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3 kw gen set re-wire

m139h2otruck

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NH
We were still looking into how to use our little 3 kw gen set to run the entire house on 240 volts, and I found this info on smokstak.com:

"Install 12 or 10 ga. jumper between LO and TB-6 and set selector in 240 volt"
or "Install jumper between S1-5 and S1-6 w/ selector in 240 volt"
This modification is so the gen set has a neutral (LO) when in the single phase 240 volt position.

Anyone ever try this? It also was suggested to use only two of the three power lugs w/ the LO for neutral in the 208 3 phase position, but you only get about 2 kw using this mod and only 208 volts across the two hot leads, not 240.

Any opinions?
 

bob130ab

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3 KW Gen

3 KW is not much power. I don't think that it will run an AC system.

I have two of them and several years ago I tried to run my 220 volt deep well pump off of one. It would pump until the pump recycled with head pressure, then the Generator's circult breaker would trip. The same thing when I tried to run a 110 V air compressor. They will run saws, lights, battery charger etc.

Good luck. If you are suscessfully, let us know how many applicants you can run.

Bob M
 

ems4ty

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3KW at 208V is only 14.42 Amps and 3KW at 240V is only 12.5 Amps, if I did my math correctly. As an HVAC Contractor, I could tell you that running most residential A/C Units from this size of a generator would most likely trip the generators circuit breaker due to the starting current required of the HVAC Systems compressor. Most inductive type of loads (such as motors) take a substantial amount of current to get them started, then they'll run at or below their rated amp rating on the data plates. As for resistive type of loads, what you see is what you get...

You would be able to run lighting, and newer refrigerator, but that's probably about it. 3KW isn't a whole lot of juice for running a house.

Just a thought...:-D
 
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m139h2otruck

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Location
NH
AC not really a problem for us in NH in December, just want to be able to use lights and keep the refrigerator running. Furnace should run on 3 kw if we only run it when the refrigerator is unpluged. Have Town water and gas hot water so not much else needed. Would love to have a 5 kw, but the size, weight and fuel use is a little high! Now looking at the 5 or 10 kw Onan air cooled diesels. Who has parts and spares for these? Saturn only shows parts for the 1.5 through 10 kw gas units.
 

m139h2otruck

Member
569
5
16
Location
NH
Installed the jumper, and got 240 volts between the two hot legs and 120 volts from each hot leg to the L0 neutral. Seem to work great.

Now, can the same thing be done with the little 1.5 kw units? Same problem. no neutral when the switch is in 240 volts.

Thanks
 

AN/ARC186

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Just remember there is a big difference between 240 and 208.(yeah, I know 32 Volts!:twisted:)
Some 240 V motor loads and electronic control units will burn out if run on 208 V
 

m139h2otruck

Member
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Location
NH
By installing the jumper, so we have a neutral, we get the correct 240 volts single phase @ 3 kw, which is what we wanted. Using two legs of the 208 3 phase setting, as suggested by someone, still only gives you 208 volts single phase and only part use of the already limited 3 kw rating (about 2 kw).

As an aside, ran the unit last night (do this every 2 weeks in the winter) and two of the cylinders died, no spark. Tested and retested the electronic system, and guessed (!) that one of the little black "potted" control units was bad, just not sure which one. Removed the easy to get at control box from the spare engine and of course it was the other side! Switched everything around and with one pull, it was running again. Saturn does not show just the little black boxes on their listing for the 4 cylinder engines, only complete retro fit kits (which is what we used to retro fit this generator). Anyone know if just the black boxes are available?
 

m139h2otruck

Member
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NH
Thanks for the link, but I needed the little "black box" inside the amp box mounted on the top (side) of the engine. Got a complete retro fit kit on e-bay for $25m + freight.
 

Jakob

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Location
Louisville, KY
Not meaning to thread-jack, but I have a couple of related questions.

Is the MEP003A a good gen set to power a home? I know next to nothing about generators. Can someone point me to a better place to get more information on these gen sets and using a military gen set to power a home? After the back to back disasters here, I want to get a generator.[FONT=Verdana,Arial,Helvetica][/FONT]
 

SCSG-G4

PSVB 3003
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To power a home with most normal loads, you will probably need a 10 or 15 KW generator. As stated earlier, the motors, when they are starting can pull a lot of amps for a short amount of time (2 to 3 times their 'running' amps) - the generator has to be able to handle the surge and not trip. Add up the amp load of everything you want to run and multiply by the voltage it takes to get the watts (or just add up the watts for the lights), add in the starting factor of the motors, and that is the size generator you need.
 

Speddmon

Blind squirrel rehabiltator
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Is the MEP003A a good gen set to power a home? I know next to nothing about generators. Can someone point me to a better place to get more information on these gen sets and using a military gen set to power a home? After the back to back disasters here, I want to get a generator
It's only my humble opinion but, as an industrial electrician and the proud almost new owner of 2 MEP-003's (waiting on EUC). 10kw should be plenty to run the "average" household. Unless you happen to have an electric range and electric hot water (but maybe even with those things depending on circumstances). Cooking a meal on an electric range could easily use 5KW on it's own. Other than those two things, really the only things you'll have to worry about is the motor loads. But keep in mind that for the most part the only motors in most homes are going to be a fridge, freezer, furnace and possibly a well pump and of course the A/C. Obviously the A/C and furnace aren't going to run concurrently (other than the furnace blower, which in most cases is negligable). The odds of the fridge, freezer and well pump cycling on all at the same time is very remote. Fridge and freezer don't have a ton of draw to begin with, accept at inrush (start-up), and again the odds of starting at exactly the same time are slim. Well pumps can pull some pretty high current, but there again probably not going to start at the same time as other things. Now for the A/C, they will have a heavy draw and a high inrush at start-up, but the running load should easily be handled by a 10kw along with lights and probably the fridge or freezer already running. However, on the A/C that initial start-up current can be reduced significantly by the installation of a starting capacitor and potential relay (any GOOD reputable HVAC tech will call this a hard start kit). This can be placed on any A/C unit at any time during it's life, not just near the end to extend it's usefullness as some would have you believe. I installed one on my brand new geothermal 2 ton heat pump (for about $30 DIY) and dropped the inrush current from 75 amps down to about 44 amps.

With all of those loads in mind, I've read and heard that the surge rating on these gen-sets is quite high due the the under rating of the military units. I would guess the surge rating to be probably 200% or more of the rated current for these sets. I can hear some people saying right now, "But what about my air compressor and shop equipment?" I can't speak for everybody, but I don't do too much shop work when I'm on back-up power. You can easily and probably fairly cheaply have an electrician come in just to "amp grab" your main lines while you're turning on appliances and flushing the toilet (to bring on the pump) and tell you what you're current draw is. Then you can figure out exactly what you'll need for size, but I still think 10KW would run most households nicely.

I personally wouldn't run my home computers or sensitive electronics on a generator just because it's "dirty" power (even with a "UPS" because most "UPS's" arent nearly as good as people think, and sailsmen say they are). TV's and the such may be ok but I would run them through a surge suppressor strip (a good one).
 

rat4spd

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If I'm not mistaken, the civilian version of the 003A is 14KW or 15KW. This should be fairly evident as the single phase rating for the 003A is 10KW. When you single phase a 3 phase generator you need to de-rate to 66%, so that in and of itself indicates about 15KW on three phase.

I don't know about surge power, but as soon as I get mine hooked up, I'll find out.
 

Jakob

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Location
Louisville, KY
I have city water and my stove and hot water heater are both gas. So I think a MEP-003A would be more than enough power for my home and maybe even a neighbor, or at least enough to keep their fridge going.
 

Speddmon

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Rat4,

I've heard the same thing about the civi gen-sets being 14 or 15 KW. However from what I have seen and read, the only thing common between the two is the Onan engine. The civi gen-sets use and Onan gen head and the mil sets use something else entirely. Plus they are WAY overbuilt. Meaning they use much larger lead wire than civi models, thus allowing you to get the full 10KW on single phase. In actuality, if you look at the reconnection diagram, and the current ratings given on the nameplate ( 104a @ 120v, 52a @ 240v, 34.7a @ 208v ), using some Ohm's law we are allowed to pull about 12 KW at 120 or 120/240 and only about 7.2 KW with three phase. That's backwards from the theory, we should be able to pull way more power three phase than single.

The Smokstak forum has a lot of good info about the Mep-003a's as well. That's where I picked up a lot of useful info. And some stuff about the civi gen-sets
 

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rat4spd

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It's three phase, so you have one more conductor. Multiply 34.7 times 208, THEN because it's three phase, multiply that times 1.73. You get 12.5 KW.
 
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