Macerator pump - voltage drops from 12.9v to 6.5v

[TurninTurtle]

Originally Posted by catman

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.
Catman

Nope... not at all.

In every computer AC power supply you have a transformer, rectifier then capacitors on the DC side to "filter" the rectifier output and make the half wave DC into a level value.
That's the purpose of capacitors in a DC circuit.... to absorb high voltage and fill in lows.

The capacitor will NOT act as a short unless its a failed capacitor.

*****************

Inadequate wire size, bad connections, etc all add up, each acting as resistors. And then there's the effect of high current demand on a battery which will have the terminal voltage (measured at the battery + and - posts) drop due to the battery's own internal resistance.

**************

Note:

In electronic motor speed controls there are input capacitors. The "chopping" of the voltage supplied to the motor causes inductive spikes which can burn out the electronics if the capacitors are not there.
Again... the capacitors are absorbing high voltage and filling in low spots.....

[Cadence]

Originally Posted by lonesoldier0408

I'm attempting to learn from the forum. I have seen capacitors in Stereo Amplification systems, DC.
I'm no electrical engineer, just asking, "What if.?"


Still surrounded by anchors.

Don't believe some of the long winded BS, Those that need to impress you with all they don't know.

[catman]

I stand corrected. I must have been thinking of an inductor.
So long ago.
Catman

[roland stockham]

Running remote high power electrical gear on a boat is always challenging and heads are normally quite a long way from the batteries. Same problem as running a windlass or bow thruster It might be worth looking at installing a small battery next to the pump (enough to run the pump for a day). You can then run a lighter charge cable to it and only need heavy cable from the battery to the pump. There is a 'law of diminishing returns' here where the cabling starts to cost more than the machinery! If you are also installing a windlass and or bow thruster it definitely starts to make sense to install a forward battery and charger possibly running off the ships 110v supply. I would definitely consider it on any aft cockpit boat of more than 30ft waterline.

[deblen]

Once a DC boat gets beyond 30-35ft and/or heavily eqpd with DC electric eqpt,it is really time to look at a 24V system-ideally.
Half the current at same wattage.

/ Len

[hellosailor]

"And remember the fuse is there to protect the wire. " Ask yourself "Which wire am I protecting?" here. The circuit wire, from the breaker panel to the device, is usually the one being protected by the fuse. But here, we have an electric motor which may be stalled out and doing its best to overheat and combust. The motor windings will be much thinner than the circuit wire, and those motor windings cost a lot more as well. I'd put in the breaker targeted to throw and stop all power to a stalled motor, before it could be damaged.

[Inhancer]

Could you run a temporary small gauge wire directly from battery to pump to confirm that pump portion is OK before changing out wiring?

[Cowboy Sailer]

A capacitor in a dc circuit is seen as an "open" not a "short"!

[roland stockham]

Originally Posted by Inhancer

Could you run a temporary small gauge wire directly from battery to pump to confirm that pump portion is OK before changing out wiring?

Which made me think. A simple test if you have one of those portable 12v power pack sold as battery boosters. Hook it up to the pump, if it runs fine the problem is in the wiring, if not it is the pump.
Actually that may also be a simple way to set up a forward battery they contain a good 12v gel battery and a small mains charger and are designed to provide high current for short periods

[Cadence]

Originally Posted by Cowboy Sailer

A capacitor in a dc circuit is seen as an "open" not a "short"!

As I recall it is a small battery across a DC circuit once it is charged. So yes it is an open. Another case of misinformation with someone saying it is a short.

[Maine Sail]

Originally Posted by hellosailor

"And remember the fuse is there to protect the wire. " Ask yourself "Which wire am I protecting?" here. The circuit wire, from the breaker panel to the device, is usually the one being protected by the fuse. But here, we have an electric motor which may be stalled out and doing its best to overheat and combust. The motor windings will be much thinner than the circuit wire, and those motor windings cost a lot more as well. I'd put in the breaker targeted to throw and stop all power to a stalled motor, before it could be damaged.

When I wire a macerator the actual switch to turn it on is a momentary switch. Once a macerator, like a Johnson, Jabsco etc. runs dry the risk of burning out the impeller increases with each second the pump remains running dry. A momentary switch, located close to the pump so the operator can hear the pump, results in the safest operation of the macerator and no chance a stalled motor will over heat because the person holding the switch can hear what's going on.

[Cadence]

Originally Posted by Maine Sail

When I wire a macerator the actual switch to turn it on is a momentary switch. Once a macerator, like a Johnson, Jabsco etc. runs dry the risk of burning out the impeller increases with each second the pump remains running dry. A momentary switch, located close to the pump so the operator can hear the pump, results in the safest operation of the macerator and no chance a stalled motor will over heat because the person holding the switch can hear what's going on.

I can agree with the switch location, however I can't see the connection to what I expect is undersized wire. I have no idea where the OP got the idea 14 gauge was the correct wire size, almost sounds like taking it from the AC National Electric Code at110VAC?.

[reed1v]

Two thoughts fwiw: First, we always used at least 8 gauge wire for general electrical systems on board, no. 6 for wires spanning any distance beyond 20 feet. Overkill but gives a huge insurance factor for preventing voltage drops, heating up of wires, and better splicing ability.

Second, are you sure your motor is not "stuck" on something it can not digest" . We had one that was misaligned from the moment we installed it. Kept trying to grind itself to death. Be sure the exit to the tank is open. In other words it may have little to do with the electrical system and more to do with the mechanical end of things.

[MAJICDAN]

Read the directions that came with your toilet. They will recommend what size wire you will need v/s the distance from your fuse box. I have 10ga on mine.

[kentobin]

Originally Posted by TurninTurtle

Nope... not at all.

The capacitor will NOT act as a short unless its a failed capacitor.

.....

Not to get into a war here and it's been at least 40 years since I took basic electronics but as I remember if you have a discharged capacitor it initially looks like a dead short until it starts charging. Then if you connect it to a circuit it will discharge accordingly and produce current corresponding to it's capacity to store it. I think the cap in this instance would discharge until it's voltage would equal that of the battery when the macerator is turned on.

To me the issue of using caps is it's just a work around for another issue and just makes things more complicated to troubleshoot when it eventually fails. Better to use heaver gauge wire and/or a better power source.

Another trouble shooting technique is to leave the macerator pump off and turn on other electric devices to put a load on the battery and see if the battery voltage drops to quickly. Make sure your battery charger is turned off. You can also take a jumper cable and run it right to the macerator pump from the battery, preferably fused, to rule out the wiring.

If I were a betting man I'd pick a bad battery especially if you have wet cell batteries and you didn't keep the water up.