Here’s an update on my (brother’s) MEP-805B. Early on (this goes back to December) I received LOTS of help from members of this forum, and a number of inquiries about this “project”.
Brother Rich bought the unit as backup 3-phase power for his business, not as an historic restoration project. He used it for about a year, and then one day it just quit like it was out of fuel. Being the family go-to guy for all things electrical, I got recruited. Bro’s business partner Hank is a good engine guy. When I got there, they had already checked out the fuel actuator and decided it wasn’t getting any power even though the wiring seemed OK. I hooked it to a variable power supply and we immediately got the engine started, so Actuator was OK. I called GAC and they said the MPU magnetic pickup should put out at least 1 volt when cranking. Tried that and nothing! Checked MPU continuity and it was open. They sold me a new one for $108, but due to UPS snafus, it got lost. So try Amazon. Same dimension and thread, they had it for $32. Refused UPS delivery a week later. Made in China, it put out >7 volts. But still no action from GAC speed control. Thought maybe the new 7V signal fried it. But it said it accepted up to 120VAC. GAC estimated a replacement was around $1K, but I could mail my unit to them and they would evaluate (not fix) it for $100. Above budget! Back to Amazon. They had what was probably a counterfeit unit with barrier strips, not plug-in to the backplane for $45. Didn’t even change the GAC ESD5500E model number! In fact just copied the GAC documentation suggesting that I call GAC’s tech support if I had any problems. Mounted it (see pix) and it worked right off the bat. Deere ran, but no volts. Steel Soldiers to the rescue! Hooked the trusty variable supply to the field winding and plenty of volts. Voltage regulator was also GAC but I wasn’t going back there. Found a “Marathon compatible” Fuerdi AVR SE350 unit for $27. Thanks Marathon for the documentation. Works great. Found that the speed control even had the loop tuning pots correctly set. Ran at 58Hz, but a quick tweak got it 60.
Bro had initially asked if we couldn’t run it without the PC. My read of the TM had the PC too involved to dump. With forum help and rereading of the TMs I was getting to the point of thinking the CIM could go. So we now had a working Deere and were making electricity. Looked at a 3 pole circuit breaker but no good bargains. Forum advice indicated that a normal CB wasn’t fast enough to protect the generator against a possible short. The way they reacted quickly enough was to have the CIM monitor current and dump the output contactor. CIM now gone to a new home. Went to eBay and found 3 “removed from equipment” 5 amp trip relays for $25 each. Replaced the 277:1 triple CT with three 200:5 CTs from Amazon for $16 each. Advice was that the Army was so conservative that this 30kw unit could probably be pushed to 60kw. If any of the relays hit the max (adjustable) it dumps the engine and output contactor.
So what about instrumentation? Back to Amazon. Turns out the 805B fuel level transducer is some sort of standard and found a % fuel level indicator that matched for $24. Also got three volt/amp (with their own CT) readouts for $16 each. Added another volt/frequency readout hooked to L1-L3 for $14. Added a water temperature readout for $17. An oil pressure readout was $26. Also added a low oil pressure cutout switch for $18. The old spring-return Reset toggle switch was wired across the oil pressure switch so you hold it while starting until pressure gets in the OK range. Also put a plain old ammeter in the alternator charging line.
What have we lost? You have to hold the oil pressure bypass switch to start. You don’t have a first-in alarm system. It just dies and you have to figure out why. There’s no low fuel warning. If we use the auxiliary fuel pump for refueling, there’s nothing to keep from over filling the tank. Over temperature doesn’t kill the system, but expert advice says that would be a plus. Easy to add. About $400 in parts now has what seems to be a reliable backup power source.
Some of the business plan has changed in the last half year. The current plan is to provide backup power to a 5 unit trailer office complex. We tried it on a 2-unit portion and when the A/C went on the 805B didn’t even hiccup. Project declared a success. Any questions cheerfully answered. All leftover pieces have gone to new homes.
Don
It's a great runner though. I was able to load test it up to 125% using a brine tank. (Check previous posts if your curious) It's a great way to put a load on these things. I was a little leery of doing this on something this big, but it worked flawlessly. Thankfully the screen is all good too. Just a little over 1100 hours on the meter. I'm sure that I'll find a good home for it.
