Busway Design

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bcl

Member
Location
Garden Ridge, TX
Occupation
Electrician (Owner/ Operator)
Recently was handed a set of prints for estimating. (20) EV chargers fed from a 400 amp/ 480v busway. They have designed such that each individual charger has its own 15kVA transformer (480/240). This designed seemed to me to be sort of silly. Why not just install a larger transformer at the beginning of the circuit and run a larger busway. The labor and material to install 20 individual transformers (and hang them 20' in the air!) seems so much more than having a transformer at the beginning of the circuit.

While you're reading this, I'm also having this issue that can't get a fast enough answer back from suppliers...and haven't installed busway in a long time. Is there a ball-park for how much you expect to pay per foot for 400 amp copper busway? Here are the details I have:

3 phase, 3 wire with internal ground (not grounded enclosure), 400 amp, 480v

The run is about 250 feet, with the final 100 feet installed as bus-plug with (20) 30 amp plugs for EV chargers.

I'm good on labor and material count, but everyone says "they'll get back to me" on price, and I'm looking for at least a ballpark I can give the GC now.

Thanks in advance!
 
Your guess is as good as mine on why the busway. I was handed a set of rudimentary prints that was designed by the EV charging company. From what I have been able to gather on busway cost, I don't see how it can be cheaper than conduit. When I look at the plans it looks like it was designed by a solar designer...no offense to the legitimate ones. I think the EV Charger company got a contract with FedEx somehow and now they are trying to piece these things together with residential chargers. They could have just installed 480v chargers. If I get the job I might be able to talk them into a better design, but I have to bid it as is for now.
 
bcl said:
Recently was handed a set of prints for estimating. (20) EV chargers fed from a 400 amp/ 480v busway. They have designed such that each individual charger has its own 15kVA transformer (480/240). This designed seemed to me to be sort of silly. Why not just install a larger transformer at the beginning of the circuit and run a larger busway. The labor and material to install 20 individual transformers (and hang them 20' in the air!) seems so much more than having a transformer at the beginning of the circuit.
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In theory I agree with one larger transfomer however voltage drop could be an issue to use one large 480/240V transformer at the beginning of the 250' run especially if all chargers are being used together and the run sees the full load. 480V goes a lot further before voltage drop becomes a concern. As for cost I am afraid I cannot help with that one. Did you try your local sales rep for GE/Schneider/Eaton/Siemens products to get an estimate? Pricing for that stuff includes a lot of pieces to make up the run so it takes longer for them to get the price together but a goos sales rep should be able to provide a cost estimate.
 
Sparky2791 said:
In theory I agree with one larger transfomer however voltage drop could be an issue to use one large 480/240V transformer at the beginning of the 250' run especially if all chargers are being used together and the run sees the full load. 480V goes a lot further before voltage drop becomes a concern. As for cost I am afraid I cannot help with that one. Did you try your local sales rep for GE/Schneider/Eaton/Siemens products to get an estimate? Pricing for that stuff includes a lot of pieces to make up the run so it takes longer for them to get the price together but a goos sales rep should be able to provide a cost estimate.
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Strange they don't install the transformer at the end of the run.
 
Sparky2791 said:
In theory I agree with one larger transfomer however voltage drop could be an issue to use one large 480/240V transformer at the beginning of the 250' run especially if all chargers are being used together and the run sees the full load. 480V goes a lot further before voltage drop becomes a concern. As for cost I am afraid I cannot help with that one. Did you try your local sales rep for GE/Schneider/Eaton/Siemens products to get an estimate? Pricing for that stuff includes a lot of pieces to make up the run so it takes longer for them to get the price together but a goos sales rep should be able to provide a cost estimate.
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Yes, tried the local reps. They are working on it, but I think busways are not common enough for them to get back to me quickly. ChatGPT doesn't even know the answer to this one. Haha.
 
Its a design choice. Unless you are being paid to design, it seems most appropriate to just do what the drawings say.

Or ask the engineer who did the design about it.

Random people on the internet are not going to know why it was designed this way.
 
petersonra said:
Its a design choice. Unless you are being paid to design, it seems most appropriate to just do what the drawings say.

Or ask the engineer who did the design about it.

Random people on the internet are not going to know why it was designed this way.
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I agree with that, it's what I'm doing...just wish it were standard a standard enough build that I could get some ballpark for what busway costs without waiting weeks for Siemens/Square D/ Eaton to get back to me. :)
 
Tulsa Electrician said:
Just for fun I would like to see the plans.
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Attached. They are simple enough to understand, except that they aren't for the actual job. These plans are from a different job, then they basically said, "Do this over there." They gave me some site plans for the actual job, but I can't get enough detail to know where the busway is going to run, etc. I'm just accounting for the worst case scenario.
 

Attachments

  • EV Chargers.pdf
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Thank you so much. I'm going to my print them out and look over closer. Pretty cool set up.

I see what there doing with the transformers now.

Again thanks for taking the time to post the drawing.
 
It occurs to me that the transformers are probably about $1000 each. Does going with 800 A bus cost more than $20 grand more than 400 Amp bus.

The cheap way to do this is two feeders of two parallel 1/0 going down each side and passing thru a junction box at each transformer and tapping off to each transformer as it passes by with a Polaris connector.
 
petersonra said:
It occurs to me that the transformers are probably about $1000 each. Does going with 800 A bus cost more than $20 grand more than 400 Amp bus.

The cheap way to do this is two feeders of two parallel 1/0 going down each side and passing thru a junction box at each transformer and tapping off to each transformer as it passes by with a Polaris connector.
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The same question I was asking myself, but my lack of familiarity with the cost of busway has me going a bit blind. The cheaper design of feeder taps from parallel 1/0 makes sense to me, and perhaps it's something they'd go for after the job is won...if the lead time on busway is not within their range. They told me they want start construction on this in just over a month. If it takes a couple weeks just to get pricing from manufacturers, I doubt if the product would be ready by April.
don_resqcapt19 said:
The last time I did any busway or cablebus the suppliers wanted a detailed isometric drawing to work from for the quote.
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This is the initial answer I received from Siemens. They were not willing to price out individual parts, even if I got them directly from the Sentron catalog. They want the detailed drawings. Since the job is design-build (based on the simple initial blueprint I was given) it's difficult to even put a bid together.
 
For those of you who are curious, I plugged this into National Estimator Cloud (I usually do this manually), and it's got material cost for 200' feeder bus, 200' plug-in bus, (20) 30 amp breakers, (20) 15 kVA transformers, (1) 400 A 22KAIC breaker at $275K. Seems high to me, but for lack of better info, it's what I'll use for today. I'd rather lose a job because I'm too high than lose money because I won it low.

Obviously labor would be higher for conduit & wire, but I wonder if the material cost considerations will make them rethink the design down the road...
 
You definitely need an isometric drawing if you are changing direction or elevations or connecting to other equipment.
For a straight run I would think a simple drawing would suffice, but you need to include things like the tap box location and hanging parameters.
 
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