Review plans please

ritelec

Senior Member
I've been wiring houses as of the past few years and have not done any commercial,industrial in a while...

Through a friend it looks like I'm wiring a new restaurant to be installed in an existing strip mall.

Looking at the prints, things don't look right. Am I out in left field or did the engineer put something together that the electrician has to re engineer to make it right..

I'm confused with the 200 a feeding the 75 kva transformer from panel HP. (at 90 amps can it be protected at 200+%)

The 200 amp disconnect feeding the two 120-208 volt panels ??? should that not be there and instead go to a trough to to main breaker panels??

The load of the two LV panels..is that too much for that transformer...??

Do the numbers and diagrams look right or is it me??
 

ritelec

Senior Member
I did review and it does look like he calls for main breaker panels. But whats up with the disconnect on the secondary ?

See any issues.. ?

Thank you.
 

Joe Villani

Senior Member
I've been wiring houses as of the past few years and have not done any commercial,industrial in a while...

Through a friend it looks like I'm wiring a new restaurant to be installed in an existing strip mall.

Looking at the prints, things don't look right. Am I out in left field or did the engineer put something together that the electrician has to re engineer to make it right..

I'm confused with the 200 a feeding the 75 kva transformer from panel HP. (at 90 amps can it be protected at 200+%)

The 200 amp disconnect feeding the two 120-208 volt panels ??? should that not be there and instead go to a trough to to main breaker panels??

The load of the two LV panels..is that too much for that transformer...??

Do the numbers and diagrams look right or is it me??
A) You can go up to 250% on the primary side. Transformer primary ocpd is fine

B) You have to comply with the distances set forth in article 240 for secondary conductors of a transformer. I am assuming it's over 25' to the panels. Just make sure there is overcurrent protection in the disconnect.

C) The loads shown in the panel schedule are the connected loads. There seems to be many appliances in which the engineer took a huge deduction as per article 220. You can always do the calculation yourself if you're concerned.
 

ritelec

Senior Member
A) You can go up to 250% on the primary side. Transformer primary ocpd is fine

B) You have to comply with the distances set forth in article 240 for secondary conductors of a transformer. I am assuming it's over 25' to the panels. Just make sure there is overcurrent protection in the disconnect.

C) The loads shown in the panel schedule are the connected loads. There seems to be many appliances in which the engineer took a huge deduction as per article 220. You can always do the calculation yourself if you're concerned.
A) I see 450.3(B) shows primary and secondary protection, transformer protection @ 250%

B) I see that section in reference to "taps".. the room may be ~ 15x15 square..

C) Huge deductions?... should I suggest going up to a 112.5 k

I'm looking for secondary protection for that disconnect. Feeding those two panels (200 and 100) .. How large should that ocp be? and then "I'm guessing" , after the fused disconnect (or breaker, but then there would have to be a continuous or 80% of observance, correct?) that would go to a trough and tap to the 200 and 100.

what kind of transformer should I be looking at.. auto? dry type?

I've been pulling up some transformers on line.. they seem to be 480 delta to 208-120 wye... thats the one right.. it's just fed with straight 3 phase no neutral from the primary 480-277 ?

grounding this transformer to building steel.. The ceiling joists that the hat channel roof is sitting on I would think doesn't count as building steel.. I'm thinking I need to locate I beam or girder.. correct?

The x0 would go to building steel sized at wire size of secondary and from transformer secondary to equipment egc would be sized to ocp correct..

Thank you
I appreciate the help... been a while
 

ritelec

Senior Member
I set up an area to review the prints and will probably be best to ask the engineer directly of my questions. But, did look alittle at them and located some info which I would like to present.

The attachment shows the two panels. In his legends he shows the disconnect or at the disconnect the size of the disconnect and fuses if a fused disconnect. The print is showing a non fused 200 amp disconnect (why at 480'277? and not 250v?)

I'm wondering why he wrapped around the room to get to the meter>panel>xformer>disconnect as it goes over all the other equipment from my first post and is about 40' away instead of going over the doorway as in this attachment which would put it more like 20' away?

The two panels LP and KP are in the kitchen wall.. that I would think is more than likely why he has the disconnect. But as Mr. Valani mentioned it would need ocp. I'm guessing because the print is showing a non fused 200 it would be a fused at 200.

But then what. A flush trough underneath the 2 panels to tap the one 200 amp secondary to a 200 and 100??

I'm not sure about this. The owner in fee yesterday mentioned the engineer was the cheapest he could find, is there a reason..? Notice the WH1.. it has circuit #2 from panel lp at 120v 440 va. is that possible or should it have been 240v ?

The self contained walk in "try 480v". no circ or not in directory. Theres an existing rooftop unit that going go to panel LP 10,12,14. I looked at it yesterday and it looks like it's going into the 480v panel of the line drawing from my first post..

I'm going to go through it some more and get all my questions together, but the two biggest questions currently are, whats the proper way to fuse and feed those two panels AND should the primary and transformer be larger? The owner in fee also said there is more equipment that is not on the plan that they will be getting.

Thank you..
 

ritelec

Senior Member
I've been thinking about this job and I may walk away from it.
The size would be a bit much for one guy in the time frame they are talking about, also, I'm thinking I will be doing some "bank rolling" which I'm not comfortable with.

Before I put this to bed, what would be proper on the secondary side of the transformer?

As It looks to me with that 200 amp non fused disconnect, potentially the 200 amp panel could call for 160+ amps and the 100 amp panel could call for 40+ amps so I'm thinking that disconnect could want to see up to 300 amps on it.

Am I correct. Doesn't sound right.
Should there be a 400 amp disconnect on it? (then I'm pretty sure there's a 1/3 or so tap rule for the 100 amp panel...but)

Besides the proper loads... what would make that diagram correct?

Just wondering.

Thank you
 

ritelec

Senior Member
Plans returned. Moving on. Wondering about that disconnect though. What would have been the right way to install the two panels on the other side of the wall. And if on the same side by transformer would the two panels with there breakers and no disconnect have sufficed ?

Oh well.
 

growler

Senior Member
I've been wiring houses as of the past few years and have not done any commercial,industrial in a while...

Through a friend it looks like I'm wiring a new restaurant to be installed in an existing strip mall.
I've been thinking about this job and I may walk away from it.
The size would be a bit much for one guy in the time frame they are talking about, also, I'm thinking I will be doing some "bank rolling" which I'm not comfortable with.

I walk away from lots of restaurant jobs. Many times I don't even look at them.

To do a restaurant and make any money you need to be really familiar with not only the electrical but the GC and even the owner to make sure the money is really there.
 
Plans returned. Moving on. Wondering about that disconnect though. What would have been the right way to install the two panels on the other side of the wall. And if on the same side by transformer would the two panels with there breakers and no disconnect have sufficed ?

Oh well.
The way it's designed I believe runs afoul of 240.21(C)(2)(3) since the conductors are not in a continuous raceway all the way from the transformer to the first OCPD... also, the distance must be under 10 feet total from the tranny to the panel in order to comply with 240.21(C)(2) in the first place.

I think the easiest way to get into compliance would be to fuse the disconnect.

Another way you could do it is to size the MCBs in the two panels to be combined less than 125% of FLA, in this case 208A = 260A total. Say, size KP at 200A and LP at 60A main breaker. Then you just have to make sure the conductors for LP and KP are less than 10 feet each and it should be compliant.

From the looks of it, this project was on a serious budget, but I think the 75kVA transformer is probably not a problem. It won't give them much spare for future but after you took the 65% de-rating for kitchen equipment that ~108kVA connected load drops down to 72 or so.

I don't think I'd have arrived at the same solution as this engineer, but that's not to say there's anything particularly wrong with their design. Except for the code issues, of course :)
 

ritelec

Senior Member
The way it's designed I believe runs afoul of 240.21(C)(2)(3) since the conductors are not in a continuous raceway all the way from the transformer to the first OCPD... also, the distance must be under 10 feet total from the tranny to the panel in order to comply with 240.21(C)(2) in the first place.
Thank you for the replies..

First ocpd??? Are you talking about the main breaker "before the meter" and not the breaker in the HV panel..??

I'm sure the owner would love that idea... not sure how the utility company would feel about it. :- )
 

ritelec

Senior Member
I'm not at a book and wanted to readed the article so googled it and got this..

Now I'm really confused. "For example"

120 amp (150 amp) primary and a 34 amp ocpd on secondary??

Not getting this..

why would you install 8's on a 34 instead of going for the 280 amps the transformer would be rated for.??

Going for the min ?? not the max?? as per the example.. never thought of it that way...why would you want to min?



Also can't tell, On top they are talking about two wire then underneath "example" they are talking 3 wire..


where's my romex.. :- )
 

david luchini

Moderator
Staff member
I'm not at a book and wanted to readed the article so googled it and got this..

Now I'm really confused. "For example"

120 amp (150 amp) primary and a 34 amp ocpd on secondary??

Not getting this..

why would you install 8's on a 34 instead of going for the 280 amps the transformer would be rated for.??

Going for the min ?? not the max?? as per the example.. never thought of it that way...why would you want to min?



Also can't tell, On top they are talking about two wire then underneath "example" they are talking 3 wire..


where's my romex.. :- )
Where did you find that example? It is WRONG.

You cannot use the primary OCPD to protect the secondary conductors for a 4 wire transformer secondary.
 
Thank you for the replies..

First ocpd??? Are you talking about the main breaker "before the meter" and not the breaker in the HV panel..??

I'm sure the owner would love that idea... not sure how the utility company would feel about it. :- )
Sorry, I should have been more specific - by "first OCPD" I mean to say the secondary overcurrent protection device. e.g. the first OCPD after the step-down transformer. And yes, the main breaker(s) in the panel(s) can serve as secondary overcurrent protection as long as they are installed to meet the applicable requirements.
 
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