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

410Customs

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Thanks for having me! This forum is full of great information about my gen set
I have been researching for a few days about this unit and its capabilities.

First off my name is Jamie, we live completely off grid in North Idaho next to a river at the base of a mountain.
We love it here! However the off grid system that came with our homestead has been needing some upgrades and changes to suit our needs.

I recently picked up this diesel genset to help repower our homestead. The house came with a Kohler propane standby generator that now with 2500 hours on it is in need of an engine rebuild
Not happy with the idea of a standby generator or chewing through so much propane each winter I have decided not to fix the kohler and to instead repower with diesel
That leads me here

I, like many before me, failed to see that this genset is 3 phase only. until AFTER I had it home
I need single phase , or I should say in order to achieve the best fuel efficiency and to keep from introducing an unbalanced load into this genset I would like to pursue actually converting this 10 wire unit to single phase
By one of two ways:

(Somebody please stop me if I am missing something)
1. Actually going inside the "head" or stator and separating the two additional wires for the 12 bolt board conversion
OR
2. Replace the AC generator with a 12 wire single phase generator

Is this possible?
I have seen it discussed many many times, but nobody has actually documented perusing either option
Here are two good threads on the issue:



QUOTE from that thread:
"the problem i see is that these are 3 phase only right? so if you run single phase you are just going to get 120-208
volts and use only 2 of the 3 windings, so you will only get a 10 kw genset. there is just no way around this if this
is a 10 wire gen head as i assume it is. so without replacing the gen head ( a viable option ) you have gained nothing over a mep-803"


QUOTE from that thread:
Its true that in a perfect world there would be no imbalance. Anytime you allow single phase loads on a multi-phase source you
WILL have phase load imbalances. What this does is causes uneven heating in coils and higher neutral currents. Normally this is a
bad thing. If the generator was wound such that each set of phase coils were organized into three quadrants each 120 degrees apart
the uneven heating would be magnified. The way these things are actually wound is the winding stagger and the angular separation is
based on the number of poles on the rotor. As an example if there were 3 coils that were 120 degrees apart the rotor would be 2-pole.
If you have a 4-pole rotor the coils will be 60 degrees apart. What this does is more closely couple the coils from a thermal perspective.
This gives you more resistance to the thermal problems that come from imbalances.

I've attached a graphic that gives you a good idea how the winding of the stator is done. This is for a motor but the basics are exactly the same.

Now.. The interesting part is even though the 804 is technically a 10 wire head it has the exact same windings as a 12 wire head.
The only difference is that 3 of the wires are connected together inside the head instead of bring brought out. What the is interesting is this
- it is theoretically possible to modify the stator to be a 12 wire setup. I've been looking around to get my hands on one (804 stator) to find

out how hard this will be able to pull off. If anyone has one, even a blown one, send it to me."


I have a 804B outside with 158 hours on it

Runs flawless and is in like new condition
I can use the 208 power I am sure, I understand this would result in using two of the 3 windings in the stator, essentially a 10K unit, not running optimum 80% of the engines load, and not getting premium fuel mileage.

I would rather actually convert this thing to single phase.
I am a mechanic of sorts and I have a custom truck shop at my house
I am not scared to take things apart and put them back together or modify machines to suit my needs


My research says the AC generator in my machine is made by Marathon Electric
single bearing
Rotating Field
Synchronous
brushless
fancooled

Coupled directly to Yanmar turbo diesel 4 cylinder


Would it be possible to simply unbolt the ac generator and replace it with a similar 1800 rpm, 15-20K power head that is single phase 240?

I would be interested in actually doing this
Many have come before me, every thread dies before it is determined how difficult it is to actually do the conversion.

Thank you!!
 
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glcaines

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I can't answer your questions. However, I have an MEP003A which is 10 kw air cooled genset and it powers my whole house with single phase 240 VAC. It runs my HVAC, ovens, lights, dryer, etc. all turned on at once, so 10 kw is more than enough power unless you have some extra-ordinary demands for power. Have you thought about selling the 804B and buying a smaller single phase unit? My MEP003A burns right at 1 gallon of diesel per hour under load. I would imagine the 804B would be even less efficient.
 

DieselAddict

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I think some of those quotes may be mine but that said I’ve not been able to get my hands on one to experiment on.

Based on the lack of solid data you may be better served by selling it and buying a generator known to provide single phase.

If you decide to go into the stator to attempt a mod please document the effort. You’ll be a trailblazer for sure.
 

Scoobyshep

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Anything is possible with enough effort. The head does have t10 t11 and t12 internally bonded, I imagine it wouldnt be too difficult to rework them (we did this at work with another head that was improperly tapped when rewound). It all comes down to your skill level and the effort you want to apply.

How about a transformer? Would be alot easier

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Scoobyshep

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Another thing to consider, if you manage to rework the head, you need to see what the control system will do with a configuration it was never designed to work with.

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410Customs

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Yes! I knew you guys were gonna say pretty much all of that haha


"The head does have t10 t11 and t12 internally bonded, I imagine it wouldnt be too difficult to rework them (we did this at work with another head that was improperly tapped when rewound). It all comes down to your skill level and the effort you want to apply."

That term "internally bonded" if you guys don't mind please explain
Meaning after it is wound it is dipped or coated?
How much work is it to find out?

Transformer is a good option? what does that entail? jumping up from 208 to 240?
I have also read about balancing the load using something on the 3rd pole?

but I have also read that an unbalanced load is not a huge deal on these stators because they are 4 poles wound 60 degrees apart so the imbalance is not as drastic as a stator that is say 180 out.

"Another thing to consider, if you manage to rework the head, you need to see what the control system will do with a configuration it was never designed to work with."

The models just before this with the 12 pole stator can semi easily be converted to single phase and they have what looks to be identical controls. It was my hope that once the required leads are "free'd from their bond" and routed outside the head, the conversion would be the same?

Do I have a good understanding of this?

My outback power inverters would be just fine with the 208 volts I am sure, I just want to be clear before we decide what is our next move
I know I have alot of questions. thanks for going down this path with me yet again

My skill level ..........well I have been known to do some crazy things :)

I am not sure if I am qualified, but I would sure like to find out.
Would get lots of huge hero points from the wife, and we could simply keep the 2000# genset we already drug home knowing it is setup properly and running at peak efficiency
 
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Scoobyshep

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Couldnt tell you how they are bonded, never opened one.

Their predecessors (00 series) requires slight changes to the controls. The 00xs are fairly dumb on the controls so they dont fuss much.

Transformer, it would probably be easiest to set the generator to 416 volt and get a stepdown transformer, (need to look carefully for one that can be retapped)

Phase imbalance has alot of room for forgiveness, worst thing you can do is run 2 legs hot and heavy and the third at 0.




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uniquify

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My outback power inverters would be just fine with the 208 volts I am sure, I just want to be clear before we decide what is our next move
I know I have alot of questions. thanks for going down this path with me yet again

My skill level ..........well I have been known to do some crazy things :)

I am not sure if I am qualified, but I would sure like to find out.
Would get lots of huge hero points from the wife, and we could simply keep the 2000# genset we already drug home knowing it is setup properly and running at peak efficiency
How many of the outback power inverters do you have? If you have 3, you could hook 1 to each pair of phases L1+L2, L2+L3, L3+L1 and should be well balanced. If you have 2, you could spread the load across all 3 phases (L1+L2, L2+L3), but not as evenly.

Never underestimate the value of hero points from the wifey. [thumbzup]
 

410Customs

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We have two inverters so the house can have 240V
However we do not use 240V anymore, even our well pump is 120

Anytime I need to weld or use my lift (240V) in the shop we run a small generator, I have a 1985 Onan 6.0 air cooled diesel genset for this
I do not like using welder, plasma cutter or large air compressors with the expensive lifepo batteries, so I set up the shop with its own generator so we do not have to.




That was the other thing I was going to ask about, adding a 3rd converter so basically the house would then be 3 phase??
I am not 100% clear on how that works
I just know that one inverter = 120V
two = 240

here is a picture of the system in question

There is no GRID here, nearest utilities are 2+ miles out
Here in North Idaho we can get tax free off road diesel as well







So nobody has ever opened a 804B stator?
I have read that it is the same 12 wire stator as the previous models?

I can find used stators / ac motors for sale online, would pictures help? I counted 12 wires coming out of one for sale on ebay, 10 large and 2 smaller leads
 

410Customs

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so one more question for this morning

How do you access the ac motor? Pull the engine? Or can the genset be pulled out the other side?
I am not afraid sounds like something that could be done in a day or two
 

DieselAddict

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Do the inverters operate in parallel and do they have transfer switches for generator power pass-through? If the answers to those questions are YES then you can't even use two phases of the generator.

If the inverters have pass-through capability then they each will have to power separate 120v branch circuits. No parallel operation.

To further we would need to know more about how the loads are wired to the power center.
 

DieselAddict

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so one more question for this morning

How do you access the ac motor? Pull the engine? Or can the genset be pulled out the other side?
I am not afraid sounds like something that could be done in a day or two
I've not torn down a 804 but if its like the smaller units that I have torn down its easiest to pull the engine and alternator together then separate them.
 

Scoobyshep

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We have two inverters so the house can have 240V
However we do not use 240V anymore, even our well pump is 120

Anytime I need to weld or use my lift (240V) in the shop we run a small generator, I have a 1985 Onan 6.0 air cooled diesel genset for this
I do not like using welder, plasma cutter or large air compressors with the expensive lifepo batteries, so I set up the shop with its own generator so we do not have to.




That was the other thing I was going to ask about, adding a 3rd converter so basically the house would then be 3 phase??
I am not 100% clear on how that works
I just know that one inverter = 120V
two = 240

here is a picture of the system in question

There is no GRID here, nearest utilities are 2+ miles out
Here in North Idaho we can get tax free off road diesel as well







So nobody has ever opened a 804B stator?
I have read that it is the same 12 wire stator as the previous models?

I can find used stators / ac motors for sale online, would pictures help? I counted 12 wires coming out of one for sale on ebay, 10 large and 2 smaller leads
Youd have to get them to sync at the right time.

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410Customs

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dammit I should have just bought a 803
hindsight is always 20/20
up here 30 miles from Canada its not as easy as it sounds to get things shipped or find good deals, so when I found this genset used we jumped on it. I did some quick research and everything I found showed me that with the 12 bolt board on the side I could easily re wire it to single phase.
Now that I drove 2 hours south to get it, hauled it home through the ice and snow, got stuck and almost slid off the road, spent a day recovering the truck and genset it is now at the house. Now I see it wont fit on the concrete block the old Kohler sits on so I need to build a new platform for it..... then of course I find out the actual model number and that it is a 10 bolt head that cannot easily be re wired.
The easiest solution maybe to sell it and get a 803.... but that takes time and more money.
So I am looking at all options on the table.
You guys are awesome for helping me
This is alot to wrap your head around

So can I hook it up to two poles, use the 208 and run it without perfect balance for a while?
Should I put some shop lights on the 3rd pole to help balance the stator?
I need to go back and take notes, head is swimming....
deep breaths...........ooooooooooofsa oooooooooofsa

This thread here:

Looks like I can buy some time running it at 208V,
Its only job in the whole world is to recharge our battery bank....... right now we are using a POS Generac portable
 
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Scoobyshep

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dammit I should have just bought a 803
hindsight is always 20/20
up here 30 miles from Canada its not as easy as it sounds to get things shipped or find good deals, so when I found this genset used we jumped on it. I did some quick research and everything I found showed me that with the 12 bolt board on the side I could easily re wire it to single phase.
Now that I drove 2 hours south to get it, hauled it home through the ice and snow, got stuck and almost slid off the road, spent a day recovering the truck and genset it is now at the house. Now I see it wont fit on the concrete block the old Kohler sits on so I need to build a new platform for it..... then of course I find out the actual model number and that it is a 10 bolt head that cannot easily be re wired.
The easiest solution maybe to sell it and get a 803.... but that takes time and more money.
So I am looking at all options on the table.
You guys are awesome for helping me
This is alot to wrap your head around

So can I hook it up to two poles, use the 208 and run it without perfect balance for a while?
Should I put some shop lights on the 3rd pole to help balance the stator?
I need to go back and take notes, head is swimming....
deep breaths...........ooooooooooofsa oooooooooofsa
You can use 2 legs (208 is usually fine for 240 loads) and wire a light or heater to the 3rd leg (few hundred watts is better than nothing).

The first one I got was a 004, which is on the big side for my application, but like you it came down to what was available and i didnt have to drive across creation and not having to break the bank. So sometimes ya gotta take what you can get and make it work

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DieselAddict

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These things have a generous engineering overhead. You can run them unbalanced no problem. You won't be able to get full nameplate out of it but if you keep your demand down around 8-9kw then its not really a problem. Its not ideal but people worry about it far more than they need to (assuming you don't go load crazy).

How about putting a battery charger on the third leg? Do a DC coupled setup between the generator and the inverters.
 

410Customs

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OOOh I like this idea, In fact we have a 12 volt battery bank that is separated from the house, we run 12V into the house for charging our phones, I pads, etc


Will it matter that the 208V load on 2 legs will be 7-8000W while just a small 110V battery charger on the 3rd leg?
I'm guessing its better then running nothing
I plan to put this genset inside an enclosed structure, so it would be nice to have a overhead light in there while its running, I can think of a few things to put on that 3rd leg


I still want to know if we can convert these 804b to single phase
I am hoping to find a picture of this ac motor online, the actual one used in this unit.
might be helpful!
 
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DieselAddict

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The way to think about it is like this, Using 2 legs means you paid for a 15kw generator but GOT a 10kw usable generator. Anything you put on that third leg gets you closer to what you paid for from a load capacity standpoint.

I think your chances of converting it to single phase is 70/30 in favor. It all depends on where those "lost" legs are physically in the alternator. I don't expect they buried them in the coil. That would be stupid. Not that companies ever do stupid things... I bet they are along the edge of the windings where the other coil end wires transition to the flying leads. Getting access to them may require digging into varnish. That is something you may want to have a motor shop do. A slip with a hard and poky thing can ruin the alternator.
 

Guyfang

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so one more question for this morning

How do you access the ac motor? Pull the engine? Or can the genset be pulled out the other side?
I am not afraid sounds like something that could be done in a day or two

OK, here we go. I asked the top Dog at CECOM if the heads can be taken apart and rewired. He told me flat out NO. NO WAY. He told me you can have the main gen stripped and rewired. You can get another main gen and install it. But you can not take it apart and rewire it.

This gen set is about the absolute easiest gen set to remove a main gen that there ever was. You need to LOOK at the TM. Read about how to pull it out. The small sets are hard. Like Dieseladdict wrote, you need to pull the engine and main gen all at once. Anything larger then a 10 KW is built differently. Its a snap.

The lost leads, as Dieseladdict mentioned are not going to be found unless you take this baby completely apart.

I love three phase, so am not a "Naysayer". I would wire my place for three phase and be done with it.
 

Scoobyshep

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OK, here we go. I asked the top Dog at CECOM if the heads can be taken apart and rewired. He told me flat out NO. NO WAY. He told me you can have the main gen stripped and rewired. You can get another main gen and install it. But you can not take it apart and rewire it.

This gen set is about the absolute easiest gen set to remove a main gen that there ever was. You need to LOOK at the TM. Read about how to pull it out. The small sets are hard. Like Dieseladdict wrote, you need to pull the engine and main gen all at once. Anything larger then a 10 KW is built differently. Its a snap.

The lost leads, as Dieseladdict mentioned are not going to be found unless you take this baby completely apart.

I love three phase, so am not a "Naysayer". I would wire my place for three phase and be done with it.
Why not 9 phase? (Yes I know its not a thing)

Photo is a glimpse of the stupidity I deal with at work.


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