re-wiring my MEP-004a for different voltages, including single phase

[smurph]

Hz is a function of RPM. Unless your genset fires up and the RPM goes sky high, then the gauge is wrong. As it turns out, the frequency gauge is the problem child of these gensets. Or rather the transducer driving it. Of the three MEP-005s I have had, I had to replace two of the frequency gauges. Luckily, a steel soldiers member has made up some digital replacement gauges. He had them in the classified section a while back but I could not find them. But he also has them on a certain auction sight we all know very well. Search for "mep-003a mep-002a frequency gauge". They work like a charm. He also has matching volt/amp gauges if you want a consistent look.

Steve

 

[captain]

Thanks for the info. I will look into those gauges. Right now its only right as it fires up and the engine is coming up to speed. Once it hits 1800rpm it settles down to 60hz and holds. I have not put it on the scope yet so I cant say its 100% accurate.

As far as the ground issue goes It is the wire that goes from the neutral lug to the ground stud on the frame. I will try it the way you suggested though and remove the other end. There are a couple thinner white wires that come down from the top to the ground stud. 2 or 3 maybe. Does anyone else have those wires going to the ground stud along with the heavy one from the neutral lug?

Thanks

 

[BadBrad1]

Personally if it was my hookup I would leave the generator bonded to the frame and ground terminal lug and just pass three wires to the house panel, two hots and a neutral. just like your power company does. I would then ground my generator from the grounding lug to the SAME ground rod as the house is attached to.

This ensures all house circuits still have a safety ground, the generator has a safety ground, and a if a neutral opens there is no alternate current carrying potential on the grounds. The rational for one ground to neutral point connection is so that you cannot accidently create a situation where you have ground wires as electrical current carriers. Current can flow between two ground rods in some instances if there is a open neutral and difference in potential (resistance) exists between two grounding points. In the above configuration it cannot happen and any hot lead to case, frame etc. is grounded preventing shock.

While this does not meet the strict definition in NEC as physically there being only one point where neutral and ground are bonded it electrically meets the requirement that the ground cannot become a current carrier and provides a safety ground on all locations. But that is just my opinion, I see no reason to run a 4 wire connection and un-bonding the generator ground IF you are grounding the generator as described above.

 

[flydude92]

Lastly is a question about the general nature of the beast. When I first fire it up the HZ peg the gauge before it calms down to 60. Does that seem about standard? I'm guessing its just an electronic thing as the engine is not over revving.

For what it is worth my frequency gauge does the same thing. My original gauge didn't read correctly from the day I bought it and it jumped on initial start up.
I recently replaced it with a good one and it also pegs on start up then settles down to 60.

 

[212sparky]

Mine does it too. I will take a video when I get home just to check.

 

[captain]

I have 2 additional small gauge wires ruining to the ground stud on the gen. From what I see on the diagrams posted early on in this thread I can only see the bonding wire to the ground stud and not the other 2. I could be very wrong in how I am reading that though.
View attachment 519373
In the above photo I circled the 2 wires. The right one has no markings at all. the left one has (written in green) M5086/2-12-9. After that it says 729B4. I can only be sure about the 29 though. The rest is very hard to read.
View attachment 519374
The left wire goes to the amphenol with the red arrow into the special relay box.
View attachment 519375
The right wire into the amphenol with the red arrow in to the AVR.

I hope this makes things a bit more clear as to what I am talking about. Thanks everyone for the continued help.

 

[res0wc18]

paging sewerzuk- paging sewerzuk.

His PM box is full and i cant contact him. fun fun.

Anyone talked to him in the last few?

 

[mromrell]

I like the very understanding wife part. Were you able to complete this project and solve the meter issues? I would like to reconfigure this unit to single phase. Currently it is a 120/208 and 240/416 configuration. MEP 804A, NSN 6115-01-274-7388, Ser FZ 58138. I would appreciate if you could point me somewhere for instruction to do so.
I watched a video you posted for a 804a but the buss bars on the back side of the board are laid out differently that on my unit (according to the ten service guy that was helping me). I might need to look at it myself to confirm. I had him come out to help as I have read so many articles of caution in doing this.

Thanks Mark

 

[mromrell]

I sent him a private message wanting to know if his 804a conversion to single 120/240 and accurate gauge readings worked out, but haven't heard back yet. if there is anyone else on that could lead the way for me? below is my question.

"Were you able to complete this project and solve the meter issues? I would like to reconfigure this unit to single phase. Currently it is a 120/208 and 240/416 configuration. MEP 804A, NSN 6115-01-274-7388, Ser FZ 58138. I would appreciate if you could point me somewhere for instruction to do so.
I watched a video you posted for a 804a but the buss bars on the back side of the board are laid out differently that on my unit (according to the ten service guy that was helping me). I might need to look at it myself to confirm. I had him come out to help as I have read so many articles of caution in doing this."

Thanks Mark

 

[bimota]

Gentlemen, it may be time to remind those interested in single phase conversions that they in fact substantially reducing the generators value and efficiency. Losing 1/3 of the generators output capacity and increasing full usage per load by 1/3.

Bottom line - converting a commercial grade long life generator to low budget residential use is NOT an effective use of resources. It is like taking a semi-truck good for a million miles and using it as a pickup truck. Because we can is not the same as we should!

 

[1800 Diesel]

Now that I have a lot of free time on my hands I was able to look at my gen and read some posts. Thanks indirectly to sewerzuk for fixing part of my issue. I now make voltage in single phase. The following quote is from him from another post in another thread. "My lead movements changed the voltage being supplied to a control transformer inside of A11 from 240v to 120v. That control transformer supplies field current. It seems to work fine on the -004a, but maybe with the higher field current in the -005a it can't "keep up?" To correct this, you would need to move the X8HH16B lead from T8 to T7 (instead of from T8 to T11, as my conversion process currently shows)." Moving X8HH16B from T11 (originally T to T7 solved the issue of no power in with the single phase mod.

Now the only problem I have left is ground and neutral bonding. In my limited understanding of electric (magic) I need to unbond neutral from ground at the generator in order to hook up to the house. I did this by removing the ring terminal from the back of L0 that is attached to the wire/ground stud on the generator frame. When I do this the generator makes no power. If I attach ground back to neutral it runs well. Is this correct or is something else misswired?

Lastly is a question about the general nature of the beast. When I first fire it up the HZ peg the gauge before it calms down to 60. Does that seem about standard? I'm guessing its just an electronic thing as the engine is not over revving.

Thanks all.

Captain--now it's my turn in the tank....I just completed a single phase mod on another MEP-004A and after checking all the wiring changes & installing the resistors on the CTs, I cranked it up & right away noticed the freq meter "pegged" downward to the left. Checked L1 & L3 and got 120v at each leg. Plugged in a light in the convenience outlet & it works. Checked frequency on each leg with an external meter. Got close to 60hz on one (didn't note whether it was L1 or L3) and my digital meter went all over the place for the other leg. Will pull recon board & verify all wiring connections again tonight. If they check out I was considering moving the X8HH16B lead from T11 to T7 like you did for the MEP-005A, (though in my case the unit is actually producing power) but there's something going wrong with the frequency. (Forgot to mention that this unit worked correctly prior to the single phase re-wire.)

Anyway, if someone can offer some insight as to which (if any) of the wiring moves would affect frequency (and it appears to be on only one leg), please do. As far as I understand the instrumentation wiring changes affect percent power & maybe the amp meter but not the freq meter.

Thanks

 

[smurph]

The frequency is set by RPM. If one leg is @ 60Hz, then the others should be too. My bet is your Hz transducer is going pear shaped. Here is how to check:

Open the operator panel with the genny producing power. Be careful! Check the terminals on the left side of the frequency transducer. It should read approx 120v or whatever the Volt gauge is reading from L0-L1. If there is no voltage at the transducer, then there are some wiring problems on the reconnect board. If there is good voltage at the transducer and the Hz gauge is still wonky, then it is the transducer. Oh, the circuit that drives the Hz gauge is hard wired. Meaning switching the panel switch to look at the different legs should not really affect the Hz gauge reading.

I have had 3 of the MEP-005. All of them have had Hz gauge problems. Sometimes they "warm up" and stabilize. But I tired quickly of messing with them and replaced them with a digital gauge made by a fellow Steel Soldiers member. He has them on a favorite auction site. Search for "MEP-003 Frequency"

Also, check the voltage at the convenience outlet. If the voltage is not stable there, then suspect wiring problems on the reconnect board. I use that outlet to check the Hz with a DVOM to verify the Hz. gauge.

In the single phase mode, L2 is not used. Checking L2 against L0 will show a wildly swinging voltage. So make sure that your wiring isn't really looking at L2 by accident. If the Hz. gauged is somehow wired up to that L2 leg, then it will do wired things.

I have converted 3 of these things. I actually put a toggle switch on them that makes it easy to go from single phase to three phase and back again (along with a jumper wire change on the reconnect board). My first conversion gave me fits because I simply wasn't prepared! I tried just jotting the wire changes down on a piece of paper and just got to it. If the wires on the back of the connection board were easier to get to, I probably would have had a better chance. The next two I did a bit differently as I went out there with a step by step written procedure. With that and the experience of the first conversion, they all went smoothly.

Just check the Hz gauge and make sure that it isn't the only problem. They go out at the drop of a hat. Work fine one day and not the next.

Steve

 

[Triple Jim]

Engine speed determines frequency. Maybe a loose connection could cause enough spikes to confuse a frequency meter.

Edit: Victim of missing new page, so I missed smurph's post above. I still think it's worth checking for loose connections.

 

[1800 Diesel]

Steve,


Just got inside from re-checking the recon board wiring. Didn't start it up after checking with it being so late. I'll go through your checklist on Friday. I'll be happy if I have a bad transducer or freq meter. The meter pegging to the lower left side really threw me off. This unit makes the fourth MEP-004A I have converted so I was definitely surprised to see the meter malfunction & assumed the worst that something was wired wrong on the board. I have a 60KW 400hz unit I can rob parts off of so I can swap the transducer & meter together.


In the meantime I documented every wire connected to the numbered lugs on the underside of the recon board. These are listed as follows:


#1-- T1, X14A8A, X14H16


#2-- T2, X15A8B, X15F16


#3-- T3, X16A8C, X16H16, X8A16B (newly moved from T3)


#4-- T4


#5-- T5


#6-- T6, X6A16


#7-- T7, X7E16A


#8-- T8


#9-- T9, X9J16C, X9K16C


#10-- T10


#11-- T11, X8HH16B ( newly moved from T8 ), X12EG16N (newly moved from T12)


#12-- T12, (plus newly added 6 gauge jumper from T2)


#13-- X13A8N


At this time I did not move X8HH16B from its new position at T11 to T7. This corrected a no field flash issue on an MEP-005A as mentioned in an earlier post on this thread, though in my case the field is being flashed & the set is producing 120V at L1 & L3.


Thanks for the good info--I'll do some checking on Friday & report back any findings.


Kevin

 

[1800 Diesel]

Engine speed determines frequency. Maybe a loose connection could cause enough spikes to confuse a frequency meter..... I still think it's worth checking for loose connections.

Jim,

I did find one of the lugs on the board that was not 100% tight when I started to back it out for identifying all the connected wires. When I put everything back in place I verified all connections were tight. Hopefully the slightly loose caused the problem with the frequency meter anomaly. I'll light it off sometime in the morning. Thanks for the assist.

Kevin

 

[1800 Diesel]

Steve,


Went out to start unit up & noticed under freq fault light on. Started up unit & the light would not clear after start-up. Set rpm with an external tach & closed main breaker & measured voltage at L1 & L3 at 120.3v. Checked frequency with an external meter & got 60.5 hz. While running, engaged start switch & under freq fault light goes out, but freq meter does not change its "pegged" condition at left side down. Checked voltage on the AC side of the transducer & read 120.3v. DC side reads 200-300 volts. I checked an operating MEP-004A while running at 60 hz and read ~0.5 volts on the DC side. Based on the extreme difference in DC voltage I will next change out transducer & freq meter.

Still watching the speed switch as a possible culprit as I had to reset it last night. Though unrelated I also noticed the fuel pump seems to run longer than normal when priming the system. Most MEP-4s that I've worked tend to start "dead-heading" (similar to the MEP-002 & 003s do) when the day tank fills up. This unit seems to continue pumping after several minutes of priming.

Edit--wondering if the wayward transducer could also be feeding a bad signal to the fault panel, hence the under freq indication??

 

[smurph]

Hmm... I doubt that the transducer is causing the under frequency. It just isn't feeding back to anything other than the gauge. So it is most likely the speed switch. It might be that your idle is so low with the speed knob all of the way in that it trips the under freq. The idle on mine is basically 48 Hz. That is with the speed knob push all of the way in. So I guess the idle RPM is just below 1500 RPM. There was a bit of variance between the 3 MEP-005s I have so I set them all the same. On one of them, if the speed knob was set at 60 Hz, then restarted, I would get an over voltage fault. So now I always start them with the speed knob fully in and then adjust accordingly. When connected to the M934, I always run the MEP at 50 Hz if I don't have anything in the back that requires 60 Hz. So I start the unit with the knob all of the way int and it takes just a few turns to get to 50 Hz.

So check that by starting at a higher RPM and see if the under freq is still a problem. If the problem goes away, you might adjust the throttle cable a bit to ensure starting at a high enough RPM.

One of my MEP-005s had similar issues with filling the day tank. Sounds like the exact same thing you are describing. The lift pumps had gummed up check valves. It would fill the day tank but never change the sound/frequency when the day tank was full. It always sounded "soft" as compared to the others. So I removed the lift pumps (pain in the rear!!!) and cleaned them up. They are quite serviceable. Problem solved. Also check that both pumps are working. Maybe one pump isn't and that is causing the issue?

The good news is that you are getting the correct voltage and freq according to your volt meter. So the rest can be sorted out. But the 60Kw 400Hz frequency meter will probably not work on your 50/60 Hz unit if that is what you are going to swap transducers with.

Steve

 

[1800 Diesel]

More bad (& confusing news)....now not getting any voltage at L1 & L3. No more under freq light (changed out fault panel). Next swap out will be a speed switch. Still confused about the strange DC voltage on the transducer. The set I installed showed no difference as far as display but I neglected to check AC or DC side of the transducer since the L1 & L3 were "dead"....

Edit--Yep I knew the 400 hz set was a no-go for a 60 hz unit...had another MEP-004A spare in the shop....

Edit & update: Changed out the speed switch and also installed another freq meter & transducer set. Started up, set speed & closed main breaker & read 120v at L1 & L3 & freq held stable near 60 hz. Onboard freq meter now working & no fault lights. Did four shutdowns & restarts with same results. Saturday will set up load test to see if the gremlins are gone...time to go get some Mississippi catfish for dinner...

 

[sewerzuk]

paging sewerzuk- paging sewerzuk.

His PM box is full and i cant contact him. fun fun.

Anyone talked to him in the last few?

Sorry about my absence from the forums recently! I have been overwhelmed with emails, PM's, and phone calls from my various youtube videos and online projects. Combine that with my 2 businesses and family life, and I have been forced to let my generator hobby slip a little bit!

Gentlemen, it may be time to remind those interested in single phase conversions that they in fact substantially reducing the generators value and efficiency. Losing 1/3 of the generators output capacity and increasing full usage per load by 1/3.

Bottom line - converting a commercial grade long life generator to low budget residential use is NOT an effective use of resources. It is like taking a semi-truck good for a million miles and using it as a pickup truck. Because we can is not the same as we should!

My conversion process does not reduce the generator's capacity at all. After the re-wire, these sets are capable of their full rated load in split phase.
I fundamentally disagree with your post; these sets make excellent backup generator sets for those of us with large power demands or extended runtimes. While a set like this may not be suitable for the average suburban home, they work quite well for a large demographic; a demographic that many of us here on the SS board fit into.

 

[R Racing]

Sewerzuk !! Its great to have you back. As you can see you have been missed !!