MEP-804B - New to me, I have a few questions

DieselAddict

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interesting! Fuel to the fire

I have nothing here that requires 3 phase, in fact we have nothing here that requires 240V! Even our well pump is 120
I would not ever be using a 3 phase load through that panel
Does that matter?

I see it looks like the 3rd phase down the middle contacts the breaker spots with the screws in them
So if I put some 120 loads on L1, some on L2 and some on L3 you are saying it would be pretty well balanced

very interesting! Learning as I go
Nope, doesn't matter. You can pull all single phase loads off of a 3 phase panel without a problem.

In industry that is done all the time. Panels that are dedicated to lighting circuits are all single phase loads even though the panel itself is 3 phase.

Don't overthink the balancing too much either. If you stay within the rated load for each phase the generator does not care. Balance it the best you can if you need MAX power but don't get carried away over it.
 

G744

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In your case, don't think of it as a 3ph panel. Think of it as an easy way to break out each leg, and size up your loads so as to keep them fairly balanced within 30% or so.

If you don't already have one, buy a good clamp-on ammeter to make your determinations on each circuit.

DDG
 

Guyfang

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In your case, don't think of it as a 3ph panel. Think of it as an easy way to break out each leg, and size up your loads so as to keep them fairly balanced within 30% or so.

If you don't already have one, buy a good clamp-on ammeter to make your determinations on each circuit.

DDG
This is how every house in Germany is wired. Three phase in, and an attempt is made to evenly spread the load. Worked here for forty forever's. Dont see why I wont there.
 

410Customs

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Saga continues!!

The batteries are not charging
I do not think they have charged once since I brought it home.
The battery charge meter, well I'm an A hole....... It has never shown a charge.
I never got around to checking out why it reads low and I never got my voltage meter out to check the batteries, because the genset just ran and ran, started each time. my volt meter needs a new 9v battery, etc etc etc like I said Im an a hole!!

Now batteries are dead and starter just clicks.
I charged batteries, preheat, prime, start, runs fine...but no charge at batteries

First thing I did is consult the TM
You would be so proud!
However I believe there is another TM for the engine specifically?
I have downloaded what I can from here but those are 804a with the isuzu

I found this just downloaded it
Yanmar engine TM


I have checked the alternator charging fuse, it is good
I have reset the battery charge circuit breaker, 25 amp and the one below it DC power something or other 7.5 amp...both appear fine.

Alternator, gauge, fuse, control panel, and battery wires/connections are good.....belt has proper tension.
I will be cleaning up the battery cable connections at the convenience port there is some corrosion there. I am charging the batteries again with a small generator

Next time I start this thing up I want to test the alternator for 28V DC at idle

As I understand it with the 804b much of the controls are 24V and this genset will shut down if the alternator is not producing power?

Also the alternator has one wire that is not connected to anything?

Is there an alternator wiring diagram?


Thank you!!!!!

I do have a 24V battery charger
Can I hook up a 24V battery charger at the slave receptacle? How?


Battle on!

TM SAYS:
SYMPTOM
12. BATTERY CHARGE ammeter shows low or no charge.
TEST OR INSPECTION

Step 1. Check BATTERY CHARGER FUSE.
CORRECTIVE ACTION

If BATTERY CHARGER FUSE (WP 0004, Figure 1) is blown, notify next higher maintenance level.
TEST OR INSPECTION

Step 2. Check fan belt.
CORRECTIVE ACTION
If loose (WP 0002, Figure 1), notify next higher maintenance level.
TEST OR INSPECTION

Step 3. Check for loose or broken wires.
CORRECTIVE ACTION
Check for loose or broken wires at the back of the battery charging alternator (WP 0002, Figure 1)
and BATTERY CHARGE ammeter (WP 0004, Figure 1). If wires are loose or broken, notify next
higher maintenance level.
SYMPTOM

13. BATTERY CHARGE ammeter shows excessive charging after prolonged operation.
TEST OR INSPECTION
Step 1. Check batteries for low electrolyte level.
CORRECTIVE ACTION
If low, refer to WP 0013, Service. If level is correct, go to Step 2.
TEST OR INSPECTION
Step 2. Check battery connections.
CORRECTIVE ACTION
If loose or corroded, notify next higher maintenance level.
 
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Guyfang

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Next time I start this thing up I want to test the alternator for 28V DC at idle

There is no "Idle" for this set. It runs at rated speed, all the time. Loaded or not loaded.

TM SAYS:

What TM?
 

410Customs

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North Idaho
I have it on my screen now
I am trying it read the tm's goes back and forth I have to flip pages to see what shunt they are talking about and this and that

I cannot get the thing to run and when I did it overspeed and shut down!!!!!!!!!
Is that because I pulled that fuse to check it?
Because I am charing the batteries?
usually it starts and runs fine now overspeed...... how does the overspeed switch work?

head swimming...... gonna keep reading I have to figure this out
 

loosegravel

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I was previously instructed by the very patient "Guy" to hold the S1 in the full right hand crank position for 4 - 5 seconds AFTER the engine starts. He was correct...this will clear up some of these faults that sometimes occur at start-up. It seems to be "a characteristic of the beast" for some of these generators. I had a low oil pressure fault on my MEP-803A unit at start-up. Holding the S1 in the crank position momentarily after the engine started would eliminate that fault. You can't hurt the starter because the engine speed sensor will kick it out when it reaches a specific speed. (Not sure what that is) I recently purchased a couple more of these units at auction. (I buy them, repair them, service them and sell them) One of them had a new alternator on it, but it was not charging the batteries. After doing some trouble-shooting I discovered that one of the wires was on the wrong terminal on the back of the alternator. Easy to fix, but it still would not charge. I then discovered that the F1 fuse was good, but one of the solder joints was broken on the back of the fuse holder. I repaired that solder joint and all was good. 28.8 vdc charging voltage. It pays to review the information that has so graciously been provided for us here on this forum. If your still confused just look at the very detailed schematics that are on the inside of the access panels on these great machines. Have a cup of coffee and relax. You will be amazed with how simple these machines really are!
 

loosegravel

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I forgot to mention that the individual wires are very clearly labeled on these machines. When you look at the schematic on the inside of the access door it very clearly shows the correct location of all of the wires on the back of the alternator. If you have an ohm meter you can check the integrity of each of the wires end to end. You'll want to disconnect the batteries if you're ohm testing though. The MEP-804B that I'm currently using will produce an over-voltage fault at start-up unless I hold the S1 on start for a few seconds after the engine starts. I don't know why this happens, it just does. If and when I sell this particular machine I will pass that information on to the buyer as well.
 

410Customs

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North Idaho
Thanks dudes!
I have a couple of ideas on what to check today

I also have a fresh cup of coffee

Keep the ideas coming!
fuse and circuit breaker seem to check out

this alternator appears to have an internal voltage regulator just like my fords
I am not sure why there is one wire not hooked to anything
Hopefully I can make some headway today

I am still in the process of installing a proper blade style transfer switch so the house can switch between main and backup generators

I will look at the generators inside schematics today yesterday I read so much oNline and in the tm I was really hopingit would be simple!
hahahahahahaha
 

410Customs

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Location
North Idaho
pics of the Hitachi 24V alt in question
Hooked the house up to the backup gen today, so all is well there
will give me time to mess w the 804b tomorrow
I have the batteries out and will charge them over night
start fresh

In the meantime, here is the alternator
appears factory
has one wire dangling, appears to be stock? I cannot find any apparent place it should go





I expected the battery charge wire(s) to be larger gauge, but them I am not used to a 24V DC generator....
Circuit breakers all check out
I do not see any burnt shunts? (I think they are called)
still trying to decipher the wiring schematics on the inside door

as always, thank you
 

410Customs

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Location
North Idaho
Thank you
I found that same diagram last night way at the end of the -24 TM (373 pages!)

So it looks like circuits 164d (w/bl) is the battery charge wire and 248a (WhT) powers the voltage regulator and the third wire 100r must be a case ground.
What is the small wire that leaves e and is dashed around the two power wires? Shielding for rf interference?

I also found that the charging system is protected by a diode and a fuse in case some bonehead hooks up the batteries incorrectly. To me a diode allows power to flow one direction, I do not think it blows like a fuse?
I know
My machine has a circuit breaker in place of the fuse I think this is the mpu that keeps getting mentioned for older unit

I have not located the diode

I am still trying to figure out what exactly the shunt is I think the tm said something about shunt provides the dc signal and is what controls the battery charging level?

took pictures of the tm so I can reference the sections about battery charging
Thanks for being patient w me!
Shunt is new to me

here is a pic of the same diagram except directly from the machine my 804b apparently has one additional wire vs the 804a

9BA24F3D-8240-42FD-AE62-B39A00051DF4.png
 
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410Customs

Member
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Location
North Idaho
Allright much progress made yesterday


I cleaned all battery connections and cable connections inside the machine
Installed the fully charged batteries
Started the machine
Was really worried as it was still not running correctly
If I release the start switch to the run position the genset would shut down immediately
Sometimes over voltage fault, sometimes over speed, under voltage abs even low oil pressure! Each time I would clear the fault and RE start

the advice to hold the switch in the start position is very sound.
I noticed I could keep it running if I held it in the start position, so I did. The engine kept running although sporadic just like a diesel that had run out of fuel and had air in the lines. I checked the fuel water separator, no water present. Oil coolant good, batteries at full charge, plenty of oil pressure so I just held the switch in start. I held it way longer then it feels like I should, but it worked. The engine began to smooth out and after a few minutes was running perfectly and I had 60hz and 120v phew!!!

however alternator still not charging batteries
With the machine at a smooth 1800rpm I got my multimeter out abs checked connections at the alternator. I have battery voltage at the battery terminal, I have a good ground and the voltage regulator wire is powered... all at 23.2 Volts = battery power. No charge from the alternator.
This tells me the alternator itself is bad

first I removed all alternator wires one at a time and cleaned the connections. No change

time to remove the alternator
Took it apart on the bench, nothing strange inside. A little corrosion some black dust but honestly it still looks very good.
no progress made there so now I am shopping for an alternator
$265!!!!! Hitachi LR235-70
35a 24v
Expensive
Little bugger

I am very happy that the machine is running properly
however it is only running w battery power, no charging

during my research I have seen many many threads for the 804a and 804b, help! Over speed fault, help running rough shuts down immediately, etc

I believe many of these threads could be solved if they simply knew to clear the faults, force it to run with the starter switch until the engine is able to work all the air out of the fuel system or until the 24v electronic controls get their power back.
All of the over speed shut downs, voltage faults etc that I had were a result of the batteries getting low while running. Slowly the generator began to run worse and worse. It went from a slight miss once in a while to sounding like it was running in one cylinder and then eventually would no longer start or run. Just like a diesel running out of fuel these things need the 24v to run on all cylinders smoothly.
It worked for me! Now i can focus on the problem at hand.

Now to get a new alternator.....$$$$$$

thank you! I am learning this machine thanks to you guys.

pics
Coming
 
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155mm

Chief and Indian
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There are plenty of other than factory parts that works as good or better than oem, just a quick jazz fingers comes up with lots of options,

 
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