transformer hook up

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wcollinge2000

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I have a question about hooking a transformer 12,500 to 480. It is a 2500kva and they want to hook a blower to it so it will be 2880 kva. well all the switches are full there is a 1000 kva transformer that they(company) wants me to connect to the switch . there is #2 going to the transformer now . they want me to hook and just make the fuses bigger like 180 amp now I know that I can increase the fuses as per 450.3 tables and other articals like 240.100. there are others but as the 1000 kva has been in service quite some time and the secondary conductors go more than 25 feet . none are fused until they get to the different mcc's on different parts of the bldg. some do exceed 100 feet all together they way exceed 100 feet in artical 240.92 This is a company that falls under this artical. what is recommended I feel that we need to up size the feeders to the 1000kva to the size of the fuses I also look at artical 90.1 b I feel that they are going to try to make me leave the wires the size they are and will try to add to the larger transformer later the load at present that will be connected to the larger one is 958 on the secondary . now that is at present I know that they want to add atleast 1800 more in the not so far future . It would not be fully loaded but there going to push the limits eventually. now this is all continuous load. motors. there is no duty reduction at all none in the plant say for maby two 5 hp's that have a mechanical restriction from keeping them both running only one of those but that does not pertain to this question. Is there any other articals that are relevant. I have 210.19 ,20,215.2 ,3 220.200 230.200 and the ones in the 450's to me it just doesn't seem right to beable to fuse the wires at such a high ampacity or am I reading into it wrong . I believe that I can go to 150 amp without changing wires to the 1000 kva but that seems to me way out of wack. or am I missing some articals some advice this is the first time working with this and I am not really sure I just don't want to do it wrong. thanks:confused:
 
wcollinge2000 said:
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I am sorry to be the one to say this... but I cannot understand your description of the situation.

You want to connect a 12.5kV to 480V, 2.5MVA xfmr up to what, or is this the source? Forget about the blower for now.

What switches are full? Does the 2500kVA xfmr feed switchgear? Is it the switchgear that has no unused switches? Shall we assume it has no available spaces to add another switch?

Does the #2 go to the 1000 xfmr or the 2500 xfmr?

Let's deal with this part first, OK?
 
there are 6 transformers now with a primary 12,475 volts. there is a bank of 6 switches that feed these transformers , we are adding a 7th transformer that is rated 2500kva. the smallest transformer is a 1000kva. the company wants me to connect the 7th transformer to the same switch as the 1000kva .there is #2 mv90 wire feeding the 1000kva transformer right now . the input amps to the 1000kva are 46 and some change and the needed amperage to the 2500kva will be 115 if i remember what I calculated that is in the ball park . any ways 161 total amps for the two . he (company) says that I do not need to change the wires to the 1000kva transformer if I just put smaller fuses in . I know this company and know that they will put the fuses needed to max this out . the next size fuse is a 170 . well figuring even if it is a supervised location there to me is no way I want to do this. I feel that the min size should be atleast mv 105 wire to both #1 as per the ampacity tables. that should cut the mustard but still seems under but the code says it should handle it. here is some more info on the 1000kva the secondary 480 volt wires go to 4 sets of mcc banks seperatly one goes 70 feet and hits a set of fuses at 800 amp, another goes 120' and hits a set of 800 amp fuses, third set goes 110 feet and terminates in a 600 amp breaker and the fourth set goes 100 feet and terminates at a breaker 600 amps. the total load is continuous load of motors and is actually 800 amps over the secondary amp rated load of the transformer. on the 7th transformer we are actually going to take one of the mcc banks load we are connecting a distribution panel with a breaker set to 3000 amps this is 480 also breaker can be set to 4000 amp the load that is new to the plant that will be added is going to be 948 amps this is new to the plant this year they are always adding new things because they think just because there is buckett space there is room to add more. xcell is seeing if the feeders 12500 volt are going to handle the added load. I am just very leary of all of this and do not trust the man that is telling me to just hook #2 and go for it it will handle it . there useing his word like he is a god . he just passed his masters license in minnesota took him 5 times. I may not be the brightest bulb on the tree but it only took me one time so I just don't always trust what he says and have yet to find where I can put these transformers on like this what says I cant make the fuses higher than what the wire can actually handle. there is danger signs popping up for me. is that a better description .I want to have an engineer do this so his name is on it.
 
wcollinge2000 said:
...is that a better description
Click to expand...
It's a better description but there are still too many questions and unknowns to give a definitive answer.
wcollinge2000 said:
I want to have an engineer do this so his name is on it.
Click to expand...
I'm inclined to agree :wink:

Wish you the best...
 
WC, I hope you don't mind, but your single paragraph style is very difficult to read. This is your second post, separated into several paraghraphs, but no ther changes. What do you think?

_______________________________________________________________

there are 6 transformers now with a primary 12,475 volts. there is a bank of 6 switches that feed these transformers , we are adding a 7th transformer that is rated 2500kva. the smallest transformer is a 1000kva. the company wants me to connect the 7th transformer to the same switch as the 1000kva .

there is #2 mv90 wire feeding the 1000kva transformer right now . the input amps to the 1000kva are 46 and some change and the needed amperage to the 2500kva will be 115 if i remember what I calculated that is in the ball park . any ways 161 total amps for the two .

he (company) says that I do not need to change the wires to the 1000kva transformer if I just put smaller fuses in .I know this company and know that they will put the fuses needed to max this out . the next size fuse is a 170 .

well figuring even if it is a supervised location there to me is no way I want to do this. I feel that the min size should be atleast mv 105 wire to both #1 as per the ampacity tables. that should cut the mustard but still seems under but the code says it should handle it.

here is some more info on the 1000kva the secondary 480 volt wires go to 4 sets of mcc banks seperatly one goes 70 feet and hits a set of fuses at 800 amp, another goes 120' and hits a set of 800 amp fuses, third set goes 110 feet and terminates in a 600 amp breaker and the fourth set goes 100 feet and terminates at a breaker 600 amps.

the total load is continuous load of motors and is actually 800 amps over the secondary amp rated load of the transformer. on the 7th transformer we are actually going to take one of the mcc banks load we are connecting a distribution panel with a breaker set to 3000 amps this is 480 also breaker can be set to 4000 amp

the load that is new to the plant that will be added is going to be 948 amps this is new to the plant this year they are always adding new things because they think just because there is buckett space there is room to add more. xcell is seeing if the feeders 12500 volt are going to handle the added load.

I am just very leary of all of this and do not trust the man that is telling me to just hook #2 and go for it it will handle it . there useing his word like he is a god . he just passed his masters license in minnesota took him 5 times.

I may not be the brightest bulb on the tree but it only took me one time so I just don't always trust what he says and have yet to find where I can put these transformers on like this

what says I cant make the fuses higher than what the wire can actually handle. there is danger signs popping up for me. is that a better description .I want to have an engineer do this so his name is on it.
 
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