I have a client that has motorized machines rated between 5hp-10hp about (10 of them) all three phase rated at 220v or 230v. Many of the motors in those machines are older and they don't show a range of voltage. These machines are going to be relocated to a new building. Currently in the building they are at now they are being fed from a 120/240 3 phase high leg system. This new building will have a work shop where all the motorized units/machines will be in for woodcutting plus another typical, office,kitchen, restroom around the building. Would it be better to provide a 120/240 3 high delta phase system and tap a 1 phase panel from the 3 phase panel 120/240 to serve the rooms or provide 120/208 3 phase service and provide buck-boost to the machines? thank you!!
New 120/240 3 phase service or new 120/208 3 phase service
- Thread starter Cartoon1
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LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
I would have to know what's available and/or what the POCO is willing to provide at the new location to answer.
Russs57
Senior Member
- Location
- Miami, Florida, USA
- Occupation
- Maintenance Engineer
I am seeing a trend where companies want to build a motor that will work here and overseas. That leaves a lot of us looking for economical motors having to settle for a service factor of one.
Given that, I'd vote for 3 phase 480/277 service and get a delta/delta transformer for the 240 volt loads (or buy new 480 volt motors) and a delta/wye transformer for the 208/120 loads.
Might be out of the question but would be better if the business grows.
Given that, I'd vote for 3 phase 480/277 service and get a delta/delta transformer for the 240 volt loads (or buy new 480 volt motors) and a delta/wye transformer for the 208/120 loads.
Might be out of the question but would be better if the business grows.
FPL?
120/240 volt, four-wire delta is determined by FPL to be the standard 3 phase voltage for loads in which individual motor sizes are greater than or equal to 7.5 hp (but not exceeding 20 hp), or, the 3 phase "demand" load does not exceed 75 KVA, or, the "total" demand load does not exceed 150 KVA, and the use of single phase, in the opinion of FPL, is impractical. When the Customer desires three phase, 120/208 or 277/480 volt will be considered the standard voltage only where, in the opinion of FPL, three phase service is required, and 120/240 volt delta service is not, in the opinion of FPL, the standard voltage for the load being served, unless otherwise mutually advantageous to both FPL and the Customer.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Agreed, or go for 240v delta if you can get it, and use 240D-to-208/120Y for L-N loads.
texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
I worked a lot years in FPL territory and Hv&Lv is right. You won't get a Y service from them for this kind of light load. They love their center tapped delta services for light commercial.
Yes, i think that is the best option. get a 277/480 3ph from FPL and add two transformers somewhere inside the building. 1 3ph 120/240 and 1 120/208 for the smaller stuff.
Yes, i think that is the best option. get a 277/480 3ph from FPL and add two transformers somewhere inside the building. 1 3ph 120/240 and 1 120/208 for the smaller stuff. I cant buy new motors, they want to use the existing motors and they are expensive.
hillbilly1
Senior Member
- Location
- North Georgia mountains
- Occupation
- Owner/electrical contractor
I don’t know if I would even bother with the 120/208 volt transformer. If you have 277/480, it can be used for the lighting loads, from the sounds of it, the remaining 120 volt loads could be run of a single phase 120/240 volt panel for office and computer loads. Even the A/C loads can be 480.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Are they NEMA or IEC design motors?
Keep in mind that machines like these often are seldom fully loaded to their capacity and you can get away with a little more in that situation than with something that normally runs near full load rating.
Can also use buck/boost easily for a small motor or where limited number of them actually need a change in supply voltage
hmmm, good point. You mean double tap the 480 y to 120/240 delta high leg transformer and provide a 3 phase panel for the motors and a 1 phase panel for the office stuff? so i would just need a bigger transformer in this case.
hillbilly1
Senior Member
- Location
- North Georgia mountains
- Occupation
- Owner/electrical contractor
Yep
i have exactly 6 machines that are rated 230v 3phase. all between 5hp to 10, so i'm not sure if this will be a better cost efficent option or not.
hillbilly1
Senior Member
- Location
- North Georgia mountains
- Occupation
- Owner/electrical contractor
You could even have a separate 120/240 volt single phase transformer and panel off the 480 volt service for the office.
zbang
Senior Member
- Location
- Roughly 5346 miles from Earls Court
'course, if the poco says "Your options are 120/240 delta or no power", I'd go with the delta feed.
(It's also not clear to me if this is an existing and energized but new-to-the-client building or new construction getting a new service.)
(It's also not clear to me if this is an existing and energized but new-to-the-client building or new construction getting a new service.)
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
I'd avoid the 480/277 service if you don't have any 480 or 277 volt loads to supply. Extra expense in transformation and losses from that transformation.
120/240 delta is simplest and least cost. If you must go with 208/120, still likely best to go with buck/boost on any equipment that won't take 208 so well. Only need minimal sized units and can connect them in open delta so only two needed instead of three per application. connect them so they are only "on" when machine is on and you have no idle losses either.
A lot of this kind of machinery seems to be EU designed and probably designed for 240 volts.
120/240 delta is simplest and least cost. If you must go with 208/120, still likely best to go with buck/boost on any equipment that won't take 208 so well. Only need minimal sized units and can connect them in open delta so only two needed instead of three per application. connect them so they are only "on" when machine is on and you have no idle losses either.
A lot of this kind of machinery seems to be EU designed and probably designed for 240 volts.
hillbilly1
Senior Member
- Location
- North Georgia mountains
- Occupation
- Owner/electrical contractor
Doesn’t sound like enough load for the poco to justify a 480 volt service. Only way to know your options for sure, is to talk with the poco engineer. I have found most very helpful.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
I'm going to be "that guy"...
It's 240/120 3 phase 4 wire, also 208/120 and 480/277. For 3 phase, the higher voltage is always first. That way 240/120 3 phase can't be confused with 120/240 single phase.
It's 240/120 3 phase 4 wire, also 208/120 and 480/277. For 3 phase, the higher voltage is always first. That way 240/120 3 phase can't be confused with 120/240 single phase.
ptonsparky
Tom
- Occupation
- EC - retired
I keep reading that and keep forgetting. Maybe I'll remember, someday.
One big problem is many texts and documents get it wrong also..
The italicized comment in my post came straight out of the FPL guidebook.
even utilities get it wrong…
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