Macerator Acting Strangely

[DeepFrz]

Check and clean every wiring connection in the circuit. Also trace and examine as much of the wiring to the motor as you can.

Clipping a voltmeter across the leads at the motor may give you a clue. If the voltage drops when the motor doesn't run well then you have a bad connection somewhere in the circuit.

[chrisjs]

Macerator pumps are pretty easy to take apart and rebuild with new impellers etc. Depending on its age it may be worth taking it off the boat for bench checking and possible refurbishment. We always carry a spare (rebuilt) unit when we cruise.

[Homer Shannon]

I got serious this morning and pulled the whole GD thing apart. There were no clogs in either the intake or output sides of the plumbing. The motor ran exactly the same with the hoses off. I took the motor into the shop and tore down the pump assembly. There was only the slightest amount of material on the cutter - certainly not enough to clog anything. The screw on the back of the motor turns the shaft freely, though stiffly. The impeller looks perfect (as is should, it's only been run ten or twenty times!) and with the impeller off, the motor turns easily and smoothly. No evidence of bad bearings.

I reassembled the motor and wired it up again in the boat as I don't have another DC power supply with sufficient amperage to run the motor with the impeller installed. What's puzzling me now is that the motor turns counter clockwise when viewed from the slotted (non-pump) end of the shaft. Is this correct?

I have the motor wired this way: Power from circuit breaker, 10AWG - RED+, YELLOW-. Connected to the motor RED to BLACK and YELLOW to ORANGE. I'm aware that color codes for DC are changing. Is this right?

When run, the motor displays the same behavior as before I removed it. It starts to run then quickly slows down, though not as much. It keeps turning slowly. I think I may be having a problem where the pump is not priming before the motor ?overheats? (it is not hot) and slows. Without the liquids in the pump there is much more friction on the impeller. The lift height is only about 14", which is well below the specified dry lift height of 48".

This is certainly looking more and more like a bad pump, but I really question how a pump, that is nearly new, could fail. Also, the failure has been inconsistent. After not running for several weeks it ran fine long enough to empty the tank and that was done in multiple small discharges with no start up issues on any of them.

I'm still buffaloed.

[Homer Shannon]

I checked the pump with the wiring as above - I had vacuum on the discharge side. Obviously the orange lead must be positive. (It would be nice if Jabsco mentioned this -they don't - I read the PDF instructions.) I think this is a red herring, I'm certain I had it wired right before I took it out or it would never have worked.

After swapping the leads, I put the intake nozzle into a bucket with a little water. Voila! Lots of strong pumping going on. Motor working fine. Now what?

[sabray]

Maybe deepfrz got it right. Maybe you have/had a bad electrical connection.

[chrisjs]

Are you sure it is meant to self prime to 48 inches?? It sounds optimistic. Perhaps the 48inch height is discharge rather than prime. In which case, perhaps the pump is not priming adequately at 14 inches either. If you can stand the mess/smell, perhaps remove the pump outlet hose somewhere between the pump and the through-hull and check for flow before, during and after the slow down begins. Other thought is a bad (weak) electrical connection. You can easily get a normal voltage reading but not enough current to drive a pump if there are poor connections or wiring. We just had a situation where the connections from a main 230V breaker were hanging in place after the connecting bolt became loose. Looked OK on the ship's volt meter and the handheld ammeter. BUT, not enough current to the AC pump.

[Homer Shannon]

No the spec is clearly 48" prime - dry; 60" wet. http://www.xylemflowcontrol.com/file...0_950-0141.pdf The wiring is 10AWG, all one piece and new with a good circuit breaker. The motor is getting plenty of power.

I got the old tank out this morning and I'll be re-doing all the plumbing over the winter. Once I've got the batteries out of the boat, I'll be able to test the motor more and I can use the old hoses to test vertical prime capability. When it runs right, it primes right up - no issue at all. And then it won't. It won't even run right. I can't fathom it.

[Captain Bill]

This kind of sounds like you're running with a dry impeller. When they get hot they start to bog down. This would indicate you are not priming. These pumps are very sensitive to air leaks on the suction side, especially when dry. If you have a suction side leak they will do as you describe because they never get to the liquid. I always lube my inpellers with either silicone grease or PTFE grease. They are also somewhat sensitive to clearance on the face of the impeller. If the cover plate is badly worn or the gasket is too thick (found this out making my own gasket during a rebuild) the pump will have trouble priming. Since you say you are getting vacuum I would suspect an air leak on you suction line.

[Captain Bill]

Also, my Jasbsco macerators are supposed to prime 10 ft. My macerators always pop the breaker when they stall, how big is your fuse/breaker?

[Homer Shannon]

I have a 30 amp circuit breaker and it's never popped. The wiring is 10awg, which is way over spec for the distance. I'm leaning towards your suggestion of an air leak. I do have the deck pump out in the same line and it could be causing an air leak. But, this idea does not explain why the thing primes and works perfectly one time and then, in yesterday's case, seconds, later it does the slow run/bog down/stop routine.

When it was miss behaving a couple of weeks ago (before it started running right and then failing again) it was bogging down as if it impeller were sticking right from the get-go. It never even tried to prime.

Today I lubricated the impeller with Fluid Film, which is good for rubber, and it did seem to help. However no lubricant is going to stay on the impeller very long. Do you think the PTFE or silicone lubricant stays on the impeller for a while? Is there any way to lubricate the impeller without taking the whole thing apart?

[Captain Bill]

30 amps is a bit big. Mine are 20. It might not be able to pop a 30 amp breaker. Air leaks can be funny things especially in a flexible hose. A slight change in position can make the difference between the amount of air a pump can overcome and that it can't. If you are filling it from the deck opening when you are flushing it, one time it may be leaking a little and one time a lot. You could have a leak in your valve that allows it to suck air through the deck opening. If I understood correctly you have one outlet from the tank with a y valve that allows you to select the deck pumpout or the macerator. If the valve has some wear or is leaking it could easily suck air sometimes and not others.

[Captain Bill]

The PTFE grease helps for a few uses. It eventually washes off. I really use it to make sure that it has some lube on the first startup after maintenance. You might be able to get enough in the discharge tube to do some good. My Jabsco macerators will run about 30 second to a minute when dry and then bog down and stop over 10-15 seconds. How long is yours running before it bogs down? My holding tank macerator is actually below the water line so I let it flood for a few seconds before I turn it on. I also turn it off before I close the thruhull so it probably always has water in it after the first use. I had to rebuild it once because I had been inland for about two years and had been using the deck pumpout exclusively. Macerators don't like to sit unused for long periods. The impeller tends to stick to the case. I could not turn it even using a screw driver bit on a 3/8 ratchet, even though the instructions say to do that. Most of my problems have been with the shower macerators. Since I moved aboard, removed the chopper, and am using them regularly they haven't given me much of a problem. I did have one impeller fail and had to replace it, but that has been it.

[Homer Shannon]

I'd agree with the idea that I'm suffering from an air leak in the deck pump out connection, except that it still does not add up.

When the pump works, it takes about 2 to 3 seconds to prime and it turns really fast, then slows somewhat as the pumping load builds. When it has its troubles, it starts slowly then goes slower and slower until it stops - exactly as if it were completely clogged. Furthermore, the pump mysteriously began working again and I was able to empty my tank in the yard. I then opened the inspection port in the tank to run in fresh water and clean out the tank. I was in the process of draining this water when the pump began acting up again. The deck port had not been touched in the whole process. Why the change and why would the pump act as if the impeller were stuck when seconds before it was wet and running freely?

Going forward I have a couple of ideas I'm going to work on.

I'm getting a new HDPE tank and the drains are going to be on top with pipes down to the bottom. This won't help in keeping the pump lubricated but it does mean that I can work on the pump without getting sewage all over the boat. There will be two drains - one for the pump and one for the deck access. Furthermore, I'm going to move the pump over onto the top of the tank, where I have good access to it, and it is a very short run to the drain outlet. (Right now the pump is under a cabinet and it is a dark and difficult place to work.)

Since all this plumbing will be above the water line, and above the holding tank for that matter, I'm not going to use marine grade hoses. I'm going to use clear reinforced vinyl tubing so I can see what is going on.

Lastly, and I'd like some feedback on this idea, what about drilling and tapping a small hole in the impeller pump body and plugging it with a short stainless or nylon screw. (Short enough not to extend past the inner edge of the impeller body.) With the pump in an easily accessible place, it would be a simple job to remove the screw from time to time and squirt in a shot of rubber lubricant. Crazy or brilliant idea?

[Mark Zarley]

It is about the amps. Put a charger on your batteries and try the motor. I had the same issue, on start up it would run fast for a few seconds, but as the battery was weak it quickly lost power and went to slow mo.

[chrisjs]

Inadequate amperage problem sounds likely to me too!!!
Could be a weak/dirty terminal connection or a chafed wire. May not be the battery.
You can easily get a "normal" voltage reading while you are not able to get adequate amps. Best to try connecting the pump directly to a decent 12V battery.