MEP-805a 3 Phase To Single Phase

[stkcode]

I have a MEP-805a and recently bought a Square D NEMA N4X circuit breaker panel with 100 amp, 2 pole interior. The rating is 104 amps at 120/208 volts, 52 amps at 250/416 volts. But thats 3 phase. My understanding is I just need to use 2 of the 3 phase (legs) to get single phase (I know it's unbalanced without a load bank of some sort).

My primary question is when going from 3 phase to single phase, there is a 30% reduction in KW. So this generator is basically a 21 KW genset at single phase. When dropping a leg for single phase, what is the amperage for 208? I'm looking at running both 3 phase and single phase to 2 different circuit breaker panels.

I bought a 100 amp 22Kva, 2 pole breaker and now that I'm about to buy the wiring, I'm wondering if perhaps I bought the wrong breaker/panel.

3 phase to single phase is something I'm fairly new to. I've been doing a little research, but as usual, theres a bunch of conflicting information out there.

Thanks.

 

[Suprman]

I have a 22k 3 phase gen I use 2 legs for single phase it was kind of already set up like that by the military anyways. You dont want too much of an unbalanced load though. I have mine set up with 2 30amp plugs I have breakout boxes for them. 120v x 30a is 3600 watts and thats the max I would ever consider pulling off each leg. If yours is a 30k you can probably get a little more but I wouldnt go too much. If you are drawing 3-phase power at the same time you will need to reduce single phase useage also.

 

[zarathustra]

Just as a reference point, think of the amperage drawn on each phase of the generator as the LOAD. So the load that a three phase generator will support is the the sum of the amperage available on each phase.

To use single phase (actually it is 2 phase, but for some reason people call it single phase), you just need two legs (phases) of the generator output. That'll give you 208 volts, but if you look at almost any 220 volt appliance it usually calls for 208/220 volts, so any unit / appliance / load that has that spec will run just fine on two phases of a three phase generator. It'll take a little more current to run, but with that rating it is designed to run at 208.

The reason you lose 33% of the capability is that in that hookup you are only using two of the three phases instead of all three; since the total current available will be the sum of the amperage that each phase will generate. By ignoring one phase you lose the 'opportunity' to consume the amperage that the third phase could generate. Hence the 'unbalanced loading from two phases cranking out amps to support the load, and the third phase doing nothing. If you could find a way to consume the third phase, lets say in a basement or a garage, or any other load you will help to balance the load.

There is one fellow on the web (I think he is on this site) that claims to run his house on two phases (208 volts), and his shop on the remaining third phase -- that would help balance the load a little. In fact, that method would probably be the best (cheapest) way to run the generator with a balanced load.

good luck

z

 

[DieselAddict]

I would suggest caution loading up the generator with a lot of 120v single phase loads. You can exceed the design for neutral current and possibly damage the generator. I've not seen inside one of these units so I can't say how they have constructed it with unbalanced loads in mind.

 

[R Racing]

Just as a reference point, think of the amperage drawn on each phase of the generator as the LOAD. So the load that a three phase generator will support is the the sum of the amperage available on each phase.

To use single phase (actually it is 2 phase, but for some reason people call it single phase), you just need two legs (phases) of the generator output. That'll give you 208 volts, but if you look at almost any 220 volt appliance it usually calls for 208/220 volts, so any unit / appliance / load that has that spec will run just fine on two phases of a three phase generator. It'll take a little more current to run, but with that rating it is designed to run at 208.

The reason you lose 33% of the capability is that in that hookup you are only using two of the three phases instead of all three; since the total current available will be the sum of the amperage that each phase will generate. By ignoring one phase you lose the 'opportunity' to consume the amperage that the third phase could generate. Hence the 'unbalanced loading from two phases cranking out amps to support the load, and the third phase doing nothing. If you could find a way to consume the third phase, lets say in a basement or a garage, or any other load you will help to balance the load.

There is one fellow on the web (I think he is on this site) that claims to run his house on two phases (208 volts), and his shop on the remaining third phase -- that would help balance the load a little. In fact, that method would probably be the best (cheapest) way to run the generator with a balanced load.

good luck

z

That would be me. I have been doing it for years. Just got a mep-806a so I can run some of my bigger machines that I have on phase converters. I'm kinda lucky in a way as I have 3 braker panels. So I do A to B on 1 panel A to C on panel 2 And B to C on panel 3 . Went once 21 days straight running that way after a hurricane.

 

[bfadewole]

That would be me. I have been doing it for years. Just got a mep-806a so I can run some of my bigger machines that I have on phase converters. I'm kinda lucky in a way as I have 3 braker panels. So I do A to B on 1 panel A to C on panel 2 And B to C on panel 3 . Went once 21 days straight running that way after a hurricane.

Hi All,


I recently bought one MEP-805A 30KW GENERATOR and shipped it to Africa for use on a farm. After servicing it by replacing the filters and fluids the technician was able to get the engine started. The problem however is that the tech says he's only able to get 110 v out of the unit and in order to get 220 which is what most appliances here are built for, he'll have to "double up" the voltage. This he however warns will not be able to produce 380V, 3 phase which some of my equipment require.

Please what suggestions can you give?