loose neutral

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samsmurf

Member
if there is a loose neutral in the panelbox will it cause the lights to flicker and also cause appliences to short out? where can I get information on this t opic can the loose neutral cause the equipment like computers tvs and vcrs to quit working or burn up also cause lights to blow out

[ May 05, 2003, 05:39 PM: Message edited by: samsmurf ]
 

bphgravity

Senior Member
Re: loose neutral

A loose neutral (grounded conductor) will cause several problems which do include flicker, pulsing, and diming lights. The main effect is excessive heating at the loose termination that will be responsible for insulation damage, and circuit voltage drop.
Generally, a loose connection is not responsible for a "shorted" appliance, but can be the reason for shorter equipment life, inproper operation, and possibly total equipment failure. :)
 

dereckbc

Moderator
Staff member
Re: loose neutral

The open neutral can cause an appliance to look as though they had a short. The open neutral will cause a high voltage on one leg of a single phase service, thereby some circuitry in appliances may appear to have been shorted, such as blown fuses, damaged power supplies, etc.
 

hurk27

Senior Member
Re: loose neutral

Samsmurf

What happens when a service looses the neutral?

The first thing is you have to understand how a single phase 240/120 volt transformer supplys power to a house.
The secondary or output of the transformer is a center tap winding.
Between the two outer connections is 240 volts.
Between the center tap (neutral) which is half way inbetween the two outer connections and ether of the outer connection is 120 volts now when the neutral connection is lost between the transformer and the load the load is left connected across the two outer connections on the transformer this of course is 240 volts.
Now if one half of this load is heaver than the other it will have a lower voltage applyed to it the lighter load will have a higher voltage applyed to it. let's say just for an example that between a phase and neutral there was a 10 amp load and between b phase and neutral there was a 20 amp load there would of been a 10 amp load on the neutral when this (neutral) connection was lost it would of shifted the voltage to the lighter load.
This is kind of like a see saw effect
This is how things burn up when a neutral is lost.
 

physis

Senior Member
Re: loose neutral

If you loose the neutral on a multiwire branch circuit or at the service entrance you have 120 volt loads connected in series and powered by 240 volts :eek:
 

Ed MacLaren

Senior Member
Re: loose neutral

Perhaps these sketches might help illustrate what the guys have been saying.

Sketch A shows voltages and currents in an example of a 3-wire circuit with an unbalanced load. Voltage drop has been omitted for simplicity.

Sketch B is the same circuit, with the neutral broken.
By the way, this is one of the reasons why loads should be balanced on multi-wire circuits.



Ed
 

physis

Senior Member
Re: loose neutral

Is what Ed posted what you wanted to know Mike?

Thanks Ed.

[ May 07, 2003, 02:08 PM: Message edited by: physis ]
 

roger

Moderator
Staff member
Re: loose neutral

Remember that if we take Ed's sketch (A), and apply an unreal world example that both legs would have absolute equal impedance, (wire length, load resistance, distance to neutral connection etc...) the neutral could be removed with no effect on either load.

Roger

[ May 07, 2003, 05:06 PM: Message edited by: roger ]
 
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