"Universal" Wiring for MEP002 and 003

[Crawdaddy]

Universal Wiring for MEP002 and 003

I have been reviewing the TM for the MEP-002 and 003 gensets since I'm going to soon be running one. I have been paying particular attention to the load terminal wiring.

Before I ask my questions, I'd like to give a little overview of my use of the generator will be. My primary use will be to power my camper, which runs on 120V at 30 amps. With the A/C, water heater, and a tv on, it consistenly uses at least 20 amps of power. It uses a 30 amp RV plug for power. However, I would also like to be able to have a pair of duplex 110v outlets and a 220V outlet available for use.

So, keeping my desires in mind, I turn to the specifications and Load Terminal Configuration diagram. The specifications says for 120 1 phase, it can do 104 amps and in 120/240 1 phase mode, it can do 52 amps. 52 amps is more than enough to power my single largest load (my camper), but, it also says to not load the legs to more than 5% difference between legs. That means I'd have to keep at least 27 amps of load on the other leg, which isn't feasible, so to run the camper in 120V mode when running the camper. No problem, I won't likely have to power any 240 volt loads while also powering the camper so I can run in 120V mode.

So, now the question comes in how to configure these outlets to provide the most versatility without burning up coils in the generator and without accidentally feeding twice the rated voltage into my camper. To run in 120V mode, I'm supposed to get my hot from L3 and my neutral from L1.
But, when I switch the genset into 120/240V mode, the L3 to L1 connection becomes 240V, and to get 120, I have to go to either L0 to L1 or L0 to L3. I cannot come up with any 1 wiring configuration that does not require me to rewire the load terminals to support my varying loads.

Any ideas? I'm still a little ways away from building this out, but I'm trying to figure out the logistics now.

 

[Crawdaddy]

I just realized I may have read and misunderstood what I read. The TM says 5% max between PHASES not legs. Does this mean that since I'm in 1 phase mode I don't particularly have to be within close tolerances between legs in 120/240 mode? Then I wouldn't need to use 120V only mode at all. That would simply everything in that I could simply wire my 30 amp RV outlet on one leg, my 120 duplex outlets on the other, and the 240 outlet across both legs and be done. But that would be too easy, right?

 

[glcaines]

When they talk about phases, they are talking about 208 VAC 3-phase.

 

[derf]

Familiarize yourself with the unit. If running your camper or any 120V only load, then run the gen in 120V single phase mode. When you want to run something 220, then run the unit in 120/240V single phase mode. Is it not a turn of a switch to change between modes?

Or, if you want to do it once and have versatility, then go with the 120/240V single phase mode and plug 1/2 of your 120V load into the L1-L0 circuit and 1/2 into the L3-L0 circuit, A/C on one, water heater on the other, etc.

You probably won't get a 50/50 distribution but as long as your not 100/0 or 90/10 you probably will not have to worry about unbalanced loads.

Load balancing is always something to consider, but you probably will not be able to kill an 002 or 003 with an unbalanced load unless you get really stupid with it.

You may have to look into wet stacking if you get an 003 and only drive 30 amps with it all the time. Diesel gens are happiest at rated RPM with a decent load on them. If you run them too much with little or no load then they sometimes do not burn all the fuel fed to them and you can get a buildup of unburned fuel that can cause issues.

For a 30A 120V load you should probably consider an MEP-701A, MEP-016B, or similar sized gen. I happen to have a 701A that I would gladly make you a decent deal on. They are a little trickier to switch to 120/240V with a neutral, you have to add a jumper, but it can be easily done. Also, they weigh around 500lbs, the 002s and 003s are ginormous.

So, now the question comes in how to configure these outlets to provide the most versatility without burning up coils in the generator and without accidentally feeding twice the rated voltage into my camper. To run in 120V mode, I'm supposed to get my hot from L3 and my neutral from L1.
But, when I switch the genset into 120/240V mode, the L3 to L1 connection becomes 240V, and to get 120, I have to go to either L0 to L1 or L0 to L3. I cannot come up with any 1 wiring configuration that does not require me to rewire the load terminals to support my varying loads.

Yes, you must change the wiring at the load terminals.

 

[Crawdaddy]

GLCaines, so I don't have to worry about uneven loading? I definitely don't want to burn out a coil in the head with heavy loads.

Derf, changing the mode switch is easy. It's that when I switch from 120 to 120/240 mode, I have to rewire everything because what was 120v in 120 mode suddenly becomes 240 in 120/240 mode. Splitting the load of the camper between the legs isn't possible because the input to the camper is a single 120v 30 amp cord and plug and I'm not willing to dig into the wiring of the camper to try to split it. So, it'd likely be 100/0 between legs.

Wet stacking is a concern, but I think I can probably load it down enough often enough to not have to worry too much about it. I really wish I had won one of thos MEP-002s at Shebly yesterday, I could have if I just bid with how low they went.

I'll give you a PM on one of those 701s you have.

 

[derf]

Yes, I watched those 002s at Shelby. I bid early and really low on them, not really expecting to get one but bidding just in case they went stupid low. They seemed to go for more reasonable prices than the ones at Polk recently.
A 701 should drive your camper perfectly at 30A max, probably more efficiently and certainly quieter than an 002 or 003.

 

[jamboly]

It sure seems like your are really trying to complicate things for a "220V outlet you would like to have" but don't indicate what you would use it for. Unless that 220V outlet is real important, I would forget abut it and go with an MEP-002A set up as 120V single phase. Keep a lot turned on in the camper, and then don't worry about dieseling.

 

[Crawdaddy]

I wanted to renew this post in hopes to get some more qualified opinions. I have now more solidified what my plans are for this generator.

First, this generator's primary goal will to be to power a shop and 3 campers that are attached to the shop's power. The shop has a transfer switch that I'll be tieing into it with 240 single-phase. I'm pretty sure all the loads are pretty well balanced between the 2 120 volt legs.

Second, I want to be able to power just my camper independently when full-shop power is not required. As previously discussed, it's a 30 amp 120V RV plug and I can't split the loads up without major rewiring of the camper. I figured I'd make an outlet box with a couple duplex outlets and the 30 amp RV socket I need to plug the camper in.

Third, I'd like the power at the load terminals at the generator to be wired in a way that I don't have to reconfigure it depending on whether I just have my camper to plug in, or power the whole shop and all 3 campers. Ideally, I'd like to wire it up for 120/24v single phase operation to an appropriate weatherproof twistlock and have various lengths of extension cable with the matching twistlock made up along with the outlet box also with the same twistlock. This way, it's moderately idiot-proof and modular to fit varying needs. I have the plans for the wiring in my head, and it looks pretty good.

So, I'm still up in arms whether I will burn up coils in the generator if while operating in 120/240 mode I exclusively plug my 30 amp camper into a 120v outlet. The TM stressed to keep loads within 5% on phases, but in 120/240 mode, it's technically only 1 phase. Am I right in this assumption?

 

[Ken_86gt]

Are you going to be running this in a 24/7 full time operation? If so, then you want to balance the loads as "best possible". As long as you are not overloading a particular phase, I don't see any problems with temporary operation like this. I have seen many 3-phase generators running a load on only one leg and they don't ever seem to have any issues, and these typically ran 24/7.

 

[Crawdaddy]

Runtimes can vary from hours to weeks. It's primarily for hurricanes, and as such power outages can last weeks in a Katrina-like situation. Fueling it for that long could be an issue, but I'd run it as long as possible and neccesary.

 

[Keith_J]

Unbalanced loads are a problem because the rotating field is excited to match the loaded windings. The windings which are not loaded experience higher voltage which can break down the insulation varnish.

 

[Crawdaddy]

Sorry to be so dense, but is that a yes or a no to causing damage to the windings for my situation?

 

[Ken_86gt]

I would like to see some real world examples of the voltage going so high that the windings are damaged. It takes a lot to cause this to happen- any appliances would fry before the voltage gets so high the insulation is damaged. I believe on these generators the insulation is rated for 600V. If you see anywhere close to 600V on the "unbalanced" leg, you probably have other issues to worry about. It is easy enough for you to test- just use your meter and look at the voltage, then decide for yourself if it is dangerously too high.

 

[Keith_J]

Sorry to be so dense, but is that a yes or a no to causing damage to the windings for my situation?

Connected for 120/240 should be fine as long as there is a few hundred Watts on each leg. You might see minor voltage differences between the legs. Just don't expect to draw more than half the rated kW off one 120 volt leg.

 

[treeguy]

How about you take your camper wire and attach it to L1 and L0 and then take your shop wire and connect it to L1, L3, and L0. To run your camper, turn the reconnect switch to 120v single phase. To run everything, or just the shop set up, turn the reconnect switch to 120/240v single phase. Does this sound too easy?

Are people still modifying the internals of the reconnect switch as mentioned in the TM bulliten for running 120v exclusivly? I've been pondering this issue and I cannot locate the correct terminals to jump. Is Crawdaddy going to run into trouble regarding this issue?

 

[CNGsaves]

Reviving old thread for same question that seemed unanswered.

What wiring setup with 30 amp RV camper cord for 120v from the MEP-002a work to handle all the OP needs?
Surely if MEP-002a can power a whole house, it can power a camper? So this needs to be heavy duty cord hardwired to lugs on MEP-002a operating in 120v 1 phase mode? True that MEP-002a needs shutdown and restarted between changing modes of power . . ie going from 120v 1 ph to 120/240 1 ph?? To "balance" load in this camper setup, could you run something on extension cord from convenience outlet to balance power being drawn from the hardwired 120v cord from lugs?

Alternatively, what wiring setup would be done to run 220volt to power a house with interlock on the main electric panel . . . ie install an outdoor 220volt weatherproof plug with appropriate sturdy cord running from the MEP-002a? Or does everybody actually install an electric box on the MEP-002a itself, then run a cord to house? Are the convenience plugs all workable when running in 120/240 1 ph mode on MEP-002a AT SAME TIME that it has 220v cable running to house running it through interlock (assuming that you don't overload it)?

 

[storeman]

Yes convenience receptacles are operable when connected off the studs.

I simply wire L1, 3, 0 to my house 400 amp service via a 220 30 amp breaker and jump from one 200 amp panel to the other with another 30 amp breaker (all protected by home-made interlocks). I also run a fused convenience distribution 120/240 box off L1,3,0 on a 20' cord which is rarely used, but is there if I need to connect a 120 or 240 load near the unit. I leave the generator setting at 120/240. Am I asking for problems?

Jerry

 

[Isaac-1]

1, don't over complicate things

2, the front panel outlets should only be used for low amp draw items, like a work light, or maybe a hand drill as they are often wired / rewired with small instrumentation sized wiring.

3, yes it is easy to switch between 120V only and 120/240V single phase, it is a simple turn of the know while the generator is off, however depending on your installation you may then need to change the way it is grounded or the wiring going from the output lugs. There is no simple answer here without detailed information on what you need to power with the generator, and how it is wired.

When connected for 120/240V single phase mode you can think of it as having a pair of 120V legs each of which can draw half the available KW rating, OR a single 240V connection that can draw the full KW rating. If your not running any 240V loads then your generally better off in 120V single phase mode as that gives you the full KW rating available on a single connection. To put that another way when looking at a MEP-002a you can think of 120/240V mode as having a pair of 2.5KW generators when it comes to 120V only loads, instead of a single 5KW generator like you would have in 120V only mode.

 

[storeman]

Okay Ike,
You have me flummoxed. What is the difference between two 2.5s feeding a 240 breaker at 120 each leg of the breaker, and a 5kw on 120/240 feeding the same input to my panel? Do I gain by running on 120 only and creating 240 at the panel breaker?
Jerry opcorn:

 

[Isaac-1]

You don't create 240V, just 120V and you gain less concern about load balancing, for the purpose of this example assume you have no 240V loads, just 120V appliances: 52 amps in 120V only mode or 26 amps in 120/240V mode.

Now lets pretend you have 2 large window air conditioners that each draw 20 amps, plus a refrigerator that draws 8 amps and lights that draw 4 amps for a total of 52 amps at 120V

In 120V only mode this is not a problem and would put you at 52 amps of load, or 100% capacity

In 120/240V mode this load would not be possible, as you have 2 legs of 120V each rated at 26 amps. the closest you could get is 20 +8 amps = 28 amps on one leg, and 20+4 amps =24 amps on the other leg. putting you over 100% load on one of the legs and under on the other one.

In reality the MEP-002a should handle over 100% of rated load, but this gives you an idea, change the numbers to make it more drastic, this is part of the reason I suspect the MEP-016 3KW models don't officially support 120/240V mode, since your dealing with only 32 amps at 120V or 16 amps at 120/240V (with wiring modification), it is just too small of slice to manage.

Ike