# Service Sizing for a Grain Bin Yard



## latitude51 (Dec 5, 2020)

Hi all! This is my first question to the forum.


I'm sizing a separate service for a farmyard. This service will be running primarily fans (blower and exhaust) for grain bins and stir bins. Since this doesn't really fit under Section 8 - Circuit Loading and Demand Factors of the CEC, I've been going by Section 28 - Motors and Generators to determine my feeder and branch circuit conductors, specifically 28-108, 1) a) because there are several fans that will be running at the same time. I think I'm on the right track with this so far...

Moving on to over-current protection, there will be breakers installed on branch circuits as per 28-200, 28-206, and Table 29 to supply each fan (some branch circuits may have multiple motors). So, as per 28-200 3) and Table 29, I will be installing breakers on each branch circuit that are rated at 250% of the FLA of the motor being supplied, correct? And the branch circuits that feed a group of motors should be based on 28-204 1), so 250% of the largest motor FLA plus the FLA of all other motors on that circuit... I think I am on the right track here also, if not, please point me in the right direction.

Now, if I understand this correctly, the service size will be based on the overcurrent protection that will encompass the entire yard, as I read 28-204 2)...


The math so far (I think): There are two sections of the yard that will be supplied from this service, “Yard A” and “Yard B”.



Yard A: (all 240V)

1 x 14 HP = 60A

1 x 10 HP = 50A

3 x 1.5 HP = 30A (10A ea)

2 x 1 HP = 16A (8A ea)



(60A x 125%) + 50A + 30A + 16A = 171A = 000 and 175A* overcurrent protection to feed “Yard A”



Yard B: (all 240V)

1 x 7.5 HP = 40A

7 x 5 HP = 196A (28A ea)

2 x ¾ HP = 13.8A (6.9A ea)



(40A x 125%) + 196A + 13.8A = 259.8A = 300kcmil AL and 300A* overcurrent protection to feed “Yard B”



Yard Service:

1 x 14 HP = 60A

1 x 10 HP = 50A

3 x 1.5 HP = 30A (10A ea)

2 x 1 HP = 16A (8A ea)

1 x 7.5 HP = 40A

7 x 5 HP = 196A (28A ea)

2 x ¾ HP = 13.8A (6.9A ea)



(60A x 125%) + 50A + 30A + 16A + 40A + 196A + 13.8A = 420.8A (YIKES!) 450A*



*As per Table 13



So, am I correct in my calculations and reading here? It seems super high! I’ve never calculated a service this way, so I’m lacking confidence on this... I’m looking forward to your input!


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## Mobius87 (May 20, 2019)

What are the owner's requirements? How many of the fans in each yard will actually be running at any given time? I know around here we have some huge seed farms that would technically require huge services, but are actually running off of ridiculously small farm services.

Often, they would rather get away with running one or two of the fans at a time, and cycle between them as required. And so I give them wiring to reflect that.

Farmers are notorious for having large pockets, but they're sewn shut so only a nickel can come out at a time.


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## varmit (Apr 19, 2009)

From the ampacities you list, I assume that this is single phase? Is three phase not available? I would hate to maintain that many single phase motors. You would need a shelf full of centrifugal switches and capacitors.

Yes, generally there would be some demand factor reduction to the service. A peak load scenario would need to be determined. Some fans could be interlocked to prevent others running at the same time. This would be a nice application for a PLC to control which bunch of fans to run.


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## canbug (Dec 31, 2015)

Farm yards are a pain because farmers are always adding loads, changing motors to whatever they have in the shop to get by. Your numbers may be high but when they are harvesting, they may have almost all the equipment running at one time or another. If you end up using your numbers, the service will be able to handle the load for many years to come and it's simple when your troubleshooting. If you start putting in controls then you will receive the call that "I can't get this running and just because another motor is operating?" That isn't going to fly. Go with your gut on this one and no such thing as to large a service on the farm. Try to talk him into 3 phase. I wired a large farm service for a grain delivery system and ended up changing it out because of the demand billing.

Tim


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## just the cowboy (Sep 4, 2013)

Quick note:
Check with them about that 14 HP motor. This is a European size motor 11KW, make sure it is not 50 HZ.

Cowboy


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## Forge Boyz (Nov 7, 2014)

just the cowboy said:


> Quick note:
> Check with them about that 14 HP motor. This is a European size motor 11KW, make sure it is not 50 HZ.
> 
> Cowboy


There are some weird horsepower motors used in grain handling equipment. Some 10HP motors used in air-over fans are rated 10-12 horsepower because of the additional cooling from the air. I was also told that some 15HP single phase motor are made as well, I think by WEG.

Sent from my SM-G970U using Tapatalk


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## micromind (Aug 11, 2007)

Do the same as most farmers, use 18/2 lamp cord. It it's a big load, use 2...........

I would size it for every fan to be on at the same time, if any of them are augers, they usually run one at a time and not for very long.


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## Cow (Jan 16, 2008)

I would do everything in my power to get them into an MCC with good nema starters, and then leave space to add more sections....

The usual homemade motor control cabinets with everything stuffed into one enclosure typically turn into a spaghetti mess with changes, upgrades, etc.


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## micromind (Aug 11, 2007)

Cow said:


> I would do everything in my power to get them into an MCC with good nema starters, and then leave space to add more sections....
> 
> The usual homemade motor control cabinets with everything stuffed into one enclosure typically turn into a spaghetti mess with changes, upgrades, etc.


And given the total HP, I'd push pretty hard for 3Ø, even if it's a 240∆...........


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## varmit (Apr 19, 2009)

Yes, the constant changing needs would make most most load shedding or limiting applications be more trouble than the savings. (Yes, I am contradicting myself.)

The peak loads would be around picking time, times of high humidity and any time grain prices went up. (Time to sell.) The price, on grain, is much higher if the moisture content is within a narrow range.


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## latitude51 (Dec 5, 2020)

Thanks for all of the replies guys, I'll try to address all of them in this one post.



Mobius87 said:


> What are the owner's requirements? How many of the fans in each yard will actually be running at any given time? I know around here we have some huge seed farms that would technically require huge services, but are actually running off of ridiculously small farm services.
> 
> Often, they would rather get away with running one or two of the fans at a time, and cycle between them as required. And so I give them wiring to reflect that.
> 
> Farmers are notorious for having large pockets, but they're sewn shut so only a nickel can come out at a time.


All of the motors that I listed could be running at the same time (worse case scenario). That's why I'm trying to sort this calculation out. There are actually many more motors that are included on this service, they just won't be running at the same time as the fans that are listed in my OP.



canbug said:


> Farm yards are a pain because farmers are always adding loads, changing motors to whatever they have in the shop to get by. Your numbers may be high but when they are harvesting, they may have almost all the equipment running at one time or another. If you end up using your numbers, the service will be able to handle the load for many years to come and it's simple when your troubleshooting. If you start putting in controls then you will receive the call that "I can't get this running and just because another motor is operating?" That isn't going to fly. Go with your gut on this one and no such thing as to large a service on the farm. Try to talk him into 3 phase. I wired a large farm service for a grain delivery system and ended up changing it out because of the demand billing.
> 
> Tim


Three phase isn't even on the table. The yard is about 2 miles from the nearest three phase line. It would cost far too much to bring it to the yard. In talking to the neighbor that has a separate service for his grain dryer, the service provider only charges him when it's in use (something like $1500/mon), otherwise, in the off season months he's only seeing a $100/mon bill to cover some fees... Something about "seasonal usage". If this is the case, then there isn't as much of a worry about billing.



just the cowboy said:


> Quick note:
> Check with them about that 14 HP motor. This is a European size motor 11KW, make sure it is not 50 HZ.
> 
> Cowboy


This, as far as I know, is what was spec'd for the main fan on the stir bin.



Cow said:


> I would do everything in my power to get them into an MCC with good nema starters, and then leave space to add more sections....
> 
> The usual homemade motor control cabinets with everything stuffed into one enclosure typically turn into a spaghetti mess with changes, upgrades, etc.


I love this idea, however, it just isn't feasible...



So, no one actually said if I'm on the right track or not, but that's okay, I found some information on the Fortis Alberta site. They have a section and some calculation worksheets with a fair bit of info. On the worksheet they have a section for electric motors and they say "For transformer size calculations 1HP = 1KVA". With that in mind, that puts me at about 75KVA for the transformer and a service size (calculated) of ~312A, this seems much more reasonable, however, that's over 100A less than my calculation... Thoughts?


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## tmessner (Apr 1, 2013)

I generally add all of the motors that could possibly run at the same time and multiply that times 1.25. You will look like a saint next year when they tell that the new dryer that they just bought is double what the old one was.


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