The local electrical company drew up site diagram for a new single phase service that is suppose to feed an existing single phase 1200A 240V MDP panel. His drawing indicates 100KW pad mounted transformer, with 3 sets of 350 AL kcmil wiring coming in. Is the 100KW size of pad mounted transformer size big enough? My calculations give me that the tranformer would have to be around 390KW?
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Single Phase Electrical Service 5
- Thread starter axd38
- Start date
axd38 mc5w any one else
Your question is should you confront your sup.
With being a small shop (60 people ) yes.
I have been terminated and promoted for the same thing.
Being eng mag, I try to make it easy to all to voice expresions.
In the MILITARY business there is not much room for error
(it kills people). The only reason I can get some sleep
is I know I have done my best to protect the 18 yr olds
and the rest of the country, that must use the equiptment I design.
It is all com gps, jammers, (defense).
To me it is not 100 or 350, it is 350 *1.4.
No questions no doubts make it last forever.
If someone else tells you different than it makes you
cry at night "RUN".
Only you have the answer.
100wrong
Your question is should you confront your sup.
With being a small shop (60 people ) yes.
I have been terminated and promoted for the same thing.
Being eng mag, I try to make it easy to all to voice expresions.
In the MILITARY business there is not much room for error
(it kills people). The only reason I can get some sleep
is I know I have done my best to protect the 18 yr olds
and the rest of the country, that must use the equiptment I design.
It is all com gps, jammers, (defense).
To me it is not 100 or 350, it is 350 *1.4.
No questions no doubts make it last forever.
If someone else tells you different than it makes you
cry at night "RUN".
Only you have the answer.
100wrong
axd38 Sorry
But it is not about an error in concept but about a
personal decision.
All the other answers did was give advice on some of the mabeys that should have been considerted.
I should not have gone into the personal aspect
but that is the best way to relate.
again sorry
But it is not about an error in concept but about a
personal decision.
All the other answers did was give advice on some of the mabeys that should have been considerted.
I should not have gone into the personal aspect
but that is the best way to relate.
again sorry
I have also found out that if a house with a larger yard needs to desalinate water using reverse osmosis they could easily be using a unit the uses a 7.5 HP 480 volt 3-phase motor. A larger unit wouod need to be sized so that the utility can turn it off during peak periods.
A reverse osmosis desalinator that uses a 1/2 HP motor will put out 600 gallons per day if running CONTINUOUSLY. Oviously, a unit that is large enough to water a lawn and/or garden would need to use a much heftier motor.
A reverse osmosis desalinator that uses a 1/2 HP motor will put out 600 gallons per day if running CONTINUOUSLY. Oviously, a unit that is large enough to water a lawn and/or garden would need to use a much heftier motor.
axd38
mc5w
Is your answer related to something, or did you get
mixed up.
Back to the original questiom.
If axd38 has the wrong answer, the reason must be
pointed out. If the only person that can do this is
"his", the question still must be asked.
The tables "numbers" not an issue,
the basies for the numbers are the issue.
How I got there, How he got there, is the question.
ASK
mc5w
Is your answer related to something, or did you get
mixed up.
Back to the original questiom.
If axd38 has the wrong answer, the reason must be
pointed out. If the only person that can do this is
"his", the question still must be asked.
The tables "numbers" not an issue,
the basies for the numbers are the issue.
How I got there, How he got there, is the question.
ASK
Ah,
As long as he builds his 1200 amp single phase service correctly he should have no problems. However, I would be a bit concered about the matter that he should consider a higher voltage such as 240/480 single phase or consider using a 3-phase voltage such 240Y416 or 277Y480 volts.
You can run a single phase 2-wire 240 volt load such as an electric heater off of a 277 volt branch circuit using a 240 volt by 32 volt buck boost transformer. This would be an autotransformer configuration that step s down a small amout. However, when using a step down autotransformer the primary side and secondary side equipment grounding conductors need to be based on the primary overcurrent protection multiplied by the primary to secondary voltage ratio. Any current carrying conductor on the primary side also needs to be the same size as the equipment ground or larger.
As long as he builds his 1200 amp single phase service correctly he should have no problems. However, I would be a bit concered about the matter that he should consider a higher voltage such as 240/480 single phase or consider using a 3-phase voltage such 240Y416 or 277Y480 volts.
You can run a single phase 2-wire 240 volt load such as an electric heater off of a 277 volt branch circuit using a 240 volt by 32 volt buck boost transformer. This would be an autotransformer configuration that step s down a small amout. However, when using a step down autotransformer the primary side and secondary side equipment grounding conductors need to be based on the primary overcurrent protection multiplied by the primary to secondary voltage ratio. Any current carrying conductor on the primary side also needs to be the same size as the equipment ground or larger.
Traditionally, single phase meters are cheaper than 3-phase meters. Besides more parts, the stators in a mechanical 3-phase meter have to be adjusted to produce equal torque.
However, electronic meters have changed that criteria. In the case of the General Electric KV and later meters the meters use the same boards regardless of the number of phases. If you look in publication GEI-52590A.pdf you will find that a form 16s 7-prong meter can be programmed to act as a form 2s single phase meter - if you remove or insulate the 3 unused prongs you can stick that 16s meter into a 2s socket!
However, electronic meters have changed that criteria. In the case of the General Electric KV and later meters the meters use the same boards regardless of the number of phases. If you look in publication GEI-52590A.pdf you will find that a form 16s 7-prong meter can be programmed to act as a form 2s single phase meter - if you remove or insulate the 3 unused prongs you can stick that 16s meter into a 2s socket!
At my utility, we will not supply single phase past 800A, and only then in special cases.
1)For overhead transformation, the secondary cables will be very large and heavy, and place awkward forces on the pole.
1)This amount of unbalanced load can begin to mess up our ability to conveniently phase balance the currents on the distribution system (and therefore balance the voltages).
2) Utilities don't stock that many 100kVA (or 167kVA) transformers compared to the three 50kVA units that a 3-phase service would require (if overhead),
3)1200A services are definitely going to require external current transformers at the metering point, whereas 400A services (320A from the utilities' POV) are sometimes handled via self-contained meters in standard meter bases.
4)Have you spec'ed the required secondary cables yet? 1200A needs multiple runs of some pretty bulky cables (I am not going to get specific as local codes vary), particularly if you have to go any great distance (120/240V systems reach a 3% voltage drop quite quickly.).
Using a 400A / three phase system is usually CHEAPER to install than a 1200A single phase.
1)For overhead transformation, the secondary cables will be very large and heavy, and place awkward forces on the pole.
1)This amount of unbalanced load can begin to mess up our ability to conveniently phase balance the currents on the distribution system (and therefore balance the voltages).
2) Utilities don't stock that many 100kVA (or 167kVA) transformers compared to the three 50kVA units that a 3-phase service would require (if overhead),
3)1200A services are definitely going to require external current transformers at the metering point, whereas 400A services (320A from the utilities' POV) are sometimes handled via self-contained meters in standard meter bases.
4)Have you spec'ed the required secondary cables yet? 1200A needs multiple runs of some pretty bulky cables (I am not going to get specific as local codes vary), particularly if you have to go any great distance (120/240V systems reach a 3% voltage drop quite quickly.).
Using a 400A / three phase system is usually CHEAPER to install than a 1200A single phase.
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