Dangers of swapping negative and positive on a wastewater pump?

[Thomas C King]

Short story: we bought our boat with a working shower pump. Then, the pump, after a couple of months, would trigger a circuit breaker when turned on. We swapped the circuit breakers around, it would still trip. We temporarily wired up a new pump, but that too would cause the circuit breakers to trip. We then started to replace the wires on the pump's circuit. However, the pump's red wire was connected to a black, and vice versa. So, I assumed that whoever installed the pump for some reason had used black wire for the positive, and red wire for the negative on the circuit. So, I replaced the black wire with a red one (see the picture below, the black wire going to the pump's red wire has not been replaced yet). Only to find out that the black wire I was replacing was indeed going to a bus bar where a bunch of other black wires ended up, and so it seems that black was indeed the negative.

 

So, we have replaced approximately half of the wiring on the circuit, and I think the pump was actually installed with the negative and positive the wrong way around. My questions are:

 

1) Is this possible, and if so how did it ever work?

2) If we are unsure whether it is wired up incorrectly, is there harm in swapping them?

 

Thanks for any input!

 

 

Edited May 17, 2020 by Thomas C King

[Sir Nibble]

That's a permanent magnet motor and needs correct polarity to work properly. It's always possible that the old pump had been repaired and the magnet case re fitted the wrong way up and polarity reversed to compensate. A motor will always take a surge of high current when starting and the circuit breaker may have become fatigued by this. If the problem persists I would replace it.

[nicknorman]

Just wondering if it would still pump despite running the wrong way. Is it a centrifugal pump? In which case it would probably work running either way.

[Thomas C King]

3 minutes ago, Sir Nibble said:

That's a permanent magnet motor and needs correct polarity to work properly. It's always possible that the old pump had been repaired and the magnet case re fitted the wrong way up and polarity reversed to compensate. A motor will always take a surge of high current when starting and the circuit breaker may have become fatigued by this. If the problem persists I would replace it.

Replace the circuit breakers? I swapped the circuit breaker for another one, but the circuit still breaks. Hence why I started replacing the cabling.

3 minutes ago, nicknorman said:

Just wondering if it would still pump despite running the wrong way. Is it a centrifugal pump? In which case it would probably work running either way.

I have no idea what kind of pump it is, I'm afraid. I've tried googling but haven't found anything. I could take a closer look if I find out what to look for.

[Sir Nibble]

I think it's an impeller pump. Ok, if you've replaced the breaker it ain't that.

[Thomas C King]

4 minutes ago, Sir Nibble said:

I think it's an impeller pump. Ok, if you've replaced the breaker it ain't that.

I might try swapping it with another circuit breaker though. Perhaps it had been swapped once before for the same reason, and I only ended up swapping it back (unlikely, I know). I suppose it's the other half of the wiring that we've not replaced yet, but I did start to wonder whether it was because of the positive and negative being swapped around.

[ditchcrawler]

So what size breaker did you swap it for and are you sure the impeller is not damaged and jamming it. Someone on Facebook has just had one all in bits because it blew a fuse

[bizzard]

Dems are impellor pumps and tend to clog up with solidified soaps and pubic hair causing high revolving resistance especially at start up. I see you have a wee filter on the intake side of it though. If you take the plate off the back 5 or 6 scres will reveal the impellor and any cloggyness. You could even remove the impellor and try the pump to see if it still trips the breaker. I'd fit a Whale Gulper instead though, which are motorized hand bilge pumps and will pass allsorts of debri and pubes.

[WotEver]

2 minutes ago, bizzard said:

I'd fit a Whale Gulper instead though,

Just what I was about to suggest myself.

[Jen-in-Wellies]

This ^^^^^^.

[Thomas C King]

4 minutes ago, ditchcrawler said:

So what size breaker did you swap it for and are you sure the impeller is not damaged and jamming it. Someone on Facebook has just had one all in bits because it blew a fuse

I just swapped it around for another circuit breaker on the circuit breaker board. So I don't really know.

[ditchcrawler]

Just now, Thomas C King said:

I just swapped it around for another circuit breaker on the circuit breaker board. So I don't really know.

So it may not have been big enough to take the current from that pump

 

[Sir Nibble]

I think the pump running dry will increase the load and thereby current. It's a devil of a job providing overload protection to a motor. Fuses, if rated to blow at an overload current will blow on start up. A slower device like a thermal breaker tends to fatigue. Once upon a time current relays with hydraulic dashpots were used.

[Thomas C King]

4 minutes ago, bizzard said:

Dems are impellor pumps and tend to clog up with solidified soaps and pubic hair causing high revolving resistance especially at start up. I see you have a wee filter on the intake side of it though. If you take the plate off the back 5 or 6 scres will reveal the impellor and any cloggyness. You could even remove the impellor and try the pump to see if it still trips the breaker. I'd fit a Whale Gulper instead though, which are motorized hand bilge pumps and will pass allsorts of debri and pubes.

The other pump we bought is a whale gulper, but its in-line fuse blew and the circuit breaker tripped when we tried to connect it to the circuit (we didn't plumb it in though). However, I did fit the whale gulper under the assumption that black was positive and vice versa.

[Sir Nibble]

The gulper is a diaphragm pump and should be happy backwards. It may however have a higher current demand than the breaker is rated for.

[Thomas C King]

1 minute ago, ditchcrawler said:

So it may not have been big enough to take the current from that pump

 

Good point. Thanks all this has been enlightening, I will try and replace the other half of the circuit without actually threading it through the walls etc. (because I now actually know which wire leads to where). I starting to think that it was the circuit breaker though that we've 'worn down' by running the pump dry? And the other circuit breaker(s) may not be up to it, although this doesn't explain the fuse blowing on the whale gulper.

[bizzard]

I'd check the on-off switch is not shorting internally, or bypass it with a bit of wire to see if the breaker still trips.

[Thomas C King]

Just now, bizzard said:

I'd check the on-off switch is not shorting internally, or bypass it with a bit of wire to see if the breaker still trips.

Good call, thanks!

[Split Pin]

It looks like a flexible impeller pump and depends on which way you want the flow depends on which way it is wired therfore cables are not Pos & Neg specifically. I have two of them and they are both wired up what most would consider the wrong way round due to the way it was necessary to mount them.

 

Demo on how they work

 

[LadyG]

this one?

https://www.foxschandlery.com/whale-gulper-220-electric-shower-waste-water-pump-bp1552-12v?gclid=CjwKCAjwwYP2BRBGEiwAkoBpAjaZj5JmWUjnSNL-GKRSHaoHhyN_XcTvk-DEY_6r6sEfsAOccdYIiBoCGIUQAvD_BwE

Edited May 17, 2020 by LadyG

[David Mack]

I would put a voltmeter on those two wires (without the pump connected) to check which is positive and which negative.

[Thomas C King]

5 minutes ago, LadyG said:

this one?

https://www.foxschandlery.com/whale-gulper-220-electric-shower-waste-water-pump-bp1552-12v?gclid=CjwKCAjwwYP2BRBGEiwAkoBpAjaZj5JmWUjnSNL-GKRSHaoHhyN_XcTvk-DEY_6r6sEfsAOccdYIiBoCGIUQAvD_BwE

The new one, yes.

[ditchcrawler]

41 minutes ago, Sir Nibble said:

  Once upon a time current relays with hydraulic dashpots were used.

With adjustable orifices 

[Sir Nibble]

6 minutes ago, ditchcrawler said:

With adjustable orifices 

Indeed. And little reset buttons that went "Clunk".

[bizzard]

How many wires going in and out of the on-off switch. Two in two out, or one in one out. If one in one out Pos+, it can't short circuit unless the switch is metal mounted on metal that connects somehow with the boats steelwork.