MEP-804A single phase 120/240 conversion issue

[foolish]

Greetings. I've been reworking a MEP-804A going from a low WYE three-phase into a zig zag 120/240 single phase conversion using the instructions for the MEP-004 conversion. Primarily using this for a completely off grid house power system for charging up my batteries during the long, dark winter months when solar doesn't cut it completely to keep everything charged up.

I managed to get a good signal to my house inverter/charger unit to the point where it would qualify the signal and charge (so good frequency and voltage when I was watching the real-time information). Only ran for about 45 seconds but after checking all the connections afterward noticed that one of the wires coming off the TB1 was hot to the touch. Reverted back to the 3-phase configuration and verified the issue wasn't there and got some diagnotics I needed for a couple of meter/monitor wires that needed to shift. After re-enabling the single phase conversion I cranked up the generator again and ran another minute. This time I did not enable the circuit or load and was able to track that the hot (!) wire was specifically going to terminal 10 on TB1. None of the other wires on TB1 were even warm.

I've got five monitor/meter wires that were connected to the backside of TB1 that are currently disconnected as I was trying to get voltages for shifts to a new appropriate terminals for the zig zag configuration. I was hoping they would line up with some of the meters noted for moves in the mep-004 conversion but no luck. The heating issue occurred even when these wires were hooked to temporary locations I originally traced as likely candidates to provide the correct feedback that would need to be tracked.

Any thoughts on why only the 10 wire (and only this one) would be getting extremely hot? Thanks...

 

[R Racing]

This sounds very interesting. Please keep us informed on your progress.

 

[foolish]

Will do. I was hoping, if this last issue can be resolved, to do an addendum to the 004-006 conversion thread. The fact that I got a qualified signal on my internal charger/inverter gives me high hopes that it is do-able. Just kind of hit a road block since the TMs for the MEP-804A leave a bit to be desired for any real troubleshooting and diagnosis. The wiring diagram is a bloody nightmare to trace... Much less the wiring harnesses themselves on what goes where. I think I'm going to have to get my helper to stand by and crank it up for 30 seconds while I grab some voltages off the T10 -> other terminals to figure out what is going on. May also neuter the internal controls and gauges down to the bare minimum since gut feeling is one may be trying to "help" and is causing the issue then work them back onto the terminals one at a time to see which is the culprit.

 

[DieselAddict]

The 804 has a 10 wire head. It is not possible to connect it zig-zag for single phase. You will burn it out trying.

 

[foolish]

(Grumble)... See that now on the wiring diagram. Thanks for pointing that out. =/ Other folks had indicated it couldn't be done but no one actually ever said -why- in any of the threads I found.

For now I'm going to switch it back to the original 3-phase configuration and run it through an autotransformer. If nothing else that'll pull me through until spring of next year when I can eyeball this a bit more and have a few months to look at long-term options available.

 

[DieselAddict]

The why is because three of the windings are premenantly joined in a {edit} Y configuration inside the head. That locks you into delta only operation.

What I've wanted to see is how possible it would be to trace wire 10 back into the generator head and find the connection point where the three windings come together. If that joint is accessable without a lot of trouble you can convert it to a 12 wire head.

 

[foolish]

I've reverted the wiring back to the original 3-phase setup (with a fancy jumper from T11 -> T12 now . I'll see if I can get access easily to the generator head a bit later today. Depending on how bad that is I may shelve this project until spring when the generator usage/need is a lot less.

For my reference on your suggestion of converting the 10 wire -> 12 wire... Should just need to detach the 10 wire from the winding serving 8 and add a line (11), likewise detach 10 from the winding serving 9 and add a line (12)?

 

[DieselAddict]

Yep. That would do it.

 

[TheAlfredo]

Anything ever come from this?

 

[foolish]

Anything ever come from this?

I didn't get time to attempt a conversion this summer due to other commitments and have just been running the MEP-804A through an auto-transformer to bump up the voltage from 120 -> 240 for the short term using a single leg of the 3 phase. Hopefully next summer I can get it broken down and see about the conversion.

If you are looking to give it a whirl yourself another member PM'ed me with this tidbit: "If you google Bar Diamond or Collins Connection a
discussion in the forum Smok Stak should come up. This connection will supposedly give you 120/240 voltage." I haven't a chance to follow it up since I'm on hold until April earliest next year when I can take the genny offline for any duration of time. Hope that helps if you are looking at trying a conversion.

 

[mciikurzroot]

Well now I am confused, that needs no response however. But seriously, I thought the 804A had all 12 leads being brought out, it was only the 804B that moved to 10 leads being brought out .. Thanks in advance .. mac/mc

 

[Triple Jim]

Why not use two legs and get 120 and 208 for the house? Do you have a load that doesn't like 208?

 

[mciikurzroot]

I'd welcome a discussion of this .. Just how much abuse will the actual unit accept, I feel like i should know this but don't have a single experience to draw from, I have just been ingrained to always try or have as much balanced as we could within the 3 legs output. For me it's a present day operational concern. When i found the 804B units I have I "assumed" they would/were 12 lead and i would be able to wire for a single phase as Guyfang has so well documented and in his u-tube video so it never occured to me to stop and count the actual wires coming from the generator output location, TILL it was home and I had already bought it. I well understand why it was likely incorporated into the manufacturing process and it by my guess saves 20.00 dollars in production cost if not more. The solution is or seems to either build in a load for the 3rd leg or just run it and see how it goes. In a thread somewhere I reviewed if single phase is your real need then you are just as well off using an 803 and have the full single phase ability. So to actually go into the generator end bell housing and sort thru the individual windings and pull back and separate T10-T11-and T12 back apart could be easy and could be hard. Once these are wound and brought out then dipped and baked and maybe even VPI'd it can be a real task. The generator body is well built and factored for a good level of abuse/ overload factor and a high heat tolerance . The 804B units i have are terrific, built in 12' and have 3-5 hours total, not reset. But my user is a single phase. My life is great, it's the self induced problems I bring into it ..

 

[DieselAddict]

The question comes down to how you intend to use it. If its for home backup then don't worry about it. Run it off 2 phases and be done. You can you can take the third phase and run it to a fridge in the garage or any other easy to connect corded loads.

If you are going for a prime power situation where the generator is your main source of electricity I would recommend you sell it and buy one that is more suitable.

You are not going to hurt it running it for hours or even days on just 2 phases. I recommend keeping any long term demand under ~8kw. Its not likely you'll need more than 5-6kw for any length of time unless you have a really big house. If that is the case you'll be better off selling it and getting something more suitable such as the previous generation MEP-004 which does have a 12 wire head.

You'll want to do a good full load (3 phase) load bank from time to time to keep the engine nice and tidy since you'll be running it well under 50% load most of the time.

 

[foolish]

Well now I am confused, that needs no response however. But seriously, I thought the 804A had all 12 leads being brought out, it was only the 804B that moved to 10 leads being brought out .. Thanks in advance .. mac/mc

Definitely an 804a according to the identification plate on the side of the generator housing and definitely 10 leads out.

 

[foolish]

I'm completely off grid and feed the 804a into a Xantrex XW 6400 to charge my battery bank when needed. The Xantrex gets really cranky about qualifying the power feed when the phase is 120 degrees out of sync when I use two legs. End result an autotransformer with a feed from a single leg gets me a good 180 degree phase that the Xantrex likes and will work with. Overall I realize the 804a was a bad choice for the application I am using it for, but the cost was so little even adding on the autotransformer cost it'll be cheaper for me to run the thing into the ground and correct the design/layout of my system with whatever I pick up next to replace it.

 

[mcii]

Chris, thanks a lot man, I just got my head wrapped around a small point and lost sight of the bigger objective picture. Your advice will work well for the mission at hand... mac/mc

 

[71Highboy]

I'm completely off grid and feed the 804a into a Xantrex XW 6400 to charge my battery bank when needed. The Xantrex gets really cranky about qualifying the power feed when the phase is 120 degrees out of sync when I use two legs. End result an autotransformer with a feed from a single leg gets me a good 180 degree phase that the Xantrex likes and will work with. Overall I realize the 804a was a bad choice for the application I am using it for, but the cost was so little even adding on the autotransformer cost it'll be cheaper for me to run the thing into the ground and correct the design/layout of my system with whatever I pick up next to replace it.

I know it is a bit bass-ackwards, but have you investigate an MG set? three phase motor, single phase 240 generator or direct DC generator (if you are looking to feed a battery bank)? You may find a set with a reduced capacity that will meet your needs and get you the waveforms needed, or if direct DC no waveforms at all

 

[Demoh]

Very interesting, I personally would unbind the 3 windings that are bound in the head to make it a 12 wire, and this answers my questions as to if the 804s were 10 or 12 wire. I havent looked at the controls of the 804s or 805s so Im not sure if those will be happy.

A motor shop should be able to do this if somebody shadetree like myself couldnt I assume.

Are the 805s 10 wire as well?

 

[DieselAddict]

All of the units above the 10kw MEP803 are 10 wire heads.