BIG HOUSE

[iwire]

All it takes is one large load, and you possibly consider 277/480 for service. The wealthy people today have big imaginations.

I have a good imagination and no a 480 volt service does not make sense for a home.

The losses from many small transformers or one large one will kill any benefit you can get from a 480 volt service.

Are you arguing for the sake of arguing? :lol:

 

[T.M.Haja Sahib]

In India,power supply company provide only three phase power supply 240v/415v to a residence when its connected load exceeds 5 h.p.This is done with a view to avoid unbalance in its three phase supply system.To avoid the same problem,resort is made to single phase power supply system also in U.S.,I think so!

 

[iwire]

In India,power supply company provide only three phase power supply 240v/415v to a residence when its connected load exceeds 5 h.p.This is done with a view to avoid unbalance in its three phase supply system.To avoid the same problem,resort is made to single phase power supply system also in U.S.,I think so!

The solution is simple here, a 208Y/120 service.

 

[kwired]

I have a good imagination and no a 480 volt service does not make sense for a home.

The losses from many small transformers or one large one will kill any benefit you can get from a 480 volt service.

Are you arguing for the sake of arguing? :lol:

I did say consider and not suggest it was mandatory.

Argue for the sake of arguing? Me? Never

I do agree if you only have one large load that it still is likely not worth installing the 480 volt service for a place that otherwise has mostly 120 volt or 208/240 volt loads.

 

[T.M.Haja Sahib]

The solution is simple here, a 208Y/120 service.

A 240v/120v single phase supply to a residence is fed by a single phase transformer.Is it in turn fed by a single phase h.v supply or not? Thanks.

 

[GeorgeB]

A 240v/120v single phase supply to a residence is fed by a single phase transformer.Is it in turn fed by a single phase h.v supply or not? Thanks.

It is fed from 1 phase of a 3 phase supply. The utility generally balances the total load, via thousands of transformers, across the 3 phases, as closely as practical.

 

[iwire]

A 240v/120v single phase supply to a residence is fed by a single phase transformer.Is it in turn fed by a single phase h.v supply or not? Thanks.

Yes, but if you notice I did not recommend a 120/240 supply, I recommended a 208Y/120 supply which is 3 phase and very common around here.

 

[T.M.Haja Sahib]

It is fed from 1 phase of a 3 phase supply. The utility generally balances the total load, via thousands of transformers, across the 3 phases, as closely as practical.

Considering that 240v single phase loads are allowed only up to 5 h.p, I think that we in India may take a long time to learn that art.........

 

[kwired]

Considering that 240v single phase loads are allowed only up to 5 h.p, I think that we in India may take a long time to learn that art.........

I can show you some 16 Hp single phase motors.

I can also show you some 50 HP motors fed from single phase service via phase converters.

When located in a rural area it is not always cost effective to have three phase service. But there are prices to pay for phase conversion also, beyond installation cost.

 

[T.M.Haja Sahib]

I can show you some 16 Hp single phase motors.

I can also show you some 50 HP motors fed from single phase service via phase converters.

When located in a rural area it is not always cost effective to have three phase service. But there are prices to pay for phase conversion also, beyond installation cost.

(MODS,please bear with my 'trolling'.)

But what is unclear to me is how you people manage with the unbalance resulting in a tree phase supply system due to heavy single phase loads imposed on it.Even a small unbalance can wreak havoc for 3 phase induction motors.

 

[iwire]

(MODS,please bear with my 'trolling'.)

But what is unclear to me is how you people manage with the unbalance resulting in a tree phase supply system due to heavy single phase loads imposed on it.Even a small unbalance can wreak havoc for 3 phase induction motors.

The power companies do have rules about balanced loading but as was mentioned they can alternate which phases they use for each single phase service.

In some of the cities around me they run a 208Y/120 network in a neighborhood and alternate which two phases they use for each home.

 

[kwired]

Which is what is done inside a building with three phase supply with all the single phase loads that are in it.

You do the best you can to try to maintain balance across the phases, paying more attention to loads that are heavier or run longer, or both.

 

[GeorgeB]

Considering that 240v single phase loads are allowed only up to 5 h.p, I think that we in India may take a long time to learn that art.........

If 5 HP is the peak load (about 4kW), that would not be realistic in much of the USA. If that is the average, it would be about (I'm rounding off heavily) 100kWh a day, more by roughly a factor of 3 than MOST residences use (I believe 1000kWh is an average monthly consumption; our Department of Energy was reported to use 14,000 kWh/year in a report I found via Google)

The average home built today will have about a 200A service. An electric water heater or electric clothes dryer uses about 5kW (call that 7hp), an oven with cooktop maybe 8-10kW (but it will cycle), and electric heat or air conditioning ... comparable. So ... 5hp AVERAGE is perhaps realistic here for a suggested maximum single phase design over the period of a day.

 

[T.M.Haja Sahib]

The power companies do have rules about balanced loading but as was mentioned they can alternate which phases they use for each single phase service.

In some of the cities around me they run a 208Y/120 network in a neighborhood and alternate which two phases they use for each home.

More than that is required,because load balancing activities are done in India also.So the riddle of why they restrict single phase load only up to 5 h.p and why single phase load can be 'unlimited' in U.S remained unsolved till last night.After sleeping over the problem,the 'right' solution dawned on me.
Here it is.The U.S power supply system is strong.The Indian power supply system is weak.The fault level in an Indian residence does not exceed 10kA,whereas the same in an American residence may exceed 70kA and so the source impedance would be so low that no appreciable change in source voltage could happen,no matter how heavy the single phase load may be.That explains the discrepancy.

 

[George Stolz]

Typical residential services do not exceed 10k.

 

[kwired]

More than that is required,because load balancing activities are done in India also.So the riddle of why they restrict single phase load only up to 5 h.p and why single phase load can be 'unlimited' in U.S remained unsolved till last night.After sleeping over the problem,the 'right' solution dawned on me.
Here it is.The U.S power supply system is strong.The Indian power supply system is weak.The fault level in an Indian residence does not exceed 10kA,whereas the same in an American residence may exceed 70kA and so the source impedance would be so low that no appreciable change in source voltage could happen,no matter how heavy the single phase load may be.That explains the discrepancy.

The 5 hp restriction may be more because of the starting surge more than the running load.

Even on three phase systems some utilities here limit size of motors unless a reduced current starting method is used.

 

[T.M.Haja Sahib]

Typical residential services do not exceed 10k.

You may be right and in that case I may need another sleeping over the same problem.....

However,please see post #91 in http://forums.mikeholt.com/showthread.php?t=140830&page=32

Anyway,higher fault level also aids in considerably higher individual single phase loading in U.S compared to that in India.

 

[T.M.Haja Sahib]

Considering that 210.6(A) forbids you from using 277V for lighting..........

But 210.6(C) allows it.

 

[iwire]

But 210.6(C) allows it.

Not in a dwelling unit.

 

[T.M.Haja Sahib]

Not in a dwelling unit.

Was it permitted in earlier versions prior to 2011 NEC? Thanks.