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Old 08-21-2017, 08:45 AM   #21
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We need to reduce amperage from 1600 amps to about 1220. Our engineer says we can do this by dialling down the digitrip in the main breaker. Has anyone done this before? Is this even possible ? The engineer says to turn it down to .7. Any insight into this would be great. Thanks in advance for any help.
You didn't say ampacity.

You want a reduction of the power bill, I'd say.

Any EE would perform a co-ordinated study before messing with the Digi-Trip.

And why is he running this by you ?

He could do it himself with a tiny screw-driver -- and in seconds.

Something's wrong about this story.
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Old 08-22-2017, 04:15 AM   #22
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W T F !

As they say " There's something rotten in the state of Denmark" !

Adjust what exactly ?

The only adjustment there could be is an over amp trip point.

You cannot just turn down a knob and expect to see the plants
power usage suddenly decrease !

So whats really going on ???

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Old 08-22-2017, 07:26 AM   #23
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Originally Posted by telsa View Post
You didn't say ampacity.

You want a reduction of the power bill, I'd say.

Any EE would perform a co-ordinated study before messing with the Digi-Trip.

And why is he running this by you ?

He could do it himself with a tiny screw-driver -- and in seconds.

Something's wrong about this story.
SHHHHHHHH!! Hush your mouth. We are hired all the time to adjust CBs after a coordination study. Can't have just any one using a small screw driver.
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Old 08-22-2017, 08:17 AM   #24
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I really wish @JDM6969 would come back and explain the reasoning. It is driving me nuts.
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Old 08-22-2017, 10:30 AM   #25
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W T F !

As they say " There's something rotten in the state of Denmark" !

Adjust what exactly ?

The only adjustment there could be is an over amp trip point.

You cannot just turn down a knob and expect to see the plants
power usage suddenly decrease !

So whats really going on ???


Complete lack of understanding of how electricity works!

Much like the difference in being shocked by a "200 amp circuit and a 100 amp circuit" in another thread.
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Old 08-22-2017, 01:05 PM   #26
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The engineer is acting like that adjustment is a dimmer switch for the entire facility
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Old 08-22-2017, 01:07 PM   #27
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The engineer is acting like that adjustment is a dimmer switch for the entire facility
Wouldn't it be great if it worked like that?


Other than costs for a larger service I don't see how having a larger service than you use would be any kind of issue.
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Old 08-22-2017, 03:47 PM   #28
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the engineer's insurance probably doesn't protect him in the case of turning that screwdriver 1/8 turn, aside from the fact that he's probably not qualified.
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Old 08-22-2017, 04:06 PM   #29
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the engineer's insurance probably doesn't protect him in the case of turning that screwdriver 1/8 turn, aside from the fact that he's probably not qualified.
Another one of those online engineering degrees?
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Old 08-22-2017, 10:09 PM   #30
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" A little bit of knowledge is a dangerous thing " !

How true !

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Old 08-23-2017, 01:39 PM   #31
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We need to reduce amperage from 1600 amps to about 1220. Our engineer says we can do this by dialling down the digitrip in the main breaker. Has anyone done this before? Is this even possible ? The engineer says to turn it down to .7. Any insight into this would be great. Thanks in advance for any help.
Is this because the existing conductors are not rated for 1600 amps? In this case you can adjust the trip rating on the breaker, but like others have said it takes a coordination study, and not just the engineer saying to turn it to .8.
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Old 08-23-2017, 03:09 PM   #32
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You (and/or the "engineer") are conflating PROTECTION with REDUCTION.

The trip settings on a circuit breaker are for PROTECTING against the excessive flow of current. The only way it "reduces" current is to trip, in which case you are "reduced" to ZERO current. Also, just as a side note, ZERO work performed, ZERO lighting, ZERO heating etc. etc....

A transformer's rating size is stating its maximum CAPACITY, but the transformer doesn't create load, it SERVICES loads. In other words just because your transformer is CAPABLE of delivering 1600A safely, doesn't have anything to do with how many amps it ACTUALLY delivers.

It all starts with your LOAD, which is work (i.e. what your facility DOES) plus losses in allowing it to do that. So if your facility is requiring 1220A for the work it does, that is what it will draw through the transformer. Period.

The transformer has some internal losses, mostly related to the load it is serving so those losses vary with the actual load. But there is a small amount of fixed losses related to the actual size (capacity) of the transformer. Those added losses are small in comparison to the load-related losses but if your transformer must be capable of OCCASIONALLY servicing a larger load, then that's just the cost of doing business.
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Old 08-23-2017, 03:36 PM   #33
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Originally Posted by JRaef View Post
You (and/or the "engineer") are conflating PROTECTION with REDUCTION.

The trip settings on a circuit breaker are for PROTECTING against the excessive flow of current. The only way it "reduces" current is to trip, in which case you are "reduced" to ZERO current. Also, just as a side note, ZERO work performed, ZERO lighting, ZERO heating etc. etc....

A transformer's rating size is stating its maximum CAPACITY, but the transformer doesn't create load, it SERVICES loads. In other words just because your transformer is CAPABLE of delivering 1600A safely, doesn't have anything to do with how many amps it ACTUALLY delivers.

It all starts with your LOAD, which is work (i.e. what your facility DOES) plus losses in allowing it to do that. So if your facility is requiring 1220A for the work it does, that is what it will draw through the transformer. Period.

The transformer has some internal losses, mostly related to the load it is serving so those losses vary with the actual load. But there is a small amount of fixed losses related to the actual size (capacity) of the transformer. Those added losses are small in comparison to the load-related losses but if your transformer must be capable of OCCASIONALLY servicing a larger load, then that's just the cost of doing business.
Thanks!

Glad you took the time to explain all that.

His response attitude took away my interest in typing.
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Old 08-24-2017, 09:13 PM   #34
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