Residential 240v issue with electric dryer

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Old 12-09-18, 07:33 AM
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Residential 240v issue with electric dryer

A friend if mine attempted to repair her dryer, via YouTube videos, and created a tangled mess. She changed out almost all the electrical components and said she was blowing up door switches, anyway horse first thing on my check is power so I check my power supply at the receptacle I have 240v Line 1 to line 2 I have 110 volts Line 1 to neutral as well as line 2 to neutral. these readings were taken with the power cord isolated from the machine as soon as I connect the power cord to the machine at the terminal block my readings change Line 1 to neutral I have 110 , line 2 to neutral I have 110, Line 1 to line 2 I have zero. What the heck is that? Simply just put the power cord on a machine with no interruption
 
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Old 12-09-18, 07:53 AM
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Did you measure at least twice? For electrical that means, after setup A you measured 240 volts and after setup B you measured 0 volts, did you go back to setup A and measure 240 volts and then repeat setup B getting zero volts?

In this specific case you connected the power cord to the machine and got 0 volts. Did you unhook the cord and get back 240 volts?

There could be a loose connection in one of the hot lines going back to the panel. Enough current (milliamperes) gets through to let your meter show 240 volts from that hot line to the other hot line. When the dryer is turned on it tries to draw 20 or so amps. The loose connection won't pass such a large current and the result is the voltage as measured beyond the loose connection dropping to near zero. The loose connection was probably there before your friend started trying to fix things.

Something else you can try: Get some wires with alligator clips on the ends (you may have to shop far and long for them now that Radio Shack is defunct) Connect a hair dryer (via the plug prongs) to line 1 and neutral and measure voltage with the hair dryer on (medium heat) and off. Repeat connecting to Line 2 and neutral. Unfortunately I have no shortcuts to find a loose connection if the above test suggests that.
 

Last edited by AllanJ; 12-09-18 at 08:35 AM.
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Old 12-09-18, 10:32 AM
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Allan has good comments. Here is one other way. Problem is the correct usage of a voltmeter.

Get a edison base test lamp with the pigtail wire leads. Screw in a 15W 120v incandescent bulb. Use that to detect 120/240, etc. That bulb will put up with 240v for a little while. Don't use a greater wattage on 240....

https://www.legrand.us/passandseymou...older/201.aspx
 
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Old 12-09-18, 10:34 AM
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Residential 240 issue

Thanks for the reply I did do the back and forth after my initial check. Especially since that was not a common occurrence, I emailed a copy of the schematic to an acquaintance of mine who is pretty sharp with this stuff, told him the scenario, and 5 minutes later, emailed me and said I got a problem with neutral somewhere.Now he's out, can't find him.
my confusion, not so far as the machine goes, but how the voltage simply disappears when all I'm doing is placing the wires in the terminal board, soon as I take them off, my 240 comes back. This just seems so out there, I wouldn't believe anyone telling me this story
 
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Old 12-09-18, 10:42 AM
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common problem; cars, industrial, residential, etc. Bad connection upstream.

Lowes shows to have that lamp socket I recommend. $3.58
 
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Old 12-09-18, 10:47 AM
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A typical dryer problem I see constantly is loose terminals at the dryer connection block but that is ruled out since you are working there.

If you are using a receptacle and a cord with a plug...... the problem is most likely in the receptacle. Usually a loose tang on one leg.
 
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Old 12-09-18, 02:34 PM
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My current home has aluminum on that run. I caught a loose connection at the breaker itself.
 
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Old 12-09-18, 02:51 PM
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Yes..... if you rule out the receptacle..... unless the line is spliced somewhere..... the next place to check is at the breaker. With the dryer connected..... you need to confirm 240vAC across the two pole breaker.
 
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Old 12-10-18, 02:45 AM
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Residential 240 issue

I think you guys are misinterpreting what I posted. I have checked the breakers I have 240 v on the output. Breaker (line) 1 to ground 110 v, Breaker (line) 2 to ground 110 v, line 1 to line 2 240 v. I check the receptacle and have the same voltage. I isolate the dryer power plug and I get the same voltages. So now I know up to and until I touch the machine with those 3 conductors I still have proper voltage. Only after I hook wires to machine terminal board do I lose the line to line voltage
 
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Old 12-10-18, 05:45 AM
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Hi, if you remove the wiring from the terminal strip that go into the dry, what readings do you get?
Geo
 
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Old 12-10-18, 01:01 PM
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Actually, you are not understanding what we are trying to say. You cannot test bad connections with a voltmeter with no load. Load the system, or alternately, use a Voltmeter with an inherent load. Like a light bulb.
 
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Old 12-11-18, 08:01 AM
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Building a 240 volt test light.

Get two porcelain lamp holders or two of those sockets pictured in the link above.

Connect gold terminal or black wire of one socket to silver terminal or white wire of the other.

Connect say 24 inch test leads (two of them) to the other two terminals or leads of the sockets respectively.

Use wire nuts to fasten wires to one another. Just twisting or tape is not good enough.

For the porcelain sockets or optionally for the rubber sockets fasten them to a piece of wood.

Put alligator clips on the free ends of the test leads.

Screw in incandescent bulbs of the same kind and size , suggest about 50 watts.

The bulbs will glow dimly for 120 volts and "full" brightness for 240 volts. This test light is not intended to detect in between incorrect voltages or voltage drops; you need a voltmeter for that.
 
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Old 12-12-18, 05:29 AM
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Electric dryer fiasco

A friend of mine attempted to repair her maytag Medc300bw dryer via YouTube tutorials and failed miserably. In the end she changed out door switch, thermal fuse, operating thermostat, breaker, and receptacle. When she tried to start it, it blew up the door switch, I corrected some wiring she got wrong, but now my 240 volts coming from the receptacle is lost when I hook up machine to power supply. Please advise
 
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Old 12-12-18, 06:35 AM
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Will be hard to tell what was done without seeing it. In console there should be a tech sheet with a wiring diagram. You will have to follow the wires out to see what she messed up. Look at the main power cord to be sure the outside wires are on the outside lugs. Sounds like she has something either pinched or a wire to ground. Check the wires to the door switch they are easy to pinch on some dryers.
 
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Old 12-12-18, 06:41 PM
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I combined your two threads. You've already received several responses and methods to locate your problem. Starting a new thread just confuses the issue.
 
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Old 12-12-18, 07:13 PM
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You have to plug the dryer in. Check it at (C). If there is no 240vAC there...... check it at the screws (B) on the receptacle. If you have it there...... the receptacle is defective. If you don't have 240v at (B) you need to check at the main breaker (A).

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