MEP002A adventure report plus anyone tied an AC gen to a grid tie inverter as a load?

[ArnieLerma]

Hello,

I own a MEP002A and have fixed all the problems it had. Cause I'm an electronics guy, NOT a diesel guy, I looked for a genset that appeared to have an electrical problem - in my case, the lower breaker/switch panel was partially off... which meant to me that the engine was probably running fine and it was...

The unit had a broken wire at the back of the connector to the control panel, and a broken off terminal on L2 connection to the circuit breaker... those things are fixed, generator starts and runs fine, but I wanted to run it under a heavy load for a while, and wondered if anyone had any experience running one into a 4Kw solar grid tie inverter?

Solar panels are a current limited DC voltage source, I figgerred i could use a 3 phase rectifier and a couple of 400V capacitors fused at 20A which is what the Sunny Boy SB4000 says to use on solar strings, - The SB4000 wants to see 200 to 500 VDC input, and current limits itself at 4056 Watts into the 240V AC Mains... Because a generator tends to be 'stiff' power source compared to solar panels I thought perhaps I should use 100 feet of 16 gauge to act as a current limit resistor... I'm doing this as I don't have a load bank, and wanted to get fuel usage per hour figure for this generator in front of me...

I made a 3phase AC to DC converter, image here, mounting the stuff on the outside of the lower MEP002A electrical cover and thought I should ask if anyone has actually done this before... although I have found personal experience to be great teacher, I have noted that sometimes it is the most expensive teacher of all..

 

[1800 Diesel]

Asking forgiveness up front but in my ignorance of exactly what you're trying to achieve here, can you explain in more basic terms? My familiarity with solar is limited but generally most folks seem to harness the solar power which the panels convert to DC which is then run through DC-to-AC inverters for home power needs. In your case it seems you're taking AC power from the generator & then trying to set up a load cell with the components you mentioned??

Since you only need abt 7 KW to load that unit to 100 % + , why not just get a few milkhouse heaters (~1500 watts each), a small breaker panel with 5 or 6 single pole 15 amp breakers and then connect individual outlets for plugging in the heaters. Another method is the salt box or some just use an old hot water heater with smaller sized element (say 3500 watt & a 4500 watt) & wire through a breaker to the output terminals.

As for fuel usage, you should see about 3/4 gph at full load...in overloaded condition you might see 1 gph....

Kevin

 

[Isaac-1]

Building an improvised load bank for a MEP-002a can be done for under about $50-$60, just go to your local dollar store buy 5 1,500 watt cheap hair dryers (many are really about 1,200 watts), these often sell for under $10 each. (Walmart.com lists one on sale at the moment at $8.40 that claims 1875 watts with free in store pickup, and free shipping on orders over $50, as well as some that show out of stock at under $7 each ), then you just need a couple of $2 120V outlets and some scrap hook up wire. Sure some 15 amp fuses and fuse holders might be nice, but what is the worst that will happen if you have a direct short you are not connecting straight to an infinite bus like an unfused wall outlet would be, you still have the main breaker at 50 amps so you might cook the insulation on your hook up wire, but your not going to arc flash vaporize anything if you use reasonable size wire. If you already have a cube heater or hair dryer around it gets even cheaper.

Ike

 

[ArnieLerma]

1800 Diesel & Isaac, you guys have managed to make me feel foolish in my obsessive false economy of not wasting a single watt...thanks for your time and advice... and the 3/4 gal/hr figure lets me know how long my storage tank would last if I needed to run it 24/7.
arnie

 

[storeman]

I believe the 002a is supposed to burn 1/2 gallon per hour at load.

 

[1800 Diesel]

1800 Diesel & Isaac, you guys have managed to make me feel foolish in my obsessive false economy of not wasting a single watt...thanks for your time and advice... and the 3/4 gal/hr figure lets me know how long my storage tank would last if I needed to run it 24/7.
arnie

Intent wasn't to make anyone foolish--just trying to help with practical solutions. It's just the engineer in me I guess. Also I wasn't familiar with the setup you had built so I had to stay on familiar ground. I think Ike was doing the same thing...most of us don't have a bunch of money floating around so we try to go the least expensive route that achieves the desired mission goals...

Kevin

 

[1800 Diesel]

I believe the 002a is supposed to burn 1/2 gallon per hour at load.

You're correct, but when we've set these up for post-hurricane use, the 0.6 gph is about right for 4-5KW load but when we load past 6 1/2 KW, the fuel burn rate goes up beyond the TM numbers & closer to .75 gph. Also, we tend to slightly overestimate fuel consumption rates for fuel tank sizing and cost of operation estimates.

Thanks,

Kevin

 

[storeman]

I understand Kevin. Wise planning.
Jerry

 

[steelypip]

Yes, I also estimate assuming 3/4 GPH consumption and generally enjoy 1/2 GPH in reality. They are as efficient as they are noisy...

 

[ArnieLerma]

Well, it's been bitter cold down here for Georgia anyway, and I don't do cold as well as I once did even with long johns on...but I got up the nerve to hook it up tonight, and the set up seems to work, the panel in the picture uses an 80Amp 3 phase 1000 V diode from china off ebay for $15 and 2 - 1800uf 400V electrolytics, the grid tie inverter says 3.35 KWH so far (its just been running 1 hour) and it is seeing 256 VDC at end of the 120 feet of wire and is drawing about 12-13 amps DC - I dont have a DC meter that goes above ten amps, I'll check the phase leads with a clamp on after a while. The fuel gauge says its used 1/16th of a tank, the load meter on the MEP002 panel says 35% of full load.

Re the hairdryers... they don't have a KW meter on 'em like the grid tie does, and I believe the way I did it, considering I had a 4 kw solar inverter there sitting there unused, when it is dark, turned out to be cheaper though I can only draw 4kw peak and I am happy I didnt burn up the grid tie inverter...which seems happy, though its software tries to optimize current draw for solar panels... it current limits at 14 amps input, and Im getting 256 VDC.

So.. this is A way to do this, and it works..

Thanks for comments I'll post fuel use and total KWH and run time when I fill the tank again, I plan to run it till I go to sleep around 1AM... or maybe later...

 

[ArnieLerma]

Yes, I also estimate assuming 3/4 GPH consumption and generally enjoy 1/2 GPH in reality. They are as efficient as they are noisy...

yeah, I assumed that the military would want the highest effeciency possible, and for an $8000 original sticker price, you'd expect it to run like an old mercedes diesel ... re the noise, I've put a little muffler on it, on the end of a pipe but would really like it to be quieter.

 

[ArnieLerma]

7 hrs run time
33% load per panel meter
Total KWH produced 21.4 per SB4000 grid tie inverter feeding it back into the power lines.
Fuel consumption 4.4 gallons
.64 gal/hr
.2 gal per KWH or about 70 cents a KWH

 

[steelypip]

Yes, that math bears out pretty well, although fuel is nowhere near the only cost of running one of these. I never said that the small MEPs are cheap to run, just that they're efficient, which they are in comparison to all the other options in that size range. My 450 Watt Sawafuji-Onan is even less efficient, but it's a great tool when I need a few watts to run the battery charger and the wood stove blower, and at half a gallon for 6+ hours runtime I don't worry much about the $/KWH produced.

A modern coal-fired steam turbogenerator (as used by the power utilities) is vastly more efficient than either, but also the size of my house, and has a start up time measured in days - not really a fair comparison.