Hello, Been studing for my test and I just got " Tom Henry 2017 Calculations" Book. In his book he states

Section 220.55: Where Two or more single-phase Ranges are supplied by a 3-Phase,4-Wire feeder, the total load shall be computed on the basis of twice the maximum number between any two phases

One of his examples says " 30 Single-phase ranges at 12kw each are supplied by a 3-phase, 4-wire,120/208 feeder. What is the demand on the feeder for these ranges?

Solution

A Phase B Phase C Phase

10 10 10

10x2=20 appliances. Column C 20 appliance =35kw

That is the answer

In annex D and mike holt it shows it should be

Section 220.55: Where Two or more single-phase Ranges are supplied by a 3-Phase,4-Wire feeder, the total load shall be computed on the basis of twice the maximum number between any two phases

One of his examples says " 30 Single-phase ranges at 12kw each are supplied by a 3-phase, 4-wire,120/208 feeder. What is the demand on the feeder for these ranges?

Solution

A Phase B Phase C Phase

10 10 10

10x2=20 appliances. Column C 20 appliance =35kw

That is the answer

In annex D and mike holt it shows it should be

[COLOR=#000000]The demand load for each two phases is 35/2 = 17.5 KW.The total demand load is 3 x 17.5 = 52.5 KWThe line current is:[/COLOR][COLOR=#000000]I = 52,500 / (1.732 x 208) = 52,500 / 360.3 = 145.7 amperes

Been jamming information in and this kind of messed me up. Every 3 Phase range calc I was getting wrong doing it like Annex D does.

Also Don't know if I should start a new topic but it should be brief answer. Its about including a Sign Circuit in commercial calculations. In Toms book he says don't assume Commercial Building are accessible to Pedestrians. Mike's books have always included even if it did not state.

How should I go about it. Only include it, or see if they state "accessible to pedestrians"

Thanks

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Been jamming information in and this kind of messed me up. Every 3 Phase range calc I was getting wrong doing it like Annex D does.

Also Don't know if I should start a new topic but it should be brief answer. Its about including a Sign Circuit in commercial calculations. In Toms book he says don't assume Commercial Building are accessible to Pedestrians. Mike's books have always included even if it did not state.

How should I go about it. Only include it, or see if they state "accessible to pedestrians"

Thanks

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