farm service upgrade 1 main or main lug

[tortuga]

I am in the pencil and paper stage of redesigning a farm service and feeder distribution system for expansion and conversion to underground distribution.
There are 2 main large agricultural buildings, a large outdoor processing area and plans for 3 more buildings.
one of the buildings has a load over 200A and will be getting a 300A feeder.
The local utility only has single phase in this rural area.
I am thinking of putting a 800A rated Main lug (Siemens P3 or P4 not sure which yet) panelboard connected to a 800A CT can and using the breakers in the panelboard as the Mains to save on the main breaker.
I have worked on many older services that are just bussbar or gutters off a CT can full of old taps to main breakers and they get kinda squirrely.
I figure the upfront cost on a panelboard will be offset by ease of maintenance and changes that happen regularly.
But now I am wondering if its more standard practice to just have a 800A main?
I'll have a 300, 200, 200 and a 125 or 150 as mains. The 125 or 150 will supply a underground outdoor feeder that will have several hoop houses and small structures 'tapped' off it with GEC and one main breaker at each structure.
What do you all think of using a P3 main lug and having 4 or 5 breakers in it as mains?
The only issue I can think of is the panelboard would not be designed to be limited to 6 mains.
But there was never a limit on those old service gutters full of taps either.
Thoughts?
Thanks in advance.

 

[augie47]

I see no problem with either method.
You might want to make note of Art 547.9(B)(3) as the EGC is different for Agricultural Buildings.

The attached is a but antiquated but useful.
http://www.adamselectric.coop/wp-content/uploads/2015/02/Agricultural-Buildings.pdf

 

[tortuga]

I see no problem with either method.
You might want to make note of Art 547.9(B)(3) as the EGC is different for Agricultural Buildings.

The attached is a but antiquated but useful.
http://www.adamselectric.coop/wp-content/uploads/2015/02/Agricultural-Buildings.pdf

Thanks Augie thats a good reference I am reading it now. My switch gear rep just informed me that the (Main Lug) Siemens P3 and P4 panelboards only come with the 'suitable for use as service equipment' label when requested, and then they limit the provisions for breakers to 6. So ill order it that way.
I like the idea of the 5 mains in this case as then there is not a single point of failure.
Cheers

 

[electrofelon]

I am in the pencil and paper stage of redesigning a farm service and feeder distribution system for expansion and conversion to underground distribution.
There are 2 main large agricultural buildings, a large outdoor processing area and plans for 3 more buildings.
one of the buildings has a load over 200A and will be getting a 300A feeder.
The local utility only has single phase in this rural area.
I am thinking of putting a 800A rated Main lug (Siemens P3 or P4 not sure which yet) panelboard connected to a 800A CT can and using the breakers in the panelboard as the Mains to save on the main breaker.
I have worked on many older services that are just bussbar or gutters off a CT can full of old taps to main breakers and they get kinda squirrely.
I figure the upfront cost on a panelboard will be offset by ease of maintenance and changes that happen regularly.
But now I am wondering if its more standard practice to just have a 800A main?
I'll have a 300, 200, 200 and a 125 or 150 as mains. The 125 or 150 will supply a underground outdoor feeder that will have several hoop houses and small structures 'tapped' off it with GEC and one main breaker at each structure.
What do you all think of using a P3 main lug and having 4 or 5 breakers in it as mains?
The only issue I can think of is the panelboard would not be designed to be limited to 6 mains.
But there was never a limit on those old service gutters full of taps either.
Thoughts?
Thanks in advance.

I am a fan of using a service rated MLO. Actually looking at a 800 or 1000 right now, with Siemens gear. The one thing to be aware of is that if the fault current is high, it may actually be cheaper to get a main because then lower cost lower AIC distribution breakers can be used with series ratings. I'm sure your gear guy will be happy to price it both ways.

 

[LarryFine]

The only issue I can think of is the panelboard would not be designed to be limited to 6 mains.

The 6-disconnect limit does not require that the capacity be limited to six, only the installation.

 

[junkhound]

The local utility only has single phase in this rural area.
.

POCO here will install multiple services with separate transformers for 200A loads that are more than a few hundred feet apart.

For ADUs in thei area, they will install separate 200A (or larger if needed) service and meter on separate building, such as an ADU.


Your customer may find it advantageous to be able to monitor the different building usage also.

 

[tortuga]

POCO here will install multiple services with separate transformers for 200A loads that are more than a few hundred feet apart.

For ADUs in thei area, they will install separate 200A (or larger if needed) service and meter on separate building, such as an ADU.


Your customer may find it advantageous to be able to monitor the different building usage also.

Thats a good point, and a elegant install, I did that a few years ago with a rural POCO and it went great. We put in the conduit and vaults and they pulled in the mv cable and provided xfromers. Ill take voltage drop at 7200 vs 240 any day. This site in particular has all the buildings pretty closely grouped though.

The 6-disconnect limit does not require that the capacity be limited to six, only the installation.

Thank you good to get your opinion as I tend to agree with all your opinions on here. It was interesting to here from my gear guy that Siemens placed a 6 disconnect limit with their labeling. I got the P4 panelboard re-quoted today with the 'suitable for use as service equipment' label and it was less expensive due to smaller buss.

I am a fan of using a service rated MLO. Actually looking at a 800 or 1000 right now, with Siemens gear. The one thing to be aware of is that if the fault current is high, it may actually be cheaper to get a main because then lower cost lower AIC distribution breakers can be used with series ratings. I'm sure your gear guy will be happy to price it both ways.

Good point, Ill have to run those numbers
Thanks all!

 

[electrofelon]

One other thing I just noticed while looking thru the Siemens catalog, when you go MLO, you can go one smaller "P-size" than if you had a main breaker. For example to get an 800A main breaker, you have to go with a P4. But you can get a 800A MLO in a P3. 1200A MB requires a P5, but can do 1200 MLO in P4. So that probably cuts cost a little too, in addition to not having the MB.

 

[Cow]

Farm work is our bread and butter.

We almost always use the 6 disconnect rule rather than a single main. Siemens is also our preferred brand. I typically lean towards the larger panelboards for farm services, because more often than not, the conduit runs are fairly long which results in pretty good sized conduits. Bigger panelboards make my job easier.

 

[kwired]

I am in the pencil and paper stage of redesigning a farm service and feeder distribution system for expansion and conversion to underground distribution.
There are 2 main large agricultural buildings, a large outdoor processing area and plans for 3 more buildings.
one of the buildings has a load over 200A and will be getting a 300A feeder.
The local utility only has single phase in this rural area.
I am thinking of putting a 800A rated Main lug (Siemens P3 or P4 not sure which yet) panelboard connected to a 800A CT can and using the breakers in the panelboard as the Mains to save on the main breaker.
I have worked on many older services that are just bussbar or gutters off a CT can full of old taps to main breakers and they get kinda squirrely.
I figure the upfront cost on a panelboard will be offset by ease of maintenance and changes that happen regularly.
But now I am wondering if its more standard practice to just have a 800A main?
I'll have a 300, 200, 200 and a 125 or 150 as mains. The 125 or 150 will supply a underground outdoor feeder that will have several hoop houses and small structures 'tapped' off it with GEC and one main breaker at each structure.
What do you all think of using a P3 main lug and having 4 or 5 breakers in it as mains?
The only issue I can think of is the panelboard would not be designed to be limited to 6 mains.
But there was never a limit on those old service gutters full of taps either.
Thoughts?
Thanks in advance.

An advantage of the main distribution panelboard method is the ability to isolate just one feed from it instead of having to turn off all of them at once. Otherwise there is nothing wrong code wise with a single main and using feeder tap rule for outdoor taps of unlimited length to supply each structure.

 

[electrofelon]

I am a fan of using a service rated MLO. Actually looking at a 800 or 1000 right now, with Siemens gear. The one thing to be aware of is that if the fault current is high, it may actually be cheaper to get a main because then lower cost lower AIC distribution breakers can be used with series ratings. I'm sure your gear guy will be happy to price it both ways.

I have some new information and have been thinking about some of what I said and want to amend some of it. I just got a quote for a 1000 amp main breaker P5 with 6 distribution breakers. 65k main, distribution breakers series rated. About $9k. P4 1000 amp MLO, 6 mains ranging from 100 - 400 amp, all rated 65k, about $4900. So that cheaper with main idea definitely not true for this combination. Perhaps it applies to other situations.

Also, consider this: One common mistake people make is to apply series ratings twice. For example three breakers A,B,C, they series rate B to A, and then series rate C to B based on the series rating for B they got from the first step. You cant do that, unless there is a triple series ratings, which are quite rare. So if you have a typical setup where there is main breaker (A), distribution (B)breakers, then branch breakers (C), then you will need to do one of the following:

1. series rate B to A, AND C to A (which you are unlikely to get a 10k miniature breaker to rate with a large frame breaker A, so you will probably need 22AIC branches)
2. Series rate B to A and if your branch breakers are far enough away then you can use regular 10AIC ones fully rated.
3. Series rate C to B, in which case note B must be fully rated because you cant generally series rate 3 devices.


So long story short, depending on the arrangement, using a main to series rate the distribution breakers down could actually hurt you by making all your branches require 22AIC.

 

[kwired]

I have some new information and have been thinking about some of what I said and want to amend some of it. I just got a quote for a 1000 amp main breaker P5 with 6 distribution breakers. 65k main, distribution breakers series rated. About $9k. P4 1000 amp MLO, 6 mains ranging from 100 - 400 amp, all rated 65k, about $4900. So that cheaper with main idea definitely not true for this combination. Perhaps it applies to other situations.

Also, consider this: One common mistake people make is to apply series ratings twice. For example three breakers A,B,C, they series rate B to A, and then series rate C to B based on the series rating for B they got from the first step. You cant do that, unless there is a triple series ratings, which are quite rare. So if you have a typical setup where there is main breaker (A), distribution (B)breakers, then branch breakers (C), then you will need to do one of the following:

1. series rate B to A, AND C to A (which you are unlikely to get a 10k miniature breaker to rate with a large frame breaker A, so you will probably need 22AIC branches)
2. Series rate B to A and if your branch breakers are far enough away then you can use regular 10AIC ones fully rated.
3. Series rate C to B, in which case note B must be fully rated because you cant generally series rate 3 devices.


So long story short, depending on the arrangement, using a main to series rate the distribution breakers down could actually hurt you by making all your branches require 22AIC.

Conductor between B and C might lower available fault current enough you don't need to look into series ratings. Short nipple from MDP to a branch panel has less resistance than running 25 feet up, over then down to a branch panel still in same room. Helps even more if the conductor is only sized per typical 100 or 200 amp panel vs 400 or 600.

 

[electrofelon]

Conductor between B and C might lower available fault current enough you don't need to look into series ratings. Short nipple from MDP to a branch panel has less resistance than running 25 feet up, over then down to a branch panel still in same room. Helps even more if the conductor is only sized per typical 100 or 200 amp panel vs 400 or 600.

Yes. This current job I have going on, that is true with some of the remote 200 amp panels being far enough away, they can have 10k devices fully rated. However there are 4 200 amp panels right next to the MDP so they are a problem. I never noticed this, but no one seems to have been able to get a 10k miniature to series rate with a 400 amp frame breaker at 65k (I didnt exhaustively go through all the big 4's literature). This is a bit of a problem for me as I need to change those 4 200A panels to 2 400A panels to get down to 6 mains. I dont really want to use 22AIC breakers in those panels. I ll have to revisit my calcs and maybe I can just do 2 250's and be ok.