Question about Home 150A Main

This is the quick one. Pay attention to the part where you start taking the load at 40% or you will end up with a huge number.

From the 2002 NEC handbook;

220.30 Optional Calculation ? Dwelling Unit. (A) Feeder and Service Load. For a dwelling unit having the total connected load served by a single 3-wire, 120/240-volt or 208Y/120-volt set of service or feeder conductors with an ampacity of 100 or greater, it shall be permissible to compute the feeder and service loads in accordance with this section instead of the method specified in Part II of this article. The calculated load shall be the result of adding the loads from 220.30(B) and (C). Feeder and service-entrance conductors whose demand load is determined by this optional calculation shall be permitted to have the neutral load determined by 220.22. The optional method given in 220.30 applies to a single dwelling unit, whether it is a separate building or located in a multifamily dwelling. The optional calculation permitted by 220.30 may be used only if the service-entrance or feeder conductors have an ampacity of at least 100 amperes. See Article 100 for the definition of dwelling unit. Examples of the optional calculation for a dwelling unit are given in Examples D2(a), D2(b), D2(c), and D4(b) of Annex D. (B) General Loads. The general calculated load shall be not less than 100 percent of the first 10 kVA plus 40 percent of the remainder of the following loads: (1) 1500 volt-amperes for each 2-wire, 20-ampere small-appliance branch circuit and each laundry branch circuit specified in 220.16. (2) 33 volt-amperes/m2 or 3 volt-amperes/ft2 for general lighting and general-use receptacles. The floor area for each floor shall be computed from the outside dimensions of the dwelling unit. The computed floor area shall not include open porches, garages, or unused or unfinished spaces not adaptable for future use. (3) The nameplate rating of all appliances that are fastened in place, permanently connected, or located to be on a specific circuit, ranges, wall-mounted ovens, counter-mounted cooking units, clothes dryers, and water heaters. Section 220.30(B)(3) includes appliances that may not be fastened in place but may be permanently connected or on a specific circuit, such as clothes dryers, dishwashers, and freezers. (4) The nameplate ampere or kVA rating of all motors and of all low-power-factor loads. (C) Heating and Air-Conditioning Load. The largest of the following six selections (load in kVA) shall be included: (1) 100 percent of the nameplate rating(s) of the air conditioning and cooling. (2) 100 percent of the nameplate ratings of the heat pump compressors and supplemental heating unless the controller prevents the compressor and supplemental heating from operating at the same time. (3) 100 percent of the nameplate ratings of electric thermal storage and other heating systems where the usual load is expected to be continuous at the full nameplate value. Systems qualifying under this selection shall not be calculated under any other selection in 220.30(C). (4) 65 percent of the nameplate rating(s) of the central electric space heating, including integral supplemental heating in heat pumps where the controller prevents the compressor and supplemental heating from operating at the same time. (5) 65 percent of the nameplate rating(s) of electric space heating if less than four separately controlled units. (6) 40 percent of the nameplate rating(s) of electric space heating if four or more separately controlled units. Section 220.21 states that for loads that do not operate simultaneously, the largest load being considered is used. In concert with 220.21, 220.30(C) requires that only the largest of the six choices needs to be included in the feeder or service calculation. Examples of calculations using air conditioning and heating are found in Annex D, Examples D2(b) and D3(c).

OMG! Call a qualified electrician out to do the work for you!

"Greg" wrote in message news: snipped-for-privacy@mb-m05.aol.com... This is the quick one. Pay attention to the part where you start taking the load at 40% or you will end up with a huge number.

From the 2002 NEC handbook;

220.30 Optional Calculation - Dwelling Unit. (A) Feeder and Service Load. For a dwelling unit having the total connected load served by a single 3-wire, 120/240-volt or 208Y/120-volt set of service or feeder conductors with an ampacity of 100 or greater, it shall be permissible to compute the feeder and service loads in accordance with this section instead of the method specified in Part II of this article. The calculated load shall be the result of adding the loads from 220.30(B) and (C). Feeder and service-entrance conductors whose demand load is determined by this optional calculation shall be permitted to have the neutral load determined by 220.22. The optional method given in 220.30 applies to a single dwelling unit, whether it is a separate building or located in a multifamily dwelling. The optional calculation permitted by 220.30 may be used only if the service-entrance or feeder conductors have an ampacity of at least 100 amperes. See Article 100 for the definition of dwelling unit. Examples of the optional calculation for a dwelling unit are given in Examples D2(a), D2(b), D2(c), and D4(b) of Annex D. (B) General Loads. The general calculated load shall be not less than 100 percent of the first 10 kVA plus 40 percent of the remainder of the following loads: (1) 1500 volt-amperes for each 2-wire, 20-ampere small-appliance branch circuit and each laundry branch circuit specified in 220.16. (2) 33 volt-amperes/m2 or 3 volt-amperes/ft2 for general lighting and general-use receptacles. The floor area for each floor shall be computed from the outside dimensions of the dwelling unit. The computed floor area shall not include open porches, garages, or unused or unfinished spaces not adaptable for future use. (3) The nameplate rating of all appliances that are fastened in place, permanently connected, or located to be on a specific circuit, ranges, wall-mounted ovens, counter-mounted cooking units, clothes dryers, and water heaters. Section 220.30(B)(3) includes appliances that may not be fastened in place but may be permanently connected or on a specific circuit, such as clothes dryers, dishwashers, and freezers. (4) The nameplate ampere or kVA rating of all motors and of all low-power-factor loads. (C) Heating and Air-Conditioning Load. The largest of the following six selections (load in kVA) shall be included: (1) 100 percent of the nameplate rating(s) of the air conditioning and cooling. (2) 100 percent of the nameplate ratings of the heat pump compressors and supplemental heating unless the controller prevents the compressor and supplemental heating from operating at the same time. (3) 100 percent of the nameplate ratings of electric thermal storage and other heating systems where the usual load is expected to be continuous at the full nameplate value. Systems qualifying under this selection shall not be calculated under any other selection in 220.30(C). (4) 65 percent of the nameplate rating(s) of the central electric space heating, including integral supplemental heating in heat pumps where the controller prevents the compressor and supplemental heating from operating at the same time. (5) 65 percent of the nameplate rating(s) of electric space heating if less than four separately controlled units. (6) 40 percent of the nameplate rating(s) of electric space heating if four or more separately controlled units. Section 220.21 states that for loads that do not operate simultaneously, the largest load being considered is used. In concert with 220.21, 220.30(C) requires that only the largest of the six choices needs to be included in the feeder or service calculation. Examples of calculations using air conditioning and heating are found in Annex D, Examples D2(b) and D3(c).

Sure would be nice to know what you have installed before the load calc.

Basically if you do not run your oven and or heat,a/c at the same time you will be fine. Except for the increase in you electric bill.

This is the quick one? :)

This is the poorest advice. Either figure it out our hire an electrical engineer. An electrican won't know.

What does a stupid electrician know? F*ck you

Yup. I didn't want to start a long thread about the intricacies of load calcs, only to give the OP a place to start. If this person is willing to get out his calculator and read the name plates of his electric appliances he should be able to see if he is approaching an overloaded panel. If nothing else it will give him an idea what the "qualified" electrician he is certainly going to call, is talking about. It also may help him identify an unqualified electrician who is trying to rip him off. Knowlege is power.

Here is an example of that type of load calc

Example No. D2(a). Optional Calculation for One-Family Dwelling, Heating Larger than Air Conditioning [see Section 220-30] The dwelling has a floor area of 1500 ft2, exclusive of an unfinished cellar not adaptable for future use, unfinished attic, and open porches. It has a

12-kW range, a 2.5-kW water heater, a 1.2-kW dishwasher, 9 kW of electric space heating installed in five rooms, a 5-kW clothes dryer, and a 6-A, 230-V, room air-conditioning unit. Assume range, water heater, dishwasher, space heating, and clothes dryer kW ratings equivalent to kVA. Air Conditioner kVA Calculation 6 A ´ 230 V ¸ 1000 = 1.38 kVA This 1.38 kVA (Section 220-30(c)(1) is less than 40% of 9 kVA of separately controlled electric heat [Section 220-3(c)(6)], so the 1.38 kVA need not be included in the service calculation. General Load 1500 ft2 at 3 VA 4500 VA Two 20-A appliance outlet circuits at 1500 VA each 3000 VA Laundry circuit 1500 VA Range (at nameplate rating) 12,000 VA Water heater 2500 VA Dishwasher 1200 VA Clothes dryer 5000 VA Total 29,700 VA Application of Demand Factor [See Section 220-30(b)] First 10 kVA of general load at 100% 10,000 VA Remainder of general load at 40% (19.7 kVA ´ 0.4) 7880 VA Total of general load 17,880 VA 9 kVA of heat at 40% (9000 VA ´ 0.4) = 3600 VA Total load 21,480 VA Calculated Load for Service Size 21,480 VA ¸ 240 V = 89.5 A The minimum service size would be 100 A. Feeder Neutral Load, per Section 220-22 1500 ft2 at 3 VA 4500 VA Three 20-A circuits at 1500 VA 4500 VA Total 9000 VA 3000 VA at 100% 3000 VA 9000 VA -3000 VA = 6000 VA at 35% 2100 VA Subtotal 5100 VA Range:8 kVA at 70% 5600 VA Clothes dryer:5 kVA at 70% 3500 VA Dishwasher 1200 VA Total 15,400 VA Calculated Load for Neutral 15,400 VA ¸ 240 V = 64.2 A

F--- the engineer! Who do you think makes your f---ed up prints and equations work?!? Step into the real world bitch!!!

This is the poorest advice. Either figure it out our hire an electrical engineer. An electrican won't know.

Then why are load calculations such a large part of the test for an electrician's license? Doing a load calc for a single family dwelling involves nothing more than simple math. No need for an engineering degree to do this calculation.

Bob Weiss N2IXK

And.we electricians know that.....unless he is ready to upgrade his service he shouldn't cook and hot tub at the same time. If the OP does want to cook "and" couple at the same time that is ok too until he trips the main or until he tries it with an amp probe on the main. If he does upgrade you still don't need math, all you need is what wire is good for 200A You can calculate that but I use a wire chart.

The load calculations are a good exercise for us electricians and are necessary in the design process but they don't do much in the real world. Electricians can do the calculations we really don't need to.

I see so many $100 answers for 10 cent problems...............Come to think of it engineers might be smarter than us electricians after all. :)

The NEC has some rules on this, but it is much easier to call the power company or take a good look at your power bill. Ask them to give you your peak load and average load. This should give you a good idea of what the actual load is. Add about 25 percent to your average load and if there is enough left for your hot tub you're probably ok. Also note the times of use. For instance, do you use the heavier loads at the same time that you will be using your hot tub? Apply some common sense and you can determine if your hot tub can be added. Here are some numbers for you: Example:

1000 watts used for one hour is one kilowatt hour. So if you used 1000 watts of power continuously for 24 hours that would be 24 kilowatt hours of energy. For 30 days this would be 720 kilowatt hours Amperes = 1000 watts / 240 volts Amperes = 4.1 amperes Take 125 percent of this and we get about 5 amperes This leaves almost 145 amperes at 240 volts for additional load on a 150 ampere service. Fact: Services are usually over sized considerably to allow for peak loading and additional loads. If your hot tub is 5000 watts is will draw 5000/240 volts or 21 amperes. Example: A 150 ampere 240 volt single phase service is good for 240 * 150 = 36,000 watts.

If this is wrong you will see plenty posts correcting this.