MEP-003A"Reconnection Switch" and Large Transformer (I Think)

[oldgenset]

I hope you can answer some questions for me. I am still learning about the generator. I just opened the service panel where the "Reconnection Switch"
is located. I did not like what I see.


First off I have no knob on the Reconnection Switch. So I don't know what position it is in. Is it only a 3-way switch or can it rotate a full 360 degrees?
If it rotates 360, can you tell me where the flat side of the shaft should be pointed for position. I have not moved it.


Can I presume that measuring voltage between L1-L0 being 120 volts, L3-L0 being 120 volts, L1-L3 being 240 volts would mean its set to 120/240 single phase?




My biggest concern is a large Black box at the bottom of the case with lots of wires looped through it and connected on top to it. I am presuming this is
some transformer of sorts. I have searched the manuals but have not found any info about its workings.


It appears to be encased in a plastic casing. My concern is that this casing is very badly cracked is several places with gaps between pieces. I think this may have happened due to diesel fuel migrating across the frame into the area and making the plastic brittle. I am looking into the possibility of maybe raising the entire compartment maybe a half inch to get it off the frame.


The generator runs and produces power. All of the gauges are working. If this is a transformer, I don't think its damaged internally, But Can I repair it in some manner?


Your input will be greatly appreciated. I am learning a lot from the information on this site and its members.
Thank you all.
It is much appreciated.

 

[Triple Jim]

Can I presume that measuring voltage between L1-L0 being 120 volts, L3-L0 being 120 volts, L1-L3 being 240 volts would mean its set to 120/240 single phase?

Correct.

My biggest concern is a large Black box at the bottom of the case with lots of wires looped through it and connected on top to it. I am presuming this is
some transformer of sorts. I have searched the manuals but have not found any info about its workings.

It appears to be encased in a plastic casing. My concern is that this casing is very badly cracked is several places with gaps between pieces. I think this may have happened due to diesel fuel migrating across the frame into the area and making the plastic brittle. I am looking into the possibility of maybe raising the entire compartment maybe a half inch to get it off the frame.

The generator runs and produces power. All of the gauges are working. If this is a transformer, I don't think its damaged internally, But Can I repair it in some manner?

That's actually two transformers that are mounted against each other, with wires looped through both. If you look at the schematic of the system, one is CT1 and the other is CVT1. They're both critical to the generator's operation. CVT1 is the magnetic amplifier that the AC regulator sends control current through to reduce exciter field current when it wants to reduce the generator's output voltage. This system of regulation is why the output voltage will often go too high, rather than too low, when there's a problem with the regulator.

Many of those transformers have cracked plastic housings by now. Mine are cracked to some extent too, but like yours, still work fine. I thought about using some electrical grade silicone sealer to seal the cracks, but haven't done it yet. Maybe this reminder will spur me into action.

 

[jamawieb]

If you can get some vice grips on the reconnection shaft, try to turn it clockwise as far as it will go. It has 3 positions 9, 12 and 3, 3 is single phase 240 and you will read voltage at L1 and L3 with L0 being neutral.

The transformers your referring to, are almost always cracked. Behind the plastic is a very hard material that everything is incased in. As long as everything works, don't worry about it.

 

[dependable]

The above probably answers your question, but I believe the flat spot on switch is facing down in 120/240.

Might be best to not turn the switch if it is in position you want. Older switches tend to get stuck in the position they were most used at in past and it can be a pain to get them to move again, involving removing fuel tank to loosen (do not fully take apart) the bolts that hold the switch together. That might be why the switch was removed, or it was broken by vise grips because it was sticking.

 

[Guyfang]

The transformers: Rule one, "If it ain't broke, don't fix it".

At best, like Triple Jim suggested, fill in the cracks. But keep in mind, that you may break/damage things in an effort to get it out and repair it. Often, the screws/nuts that hold the wires to the terminals are almost impossible to get off. Or they simply snap off. THEN you have a perfectly good transformer without a connecting screw/nut. When I brought it up to a CECOM tech rep many years ago, about the transformers and the cracking, he just laughed at me. Told me to tattoo rule one on my hand.

 

[cuad4u]

120V between L3 and L0 AND between L1 and L0 and 240V between L1 and L3 definitely indicates the reconnect switch is in the 120/240V single phase position. Reconnect switches can be VERY problematic. If you think all you will ever use is 120/240V single phase, I WOULD LEAVE THE RECONNECT SWITCH AS IS. This is from someone who has tried (with some success) to un-stick stuck reconnect switches.

 

[jamawieb]

This is a tip for anyone who has had a stuck reconnection switch. If you take the side cover off the distribution box, where you can see all the wire. Spray the reconnection switch, all over with WD-40 and gentle tap the front and back of the reconnection switch with a hammer, while trying to move the switch. With a little time the switch will release and then move the switch in between all the positions SEVERAL times. I've unstuck about 20 reconnection switches this way.

 

[oldgenset]

WOW! Not only does the switch look like a beast, It IS a Beast. I Promise to take ALL of the advice about this switch Very Seriously. I may should some wd40 on It But even Then I may just let it seep in for a very long time. As for the Transformer(s), A good adage may very well be "Let Sleeping Dogs Lie"
Thank "ALL" of you.

 

[Guyfang]

When I thought back to all the S-8 switches I ever changed, none went well. Always some kind of problem. We never removed one without having a new or good/tested switch on hand.

Never, I say again, never, remove an electrical device, by removing wires, and marking them with the terminal number that the wire came off of. I can hear the laughing now! My shop always got the "gems" that no one else could fix. A good number of times, we found that wires had been connected in places they were not suposed to be connected. So if you replace wires someone else connected in the wrong place................... Well you get the idea. When you do an electrical job, and dont have the schematics at hand, bad things can happen!

 

[jamawieb]

Also with replacing the reconnection switch, apparently the military used 2 different ones. Some of the older units have several more terminals on the switch and on the units that have less terminals, they piggybacked several wires together. So it could be a little difficult if you have two different switches.

 

[cuad4u]

Stuck reconnect switches are very common. If all you will ever use is 120/240 single phase I would leave it alone. However if you need single and three phase power you have been given good advice here. I have been about 90% successful un-sticking stuck reconnect switches by carefully loosening (NOT REMOVING) the long bolts that hold the switch sections together, spraying WD40 into the spaces between the switch sections, waiting, wiggling the switch knob, repeating, waiting, repeating etc. Then finally I take a 3/4 X 12 inch brass drift rod and place it against the switch (especially the front end) and giving the brass rod several good careful raps from a hammer and trying to turn the knob. Repeat. Repeat. Repeat. If you cannot get it un-stuck and if you need single and three phase power, I would highly recommend that you replace the entire "reconnect box" with a known good one and not try to replace the switch. In the long run you will be glad you did.

 

[dependable]

Above is my experience also, I have an 003 that came with a newly installed reconnection switch from the military. It never did work right, ended up replacing the whole box, after many hours of trying to sort it out.

 

[Smallblockfuelie]

Thanks, gents. I had 2 reconnect switches stuck in the 3 phase position. It took me the afternoon to do, but they’re both back in single phase 120/220. For those of you who are visual learners like me, I’ve got a few pictures. I ended up disconnecting the fuel lines and straps from the fuel tank, in addition to what you see in my pictures, to get to it. Once the two nuts were loosened off it went smoothly. PB blaster, a rubber mallet and working the switch carefully and all went well.

 

[Guyfang]

Good Job! Good pictures!