240/480 single phase design considerations

[tortuga]

Greetings all.
Working on a project with only single phase available for miles (again).
I am looking at about 112.5kva in load. It has come to my attention that all the equipment can be run at 240V including the lighting.

I am considering either a 600A 120/240 service or a 250A 240/480 service.
Its a rural area and there are some wire distances involved. Doing voltage drop at 480V appeals to me.
The transformer manufacturer offers a 7.2kv : 240/480V pad-mount in a range of sizes that would work nicely.
Also the metering might workout a little simpler.
(They also make a single phase 277 model)
I have worked with 480 three phase but not much 480 single phase.
I have checked the code and see 240/480 is not a 240.5 'standard voltage' , however 240 and 480 both are standard voltages.
Also Table 430.248 does not list any 480V single phase motors, not a big deal though.
It appears Square D I-line panels might be able to have 2-pole breakers configured to just use the a and c phases, and a 250A 480Y/277 main breaker can be used as single phase.
Other considerations are 200.10 will block using NEMA '6-' receptacles but I could use NEMA '7-' (277V) and 406.5 grouping of receptacles with over 300V L-L.
Color code would be brown, orange with grey neutral.
I am curious if anyone see's any other NEC issues with such service and if any of you have experiences with a 240/480 service?

Thanks in advance.

 

[LarryFine]

I would start with:

Tell us more about your loads. What loads can work with 480v 1ph, and what loads must receive 120 and/or 120/240v?

I always start with the loads that must be served. High voltage is electrically and financially more efficient, but requires transformers, so you might have to figure both ways to compare total costs.

 

[tortuga]

Water pumping 5 - 7.5HP 240V
Large 48IN agricultural fans 240V motors
Supplemental greenhouse lighting 1kw HPS lights (typical 240V horticultural ballasts these really add up)
Yard lighting 400W MH ballast has taps for 120/240/277
LED task lighting says 100-277 V input.
HVAC equipment -240V single phase 1.5 - 12kw range.
Resistance electric heating (I can pick the voltage).
Industrial dryer / dehumidifier 240V.
A walk-in cooler -240V compressor.
Not any 120/240V slash rated loads like I typically see in residential, I have not got a complete equipment list yet though.
There is some existing 120/240 service at the site I will likely pull a feeder from or I could use a small step down to create a small 120/240 panel for a few GFCI's and small 120V loads.

 

[LarryFine]

It looks like you shouldn't bother with any 480v equipment. Unless you can get the POCO to bring you a primary and a transformer, I suggest 480v to the building, and a transformer to provide 120/240v to everything.

 

[ActionDave]

It's not unusual around here to see an agricultural property with 480V single phase feeding some phase converters to run three phase motors.

About the only other thing you would be able to run 480V is pole lighting.

 

[tortuga]

Thanks for the input, good ideas.
So do you all see any problems supplying 240 loads as 240 L-N like we do 277?
There would be no 480 'loads' other than MWBC's that are used to efficiently supply 240 L-N loads.
However I learned today that a 480V VFD can be up sized to run off 480 single phase in these applications.

Thanks again!

 

[LarryFine]

240v to neutral will affect breaker ratings. That's why I suggested the grounded-neutral 120/240v.

You're certain to need at least one 120v circuit.

 

[electrofelon]

I actually really hate this 120v thing we got stuck with, but.....There is something to be said for going with standard 120/240 over some bastard oddball thing.

 

[LarryFine]

Looking again, I partially misunderstood the utility and the entire question, thinking you were asking about getting power to the site. I read it again, so:

If you can get a 7.2kv to 120/240v transformer, skip the 480v completely.

Unless this is a huge building, using 480v will require additional transformers.

Is it multiple buildings or structures? What is the site layout? Have a plan we can see?

You mentioned a concern with wire distances and voltage drop. More info?

250v equipment is less expensive, even at the higher amperage, I believe.

Are we discussing electrical efficiency or cost effectiveness, or both?

 

[yuhong]

I actually really hate this 120v thing we got stuck with, but.....There is something to be said for going with standard 120/240 over some bastard oddball thing.

It was not that long ago that I mentioned that I was wondering why REA in the 1930s did not consider 240V outlets and 240/480V service.

 

[tortuga]

Looking again, I partially misunderstood the utility and the entire question, thinking you were asking about getting power to the site. I read it again, so:

If you can get a 7.2kV to 120/240v transformer, skip the 480v completely.

Unless this is a huge building, using 480v will require additional transformers.

Is it multiple buildings or structures? What is the site layout? Have a plan we can see?

You mentioned a concern with wire distances and voltage drop. More info?

250v equipment is less expensive, even at the higher amperage, I believe.

Are we discussing electrical efficiency or cost effectiveness, or both?

Yes thanks the options I am pondering are 7.2kV to 120/240v or a 7.2kV to 240/480v transformer single phase.
Its a commercial greenhouse;
80kW of horticultural lighting @ 240V (about 20 20A circuits).
The other 30kW of motors, heaters and HVAC are all 230V nameplate.
Largest motor is around 7.5HP all the rest are fans or less than 2hp.
Its about 275 feet of conductor run from likely utility transformer location to greenhouse (looking into closer placement but thats worst case)
For the 240/480 service It would be a 235A load, 250A meterbase/main and feeder, single pole 277V breakers for the lighting and 240V stuff.
For a 120/240 it would be a 470A load, 600A service with a large 800A CT can (utility provides a 400 or 800) and a few parallel conduit runs,
two pole breakers for the 240V stuff probably three 200A panels (something we have done lots of).
Something kinda like this:

 

[kwired]

It was not that long ago that I mentioned that I was wondering why REA in the 1930s did not consider 240V outlets and 240/480V service.

Because those rural customers were buying the same 120 volt appliances to put in their homes as everyone else was, and if it was a higher capacity load it may have been 240 volt, just like for most everyone else.

 

[kwired]

Yes thanks the options I am pondering are 7.2kV to 120/240v or a 7.2kV to 240/480v transformer single phase.
Its a commercial greenhouse;
80kW of horticultural lighting @ 240V (about 20 20A circuits).
The other 30kW of motors, heaters and HVAC are all 230V nameplate.
Largest motor is around 7.5HP all the rest are fans or less than 2hp.
Its about 275 feet of conductor run from likely utility transformer location to greenhouse (looking into closer placement but thats worst case)
For the 240/480 service It would be a 235A load, 250A meterbase/main and feeder, single pole 277V breakers for the lighting and 240V stuff.
For a 120/240 it would be a 470A load, 600A service with a large 800A CT can (utility provides a 400 or 800) and a few parallel conduit runs,
two pole breakers for the 240V stuff probably three 200A panels (something we have done lots of).
Something kinda like this:

View attachment 2551605

With amount of load you have, and majority of it being 240 volt rated, plus longer circuit lengths, I'd probably take a serious look at 240/480 myself. Downside is you about need I-line panels like you mentioned which are pricey, but may be offset by copper saved.

You can run three phase motors (240 or 480) from upsized VFD's like you mentioned, or run single phase motors @ 240 volts. 480 volt single phase motors are pretty rare and most I have seen are more or less OEM type motors for specific equipment and not general purpose motors. We have some irrigation systems that are hydraulic driven and preferred pump motor is three phase, but they do offer a 10 HP 240/480 single phase motor for those systems. About the only 480 volt single phase motor I have ever seen other than some 480 volt single phase blower motors for HVAC condenser units - again a definite purpose instead of a general purpose motor.

You can always add a small transformer for what little 120 volt loads you may have. Makes more sense than having to step up and then step down again for a long circuit.

 

[topgone]

Yes thanks the options I am pondering are 7.2kV to 120/240v or a 7.2kV to 240/480v transformer single phase.
Its a commercial greenhouse;
80kW of horticultural lighting @ 240V (about 20 20A circuits).
The other 30kW of motors, heaters and HVAC are all 230V nameplate.
Largest motor is around 7.5HP all the rest are fans or less than 2hp.
Its about 275 feet of conductor run from likely utility transformer location to greenhouse (looking into closer placement but thats worst case)
For the 240/480 service It would be a 235A load, 250A meterbase/main and feeder, single pole 277V breakers for the lighting and 240V stuff.
For a 120/240 it would be a 470A load, 600A service with a large 800A CT can (utility provides a 400 or 800) and a few parallel conduit runs,
two pole breakers for the 240V stuff probably three 200A panels (something we have done lots of).
Something kinda like this:

View attachment 2551605

It depends on what your goals are! If you wanted to design things to be economical, a higher primary voltage is desirable! If your primary line around 5 miles, and for a load of 112.5 kVA, methinks a 13.2 kV line fits, IMHO. IIRC, there is a formula for estimating the economical voltage for a distribution line.

 

[kwired]

It depends on what your goals are! If you wanted to design things to be economical, a higher primary voltage is desirable! If your primary line around 5 miles, and for a load of 112.5 kVA, methinks a 13.2 kV line fits, IMHO. IIRC, there is a formula for estimating the economical voltage for a distribution line.

That 5 mile portion is likely more up to the POCO. If all you are getting is single phase and it is a 13.2/7.2 kV system you are likely getting 7.2 run those 5 miles.

If you really want it and they will do it, they may run two phases and neutral and you could get open delta system. Still be 240/480 with a high leg or 120/240 with high leg, but may have some merits to just have three phase instead of single phase.

 

[yuhong]

Because those rural customers were buying the same 120 volt appliances to put in their homes as everyone else was, and if it was a higher capacity load it may have been 240 volt, just like for most everyone else.

The point would be to eventually convert all appliances to 240 volt as well. Even Europe used 110 volts in the early days, but by the time of the REA 220 volts was already catching on there.

 

[LarryFine]

I still don't see the advantage of 480v, as there are no 480v loads. Is the idea to use a grounded neutral like a 120/240v system, and all 1p breakers? There will be no 277v anywhere.

Where will the utility end, and your responsibility start?

 

[tortuga]

I still don't see the advantage of 480v, as there are no 480v loads. Is the idea to use a grounded neutral like a 120/240v system, and all 1p breakers? There will be no 277v anywhere.

Thats exactly right, its a 480V single phase transformer center tapped grounded 240V to ground instead of 277.
http://ermco-eci.com/documentation/#2
There may be no advantage other than voltage drop on MWBC's that are pretty long,
We can run a ballanced MWBC 240/480 'boat' allot farther than a balanced 120/240 boat.
Single pole contactors vs two pole and if there is savings on service wire and panel gear ill do it.

The the receptacles and breakers will be standard 277V 'rated', just like 208V systems use higher rated 240V breakers.
Remember its just an idea I am kicking around

Where will the utility end, and your responsibility start?

Its more of a team effort
The utility will take responsibility for the xformer, the meter can is the demarcation point (or base if 240/480) NEC ends there
but not our responsibility as we install the utility conduit and vault to the NESC also.

The 7.2 kv line is really long the 5 miles was me taking a wag and on the long side, its a 1/0 concentric in a single PVC conduit, older parts along the highway are direct burial and then overhead single w/ neutral.
Cheers

 

[kwired]

The point would be to eventually convert all appliances to 240 volt as well. Even Europe used 110 volts in the early days, but by the time of the REA 220 volts was already catching on there.

Unlike European countries the US didn't have a major destruction of infrastructure in the war and have to rebuild. Might not be only reason they switched voltage, but still is easier when starting over than when dealing with what is there.

 

[yuhong]

Unlike European countries the US didn't have a major destruction of infrastructure in the war and have to rebuild. Might not be only reason they switched voltage, but still is easier when starting over than when dealing with what is there.

Though keep in mind this is just before World War II. I wonder if it was in the 1920s that 220V caught on in Europe.