# Melted transformer lug



## running dummy (Mar 19, 2009)

Received an emergency call out early this Thursday morning to visit one of our regular customers active Data Center. The property manager called me while I was on my way and was informing me of his "troubleshooting" findings and that no breakers have popped so he didn't know what else it could be. 

The facility had lost power sporadically in a portion of the building. Pretty much all non critical loads, minus one fire nac panel. 

The first thing I did was open the panel I thought to be the culprit. (No breakers were marked so it was more of a hunch). Panel had lost power on "b" phase. 

Tracked the pipe to a 30kva transformer that was suspended directly above the panel in a drop ceiling. 


Here were my findings:


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## Rollie73 (Sep 19, 2010)

Yup..........looks like a connection to me.


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## Deep Cover (Dec 8, 2012)

running dummy said:


> Received an emergency call out early this Thursday morning to visit one of our regular customers active Data Center. The property manager called me while I was on my way and was informing me of his "troubleshooting" findings and that no breakers have popped so he didn't know what else it could be.
> 
> The facility had lost power sporadically in a portion of the building. Pretty much all non critical loads, minus one fire nac panel.
> 
> ...


Yep...that's a problem.


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## running dummy (Mar 19, 2009)

Wire had completely burned through and had no physical connection to speak of.

I cleaned the terminal as best I could and replaced the wire and lug to get them full power. I informed the property manager that this was a temporary fix and that the transformer terminal was permanently compromised. 

I called and emailed Square D technical support to confirm my suspicion that we will, more than likely, have to replace this transformer as there is no way to replace this terminal in the field, due to factory connections. 

I doubt any further action will be taken.


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## Deep Cover (Dec 8, 2012)

I didn't see much (if any) damage to the transformer side. Couldn't you run a wire brush to clean the connection and install a new lug?


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## Big John (May 23, 2010)

Check out the discoloration on the winding lead. If it really severely overheated, that can compromise the winding insulation or even the connection brazing.

The safest bet is to condemn it.


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## running dummy (Mar 19, 2009)

Big John said:


> Check out the discoloration on the winding lead. If it really severely overheated, that can compromise the winding insulation or even the connection brazing. The safest bet is to condemn it.


That is similar to what I told my customer. I couldn't tell him "A- OK" and run it for another 30 years. :lol:


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## HARRY305E (Jun 14, 2013)

Big John said:


> Check out the discoloration on the winding lead. If it really severely overheated, that can compromise the winding insulation or even the connection brazing.
> 
> The safest bet is to condemn it.


I agree with John here You're better off with a new transformer.


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## Deep Cover (Dec 8, 2012)

I see the discoloration now. It really is surprising how often the correct answer should be "It needs to be replaced.".


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## greenman (Apr 20, 2012)

$$$$:thumbsup:


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## Safari (Jul 9, 2013)

I have come across that where I work and mostly the cause is due to
1.loose connection
2.incorrect fitting of the lug to the cable.

in my case its mostly industrial.
did you try to find why blue phase not red or yellow? 
what could be the cause ?

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## RIVETER (Sep 26, 2009)

Depending on the strength of the insulator bar holding the terminals I think that it was a good fix. I would shoot the connections with an IR camera and document that, if it is okay. Shoot all three phases and record the amperage, as well. The factory weld does need verification and the camera will show if it is compromised. If the winding insulation does not look overheated it probably was not.


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## Safari (Jul 9, 2013)

let us know the outcome am intrested to know 

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## varmit (Apr 19, 2009)

I notice basic 1/4 inch bolts, with probably no lock washers. The xfmr. connection tabs are probably 5/16 or 3/8 holes. This makes for a poor connection. I have seem this scenario before, but usually not his dramatic.

If the xfmr. tab has been this hot, the problem will probably return.


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## 360max (Jun 10, 2011)

...probable a case of a loose connection. The connection at the bonding jumper also needs to be addressed, its wrong and an NEC violation (3 wires 1 terminal), also wire brush paint off TF frame for a solid connection


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## piperunner (Aug 22, 2009)

Well the bolts used are not factory grade 5 bolts looks like no torque used and never inspected by a electrical inspector which is the problem today .
Was it in hard pipe ? so the vibration made it worst then if it was flexed in you know I could not keep that out of the picture . Other than that it looks like something that just gets done by truck slammers . Typical hack job LOL


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## Nom Deplume (Jul 21, 2013)

piperunner said:


> Well the bolts used are not factory grade 5 bolts looks like no torque used and never inspected by a electrical inspector which is the problem today .
> Was it in hard pipe ? so the vibration made it worst then if it was flexed in you know I could not keep that out of the picture . Other than that it looks like something that just gets done by truck slammers . Typical hack job LOL


So just from the photo you can tell that the bolts weren't torqued, no electrical inspection, that it was hard piped and the vibration was the cause. Also installed by a trunk slammer. I also doubt that grade 5 bolts would make a difference since the failure was where the wire connected into the lug and not where the lug connected to the bus.

It looks like most transformer installations that I have seen.


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## Next72969 (Dec 9, 2012)

Nom Deplume said:


> So just from the photo you can tell that the bolts weren't torqued, no electrical inspection, that it was hard piped and the vibration was the cause. Also installed by a trunk slammer. I also doubt that grade 5 bolts would make a difference since the failure was where the wire connected into the lug and not where the lug connected to the bus. It looks like most transformer installations that I have seen.


 i dont mean to be rude but you do know who youre talking to right? :jester:


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## Deep Cover (Dec 8, 2012)

Next72969 said:


> i dont mean to be rude but you do know who youre talking to right? :jester:


LOL...:laughing:


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## piperunner (Aug 22, 2009)

nt


Nom Deplume said:


> So just from the photo you can tell that the bolts weren't torqued, no electrical inspection, that it was hard piped and the vibration was the cause. Also installed by a trunk slammer. I also doubt that grade 5 bolts would make a difference since the failure was where the wire connected into the lug and not where the lug connected to the bus.
> 
> It looks like most transformer installations that I have seen.


Well I guess you not doing it correct my friend.
Yes by looking at that photo I can see the screw head there not grade 5 bolts no washers if you install transformers like I do you use the factory bolts that come with the lug kits for each transformer .
Hex head grade five with a washer on the bolt side and a lock washer on the nut side . They come with the transformer as a lug kit from S-D if you read the instructions with the transformer you would understand why .Grade five is for temp and torque over time hex head they have a mark on the head of the bolt it has three radial marks on top . If you don't use this stuff burn it up or pay for your transformer when it blows from vibrating the lugs loose .:thumbup: Plus by looking at that transformer it was done by a idiot Iam surprised they didnt use a toggle bolt on the lugs


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## MHElectric (Oct 14, 2011)

360max said:


> ...probable a case of a loose connection. The connection at the bonding jumper also needs to be addressed, its wrong and an NEC violation (3 wires 1 terminal), also wire brush paint off TF frame for a solid connection


I agree that the bonding jumper should have been done with double lugs. Not really something that would cause problems, but yes, its a listing violation. A guy I worked with at another company, used to do all his transformers like that. For some reason, the inspectors never gave him any problems for it either.


Nom Deplume said:


> So just from the photo you can tell that the bolts weren't torqued, no electrical inspection, that it was hard piped and the vibration was the cause. Also installed by a trunk slammer. I also doubt that grade 5 bolts would make a difference since the failure was where the wire connected into the lug and not where the lug connected to the bus.
> 
> It looks like most transformer installations that I have seen.


:thumbsup:


Big John said:


> Check out the discoloration on the winding lead. If it really severely overheated, that can compromise the winding insulation or even the connection brazing.
> 
> The safest bet is to condemn it.


Yeah, some repairs you can slide by with, but this would really be something that would be better to not give any warranty on unless they pay for a replacement transformer. 

It might be good, it might not. Hard to say. But there certainly is a BIG "what if" factor to consider here. Good post.


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## Nom Deplume (Jul 21, 2013)

Next72969 said:


> i dont mean to be rude but you do know who youre talking to right? :jester:


What difference does it make? Do you know who I am?




piperunner said:


> nt
> 
> Well I guess you not doing it correct my friend.
> Yes by looking at that photo I can see the screw head there not grade 5 bolts no washers if you install transformers like I do you use the factory bolts that come with the lug kits for each transformer .
> Hex head grade five with a washer on the bolt side and a lock washer on the nut side . They come with the transformer as a lug kit from S-D if you read the instructions with the transformer you would understand why .Grade five is for temp and torque over time hex head they have a mark on the head of the bolt it has three radial marks on top . If you don't use this stuff burn it up or pay for your transformer when it blows from vibrating the lugs loose .:thumbup: Plus by looking at that transformer it was done by a idiot Iam surprised they didnt use a toggle bolt on the lugs


I'm not saying that the installation was perfect and the points you made wouldn't make it a better installation.
I'm saying that none of the points that you made have any contributing factor in the failure that was presented by the OP. 
The pictures clearly show that the failure was the connection of the wire in the set screw lug and not the connection of the lug to the buss.

I have installed a couple hundred transformers of the years and only had factory lugs a few times. We always use regular lugs and grade 3 hardware without any failures. 
Also there isn't any code requirements that require a flex connection to a transformer. That's why there are vibration pads inside the transformers and their bolts must be loosened.

I agree that the X0 connection isn't properly made, but it had nothing to do with the failure either.


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## 360max (Jun 10, 2011)

piperunner said:


> nt
> 
> Well I guess you not doing it correct my friend.
> Yes by looking at that photo I can see the screw head there not grade 5 bolts no washers if you install transformers like I do you use the factory bolts that come with the lug kits for each transformer .
> Hex head grade five with a washer on the bolt side and a lock washer on the nut side . They come with the transformer as a lug kit from S-D if you read the instructions with the transformer you would understand why .Grade five is for temp and torque over time hex head they have a mark on the head of the bolt it has three radial marks on top . If you don't use this stuff burn it up or pay for your transformer when it blows from vibrating the lugs loose .:thumbup: Plus by looking at that transformer it was done by a idiot Iam surprised they didnt use a toggle bolt on the lugs


...the fail point was at the wire connection, as the pic clearly shows, it had nothing to do with pipe/flex connection or bolt grade.


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## gnuuser (Jan 13, 2013)

nickson said:


> I have come across that where I work and mostly the cause is due to
> 1.loose connection
> 2.incorrect fitting of the lug to the cable.
> 
> ...


sometimes wire color conventions are different and the original installer probably used what they had.
I see this often in industrial settings.(conductor color misuse)

just noticed your location I haven't been there in over 40 years magnificent country tour while in military:thumbsup:


to the op overheated connection to the windings would be a prime indicator to replace the xformer.
if just the conductor burned off without physically damaging the lug then it would at least warrant a megger test befor restoring power.


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## running dummy (Mar 19, 2009)

-just regular 1/4-20 bolts were used, no lock washers on any. (I used it on my lug when I installed the new one and checked all other connections. Seemed fine)

-transformer was hard piped

-I amprobed all three phases and it seemed fairly balanced. Nothing out of the ordinary. This place is pretty old though, not saying it wasn't an old issue that isn't present anymore. I also feel that this was more than likely a poor connection on the wire terminal of the mechanical lug at the time of the original install. 

I will give an update once the Square D emails me his response.


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## 8V71 (Dec 23, 2011)

running dummy said:


> I also feel that this was more than likely a poor connection on the wire terminal of the mechanical lug at the time of the original install.


I think everyone here will agree with that. Long convoluted threads are more fun though.


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## 8V71 (Dec 23, 2011)

Next72969 said:


> i dont mean to be rude but you do know who youre talking to right? :jester:





Nom Deplume said:


> What difference does it make? Do you know who I am?
> 
> 
> Also there isn't any code requirements that require a flex connection to a transformer. That's why there are vibration pads inside the transformers and their bolts must be loosened.


You need to be a regular here to understand the humor in Next's post. 

Piperunners mention of flex was also thrown in as sarcastic humor. :laughing:


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## Safari (Jul 9, 2013)

gnuuser said:


> just noticed your location I haven't been there in over 40 years magnificent country tour while in military



well 40years is a long time.so much has changed since.
glad to know you were here 
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## retiredsparktech (Mar 8, 2011)

running dummy said:


> -just regular 1/4-20 bolts were used, no lock washers on any. (I used it on my lug when I installed the new one and checked all other connections. Seemed fine)
> 
> -transformer was hard piped
> 
> ...


I had the same type of repair about ten years ago. I repaired it the same way as the O.P.
Those Illsco terminals aren't the greatest for heavy current. With the screw slot set screw, you really can't get that tight of a connection. It's obvious that the other connections were OK.
It looks like the hardware used was included with the transformer. It's the same as the hardware used on the taps.


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