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#189303 - 09/30/09 07:13 PM Appliances causing voltage dip
jdot77 Offline
Member

Registered: 03/06/07
Posts: 16
Loc: Riverview, Fl
Hey guys, just would like your feedback. What is the main cause of Voltage dip when appliances are first turned on. I understand that there is a inrush of current, but the thing that has me is that you dont see it in every house. Why only some places? There has to be more to this, any comments welcome. Thanks
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#189304 - 09/30/09 07:26 PM Re: Appliances causing voltage dip [Re: jdot77]
renosteinke Offline
Cat Servant
Member

Registered: 01/22/05
Posts: 5305
Loc: Blue Collar Country
This is a real suggestion that you have a loose, high-resistance connection somewhere .... might even be on the neutral wire.

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#189305 - 09/30/09 07:34 PM Re: Appliances causing voltage dip [Re: renosteinke]
twh Offline
Member

Registered: 03/11/04
Posts: 898
Loc: Regina, Sask.
Usually motors like old fridges, old deep freezes and air conditioners cause the problem. Besides bad connections, I had a long drop from the power company that was undersized and a pole transformer that was overloaded.

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#189306 - 09/30/09 08:00 PM Re: Appliances causing voltage dip [Re: twh]
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
It can also be put down to under-sized wiring to the sub-circuits.
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#189314 - 10/01/09 08:01 AM Re: Appliances causing voltage dip [Re: Trumpy]
ghost307 Offline
Member

Registered: 05/09/05
Posts: 884
Loc: Chicago Illinois USA
It depends on how stiff your part of the power grid is. I get the same problem with my large motors because I'm one of 3 houses fed from a small transformer. It can handle the normal running load fine, but the only way that it can deal with the high current draw is by sacrificing the voltage. Once the starting surge is gone and the current drops to steady-state, the voltage can come back up again to where it belongs.
It's REALLY noticable if you have a small emergency generator and only sized it for running loads, not starting loads. You can actually dog the generator down to the point where it dies if you get the sizing wrong enough.
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#189396 - 10/05/09 09:21 AM Re: Appliances causing voltage dip [Re: ghost307]
sabrown Offline
Member

Registered: 12/12/02
Posts: 297
Loc: Ogden, Utah, USA
Bad connections are the most common cause I have found.

Though very non-typical, look also at the distance you may be from the transformer, My house was similar to ghosts except there were 5 total homes and mine was over 500' from the 25KVA (pole pig) transformer. Giving the power company credit, I could not tell when anyone else turned on a large load, but my own large loads were very noticable. I could show them on paper why the arge voltage drop during motor startup, but because they did not want to own up to the problem at the time, they tried to show me with an averaging recording meter that things were OK and that my delivered average voltage was 127 VAC on both lines. I am now on a new line and transformer within 200' and no complaints.

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