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Old 09-08-2019, 07:09 AM   #1
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Balance your loads and draw less amps

There is a great article in the MTOA Turtle Times that explains this and "the smart Y"

If you have a 250v A/C panel on the boat and your pluged into a 250v 30amp receptacle on shore (or running the gen set). If you balance your loads you will draw less current (amps). Example: If you have 50amps of 125v loads on one side (L1) to nuetral you will be drawing 50amps. If you move half the loads to the other leg (L2) to nuetral you will draw 25 amps total thru both legs and your nuetral current (amps) will go to zero. This is because the two legs L1 and L2 are 180degrees out of phase so they feed each other. This is also why one nuetral wire can service both hot legs and not have to be double the size.

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Old 09-08-2019, 07:26 AM   #2
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To summerize an simplify: If you have a 250volt A/C panel you should have two verticle rows of switches each row is a leg of the 250v. If you turn a switch on in one row and it draws 20 amps you can turn a switch on in the second row of equal load and it will still only draw 20 amps. Conversely if you were to turn on a second switch of equal load in the first row you would be drawing 40 amps and if you were hooked to a 30amp 250v receptacle it would trip.
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Old 09-08-2019, 07:51 AM   #3
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Sounds like this would be useful in one or more of these 3 cases:
1. the manufacturer did not configure the boat you own correctly
2. a previous owner messed up the initial design
3. you previously made … or are currently making changes which unbalanced the loads
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Old 09-08-2019, 08:02 AM   #4
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It's a possibility...but not all boats, adapters and dock pedestals guarantee this will happen.


Nice to be set up for it...but like many boats and operators....a second "row" panel has been added and it is all heating or air conditioning because of "seasonal use". So at this point....one must understand the basics of this load balancing to understand is it necessary enough to overcome the convenience of not dragging out a second cord when not needed.


Boats can be wired and used so many different ways, the only sure fire way to have your boat set up best for you is to have a local that 'knows" their stuff review your boat and your cruising needs.


Specifics can be answered in threads...generalizations either require the understanding of pages and pages of mixed answers or a hands on review and recommendations.
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Old 09-08-2019, 11:38 AM   #5
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Seems we have skipped over practical real word issues to discuss theoretical possibilities. First we need to set the boat up to work with inverter and non inverter loads. Then we need to set things up to work with only one 30 amp source. Then we set things up to work with a 50a 125/240 source. Finally we now can talk about load balancing. Oops did I skip the old 208v issues.
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Old 09-08-2019, 12:48 PM   #6
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Originally Posted by tiltrider1 View Post
Seems we have skipped over practical real word issues to discuss theoretical possibilities. First we need to set the boat up to work with inverter and non inverter loads. Then we need to set things up to work with only one 30 amp source. Then we set things up to work with a 50a 125/240 source. Finally we now can talk about load balancing. Oops did I skip the old 208v issues.

...


Wayyyyyy too many theoretical discussions...must drive new boaters insane.
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Old 09-13-2019, 01:18 PM   #7
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For general interest and to demonstrate the options out there for boat AC panels we have two separately switched 240VAC rows of breakers and a 110vac row that the Inverter powers. The generators are also 240VAC. Most of the machinery on the 240VAC legs is 240VAC except the 110vac water heater, washer and the Inverter/Charger which unfortunately only takes 110vac on one input. It is one of the major draws so I have a two way switch so I can take it from one 110vac leg to the other to balance the loads on the generator. It also canít be stacked with another IC so until it gives up the ghost I have to juggle it. So if you are getting a new Inverter/Charger look at your options for inputs, outputs and the ability to be stacked.
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Old 09-13-2019, 02:58 PM   #8
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I am a little puzzled about the interest in balancing two legs of a 240V circuit. Yes, moving a load from the heavier used leg to the lightly used leg will result in less current in one and more in the other, but what good is that?

Presumably the wiring is sized to handle maximum loads, right? You won't save any voltage drop (and concomitant heat and wattage loss) because the voltage drop on one leg will be offset by an increased voltage drop on the other. So what is the big deal?

240V legs are unbalanced all of the time along the dock, depending on who is using single phase 120V and on which leg, but over lots of boat pedestals they generally all balance out.

I suppose there might be some advantage to balancing the legs from an on board genset, but not sure. Maybe balanced legs will smooth out the rotational torque required from the engine. Anyone know and does it matter?

David
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Old 09-13-2019, 03:14 PM   #9
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I agree David....tradeoffs, tradeoffs, tradeoffs.


The perfect world vs most of ours.


Now for some it might help...but then the perfectionists might say just upgrade anyhow so "you are not getting away with something"....even though it might be sound engineering.
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Old 09-13-2019, 06:39 PM   #10
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If you really want to reduce current flow, then optimize motor load power factor with capacitors. But that is for those that have to tweek because they can.
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Old 09-13-2019, 06:59 PM   #11
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Obviously David and I agree on this rather silly issue. Remember this thread was originally titled "draw half the power..." Even retitled, somewhat correctly, the fact remains you don't, as I pointed out before, draw one less amp or one less volt or one less watt. All you accomplish, maybe, is not overloading one leg and tripping a breaker. But that's what a proper panel accomplishes to begin with. The point of this thread continues to escape me, which of course, isn't saying much.
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Old 09-13-2019, 08:11 PM   #12
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If you really want to reduce current flow, then optimize motor load power factor with capacitors. But that is for those that have to tweek because they can.
Reactive power discussions are not allowed.
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Old 09-14-2019, 05:23 AM   #13
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"The point of this thread continues to escape me, which of course, isn't saying much."

Lowering the amps per leg should have crappy plugs melt their pins less often.
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Old 09-14-2019, 06:01 AM   #14
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There is a great article in the MTOA Turtle Times that explains this and "the smart Y Bud
Bud
Two questions. First, what is the background of the person who wrote the article? Second, does the article pertain to those of us who don't use a smart Y?
Thanks
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Old 09-14-2019, 09:15 AM   #15
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"the fact remains you don't, as I pointed out before, draw one less amp or one less volt or one less watt."

The fact that when you balance your 125v loads your nuetral current goes to zero. How does that square with your rant.

where electricity is concerned there are three different types of people.
1. who understand it
2. who do not understand it
3. who want to undrestand it.
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Old 09-14-2019, 09:24 AM   #16
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Quote:
Originally Posted by djmarchand View Post
I am a little puzzled about the interest in balancing two legs of a 240V circuit. Yes, moving a load from the heavier used leg to the lightly used leg will result in less current in one and more in the other, but what good is that?

Presumably the wiring is sized to handle maximum loads, right? You won't save any voltage drop (and concomitant heat and wattage loss) because the voltage drop on one leg will be offset by an increased voltage drop on the other. So what is the big deal?

240V legs are unbalanced all of the time along the dock, depending on who is using single phase 120V and on which leg, but over lots of boat pedestals they generally all balance out.

I suppose there might be some advantage to balancing the legs from an on board genset, but not sure. Maybe balanced legs will smooth out the rotational torque required from the engine. Anyone know and does it matter?

David
When you have two 20amp loads on one 125v leg you are drawing 40 amps on that leg and on your nuetral. When you switch one of those 20amp loads to the other leg (L2) you then draw 20 amps through both legs but your nuetral amps go to zero
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Old 09-14-2019, 09:25 AM   #17
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BUT.....if you measure the amps or watts at all the appliances...you get a certain number....certainly not zero....even on the neutrals.


if All your appliances leaked to ground and not neutral...same result....not amps on neutral line.


So while I barely understand all about AC power....I know that if you are using X numer of watts to run appliances....its coming from somewhere...and returning (to a point) as it's not "free" power.
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Old 09-14-2019, 09:27 AM   #18
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Reactive power discussions are not allowed.
An analogue.......



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Old 09-14-2019, 09:28 AM   #19
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Balancing loads minimizes the power carried by any 1 wire in the system, but total power flowing is still the same.
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Old 09-14-2019, 09:46 AM   #20
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BUT.....if you measure the amps or watts at all the appliances...you get a certain number....certainly not zero....even on the neutrals.


if All your appliances leaked to ground and not neutral...same result....not amps on neutral line.


So while I barely understand all about AC power....I know that if you are using X numer of watts to run appliances....its coming from somewhere...and returning (to a point) as it's not "free" power.
Your nuetral amps from you boat a/c panel to your appliance is drawing the appropriate amps for the appliance, But the nuetral wire from your a/c panel to your source either gen set or dock draws zero amps if 125v loads are balanced.
It is a result of the lwo legs being 180 degrees out of phase thet
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