Single 4160v generator vs 8 low voltage?

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jroscow

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Hello friends,

Working on a small personal project. I’m currently building 8 structures on a 200 acre parcel. They’re about 800 feet apart on average. 6 of them are residences with around 6,000 sqft on average. 2 of them are large heated and cooled clear slan garages of 20k sqft each. Total of around 2,500 feet from the road to each structure in aggregate.

Instead of having a low voltage (220) backup generator at each location - would it make more sense to have a single larger generator that is the same voltage coming in from the power company at the road. Then I’d imagine you could step down at the individual buildings like normal.

Budget is around $300k for the generator but could go above if needed

Curious what you’ve seen work for this kind of deployment. I really enjoy this forum and seeing the knowledge of everyone here. Thanks for the time!
 
One generator = single point of failure. And it's going to be an uncommon setup so it'll be harder to maintain and harder to repair.

I'd go with the same generator you'd put on a structure that size anywhere else. Heck, you ought to get a discount for buying 8 of them at once.
 
zbang said:
One generator = single point of failure. And it's going to be an uncommon setup so it'll be harder to maintain and harder to repair.

I'd go with the same generator you'd put on a structure that size anywhere else. Heck, you ought to get a discount for buying 8 of them at once.
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That’s how I’m leaning now! Thank you
 
jroscow said:
Hello friends,

Working on a small personal project. I’m currently building 8 structures on a 200 acre parcel. They’re about 800 feet apart on average. 6 of them are residences with around 6,000 sqft on average. 2 of them are large heated and cooled clear slan garages of 20k sqft each. Total of around 2,500 feet from the road to each structure in aggregate.

Instead of having a low voltage (220) backup generator at each location - would it make more sense to have a single larger generator that is the same voltage coming in from the power company at the road. Then I’d imagine you could step down at the individual buildings like normal.

Budget is around $300k for the generator but could go above if needed

Curious what you’ve seen work for this kind of deployment. I really enjoy this forum and seeing the knowledge of everyone here. Thanks for the time!
Click to expand...
I must be missing something. So do you have a primary service and a customer owned MV distribution system that powers a transformer at each structure? Does infrastructure exist yet or is this in the design phase?
 
I wonder what the lead time for a 4160v 400kw (probably single phase) generator is?

Not exactly like you'd find one in the used market
 
electrofelon said:
I must be missing something. So do you have a primary service and a customer owned MV distribution system that powers a transformer at each structure? Does infrastructure exist yet or is this in the design phase?
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Design phase - only have primary service at the curb currently

The initial design they presented was probably pretty normal - primary service underground (they gave us specs as to conduit size, maximum bend, separation from other conduits like gas, water, low voltage fiber). Then they want to come pull the primary service themselves to within 100-200 feet of each structure to transform down. They’d own the transformer in this case.
 
jroscow said:
Design phase - only have primary service at the curb currently

The initial design they presented was probably pretty normal - primary service underground (they gave us specs as to conduit size, maximum bend, separation from other conduits like gas, water, low voltage fiber). Then they want to come pull the primary service themselves to within 100-200 feet of each structure to transform down. They’d own the transformer in this case.
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Ok so it sounds like all the MV distribution is utility owned? I cant image them letting you put an MV transfer switch in their lines....
 
jroscow said:
Looking at 400kw natural gas after chatting with generac about what would be powered
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Natural gas doesn't seem like the most resilient fuel supply for an emergency backup generator, I'd use diesel. I also wouldn't use generac. 400kw isn't THAT big, usually LV at that size. Probably cheaper to get a unit substation to step it up than get a MV generator.

All that said, I'd keep the MV distribution on the utility side, put a padmount at each structure and a diesel generator and ATS for each structure.

Also consider if there is a problem on the MV distribution your backup generator will be useless for the exact prolonged outage where you would need a backup generator. See 2004 Bellagio power outage https://www.eng-tips.com/viewthread.cfm?qid=93479
 
Joethemechanic said:
Is this all single phase? How many transformers?
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Just based on what generac said and the initial design from the power company (that does not include a single generator) - 8 transformers since each site is decently far apart.

electrofelon said:
Ok so it sounds like all the MV distribution is utility owned? I cant image them letting you put an MV transfer switch in their lines....
Click to expand...

Maybe not - they said they’d want to inspect it and have access to it if needed. I don’t mind where the generators goes even if I need to parcel off a little chunk of land to deeds to them if it makes them feel better about it! That being said, a generator per structure is much easier just thought a single large one could be better given the cost of doing 8 individual smaller generators
 
Todd0x1 said:
Natural gas doesn't seem like the most resilient fuel supply for an emergency backup generator, I'd use diesel. I also wouldn't use generac. 400kw isn't THAT big, usually LV at that size. Probably cheaper to get a unit substation to step it up than get a MV generator.

All that said, I'd keep the MV distribution on the utility side, put a padmount at each structure and a diesel generator and ATS for each structure.

Also consider if there is a problem on the MV distribution your backup generator will be useless for the exact prolonged outage where you would need a backup generator. See 2004 Bellagio power outage https://www.eng-tips.com/viewthread.cfm?qid=93479
Click to expand...

That’s where I’m leaning now. The smaller individual LV generators seems like the way to go. I have a ”bi-fuel” (diesel and natural gas) at a lake house and it’s worked great. We lost power for 5 days in 2011 tornados and natural gas worked great……for 3.5 days until the “backup generator for the pumps” exhausted (according to the local utility)

Thanks again for all the sense talking and expertise. Leaning heavily towards a more “normal” install.
 
jroscow said:
That’s where I’m leaning now. The smaller individual LV generators seems like the way to go. I have a ”bi-fuel” (diesel and natural gas) at a lake house and it’s worked great. We lost power for 5 days in 2011 tornados and natural gas worked great……for 3.5 days until the “backup generator for the pumps” exhausted (according to the local utility)

Thanks again for all the sense talking and expertise. Leaning heavily towards a more “normal” install.
Click to expand...

Is this project in Nashville? I'll trade you some generators for an acre of the land (with utilities and road access) :D
 
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