MEP-701A MEP-016b Voltage Selector/Ground Question

[skinnyR1]

Hi. I picked up a low hour (152) MEP701A for a decent price a couple of months back. It is in excellent condition. I converted it over to two 12V batteries with ETN's kit, and changed the voltage regulator since it was over charging.

This is where I am currently;

The battery charging circuit reads around 31V, which I guess is normal. Seems high to me, but people say it is fine on here.

L0 has the wire running to ground, so it is ready for 120/240V house voltage.

It fires up and these are the reading I get on the voltage gauge on the panel in 240 single:

V1-V0 120V
V2-0 120V
V3-V0 0
V1-V2 240V
V2-V3 120
V3-V1 120

What confuses me is the fact that I am getting 120v between 2 and 3. There is no continuity between L3 and the other lugs, where as the other three do have continuity to one another.

Anyone have any possible insight? I am mainly going off of this thread here, where as the OP gets 0 volts between 2 and 3.

http://www.steelsoldiers.com/showthread.php?82832-MEP-016B-Voltage-Selecotr

Thanks for the help.

Edit: There is additional help here in this post, but I don't necessarily see an answer to my question. Slightly confusing....
http://www.steelsoldiers.com/showthread.php?76248-Center-Tap-Neutral-for-016B/page2

 

[Isaac-1]

Internally this is a 12 lead generator, the voltage reconnection switch just connects these leads in various combinations for your selected voltage. There are 2 possible connection combinations that can supply 120/240V single phase, those being double delta and low zig-zag, I think the MEP-701a uses low zigzag, but would have to check the manual, either way both layouts use all the windings as a result you likely will see some voltage when measuring what would have been a line connection in 3 phase mode, unless those points cancel each other out. Note there are mistakes in the labelling on the connection chart in the MEP-016b manual, still it might help you visualize what is going on.

Ike

p.s. also check to make sure you don't have a grounding jumper installed to the wrong output lug inside the the control box (back side of the lugs)

p.p.s. this is odd, it appears the question I was answering has vanished, but my reply is still here

 

[skinnyR1]

I don't know why my original post disappeared. Thanks for the reply Isaac.

Basically, the original question was why am I getting voltage from L3-L1 or L2-L3 in single phase 240v. I am not using 3 phase, does that matter? LO is grounded to the frame and I get the correct 120v or 240v readings from the correct lugs, I am just confused as to why I have voltage from L3 when there is no continuity to the other lugs when the unit is off.

 

[Isaac-1]

It may also help to visualize the meter as connected to the tie points that would become L2 and L3 if the voltage reconnection switch were set to the appropriate 3 phase voltage.

Ike
p.s. on the continuity issue, you would have the resistance of the windings when the generator is off, I don't know the amount off hand, but it would be several ohms. You seem to be thinking your getting duplicate readings of the same winding combination to get matched voltage numbers, when I think (without working through the combinations) you are likely getting other combinations of the windings from what would be half way points in the normal L1-L2 view of 120/240V split single phase (sort of what you could imagine as L0.5 to L1.5, but not exactly)

 

[skinnyR1]

Ok. So can I ignore the fact there is voltage from L3 to L2 or L1? There is another post on here where the user gets different readings, and I know ETN posted something a while back where L3 has phantom voltage.

Maybe thats why my original post disappearred, as I had links to other threads.

 

[skinnyR1]

Here is one thread that sorta touches on the fact that L3 acts as a ground. But the thread trails off so I am not sure what to make of it. Post #9 in this.

http://www.steelsoldiers.com/showthread.php?76248-Center-Tap-Neutral-for-016B

 

[skinnyR1]

And in this thread, you can see there is zero voltage across 2 and 3, where as I have 120.

http://www.steelsoldiers.com/showthread.php?82832-MEP-016B-Voltage-Selecotr

since my original post disappeared, again, here is what I have for readings;

V1-0 120
V2-0 120
V3-0 0
V1-2 240
V2-3 120
V3-1 120


Thanks for the help.

 

[ETN550]

And in this thread, you can see there is zero voltage across 2 and 3, where as I have 120.

http://www.steelsoldiers.com/showthread.php?82832-MEP-016B-Voltage-Selecotr

since my original post disappeared, again, here is what I have for readings;

V1-0 120
V2-0 120
V3-0 0
V1-2 240
V2-3 120
V3-1 120


Thanks for the help.

What you are posting above makes sense if L3 and L0 are connected internally by the reconnection switch. The generator is a 3 coil, 6 lead machine.
In the 240 single phase mode the coils are in a zig zag configuration and L0 is connected to the T4/T2 junction on the 240 volt diagram fig 4.1 pg 4-3 in the "Operator's" manual. Incidently, that 240 single phase zig zag diagram is improperly labeled. T3 and T5 are reversed and the second T2 (closest to L2) should be labeled T6. And of course the "120v" in the box should be "240v". You would think they would check their diagrams for errors before publishing. And, importantly, the diagrams do not indicate other connections that do exist if there is no output to be taken at a given lug. For example the T4/T2 junction is most assuredly neutral and connected to L0 but this is not shown in the diagram.

Realize that the manual makes no mention of the 120/240 capability of the machine in any of the literature. However, all of the units I have come across so far, of the 016B and 701A variety all have a 10gage white ground wire run from the ground lug on the base of the frame to the backside of the L0 lug inside the control box, thus grounding L0. I am just speculating that the "Ground Safety Modification" sticker near the name plate has something to do with this. The voltage reconnection switch wiring does not match the diagrams and L0 is now the ground in all cases as the machine is delivered. These differences plus whatever changes they made on the reconnection switch from the manual give the machine its 240/120 capability.

So, in the one application where it is desired to tie into a house and the tie in is going to be 120 volt single phase then the ground wire on the backside of L0 must be disconnected from L0 and moved to either L1 or L2 thus establishing a ground and common neutral on one of those leads. In the 120 single phase mode the L0 is connected to the T3/T5 junction of the delta configuration and L0-L1 will read 60 volts as will L0-L2. Therefore, the ground wire must be detached and reset to either L1 or L2 (your choice of which will be the neutral) when in 120 single phase mode or else it will not match the house and there will be a direct short of 60 volts at the generator. This ground wire move is only needed for the 120 single phase operation and only if the generator is going to interface with the house.

If the generator is connected to the house in the 240 single phase mode (giving 240 L1-L2 and 120 L1-L0 and 120 L2-L0) then L0 is the neutral and the ground wire from the lower frame ground lug to the back side of the L0 lug remains in place on the L0 lug - no change necessary.

Your machine as it sits with the ground safety sticker and the L0 wire to frame ground will produce as follows:
120 volt single phase switch setting
L1-L0, 60 volts
L2-L0, 60 volts
L1-L2, 120 volts
L3 to anything else, I don't have a measurement

240 volt single phase switch setting
L1-L0, 120 volts
L2-L0, 120 volts
L1-L2, 240 volts

Both three phase settings will produce per their respective diagrams on fig 4-1 on page 4-3. On the 120 three phase diagram the lower T-6 opposite the T-2 should be labeled T-5

 

[ETN550]

I don't know why my original post disappeared. Thanks for the reply Isaac.

Basically, the original question was why am I getting voltage from L3-L1 or L2-L3 in single phase 240v. I am not using 3 phase, does that matter? LO is grounded to the frame and I get the correct 120v or 240v readings from the correct lugs, I am just confused as to why I have voltage from L3 when there is no continuity to the other lugs when the unit is off.

Ignore what is going on behind the curtain! If your particular reconnection switch setting does not utilize a certain lug such as L3 for output then don't worry if there is voltage at that particular lug. It will not be connected to anything. The voltage reconnection switch is complicated and what is on our machines is not what is in the manual. There are probably compromises in the reconnection switch design and the switch may have had to be made even more complicated if it had to switch off unused lugs. As long as the switch is made to direct the correct voltage to the correct lugs for a particular switch position I don't think the Engineer cared about what voltages there were at lugs not used at a particular switch setting. Just my theory...

 

[Isaac-1]

ETN550, thanks for clearing up the details, you work with these more than I do, although it should probably be strongly noted that some units may be wired differently. For example my MEP-701a came with the ground jumper on L2 and has no ground modification labelling, panel outlet was also wired wrong using only 1 fuse and the hot side jumper was not cut.

 

[skinnyR1]

Ok, thanks for the help. That does shed some light on it. I should just ignore the voltage associated with L3. I take it as it is acting as a internal ground for some reason, but is not a neutral like L0.

I am going to do some tests and see what can be determined. L0, 1 and 2 all have full continuity to each other in single 240, while 3 does not. So maybe it does have something to do with other windings and 3 phase.

On another note, I had a bad battery charging regulator, and I changed it out with the ebay one. I was getting 36 volts when charging. Now, with the replacement, I am getting around 31V. Is that too high of a charging rate, will it boil my batteries? It seems high to me for a 24V system.

 

[Triple Jim]

31 volts is at the high edge of charge voltage for a flooded 24V battery. If it doesn't go higher, and if you keep an eye on the electrolyte level, you should be OK. You can find lots of information on the web, of course. Here's some: http://www.solarnavigator.net/battery_charging.htm The Bulk and Absorption sections apply. Feeling the batteries once in a while to make sure they're not getting hot would also be a good idea for the next few runs.

 

[Isaac-1]

I would also say keep and eye on it, check the electrolyte levels in the battery and see what happens as the battery / batteries get charged.

 

[skinnyR1]

It is two brand new (i assume with recycled materials) 12V tractor batteries in series. Would that make a difference at all as to the voltage draw to it?

 

[Triple Jim]

No, for a given cell capacity, two 12V flooded lead-acid batteries in series are electrically the same as one 24V battery or four six volt batteries, etc. The charge voltage really is a function of volts per cell, and in this case, 2.58 is about the upper limit for your 12 total cells.

 

[ETN550]

ETN550, thanks for clearing up the details, you work with these more than I do, although it should probably be strongly noted that some units may be wired differently. For example my MEP-701a came with the ground jumper on L2 and has no ground modification labelling, panel outlet was also wired wrong using only 1 fuse and the hot side jumper was not cut.

Isaac, You bring up a very good point of knowing how the machine is configured before it is run. Interesting that your 701A was set up as you described, which may actually be in accordance with the manual. I have only had a few 016Ds to play with and they seem to follow the the same arrangement as your 701A.

Maybe at some point we can find literature on what the "ground safety modification" actually consisted of. Sooner or later someone on this board may be able to chime in with knowledge or know someone who spent time in the military working on these smaller MEPs.

 

[Isaac-1]

One can hope, my MEP-016D Yanmar conversion had a real creative mess in the control box. It "worked" or at least seemed to when I bought it which is strange enough, the hour meter read 0.4 hours, it turned out to be a 24VDC hour meter connected to the 120VAC line output tapped off one of the panel outlet fuses, and the way it was wired the the front panel outlet was wired through the tiny (20-22GA?) wires that ran to the hour meter. On top of that the wiring diagram panel had the rivet holes ripped out and it was just laying loose on top of the voltage regulator.

 

[skinnyR1]

My original post has been restored, if that provides any additional info to anyone who didn't see it before.

 

[helomedic1171]

Raising this one back from the dead -

Do I simply move the ground from the L0 to the L2 in order to run 120/1ph? I don't need to change anything from L2 to make it my neutral leg?

Also, I'm using 8ga (or maybe 6ga? Can't tell) cable for my power cable. There are 3 (red, blk, wht) power wires and 3 ground wires (all green).

As of now, I'm planning to use :

Red-> L1 for power
Blk-> L2 for neutral
Wht (not used)
Grn -> ??? (Do I hook these to frame ground?)

The end goal is to have 30+amps (120/1ph) to run a camper using an RV receptacle at the end of this cable.

 

[Guyfang]

The problem is, that you have now asked the same questions in two different threads. The forum rules state that this is not to be done. So, Pick one, and stay with it. What you should do is start your own thread. Gives you better visibility, and better help.