Step down transformer with generator, Riser

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Npstewart

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Hello everyone. Ive designed projects with several step down transformers, and designed several with generators, just never both in the same project. I put together a quick riser so I could wrap my head around this. I dont know my loads yet, so im not concerned about wire sizing and ground size yet. I just wanted to post the riser attached to this post so I could make sure im on the right track here. More opinions the better! thanks :)

PS. What determines if your a "member" "junior member" etc on this fourm? I just joined this year and im already a "member" but some people on here have been members since 2006 and it still says "junior member".
 
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charlie b

charlie b

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Looks fine to me. I presume the rectangle within rectangle at the generator is intended to be a generator breaker. A riser does not really convey any information related to distances, so I have to also presume the normal and backup disconnect and breaker are close enough to the wall to be able to count as the building's main disconnecting means.
 
charlie b

charlie b

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Staff member
Location
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Retired Electrical Engineer
Npstewart said:
PS. What determines if your a "member" "junior member" etc on this fourm? I just joined this year and im already a "member" but some people on here have been members since 2006 and it still says "junior member".
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I think it has to do with the number of times you have posted a comment. I do not know the minimum number to become a "member" or to become a "senior member." My guess is 50 and 100, but we might tell after you post another 23 times. :D
 
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Npstewart

Senior Member
lol, maybe I post too much. I get so much great input from people on here though, I try to post any question that comes up hoping that other people will learn just as much as I do.

Im not sure how far the generator will be yet either but im glad im on the right track. I think there was a similar post last week regarding this same type of installation but I couldn't find it.
 
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Joe Villani

Senior Member
Location
Westchester County NY
Step down transformer with generator riser

Step down transformer with generator riser

It looks good.

One suggestion I have is to identify the transfer switch as either 3 pole or 4 pole. (for sds purposes). I have also seen notes telling the installer to bond or not to bond the neutral at the generator, depending on the system you are designing.

Sometimes the more information you give the plan reviewer the easier it is getting the permit.
 
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Npstewart

Senior Member
I was just looking into that now actually. Thanks for the advice. Once I have this thing completed and I have my loads figured out then I will re-post the completed riser and some panel schedules. Right now im feed the transfer switch with a 3p breaker from panel MDP.

Im up in the air right now on the Xfrmr size. My load is approximately 90KW on the secondary side of the Xfrmr (208-3). I may have some other loads to add to that though, im up in the air whether to go with a 112.5 KVA Xfrmr or a 150 KVA xfrmr. I know its not good to oversize a xfrmr. I guess ill see what my definite final load is on the secondary side.
 
C

Cold Fusion

Senior Member
Location
way north
Npstewart said:
Hello everyone. Ive designed projects with several step down transformers, and designed several with generators, just never both in the same project. I put together a quick riser so I could wrap my head around this. ...
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You might consider going with standard one-line format and symbols instead of this "riser" format.

I've seen riser format used a few times and it is always confusing compared to a one-line.

cf
 
C

Cold Fusion

Senior Member
Location
way north
benaround said:
I don't like the way the two ground rods are tied together.
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Most important: Do you like Frank, Frank A, ben, benaround, or something else?

Second:
Can't leave the two grounding electrodes not tied together. So how would you like to see the two ground rods tied together?

cf
 
Hameedulla-Ekhlas

Hameedulla-Ekhlas

Senior Member
Location
AFG
Npstewart said:
QUOTE]

Hello everyone. Ive designed projects with several step down transformers, and designed several with generators, just never both in the same project. I put together a quick riser so I could wrap my head around this. I dont know my loads yet, so im not concerned about wire sizing and ground size yet. I just wanted to post the riser attached to this post so I could make sure im on the right track here. More opinions the better! thanks :)
Click to expand...

It is ok but the riser drawing is not good. It looks like you have shown a section.
PS. What determines if your a "member" "junior member" etc on this fourm? I just joined this year and im already a "member" but some people on here have been members since 2006 and it still says "junior member".[/
Click to expand...

To become a senior you have to get 100 marks (posts).

What is the limit to become a moderator anyone knows?
Click to expand...
 
N

Npstewart

Senior Member
The riser is just diagrammatic. I'm not sure what you mean about the section. Post one of your risers on here so we can get some tips.
 
kingpb

kingpb

Senior Member
Location
SE USA as far as you can go
Occupation
Engineer, Registered
With generators, transformers, and services, I think it would be better to provide a single-line and a three-line diagram. The neutral and grounding gets tricky when you have a transfer switch.

Check IEEE 446 for some good examples on how to do these systems.

Risers are OK for commercial type projects, and to show physical locations, but are limited otherwise.
 
N

Npstewart

Senior Member
The load on my generator panel is 14.5 KW which is about 40.3 amps. I was going to spec a 20KW generator and then put this on a 60A breaker. That sound right?
 
kingpb

kingpb

Senior Member
Location
SE USA as far as you can go
Occupation
Engineer, Registered
It is not possible to confirm or deny the size of the generator or transformer without knowing the loads it is serving and the sequence in which the loads are added to the generator.
 
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Npstewart

Senior Member
OK. I finished the riser with a couple exceptions. Just posting it back on here because I said I would, as always the more comments the better. For some reason I dont tend to get a lot of responses when I post on an existing thread, hopefully I will this time :)
 
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