Transformers &

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JDB3

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San Antonio, Texas
A friend of mine contracted to have a house built. The builder gave him an estimate (?) with a cost/plus worked into it.

The contractor estimated (he said) the underground based on another house (from transformer at the road to the house some 550 +/- feet). The other house's underground was $6,500. Since this house was a longer run he bumped it up to $10,000.

The electrician told him "no way". Just over 3,500 square feet house with heat pumps. My load calculation for the house came to around 230 amps PLUS he is planing to build another structure at a future date! Their bid ended up being $33,000 for the underground (meter rack at the transformer by the road, run conduit with wires to the house).

Would any of you'll think that "step up" / "step down" transformers work in this situation to lessen the cost? :unsure:
I haven't worked with this set-up at all.

Thanks for any input !
 
Here is the most economical way I know of for a situation where step-up is needed. You'll have to run the numbers to see if step-up is a good fit for your situation. See attached. See attached.
 

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JDB3 said:
....Would any of you'll think that "step up" / "step down" transformers work in this situation to lessen the cost? :unsure:
I haven't worked with this set-up at all.

Thanks for any input !
Click to expand...
It is almost always cheaper to just buy a size or two bigger wire than it is to buy two transformers, disconnects, extra wiring and conduit, concrete pad to set the transformers on, etc......
 
ActionDave said:
It is almost always cheaper to just buy a size or two bigger wire than it is to buy two transformers, disconnects, extra wiring and conduit, concrete pad to set the transformers on, etc......
Click to expand...

Agreed. And I’d you don’t like prices especially for service entrance look at aluminum. Unlike copper prices have barely moves the needle. As far as the anti-aluminum BS, the utility is feeding an aluminum transformer with aluminum lines. You are just extending that. Once at the distribution panel switch to copper. Just go up a size:
 
If one figured a 400a load, triple parallel 600al would get you 3% vd at 550ft. Cost of wire and 3" sch 40 PVC gets you at $20k pretty fast.

100kva transformers are about $3600ea. One set of 500al in 3" gets you about $2700 in wire, $4k in conduit. $1000 in disconnects.

You'd probably come out $5000 ahead on a 400a service stepping up to 480v.
 
ppsh said:
If one figured a 400a load, triple parallel 600al would get you 3% vd at 550ft. Cost of wire and 3" sch 40 PVC gets you at $20k pretty fast.

100kva transformers are about $3600ea. One set of 500al in 3" gets you about $2700 in wire, $4k in conduit. $1000 in disconnects.

You'd probably come out $5000 ahead on a 400a service stepping up to 480v.
Click to expand...
I would never go to 480. If you're going to go transformers, go to pad mounts @ 7.2KV
 
ppsh said:
If one figured a 400a load, triple parallel 600al would get you 3% vd at 550ft. Cost of wire and 3" sch 40 PVC gets you at $20k pretty fast.

100kva transformers are about $3600ea. One set of 500al in 3" gets you about $2700 in wire, $4k in conduit. $1000 in disconnects.

You'd probably come out $5000 ahead on a 400a service stepping up to 480v.
Click to expand...
A 400A service does not equal 400A of load, and I would never figure 3% voltage drop since everything is made to work on 10%.
 
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