other line 2 but this kills me. The third wire Neutral (no 4 th wire) is the BARE ground wire. You can't have a bare wire carry current and the neutral is needed for the clocks and such. I tell them this is wrong as a neutral can't be a bare wire as it carries current. Response is the building inspector passed it so it must be OK. I leave the breaker off and have them sign the invoice stating so.

Offline Patricio

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Re: Interesting electrical problem I thought I would share..
« Reply #5 on: June 27, 2013, 11:34:14 PM »
I found something similar on a couple of Roper dryers.    Test for voltage every where on a non working machine.   Finally I clamp leads on timer wires & pushed start button.  Voltage dropped out & I had it, timer contact resistance dropped the voltage, current would not flow.  When I released start button voltage returned.  Diagnoses -  bad timer.
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Offline ApplianceGuru

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Re: Interesting electrical problem I thought I would share..
« Reply #6 on: June 29, 2013, 12:19:13 AM »
You can't have a bare wire carry current and the neutral is needed for the clocks and such. I tell them this is wrong as a neutral can't be a bare wire as it carries current. Response is the building inspector passed it so it must be OK. I leave the breaker off and have them sign the invoice stating so.

Yeah, it doesn't seem very safe, does it.  However, it does work just fine 99.99% of the time.  You probably understand this, but I am going to go over it for those who might not understand why.

The issue is not whether the wire is carrying current, but whether or not YOU wlll carry current.  Nuetral is assumed to always be at zero voltage potential relative to ground.  In theory, the neutral wire is the easiest electrical current path to ground.  We should be able to touch that bare wire anywhere and not get shocked.

The problem arises when a loose or dirty connection occurs somewhere along the neutral wire.  Then suddenly a human becomes a better path for electricity than the bare write.

ZAP!

This is no different than a three-prong dryer/range cord.  I can see this passing code as long as all three wires are enclosed in an insulated tubing or sheath.  The four prong dryer/range cord is a little safer, since it's ground connection comes from the neutral at the breaker box, instead of nuetral at the appliance.
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