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Old 04-02-2014, 19:11   #1
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Ac voltage drop?

On our newnto us leopard 38, I have noticed the ac line in volt meters drop from about 110ish to 100-105. When the ac unit kicks on. We have fairly long (50ft) shore power cords. Both lines in seem to do it. Is this normal?
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Old 04-02-2014, 19:21   #2
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Re: Ac voltage drop?

Look at the ends of your shore power cords and feel them when the AC is running. You might have a bad connection that is burning the end or heating it and it soon will be burnt.

The problem can be just as much in the socket end as the cord end. If that is your problem, replace it all.

David
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Old 04-02-2014, 19:23   #3
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Re: Ac voltage drop?

http://www.bestboatwire.com/voltage-drop-calculator

A guess would be the dock wiring is undersized for it's length. At 20a your cables will lose ~2v.
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Old 04-02-2014, 19:23   #4
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Re: Ac voltage drop?

Quote:
Originally Posted by djmarchand View Post
Look at the ends of your shore power cords and feel them when the AC is running. You might have a bad connection that is burning the end or heating it and it soon will be burnt.

The problem can be just as much in the socket end as the cord end. If that is your problem, replace it all.

David
Of course the problem might be from the shore power pillar back , back a long way !!!

Dave
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Old 04-02-2014, 20:07   #5
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Originally Posted by DotDun View Post
http://www.bestboatwire.com/voltage-drop-calculator

A guess would be the dock wiring is undersized for it's length. At 20a your cables will lose ~2v.
Can this cause any damage or issues with our equipmemt?
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Old 04-02-2014, 20:09   #6
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Re: Ac voltage drop?

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Can this cause any damage or issues with our equipmemt?
Your daughters will spend slightly longer drying their hair !

Dave
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Old 04-02-2014, 20:13   #7
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Re: Ac voltage drop?

The V-drop may be caused by poor PowerFactor aka PF. Do you have the specs on the AirCon? Many older units, ie more then 4 years old PF near unity wasn't mandated. It is now mandated on new units.

Use a good quality True RMS meter with Htz setting. put the prongs in an ac outlet onboard. It should read 60-61 cycles. Now turn on the AC, and if the cycles drop it's a power factor issue.

Lloyd

Quote:
Originally Posted by Dulcesuenos View Post
On our newnto us leopard 38, I have noticed the ac line in volt meters drop from about 110ish to 100-105. When the ac unit kicks on. We have fairly long (50ft) shore power cords. Both lines in seem to do it. Is this normal?
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Old 04-02-2014, 22:43   #8
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Re: Ac voltage drop?

I don't mean to knock anyone but PF or power factor has nothing to do with the frequency (60 HTZ). Power factor is the difference between true and apparent power used. A device with low power factor (< 1.0) will draw more current and cost more to run. You are most likely seeing a voltage drop caused by bad connections or dock wiring as pointed out before. Running equipment on a voltage lower than specified can caused early motor or compressor failure as they will tend to draw more current at lower voltages and run hotter.

John
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Old 04-02-2014, 23:18   #9
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Re: Ac voltage drop?

Bad PF will magnify the V-drop, and connection issues.

From the grid it will be overcome, but from a generator, the cycle drop will not be able rebound.

So one step at a time.

I'm just trouble shooting... one by one. If I try to lay it out all at once it would be over-whelming.

Lloyd

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I don't mean to knock anyone but PF or power factor has nothing to do with the frequency (60 HTZ). Power factor is the difference between true and apparent power used. A device with low power factor (< 1.0) will draw more current and cost more to run. You are most likely seeing a voltage drop caused by bad connections or dock wiring as pointed out before. Running equipment on a voltage lower than specified can caused early motor or compressor failure as they will tend to draw more current at lower voltages and run hotter.

John
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Old 04-02-2014, 23:21   #10
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Re: Ac voltage drop?

So yes, V-drop is current related. and PF is an issue.

Lloyd

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Originally Posted by irwin37 View Post
I don't mean to knock anyone but PF or power factor has nothing to do with the frequency (60 HTZ). Power factor is the difference between true and apparent power used. A device with low power factor (< 1.0) will draw more current and cost more to run. You are most likely seeing a voltage drop caused by bad connections or dock wiring as pointed out before. Running equipment on a voltage lower than specified can caused early motor or compressor failure as they will tend to draw more current at lower voltages and run hotter.

John
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Old 05-02-2014, 06:36   #11
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Re: Ac voltage drop?

Power factor on a single boat means absolutely nothing to a commercial power grid. Unless the OP was talking about running off his generator, the PF is meaningless to his issue.

We experience this often in many marinas and it is related to the quality and condition of their wiring/power. However, the marinas we are in are often wired with whatever wire is available and strung through the water with multiple connections, etc - so these power drops are understandable.

I would expect US marinas wired to code to be better.

Mark
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