480 or 240 3 phase for new service
480 or 240 3 phase for new service
(OP)
Other than the obvious difference of wire size for different applications, is there a significan difference in energy consumption when comparing 480 3phase to 240 3phase?
Thanks
Thanks






RE: 480 or 240 3 phase for new service
When you are in the grey area, the deciding factor is often the large loads that you have to serve. If you have a big motor, 480V will be better. But if all loads are small, you can go with 208V and eliminate the double transformation.
RE: 480 or 240 3 phase for new service
Very roughly, an economic breakpoint for 208- (240- may be discouraged for new service) versus 480-volt service for motor load is 15-30hp. Future growth favors the higher voltage.
RE: 480 or 240 3 phase for new service
Thanks again.
RE: 480 or 240 3 phase for new service
The only advantage of 208V is simplicity. If the majority of your loads are small 120V loads, I'd go with 208/120V. If you have a lot of larger loads (heating, water heaters, air conditioners, motors, etc), 480V probably makes more sense. Many utilities will limit the size of 208V service they will provide. Also, 480V motors are more readily available than 208V three-phase.
RE: 480 or 240 3 phase for new service
A “for instance” comparison of magnetic starters for a NEMA size 1 rating: 200/230V 3ø — 7.5 HP and 460/575V 3ø — 10 HP. The higher voltage offers copper savings in motor circuits.
RE: 480 or 240 3 phase for new service
Go with the 480v system. Smaller conductor sizes, easier to work with, cheaper to install, easy to modify. A 20hp 480v motor will probably cost double to install at 208V. I have also found by experience there are greater heat losses and a higher incidence of bad connections with larger conductors. For example; do you think you can tighten a connection for say a #3 conductor inside a tiny disconnect with an allen key or flat screw driver sufficiently? Or do you think it would be easier to tighten a #10 with a flat? The guy connecting the #3 conductor 9 times out 10 will not tighten the conductor down properly but he will with a #10.
Think about it, all that current heating and expanding connections leads to bad connections and voltage dip and lights fading and whatever else.
RE: 480 or 240 3 phase for new service
RE: 480 or 240 3 phase for new service
25-35 years ago 480/277 volt, 4-wire wye was rare in U.S. small commercial applications. That is not at all true today. Even rather small strip malls and convenience stores are going to the higher voltages as the loads are predominately lighting, air conditioning, and refrigeration. Typically, most of the lighting is 277 volt in these applications with the three phase loads being 480 volt. The reduced wire size and wide availability and low cost of 480/277 volt equipment offsets the cost of step down transformers for minimal 120 volt loads.
Frankly, I am surprised that computer work stations and other office equipment are not widely available in 277 volt versions for the U.S. market.
Greg May
Two Sockets - Two Meters, Inc.
WEB: socket-two-me.com
RE: 480 or 240 3 phase for new service
RE: 480 or 240 3 phase for new service
Consider the comments above regarding you loads, cable sizes, etc... if your considering servicing a load, also approach your local utility, they'll provide what options, services, and voltages levels required and/or recommended...
for a small customer, I don't think the power factor issue will arise; if you are a large customer, I don't think the voltage level will be an issue --
RE: 480 or 240 3 phase for new service
Does anyone have any experience with Green Credits? The term has been thrown around alot when dealing with new projects.
From my understanding, companies can increase there environmental standings by purchasing green credits...
Is there a financial payoff as well?
Thanks
RE: 480 or 240 3 phase for new service
Sorry... not where I wanted to put my post.
Forgive me.
RE: 480 or 240 3 phase for new service
The PF issue only arose after the bill arrived.
Consider a service to a school athletic field during the summer. PF is calculated from kWh and kvarh. Schools out, so the main load is the no-load losses from one or more dry transformers > very low PF. Every percent below 95 is used to adjust the demand charge upward by a percent. Although energy use was low, the field lights were on long enough to set a normal demand. School paid maximum possible for the smallest energy use. They would have been ahead paying for the extra losses of 240 equipment and avoiding the PF penalty. This customer is not the only one. When getting the utility recommendation, make sure you understand the different rate structures.
RE: 480 or 240 3 phase for new service
ElectronClem
RE: 480 or 240 3 phase for new service
RE: 480 or 240 3 phase for new service
You have described a worst case scenario for PF penalty billing. A very poor load factor combined with an average PF calculated from Kwh and KVarh is very unfair (in this case)and has little relationship to what it costs the utility to serve this load.
Rather than investigating going to a lower voltage to avoid the PF penalty, you should simply add a PF correction capacitor to just offset the lagging KVars required by the idle transformer. Case closed.
Greg May
Two Sockets - Two Meters, Inc.
WEB: socket-two-me.com
RE: 480 or 240 3 phase for new service
As far as I know, no one is suggesting changing the service. The time to investigate is before the system is designed. Yeah, caps would do it. So would (a) switch(es) to turn off idle transformer(s). Unbudgeted for expenses like high electric bills and electrical work can always be handled by chopping another day off the too short school year. Anyway, I wasn't writing to ask for advice, but to give it. Sounds Clem might be at a better point to investigate rate structures than the school is. I'm just suggesting he do so.
RE: 480 or 240 3 phase for new service
A friend who owns a machine shop took up residence in a building with 120/208V service until his second CNC machine showed up. The second machine put him over the top of the 65 kVA available. Now he's got 150 kVA available, and runs his 120/208 loads from a small 480/208 D-Y transformer and panelboard.
I apologize if a facsimile of this post shows up as well. My first post, and I think the last try went to the infamous /dev/null, but it may still be floating around somewhere.
RE: 480 or 240 3 phase for new service
There is a lot to consider along with energy consumption when choosing service voltage. Chapter 3 in IEEE Std 141 {red book} may be worth review.
RE: 480 or 240 3 phase for new service
Not trying to step on toes here, but these have been considered.
RE: 480 or 240 3 phase for new service
Other than the obvious difference of wire size for different applications, is there a significant difference in energy consumption when comparing 480 3phase to 240 3phase?
///480V power distribution system will experience higher leakages than 208V (rather than 240V) over longer period of time since dust, moisture, etc. are relatively more detrimental to higher voltages than to lower voltages.
Beside the energy consumption, there are other factors involved, e.g.
1. Size and total consumption of the project. The standard 208V three phase transformers end at 2000kVA. Anything above will be noticeably costlier.
2. Nature of loads. Some 480V loads tend to have smaller dimensions, tend to be lighter, more efficient, more perfected, in some instances more readily available, etc. However, some projects have many 120V loads and outlets, which favor 208V/120V power distribution.\\\