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Old 28-07-2016, 19:36   #31
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Re: Macerator pump - voltage drops from 12.9v to 6.5v

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I installed a brand new Jabsco 18590-2092 macerator pump on our boat. it is connected to a switch and then to an approximately 15' run of 14 gauge wire to the breaker panel. When I measure the voltage at the switch it reads 12.9v, but the moment I turn it on the voltage drops to 6.4v and the pump sounds very labored. After 5-10 seconds the breakers trips. Any ideas before I start ripping everything apart?
The first thing I would do is take a known good battery and some #8 wire and go directly to the pump and connect it. If the pump performs, this would eliminate the guess work. Once this is eliminated. I would reconnect all and measure the voltage at the battery. The voltage should not drop to less than 9.5 volts. If less at the motor, I would check the voltage drop on the positive wire and then do the ground wire. Then refer to the pump manual and check what size of wire is recommended. Once this is done give us more information...
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Old 28-07-2016, 22:54   #32
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Re: Macerator pump - voltage drops from 12.9v to 6.5v

measure the current in the wire. I had a mac pump pulling 40a last week and tripping the breaker. pump blocked

if you are pulling 40a and droping to 6v I would probaly consider that normal for the wiring...

if you are pulling 10-15a. but droping to 6v it's a wiring issue between the battery and the location you are measuring.

if you droping at the swtich the 14awg wire between the switch and pump is irrelevant at the moment.
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Old 29-07-2016, 01:46   #33
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Re: Macerator pump - voltage drops from 12.9v to 6.5v

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Originally Posted by MondayNever View Post
... After 5-10 seconds the breakers trips...
What is the rating of the breaker?
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Old 29-07-2016, 08:04   #34
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Re: Macerator pump - voltage drops from 12.9v to 6.5v

We all agree that a 14 gauge wire is way to small. But even then it can't explain such voltage drop. In my opinion, the problem is the battery that can't support such load(10 amps?). Or somewhere in the circuit between the battery and the pump there is a major resistance. The best way to found out is to mesure voltage under load AT THE BATTERY.
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Old 29-07-2016, 08:11   #35
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Re: Macerator pump - voltage drops from 12.9v to 6.5v

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I would reconnect all and measure the voltage at the battery. The voltage should not drop to less than 9.5 volts.
Any marine battery, especially a house bank, dropping to 9.5V under a macerator load, is beyond done for...
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Old 30-07-2016, 19:39   #36
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Re: Macerator pump - voltage drops from 12.9v to 6.5v

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A capacitor in a dc circuit is seen as a dead short. Once the capacitor has reached its full charge it is a short. The only reason it works on AC is it is continuously being charged and discharged on every cycle.
I would suggest a minimum of #10AWG for any high draw motor loads.
If you measure the static resistance of the pump with an ohmeter you can calculate the start up current. once you have the start up current you can determine the wire size.
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Sorry dude, a capacitor blocks DC, shorts AC. A capacitor on a DC line to ground is intended to "filter" out any AC component.

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Old 31-07-2016, 02:27   #37
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Re: Macerator pump - voltage drops from 12.9v to 6.5v

Wire sizes won't make any difference at all if the builder put a right angle elbow right on the pump discharge. This was from a builder on a brand new boat. It would immediately clog up. After pumping out the holding tank from the top a few times I got rid of the macerator and emptied the tank with a Whale diaphragm pump. This was in the good old days. I wouldn't recommend it now.
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