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Thread: MEP-003A hook up question

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    Default MEP-003A hook up question

    My new generator runs great, and the two 110 outlets work fine. I have printed out and read the tm, but I dont fully understand the knob on the full right hand side of the panel that reads voltage and the knob that changes the voltage and phase output.
    How would I want to set up the generator to output 220 to feed a panel during a power outage?


    Thanks for any help
    Jim

    M62A2
    M813
    MEP-003A

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    Quote Originally Posted by drjconley View Post
    My new generator runs great, and the two 110 outlets work fine. I have printed out and read the tm, but I dont fully understand the knob on the full right hand side of the panel that reads voltage and the knob that changes the voltage and phase output.
    How would I want to set up the generator to output 220 to feed a panel during a power outage?


    Thanks for any help
    Jim

    M62A2
    M813
    MEP-003A
    #1 - Have an electrician install a disconnect switch and power inlet box & cable.

    #2 - Have everything correctly grounded. Use a grounding rod at the generator.

    The voltage adjustment knob to the far right is to fine tune the voltage.
    Put a volt meter on the 110 outlet and you can fine tune the voltage with it..

    Ensure that you’re getting 60 Hertz. This is adjusted with the throttle knob. If you idle the generator too low it will damage it.

    For 120/240 set the "AC Outlet Reconnect Switch" to 120/240 1PH and set the ammeter/voltmeter transfer switch to the setting in the image below.

    Look at the diagram on the door to the cable connections and compare it to the "AC Outlet Reconnect Switch" and look at how it wired below and you will get the idea...
    LO is your common
    L1 & L3 each put out 120 so together you get 240.

    Be sure to have the breaker off until after the generator has warmed up and you verify that your settings are correct and you’re getting the correct output.

    Have your electrician verify the output before feeding it to your house.

    Anyone else chim in with anything I left out..
    Andy...
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    Last edited by coyotegray; 09-12-2009 at 21:19.
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    Keep in mind I do not own a MEP-003a, but do own a smaller 3kw MEP-701a and have skimmed over the MEP-003a TM. First a little basic theory your generator internally is either a 6 or 12 lead reconnectable generator (the distinction does not matter for our purposes here) these leads are reconnected in various combinations by the voltage selector switch by the circuit breaker (never turn this switch with the unit running). In practical terms what this means is your generator can be set to output 120/208V Wye 3 phase power (used in commercial 3 phase equipment), 120V single phase only power or 120/240V split phase (often also called single phase) used in household electrical connections. On the generator power connector you will find screw down split lugs marked L0,L1,L2,L3, in 3 phase mode all 4 connectors are used, in 120V only mode only 2 are used, and in household 120/240 split phase 3 are used (2 lines and a neutral). This is where things start to get confusing because these military generators use a different labeling system than residential 120/240 service with its L0 (neutral), L1 (line), and L2 (line). When the selector switch is in 120/240 mode and you are wanting to connect to a residential system (through a transfer switch for safety reasons) then generator L0 connects to house L0 as neutral, Generator L1 connects to House L1 (line ), then Generator L3 connects to house L2 (line) (note the is L3 to L2). This gives you 120 Volts measured from either line to neutral and 240V measured Line to Line. Measuring these line to line and line to neutral volts and amps is what the selector switch on the CONTROL PANEL does, for single phase operation you will only use some of the possible settings for measurement. At this point you may be asking why have both a 120V only and a 120/240 single phase setting on the voltage selector switch, the answer is in 120V only mode you get access to the full output of the generator, in 120/240V mode the output is split into 2 halves with half the output going to each line output and the return coming back through the neutral, in this mode it is more important to balance your loads and so you never draw more than half the total output out of either line (again back to the use of that meter selector switch on the control panel).


    Ike

    p.s. another important question when wiring a generator up to a home system is the ground bonding of the neutral connection all the references in the TM will talk about grounding L0 (neutral) to the frame and to a ground rod at the generator for stand alone operation. When used with a transfer switch it may be necessary to unbond L0 at the generator from the frame, or use a transfer switch that has a switched neutral if the MEP003 will not run unbonded. The important thing here is that your neutral is only bonded to ground in 1 place (this is usually at the service entrance for a home) this is a point where you should talk over your plans with your local electrical inspector or other electrical professional as code requirements vary from region to region.

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    Quote Originally Posted by Isaac-1 View Post

    Ike

    p.s. another important question when wiring a generator up to a home system is the ground bonding of the neutral connection all the references in the TM will talk about grounding L0 (neutral) to the frame and to a ground rod at the generator for stand alone operation. When used with a transfer switch it may be necessary to unbond L0 at the generator from the frame, or use a transfer switch that has a switched neutral if the MEP003 will not run unbonded. The important thing here is that your neutral is only bonded to ground in 1 place (this is usually at the service entrance for a home) this is a point where you should talk over your plans with your local electrical inspector or other electrical professional as code requirements vary from region to region.
    Ike, thanks for that info.. The electrician who did my setup was in a big hurry and I think he didn't pay attention to the fact that I had it hooked up to a ground rod. I also think he was new..

    It all makes complete sense. These were designed to be used in the field where the generator was the "service entrance" and so would be the ground location.

    Thanks,
    Andy...
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    I understand everything except the transfer switch. How and why is L3-L1 selected and how does it differ from the other single phase position. I will have my electrician friend read this thread prior to a test run on the house.

    Thanks again,
    Jim

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    Jim, I am not sure I understand what you don't understand, but here goes a try. Just to clarify the transfer switch is the device you use to wire the generator into your home wiring it lets you select between the utility company power and generator power it is also used to prevent back feeding on the power line and killing a line tech when the voltage would be stepped up by the pole top transformer. On most civilian reconnectable generators there is no voltage selector switch like the MEP003 has by the breaker, instead a technician would manually reconnect the leads and in the case of 120/240v single phase power they would usually be brought out as leads marked L0, L1,L2 just like you find in household wiring with L0 being neutral and L1 & L2 being the lines/hots. For some reason, maybe having to do with the selector switch design the MEP-003 brings 120/240 single phase out on the terminals marked L0,L1 and L3 with nothing on terminal L2 as can be seen in the top middle photo Andy posted. So L0 and L1 are the same your household wiring, but L2 on your house wiring/transfer switch wiringg would be connected to L3 on the MEP-003 wiring lug.

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    Quote Originally Posted by coyotegray View Post
    Ike, thanks for that info.. The electrician who did my setup was in a big hurry and I think he didn't pay attention to the fact that I had it hooked up to a ground rod. I also think he was new..

    It all makes complete sense. These were designed to be used in the field where the generator was the "service entrance" and so would be the ground location.

    Thanks,
    Andy...

    Andy the generator frame can and should be connected to a ground rod, the important thing in most transfer switch installations is that the generator neutral to frame ground strap be disconnected so the only neutral to ground bonding takes place at the service entrance. Again this is in most situations.

    Ike

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    Quote Originally Posted by Isaac-1 View Post
    Andy the generator frame can and should be connected to a ground rod, the important thing in most transfer switch installations is that the generator neutral to frame ground strap be disconnected so the only neutral to ground bonding takes place at the service entrance. Again this is in most situations.

    Ike
    So the issue isn't having 2 earth grounds, it's having 2 neutral to ground bonds within the same system...correct..? I would still connect the ground cable running from the power inlet to the generator frame that is also connected to a grounding rod at the generator, but the neutral post should not be connected to the generator frame??

    Thanks,
    Andy..
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    Sorry for being a little confusing. I was refering to the ammeter voltmeter transfer switch on the generator itself. I already have a transfer switch on my house, but my current generator is way to small. I can set the generator to the setting andy recommended, but I dont understand what the six different settings represent.

    Thanks,
    Jim

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    Great replies to the post guys. I learn something every time I read a thread like these on here. Thank you.

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