MEP-016b/MEP-701a A/C Hookup Confusion

[coyotegray]

Ok, I'm a wrench, not a sparky. I have been going over how to hook up a MEP-016b/MEP-701a for 240v single phase. My head hurts.

I have reviewed related threads and the TMs and get what look to me to be conflicting information.

At one point it states;

"For 120 volt single phase, 120 volt three phase, or 240 volt single phase modes, connect a #6 AWG stranded conductor between the output terminal stud L-2 and frame (ground terminal stud)"

The it states;

In the 240 volt single phase mode, the output
receptacle “NEUTRAL” lead is NOT GROUNDED. When L-2 is
grounded in the 240 volt mode, both leads to the
receptacle will measure a potential with respect to
ground. Serious damage may result if the output
receptacle is grounded. Paragraph 2-5.1.

Then;

2) For 240 volts,single phase; connect cables to terminals L1 and L2.

And refers to the attached image..



It gives no information I could find about setting the voltage & current setting on the panel..

In another thread I found the following...

"Set the switch to 240 single phase. L1 and L2 are your two hot lines. Install a jumper from S1-5 to S1-6. L0 will now be neutral. Don't use any other switch"

Just where is S1-5 or 6..? I looked all over the inside of the box..

ETA: My intent is to provide household power...

Thanks,
Andy..

 

[yeehaa]

I have 3 MEP 701A's, none of them match the schematics in the manuals, or the data plate that lists the connections on the side of the acoustic cover.

There is a schematic inside the control box that I verified as correct with my multimeter. To see the schematic, remove the top acoustic panel, open the control panel (3 1/4 turn screws on top of panel), loosen the bolts on either side of the control box and lift the top of the control box.

Based on that schematic, L0 is neutral, L1 & L2 are hot when the mode switch is set to 240V. The frame ground should be tied to the house ground.

This gives you 120V from L1 to L0, & L2 to L0, and gives you 240V from L1 to L2.

I have verified this when the generator is running.

You don't need to jumper anything if your MEP 701 is like mine.

 

[Isaac-1]

A couple of notes, first note the mistake in the 240V connection diagram you posted from the tech manual (marked 120V). Also be aware at least in my case the front panel convenience outlet is wired up as a single 15 amp outlet with 2 spare fuse holders. So it is probably best not to trust anything in the diagrams and trace out your particular unit with a multimeter.

Ike

p.s. I recently found a MEP-016B listed on ebay that shows a label stating "ground safety modification completed" next to the model data plate

 

[dependable]

I believe S1-5 and 6 are on the main voltage switch, the one you see inside the panel on the right. My understanding is that the S!-5 to S1-6 jump was originally posted for the mep 016 a & c Not sure it is the same as mep 16 b or the 701a. If anyone has tried this on a 016b or 701, please post.

 

[yeehaa]

If your Mep 701 matches the schematic I posted, no jumper is needed.

 

[coyotegray]

I have 3 MEP 701A's, none of them match the schematics in the manuals, or the data plate that lists the connections on the side of the acoustic cover.

There is a schematic inside the control box that I verified as correct with my multimeter. To see the schematic, remove the top acoustic panel, open the control panel (3 1/4 turn screws on top of panel), loosen the bolts on either side of the control box and lift the top of the control box.

Based on that schematic, L0 is neutral, L1 & L2 are hot when the mode switch is set to 240V. The frame ground should be tied to the house ground.

This gives you 120V from L1 to L0, & L2 to L0, and gives you 240V from L1 to L2.

I have verified this when the generator is running.

You don't need to jumper anything if your MEP 701 is like mine.

That worked for me. Thanks!!!

 

[dependable]

Thanks for that Yeehaa. I may need my 701 as a backup sooner than I thought. The unit runs and seems to charge well. Besides the hookup, to run 1 phase 240 to house, what is recommended setting for volt setting; V10 V20 V12 V30 V23 V31 and Current setting L1 L2 L3. I have a manual, but know it is full of mistakes. Hurricane Earl due to hit the cape by tomorrow night. Expect to loose power for a bit, maybe longer. Any reply before that appreciated.

 

[dependable]

Adding to the above post, I already have main shut off and hook up for a 5kw gas genset. I am not an idiot and will fry no line workers.

 

[Isaac-1]

It took a moment to figure out your question, those knobs are to control what the voltage meter and the amp meter are reading (many of the positions are only useful when set for 3 phase), it helps to understand how a generator works to know what your looking at. I know you have a storm on the way, and it looks like you have it configured for 120/240 split single phase (household voltage in the US). The voltage selectors show the voltage between the various legs L-1, L-2 and L-3 as well as L-0 which is commonly neutral. In your case you are operating it in a mode it is not designed for, so some of this is guessing since the amp meter shows % of load not a number of amps (you may want to buy or borrow a cheap amp clamp meter to confirm output so you don't overload it). My guess is the voltage switch should show 120V as either 1-0 or 2-0 and 240V at 1-2 (there is an adjustment knob to raise or lower the voltage, frequency should be 60 hz, and is controlled by the knob below the panel on the right) The current selector will probably show something in the L-1 or the L-2 position, I am not sure if this will be half, double, or true to your amp draw. One thing to remember when you have any generator configured for 120/240 split phase is you are in effect getting 2 sets of 120V connections each at half the rated output of the generator, you want to keep these two halves balanced of else you may let the magic smoke out (this is probably why 120/240 is not supported on this small of military unit). If you don't have any important 240V loads (well motor, etc) you might be better off setting the generator to 120V only and wiring it in appropriately or use extension cords. Connected at 120V only single phase you get the full output of the generator with no load balancing concerns.

Ike

 

[dependable]

Thanks for that. It is the well motor that is my major concern. Perhaps I can use known gas generator to run well and the 701 to keep the freezers running.

 

[Isaac-1]

I would opt for the other way around, if it is for both the MEP-701 has a much larger reserve starting capacity for motors than a similar sized civilian unit (I think it is 400% of rated load for 30 seconds).

Ike

p.s. note when you have a generator wired for 120/240 you will be drawing from the whole unit on the 240 V loads like your well pump, it is only the 120V stuff you have to worry about balancing (if you have a refrigerator and a deep freeze, then you would want to make sure one was on one leg, and one on the other)

 

[yeehaa]

Wow, this thread came roaring back to life

In no particular order:

120/240 is absolutely a mode this unit was designed for. The schematic in the lid of the control box makes that clear.

I have load tested 2 of my MEP 701A's to 6KW/6KVA (power factor of 1) in 120V mode (50Amps). The breaker specs on page 1-6 of the -34 manual lists the minimum trip for poles 1 & 2 as 54 Amps. This unit should have no problems sourcing 6KW at 120/240V without tripping the breakers. Btw:no load to 2x rated load resulted in 1 volt of droop (from 121V down to 120V) & 4.5 hz frequency reduction (from 64.5Hz to 60Hz). Running at 2x rated load will shorten the life of the generator, running full load 24x7x52 with the occasional 2xload surge is what it was designed to do.

V10 &V20 should read 120 on the volt meter, V12 should read 240. Comparing the amp meter reading for L1 & L2 will show how well your load is balanced.

Surge for the MEP 701A is 200% of rated current for 10 seconds.

A balanced load is best, but this generator is designed for full load on L1-L0, and L2-L0 is designed the same as L1-L0, so you should have no problem running a 3KW load in 120/240V mode even if the load is entirely supplied by either L1-L0 or L2-L0. These things are way over-designed compared to a civilian/commercial generator.

How you allocate your generators should depend on how much of each type of fuel you have access to, as well as what the loads dictate. Generators are more fuel efficient near their rated load than when they are lightly loaded.

 

[Isaac-1]

Yeehaa, where are you finding the surge rating of 200% for 10 seconds, the only place I find that reference is in the test schedule in -34 manual where it seems to be referring to the max short circuit trip time for the breaker which you have noted as a minimum of 54 amps (maximum of 70).

Ike

 

[yeehaa]

Issac-1,

You are correct that I got the 2x load for 10 seconds from the tests described on page 10-2 of the -34 manual. I interpreted the "rated current" as the generator current, not the breaker current. At the top of the table it mentions MIL-STD-705. I googled it, and looked up the section 625.1 refered to in the table. It references "rated load, rated voltage, and rated frequency (speed)" and "rated current". While it doesn't explicitly state it, "rated" anything appears to be the generator rating, as opposed to a component rating.

While I haven't found a specific surge rating, the 2x load for 10 seconds is a defined capability and seems to be a reasonably conservative definition without doing some tests and risking damage to the generator or load.

Here's the link to MIL-STD-705 - http://www.wbdg.org/ccb/FEDMIL/std705c.pdf
625.1 is on page 267