190v in house? fried dish washer


  #1  
Old 05-24-06, 10:00 AM
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190v in house? fried dish washer

heyho,
my parents asked me to fix the dishwasher. someone told them that BOSH dishwashers draw a lot of amps and the wiring to the machine needs to be replaced. the connections at the unit fried the wiring a little bit and the machine wouldn't work.

the unit only has 16 guage wire on it, and right now there's 14 guage wire running to the unit - but its coming from a 20 amp breaker.

wierd thing is, when i tested the volts coming out of this wire my meter read 190v. and then, when i went to check it on other outlets the whole house reads 190v. whats going on? is my meter broken? or could the house be really recieving 190v? i'm going to check my meter in another town soon and i'll post what it reads.

as for the dishwasher, should i replace the breaker or the wiring? anybody know if BOch dishwashers would need to draw 18 amps? if so, why would it be wired with 16 guage wire?

thanks a lot for your inputs.
max
 
  #2  
Old 05-24-06, 10:19 AM
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Several things.

Manufacturers are allowed to use smaller wire in their appliances than the NEC requires for the wiring that you and I and anyones else installs. The 16 gage wire in the dishwasher is fine, assuming that it is original to the dishwasher.

The 14 gage wire in the wall that is on a 20 amp breaker is a problem. You must either install 12 gage wire, or change the breaker to be a 15 amp breaker. I am not familiar with BOSH dishwashers, but you can check their web site, the owners manual or call their 800 number and find out what size circuit is required. I would be surprised if it's a 20 amp circuit, but if it is then you need 12 gage wire and a 20 amp breaker.

As for reading 190 volts.

First check your meter. The battery may need to be replaced.

Next, check the incoming panel wires at the panel. Measure both hot wires against the neutral and against the ground.

Then measure at locations in the house on both sides of the incoming power. This does not mean both sides of the panel, but means a circuit fed from one incoming hot wire and a circuit fed from the other incoming hot wire.

If you really do have 190 volts on one hot wire, then you probably have 50 volts on the other. if this is the case then immediately turn off your main breaker and call the power company. This would indicate a problem with the neutral, which is not good. The power company will come out and check their side of the service. They may also look at your side, and may even fix a problem they find. They will at least verify that their side of the service is fine.
 
  #3  
Old 05-24-06, 10:23 AM
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It sounds like you have a meter problem. Is it analog or digital?
If the voltage throughout the house is 190 volts you would be having more problems.
The 14 ga wire and 20 amp breaker don't match. A DW circuit can be 15 amp although 20 amp wiring is obviously OK. The breaker can't be larger than the wiring.
I suggest you get the model number of your DW and visit the mfg web site. You should be able to get the tech specs.

On edit -

Here's what I got from the Bosch web site - It's copied from the install PDF for their top line DW

The
dishwasher is designed for an electrical supply of 120V, 60
Hz, AC, connected to a dishwasher-dedicated, properly
grounded electrical circuit with a fuse or breaker rated for
15 amps. If the dishwasher is connected with a food
disposer, a 20 amp (and no higher) fuse or circuit breaker
may be used. Electrical supply conductors shall be a
minimum #14 AWG copper wire.
Regardless of where the electrical supply cable enters the ....
 
  #4  
Old 05-24-06, 12:12 PM
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>Here's what I got from the Bosch web site ...
> Electrical supply conductors shall be a minimum #14 AWG

Of course that is with the 15A OCPD only.
 
  #5  
Old 05-24-06, 12:32 PM
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If your voltage turns out to be actually 190 volts That could very likely be an open neutral on the service panel. You should be measuring some low voltage as well as the high voltage in that case.
 
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Old 05-24-06, 05:54 PM
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Why wouldn't there simply be no power if you lost the neutral? Where is the current coming from, when one black wire is hooked up to one separate leg (as in a wall recepticle), that would cause that leg to increase it's voltage because the other leg LOST the same amount of voltage?

Can someone explain this in easy terms for all of us here to understand? Please do not simply use a term such as "backfeed" without explaining exactly where the backfeed juice enters at.
 
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Old 05-24-06, 05:57 PM
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Daveyboy, with a missing nuetral you have a series 240V circuit.

Two loads in series with the applied voltage at 240V.
 
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Old 05-24-06, 06:00 PM
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Originally Posted by Dnkldorf
Daveyboy, with a missing nuetral you have a series 240V circuit.

Two loads in series with the applied voltage at 240V.
Now explain THAT further, please. What is a "series 240 (volt) circuit" ?
 
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Old 05-24-06, 06:26 PM
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I'm not as good as explaining things in detail, as say winnie is, but I'll try....

Take a simple circuit..120V source with a 12 ohm load. We will find 10 Amps of current flowing and the load will drop all the apllied voltage..ie voltage drop across the load.

Now let's take 2 loads..in series. Lets say (2) 10ohm loads with a 240V source. we would have 12 amps current flow, with a voltage drop of 120V across both loads....

Now if these (2) loads were different values say a 5 ohm load and a 15 ohm load, the current would stay the same, but the voltage dropped across each load would be different. the 5 ohm load would have a 60V across it, but the 15ohm load would see 180V dropped across it.....

I'll see if I can't find a diagram on the web that would make it easier to understand...or maybe someone else can explain it better than me...
 
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Old 05-25-06, 04:42 AM
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The neutral that we are suggesting that might be missing is the neutral from the power company transformer to the main panel. It is not the neutral from the dishwasher to the panel, or any neutral on the house side of the main panel.

The power company supplies power as 240 volts on two wires. These are the two hot wires that enter the house. When you measure ac voltage between these two hot wires, you get 240 volts.

The power company also supplies a third wire, which we call a neutral. This neutral is electrically between the two hot wires. When you measure ac voltage between either of the two hot wires and this neutral, you get 120 volts.

(The voltages 120 and 240 are approximate. You may get a little more or a little less, depending on how far you are from the transformer and on other factors.)

For straight 240 volt loads (such as electric water heaters) only the two hot wires are used. Current flows on the two hot wires. In fact, for straight 240 volt loads, the neutral is not even connected.

For straight 120 volt loads (such as lights, televisions, and most things in the house), one of the hot wires is used, and a connection from the neutral is also used.

For combination 240 and 120 volt loads (such as electric dryers and electric ranges) all three wires are used. The 240 volt portions of the device use the two hot wires. The 120 volt portions of the device use one hot wire and the neutral.

Now here is where it gets a little tricky.


If you only run straight 240 volt loads in your house, the neutral wire to/from the power company carries no current. All the current is carried by the two hot wires.

If you use a single 120 volt load, then one hot wires and the neutral carry the current.

But because there are two hot wires, and because the neutral wires is between the two hot wires, if you use two 120 volt loads that require the same current (such as two 100 watt lights), and if they each are connected to a different hot wire from the power company, then the neutral wire to/from the power company carries no current.

Likewise, if you have two loads, one is a 100 watt light and the other is a 60 watt bulb, and each is connected to a different power company hot wire, then the current imbalance runs on the neutral. In this case that imbalance is the amount of current needed for 40 watts.

In other words, the neutral wire to/from the power company carries the difference in current between the two hot wires. This is why, in some situations, a smaller neutral wire is allowed.

Let's go one step further. Say the neutral to the power company is open, and we still have the same 100 watt and 60 watt light bulb in use (and nothing else). The neutral current has no neutral wire directly back to the transformer. So instead of 120 volts on each light bulb, with each light bulb using the current it needs, you instead have 240 volts. The voltage across one light bulb rises above 120 volts, and the voltage across the other falls below 120 volts.

I hope that helps.
 
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Old 05-25-06, 05:55 PM
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racraft,

Very well put. Easy to follow. Well paragraphed.

But where you really got to the point of the imbalance is in the last few paragraphs and specifically in your last paragraph, you explain how the imbalance shows up as different voltages, over and under the expected, if the neutral was lost outside the house at the transformer. (Actually I never knew a neutral wire was involved with the transformer. I thought it was just the two hot legs.)

So with Max, who was getting 190v...he then should have found some other outlets that had 50v, then? And if so, why should some outlets chose to be 190 and the others 50, instead of the other way around? And by what exact pathway is the additional 70 volts taking?

I guess I just don't follow, because my preconceived notions, even about the transformer, are probably wrong. I just thought a neutral wire was isolated completely as a ground wire is... and that the transformer's function was only in reducing the voltage of the two hot legs, only. And that the hot legs stayed separate of everything else (neutral or ground) until it got back to the poco's generator.

Please explain further.
 
  #12  
Old 05-25-06, 08:42 PM
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i guess that was a good brain teaser guys.

also, i've determined the meter is bad. i'll try the battery, but it's picking up 190v in another house too in across town. i didn't think the battery could have gone bad so quickly, because its only a couple months old and i havn't used it that much, plus, they make you unscrew the box to replace the battery.

but, since the computers weren't blowing up etc. i figured the chances were small i really had 190v in the house.

thanks for all the info though.!!!

diy rocks.
max
 
  #13  
Old 06-07-06, 12:40 PM
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Originally Posted by maxslomoff
also, i've determined the meter is bad. i'll try the battery, but it's picking up 190v in another house too in across town
Max,
What kind of meter is it? And what setting is it on? While we generally refer to 120v, the 120v is actually the RMS voltage. The peak voltage if viewed on an oscilliscope is around 170v. So I'm wondering, if your meter isn't set to AC volts, or possibly reading the DC voltage or something along those lines.
190v peak is about 134v (190 * .707), which while on the high side, is reasonably close to the standard 120v expected reading.

But now I'm curious if the meter is actually broken.

-Mike
 
 

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