MEP-016D voltage and wiring

[ETN550]

I think Ike has it figured out. Running the house on L1 / L2 with a frame ground on the generator will work fine. You automatically get the ground reference by making a connection to the neutral (bonded to ground) at the house. Phantom voltage sounds correct based on your findings. Different meters will read differently when these stray voltages are measured and have no real current backing them up.

So when running, frame grounded, L1 hot to house L2 neutral to house, load it up some, confirm L2, L0, and L3 output lugs as Zero to frame ground and you have proved 1) Your House ground and gen ground are both solid, and 2) the generator head is floating and not grounded. If so, you may bond the L2 at the generator to the generator ground if your code or application requires it.

Think of it this way: When none of the output lugs are grounded to the frame (internally or externally) the gen head has no reference. Depending on leakage, the L1 and L2 measurement to ground could be anywhere from 0 to 120 each but the sum of L1 to GND + L2 to GND = 120. By grounding an output lug the generator head is now referenced to ground. Since Neutral is referenced to ground in the house the selected L2 lug becomes neutral when grounded to the previously grounded gen frame.

Grounding the frame only protects the operator if the operator is grounded and touches the frame when there is a direct internal short (failure) in the generator head.

Grounding the output lug serves the purpose of matching the house and establishing the common reference between house and generator head.

 

[stoneburner]

ETN550 - you lost me...again. I did end up wiring to my garage load center with main shut off and only one breaker on (serving duplex outlets) - L1 to hot bus, and L2 to the neutral bus. I did not ground the frame; I assumed that the frame ground lug will be grounded by its own ground rod when operating as a house back-up, not grounded to L2. So, I will only have L1-L2 wires to the house transfer switch. Of course, correct me if I'm wrong.

Wired up to my garage load center, I ended up measuring (at the outlet) hot to neutral 120 volts; hot to ground 120 volts, and neutral to ground 0 volts. I did not apply a load at that time, but when running with a 10 gauge extension cord wired to L1-L2 during our 11-day power outage a few weeks ago, I did pull approximately 18 Amps @ 120 volts, and it performed fine.

Again, thank you both for your help and patience. I have learned a ton already!!

Mike

 

[ETN550]

You are good to go. Turn on some stuff and pull some load. Watch the load meter. 100% on your load meter with resistive type loads is about 4kw.

Eventually the frame lug on the generator skid should be grounded to any good source of ground for personal protection, preferably a ground rod driven 6 - 8 ft in the earth. If a failure were to occur within the generator head and cause an internal short resulting in generator power being applied directly to the frame then the ground will protect the operator. Grounding the frame protects the operator from electrocution in case of an electrical failure in the generator head or in the control box while running if the operator was touching the frame or controls.

Grounding the L2 neutral at the generator is up to you. Ike knows the codes better and, hopefully will comment some more on that issue. The machine won't care either way. It is a code compliance issue.

 

[aceofspd]

This is exactly what I am doing. I am glad to learn about clearing any added grounds. So to connect a manual transfer switch I would attach both hots to L1, neutral to L2, then is it OK to attach the green ground to the frame Lug?
Also wondering, when my 016D is in 1ph 240 volt, I show 120 volt from either L1 OR L2 to either L0 or L3, does that mean my unit is already set up for 120/240? Will I need to figure out if either/neither /both is/are grounded to the Frame?
sorry to

 

[aceofspd]

sorry, double posted. can I delete?

 

[1800 Diesel]

Ok, I will try to keep this simple, and this only pertains to wiring in 120V single phase only mode, other modes like 120/240V will be different.........Ike

Ike,

I would like to set up an MEP-016D for 240V single phase--in other words similar to how an MEP-002A would be configured to provide (2) 120v circuits or if I need 240v I can connect to the two output terminals accordingly, plus neutral. The panel has two switches that I have no documentation on--the left hand side has a switch labeled "SELECTOR" with V 3-0, V 2-0, V 1-0 & V 1-2, V 2-3 & V 3-1 settings & the switch on the right side is labeled "CURRENT SELECTOR" with settings marked 1-1, 1-2 & 1-3. These are the two switches I'd like to have set properly to have two legs producing 120v to neutral each.

I did remove the cover of the control cubicle & saw the switch on the upper left side. It was set on 120v single phase, so I assume I need to set it on 240v single phase position along with the above two switches properly set.

Thanks,

Kevin

 

[Isaac-1]

If it has not been modified a MEP-016D in 240V mode is just that 240V line to line with no neutral, not 120/240 split phase like you get out of a MEP-002a when set to 120/240V mode. You can add a jumper wire to get a neautral, but it must be removed to make the reconnection switch work right if you ever want to set it to 120V or 3 phase mode later on. Search here on MEP-016 jumper and you will find a thread telling you which points to connect it to.

As to understanding the knobs, the one in the control box controls the output voltage, and is what I am talking about above, the front panel knob simply controls what the meter is reading.

 

[1800 Diesel]

If it has not been modified a MEP-016D in 240V mode is just that 240V line to line with no neutral, not 120/240 split phase like you get out of a MEP-002a when set to 120/240V mode. You can add a jumper wire to get a neautral, but it must be removed to make the reconnection switch work right if you ever want to set it to 120V or 3 phase mode later on. Search here on MEP-016 jumper and you will find a thread telling you which points to connect it to.

As to understanding the knobs, the one in the control box controls the output voltage, and is what I am talking about above, the front panel knob simply controls what the meter is reading.

Thanks Ike. I guess I'm not real clear about what to do but I'll check out the threads on the jumper settings required to provide a neutral. Hopefully I'll be able to figure out what voltages can be configured. If it's only 120v, I can live with that--just wanted to have an option to power single phase 240v equipment if that's possible...

Kevin

 

[sink1978]

Hi,

I have a new to me MEP-016D that is doing that exact same thing below. I want to run the generator in 120v single phase only mode. I have my generator grounded via the frame to a 6' long copper grounding rod driven into the ground. The generator starts and runs fine. It shows proper voltage on the gauge on the front of the control panel. I also have the switch set at 120v single phase internally. When I measure across L-1 and L-2 I get 120 volts. But if I measure either one to ground I only get 60 volts out of each lug. I also looked to see if I had continuity between L-2 and ground and it does not look like I do. I don't appear to have continuity on any of the lugs to ground. I looked at the wiring from the lugs and it looks likes L1 thru L3 go to the main breaker and then over to the voltage selector switch and I haven't traced it any further from there. I thought I would revive this old thread as at least the initial problem below seems like the same problem I do. Does anyone have any suggestions? I am better at turning wrenches than working through electrical issues but am always willing to learn. Just want to make sure I don't fry the generator or worse yet what ever I am powering with it. I tried following the thread below but I don't know that I get with the final resolution was.


Thanks

Hi, All! I have been gathering tons of info from this site for the past month or so, done tons of searches, and I'm still coming up empty-handed on answers to my particular question.

I recently got an MEP-016D with 1 hour on the engine. I have been planning to run this generator as an emergency back-up in 120 volt 1-phase only. I just had an electrician friend help wire up my transfer switch, and I was hoping he could help me figure out which of the L-1 L-2 terminals was my neutral for house wiring.

We ran the generator in 120 1-phase mode (with the frame grounded) and measured 120 volts from L-1 to L-2, but then both of the terminals measured around 60 volts to ground. Does anyone know if this is "normal" behavior out of this generator? We were expecting 120 volts form one of the terminals to ground (which would have determined which terminal goes to ground).

Has anyone had any luck wiring one of these up to a transfer switch? I was hoping to keep it at 120 volts so that I wouldn't have to bother with load balancing...but, if it comes down to it, I will just add the jumper and use it in 120/240 mode.

Any help would be appreciated!!

Thanks for a great site.

Mike

 

[Isaac-1]

When operating in 120V single phase only stand alone mode, you need to add a jumper between L2 and the frame ground, both should then be connected to the ground rod. In other voltage modes this jumper may be connected between L0 and the frame ground, so you need to check and move the jumper if it already exists. This jumper is usually connected to the back side of the wiring lugs inside the control box, not the outside of the lugs where your other wiring goes.

The end result you have in 120V single phase only mode will be 120V between L1 and L2, with L2 grounded to the frame and to the ground rod. The situation you have now is a floating ground, and therefore 60V to ground from either line. This can get confusing since in typical household wiring you get 120V between L0-L1 or L0-L2.

If you are wiring this up to a house through a transfer switch things get a bit more confusing.

 

[sink1978]

Thanks for the info. I don't plan on using a transfer switch. I have a heavy duty extension cord with a three plug head on it I plan on just plugging things directly into through extension cords. I don't plan to run much with it just Fridge/Freezer some lights, Maybe a TV.

This generator only has about 200 hours on it. When I checked for continuity to ground on all the lugs none seem to exists. Just curious what set up would have been used by the military for this without having a specific ground?


Also when hooking up the jumper to ground from L2 what do I do with the other wires currently going to L2 on the back side of the lug. Do I leave them all connected? What gauge of wire do you recommend to make this jumper out of? Is there any place specific in the box that is easy place to jump this to ground?

Thanks for your help on this.

Mike

 

[Isaac-1]

I just have a moment to type, so will be quick

The only wire on the back side of the lugs you want to touch is the jumper going to the frame ground, if it does not exist, don't do anything to the other. The jumper should be made out of #6 stranded wire, as to ease of routing, I can't say much since mine is in and ASK housing (MEP-701a), but the frame ground lug is almost directly below the output lugs, so should not be too hard. It is possible this jumper was never installed to begin with, and it is even possible the lack of this jumper and seeing a floating ground is why it was discarded with only 20 hours on the meter. If you have not already done so look over the TM as much of this is covered, just not in an organized manner.

 

[sink1978]

Hi,

Just a few more questions. I want to make sure I don't break or fry anything. I found no jumpers going to frame ground. In mine I didn't see anything below the lugs that would look like a good grounding spot. It seems weird that it wouldn't had a ground connected as it has 225 hours on the clock. The main wires coming off the lugs go to the breaker. My question is on L2 do you leave it connected to the breaker and ground it at the same time? Which manual is best to work with. From what I have found it looks like you use the MEP016A or C manual to work the controls. It just doesn't cover the engine. I could take a picture of what I am seeing if that would help describe what I am looking at. I really appreciate your help with this.

Thanks

Mike

 

[Isaac-1]

Sorry I was picturing the layout on the MEP-016B, the concept is the same though, you need to add a jumper between L2 and the frame ground, both connected to your ground rod for 120V single phase only operation. Nothing else needs to be disconnected unless you have another frame ground bonding jumper in place. Your measuring 60 volts to ground does suggest you may have a L0 grounding jumper though, can you describe exactly how you measured that 60 volts to ground?

 

[sink1978]

I hope I am not confusing the situation. I have the MEP-016D. I was asking about the other models because I thought or had read someplace that you need to look at the manual for the A or C model to get instructions for operating the controls of the generator. The engines are obviously different.

When I measured voltage across L1 and L2 I got 120 volts at 62Hz. I had read L2 should be the neutral so I also measure voltage from L1 to my cooper ground wire going to the grounding lug on the frame. I got 60 volts there. I took the same measurement on L2 and got the same voltage of 60 Volts. I also set my meter to check continuity between each lug and the frame ground lug and I got no continuity on any of them. From what you are describing below all I need to do is run a jumper from L2 to ground? Seems like since I was measuring voltage from this plug it would spark or burn something up, but I guess not? I guess doing so makes the full voltage come out of L1?

Thanks again for your input.

Sorry I was picturing the layout on the MEP-016B, the concept is the same though, you need to add a jumper between L2 and the frame ground, both connected to your ground rod for 120V single phase only operation. Nothing else needs to be disconnected unless you have another frame ground bonding jumper in place. Your measuring 60 volts to ground does suggest you may have a L0 grounding jumper though, can you describe exactly how you measured that 60 volts to ground?

 

[Isaac-1]

I would confirm that you have no continuity between L0 (as well as all the other output lugs) and the frame frame first, then if not proceed as we have discussed and add the L2 to frame/ground jumper. This would in effect make your L2 your neutral connection.