This is my first post because I'm in a rut. I'm a 91D and recently took a full time position in a maint shop. I have parallel units on a trailer that fail to properly synchronize via the transfer box. All connections seem to be in order; the TM has steps to troubleshoot, but sends it to the next level main, aka me, when the units fail to synchronize. I'm not sure how to proceed now. I want to put a load box to each 803A separately and make sure they can handle to load, but what's next? Any suggestions???
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parallel 803A's on MJQ-37
- Thread starter Dubie
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Ray70
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I'm just shooting from the hip here, but one thing I'd suspect is a possible bad or stuck magnetic contactor inside the parallelling box.
Honestly, the gen's themselves use very similar contactors and they sometimes get stuck and a good way to fix it ( believe it or not ) is to just whack it with a rubber mallet.
If your unit seems like a contactor is not closing.... give it a few taps with a mallet!
Honestly, the gen's themselves use very similar contactors and they sometimes get stuck and a good way to fix it ( believe it or not ) is to just whack it with a rubber mallet.
If your unit seems like a contactor is not closing.... give it a few taps with a mallet!
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The Hertz of each generator needs to be identical to allow paralleling. So if either generator is off a little, you will not be able to parallel. Next, the alternating current waveform has to match between each generator before the transfer can occur, otherwise loads will suffer and the generators will have a "short" between them.
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Dubie,
First, have you read the TM for the proper procedure to put the gen sets in Sync? There is an "Old Configuration" and a "New Configuration". for the MJQ-37. I have attached the TM.
Go to PDF reader page #49, and start there. If you tell me you have read the TM and have followed the steps for your model, we can start the Troubleshooting process. If you haven't read the TM and followed the steps, do so.
Normally its not hard. The instructions should be on the box also, if I remember right. Fire up both sets. I think set #1 is the front set. Flip up S5 AC interrupter switch on the gen set, to on, for gen set#1. The top light should come on, on the control box, Gen Set #1 ON. Then toggle the switch on the control panel ON/OFF ON LINE GEN SET #1. The ON LINE light should come on, for Gen Set #1, and it should be on line., powering your load.
To sync the second set:
I think set #2 is the back set. Flip up S5 AC interrupter switch on GEN SET #2. The top light should come on the control box. Gen Set #2 ON. That means gen set #2 is supplying power to the switch box, but is NOT on line. At that point, flip up the TRANSFER switch. The two lights should start flashing. Adjust the Hertz (frequency) knob up or down to get the lights to slow down flashing, on the set #2. When you have them flashing on a few seconds, off a few seconds, you are about right on. Then, when the lights go OUT, flip up the the toggle switch on the control panel ,ON/OFF ON LINE GEN SET #2. The ON LINE light should come on, for Gen Set #2, and it should be on line, in sync, sharing the load with Gen set #1. Then you can take Gen Set #1 OFF line and gen set #2 is carrying the load.
Two things to remember. VERY important.
1. Make sure that the load cables from the gen sets to the sync box are hooked up THE SAME!!!!! That means L1 with L1 and so on down the line. If the sets are hooked up wrong, you CAN NOT get them to sync.
2. DO NOT flip the second set on line with the lights on. When both lights are on, the sets are out of sync. There should be, (was at least when I did this) a Phase alignment circuit that will not allow you to put the second set on line when both sets are not in sync. But I have seen it happen, that the circuit didn't work, or was hooked up wrong or was missing. So only put the second set on line when both lights are OUT.
If the sync system will not work, and you are doing everything right, then probably the wiring in the box is wrong. All it takes is two wires to be switched, (in the wrong positions) and the Phase Circuit will not allow you to sync.
Balls in your court.
Oh, yeah. A 91D used to be called a 52D.
First, have you read the TM for the proper procedure to put the gen sets in Sync? There is an "Old Configuration" and a "New Configuration". for the MJQ-37. I have attached the TM.
Go to PDF reader page #49, and start there. If you tell me you have read the TM and have followed the steps for your model, we can start the Troubleshooting process. If you haven't read the TM and followed the steps, do so.
Normally its not hard. The instructions should be on the box also, if I remember right. Fire up both sets. I think set #1 is the front set. Flip up S5 AC interrupter switch on the gen set, to on, for gen set#1. The top light should come on, on the control box, Gen Set #1 ON. Then toggle the switch on the control panel ON/OFF ON LINE GEN SET #1. The ON LINE light should come on, for Gen Set #1, and it should be on line., powering your load.
To sync the second set:
I think set #2 is the back set. Flip up S5 AC interrupter switch on GEN SET #2. The top light should come on the control box. Gen Set #2 ON. That means gen set #2 is supplying power to the switch box, but is NOT on line. At that point, flip up the TRANSFER switch. The two lights should start flashing. Adjust the Hertz (frequency) knob up or down to get the lights to slow down flashing, on the set #2. When you have them flashing on a few seconds, off a few seconds, you are about right on. Then, when the lights go OUT, flip up the the toggle switch on the control panel ,ON/OFF ON LINE GEN SET #2. The ON LINE light should come on, for Gen Set #2, and it should be on line, in sync, sharing the load with Gen set #1. Then you can take Gen Set #1 OFF line and gen set #2 is carrying the load.
Two things to remember. VERY important.
1. Make sure that the load cables from the gen sets to the sync box are hooked up THE SAME!!!!! That means L1 with L1 and so on down the line. If the sets are hooked up wrong, you CAN NOT get them to sync.
2. DO NOT flip the second set on line with the lights on. When both lights are on, the sets are out of sync. There should be, (was at least when I did this) a Phase alignment circuit that will not allow you to put the second set on line when both sets are not in sync. But I have seen it happen, that the circuit didn't work, or was hooked up wrong or was missing. So only put the second set on line when both lights are OUT.
If the sync system will not work, and you are doing everything right, then probably the wiring in the box is wrong. All it takes is two wires to be switched, (in the wrong positions) and the Phase Circuit will not allow you to sync.
Balls in your court.
Oh, yeah. A 91D used to be called a 52D.
Last edited:
Howdy,
NOTE; Don't use the term parallel for what you are doing.
You are running 1st generator with load, syncing, and 2nd generator picks up load, as you shut off 1st generator.
dual MEP-802A's and dual MEP-803A's power plants do not parallel.
True parallel operation is reserved for the MEP-804A and higher. With a control cable attached to each for electronic control.
NOTE; Don't use the term parallel for what you are doing.
You are running 1st generator with load, syncing, and 2nd generator picks up load, as you shut off 1st generator.
dual MEP-802A's and dual MEP-803A's power plants do not parallel.
True parallel operation is reserved for the MEP-804A and higher. With a control cable attached to each for electronic control.