Wondering is anyone would have some insight on a vacuum issue we are having. I run a omnitech selexx pal with 2 becker 10 hp pumps and we run off of a 50 hp phase converter. I had the converter professionally installed and balIanced.We were getting a overload alarm when running both pumps for maybe 45 seconds. When running only 1 no problem. Now pump 2 won't turn on at all only get a click when hitting the on button. I swapped the wiring for the pumps around so I know that both pumps are working. I did just have one of the pumps rebuilt as well.

Check the switches. Ours have amperage dials. One was not set correctly when new. It can cause what your describing.

I did check the amperage dials and those units have also been replaced. I switched one to the other and they are working correctly. I will try swapping out the switches in front of those amperage switches and see what happens.

Check your wiring to the pumps. I am guessing you have one set of wires from the panel feeding them both. If you have an inadequate wire gauge or a loose connection the amperage will shoot up to an unacceptable level when you turn on the second pump. Also measure the amperage when both pumps are running (if you can do that) combined and individually.

Make sure they are rotating in the correct direction also.

Look for the most simple thing first.

I checked all connections and noticed I may have had a loose connection to the OL20 relay. I can now turn both pumps on at the same time but when I turn on the suction one slows almost all the way down. I can run them individually with the suction running but not together.

Did you check the vanes on the pump that was not rebuilt?

Did you verify the amperage each is drawing.\?

I have checked the veins and they look good on both pumps. These are all measurements not under load. This amperage:

From converter:
L1-L2:362
L1-L357
L2-L3:357

To ground:
L1-176
L2-321
L3-176

Out of transformer:
L1-L2:326
L1-L3:326
L2-L3:343

To ground:
L1-9
L2-20
L3-11

-Thanks

Here is a revision of the last post as I had a bad test meter.

I have checked the vanes and they look good on both pumps. These are all measurements not under load. This amperage:

From converter:
L1-L2:248
L1-L3:243
L2-L3:258

To ground:
L1-122
L2-220
L3-117

Out of transformer:
L1-L2:225
L1-L3:220
L2-L3:236

To ground:
L1-15
L2-20
L3-13

-Thanks

I think the under load numbers are the ones we are interested in. That is where a connection or wire problem will show itself.

We recently diagnosed a very odd wire problem. We have a CNC machine with 2 - 15hp spindles. On one the frequency drive was faulting out. We swapped the wires to the other speed control and it faulted. We swapped the power only and it faulted. So we determined it was the power wire going to the spindle. A 10 gauge (?) wire, not a thin one. We swapped out the wire for $140 and it was fixed.

We cut the cable open and on one lead a single strand had worked its way through the insulation and was sticking out 6". It was the oddest thing we had ever seen. You have to be systematic and logical.

Here is the numbers under load:
OL20(pump 1)

L1-L2: 212
L1-L3: 214
L1-L2: 215

OL21(pump 2)

L1-L2: 212
L1-L3: 215
L1-L2: 214

-Thanks

I am sorry Brent, we need to know the Amps not volts. I neglected to mention that.

I'm not sure I did this correctly or not. I clamped around each wire running to the pumps from the OL20 & OL21.

OL20 Pump 1:
L1-25.5
L2-27.6
L3- 29.6

OL21 Pump2:
L1-29.5
L2-26.6
L3-27.2

-Thanks

Never used a phase converter but this looks odd:

To ground:
L1-122
L2-220
L3-117

Is that normal?

Yes, I called the roto phase company and they said that reading is correct.

I am getting a large voltage drop when I turn the second pump on. The phase converter is definitely large enough to run both pumps. I am going to try wiring the pumps directly from the converter into the machine to see if that takes care of the voltage drop.

The voltage seems ok, the amperage seems ok.

Are the pump motors wired internally correctly? There is a plate on the motor that depicts how the jumpers have to go for each voltage.

If that is not it I am out of ideas.

Might be the contactor. Had the same problem with mine off and on for some time. Changed the contactors and works problem free now for months. Those particular contactors on the Omnitech are know to be problematic as the machine ages. Get a replacement at Graingers.

After talking to a tech at Becker Pumps to looks like one of my pumps has a smaller motor(7.5hp) Chinese motor that draws more amps than the US Becker motor(10hp) and is causing the overload. I can actually run both pumps simultaneously until the router head starts then the it shuts down and I get the overload alarm. I guess I will be running only one pump for now. I am now going to try to take the 5' x 10' table to a 4' x 8' table. I will have to plug the vac holes on part of the table.