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What Size Cable Do You Suggest to Power My House?

07/06/2010 7:28 PM

I have been told I need a 95mm cable to power my house.

It's 11kw single phase. I have been told that the reason for the cable being so big is because of the distance from the transformer, the distance is 75 meters

I thought the cable size suggested is too heavy for the job, would anybody like to help

thanks

david

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#1

Re: what size of cable do you suggest

07/06/2010 7:59 PM

What voltage and how many phases?

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#2

Re: What Size Cable Do You Suggest to Power My House?

07/06/2010 10:52 PM

You probably mean the total section of the 2 or 3 conductors plus earth (ground) together in one cable? and 95 mm2. What part of the world you are posting from? Is the cable underground? In pipe or not? And what is the climate there? This is additional to Tornado's questions.

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#3

Re: What Size Cable Do You Suggest to Power My House?

07/06/2010 11:54 PM

I am not the one to tell you what size wire you need. I am the one to tell you that this is an operation that you will do now, and live with for the next generation. When my parents house was built, it has 220 volts and sixty amps service. Now most houses are built with 220 volts and 200 amps.

Don't try to save a few dollars now, and then find that five years from now that you want to add a workshop, or a barn, or another building, and you need to replace the service line going to your property. The results of voltage drop, are higher working temperatures, higher power usage, and shorter appliance life.

Do it once. Do it right. And be done with it. Some times good enough just ain't good enough. Good luck.

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#5
In reply to #3

Re: What Size Cable Do You Suggest to Power My House?

07/07/2010 12:44 AM

With what we know now - nothing - is this a best advise from Uncle Bob. GA from me. Uncle D.

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#13
In reply to #3

Re: What Size Cable Do You Suggest to Power My House?

07/07/2010 11:36 PM

GA from me too! One other item David did not provide: Is it copper or aluminum?

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#4

Re: What Size Cable Do You Suggest to Power My House?

07/06/2010 11:55 PM

BTW, welcome to the insanity.

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#6

Re: What Size Cable Do You Suggest to Power My House?

07/07/2010 12:59 AM

1) Calculate the current required to go through the cable with all the anticipated loads.

2) look at the total resistance of various cable sizes of 150 meters length (there and back).

3) If the IxR voltage drop at the load end is at least 98% that of the source end then you'll be fine, much larger cable is overkill.

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#7

Re: What Size Cable Do You Suggest to Power My House?

07/07/2010 2:48 AM

Hi everyone, thanks for responding. More info: Its going to be 240v. Single phase, it will be in ducting under the ground, It is for a 4 bed room house. And the main heating in the house is wood and coal. And one electric shower in the spare room and electric oven and hob in the kitchen. Hope this is enough.info to get a clear answer Thanks david

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#8
In reply to #7

Re: What Size Cable Do You Suggest to Power My House?

07/07/2010 4:29 AM

In my area single phase supply connection means 5 amp or 10 (15) amps tariff energy metering (CT is not applicable) beyound which the utility requires for a three phase domesic connection (CT's applicable).

For design considerations your electric oven alone will be estimated 4500 KW.

Before cable sizing check with the requirements of the utility you wish to be connected. (Single or three phase connection).

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#9
In reply to #8

Re: What Size Cable Do You Suggest to Power My House?

07/07/2010 8:36 AM

For design considerations your electric oven alone will be estimated 4500 KW.

I would add (for design considerations, of coarse) a medium power hydraulic press (about 10,000KW).

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#15
In reply to #9

Re: What Size Cable Do You Suggest to Power My House?

07/08/2010 2:20 AM

indel said

"For design considerations your electric oven alone will be estimated 4500 KW."

I seriously question this statement.

It would have to be the mother of all ovens to consume 4.5 MILLION WATTS.

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#26
In reply to #15

Re: What Size Cable Do You Suggest to Power My House?

07/08/2010 8:47 AM

Honorable Guest,

I reproduced, in bold font, what the ante-writer posted

(post # 8 from mountk2).

Then, I added my comment, in normal font. Because the writer did miss a decimal coma (4500KW instead of 4.5KW) I thought that would be an engineer joke to consider - for design only - another heavy load (11000KW). At the end I set that emoticon to show that I was joking.

I am ready to explain it one more time, if necessary. Have a wonderful day!

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#30
In reply to #26

Re: What Size Cable Do You Suggest to Power My House?

07/08/2010 9:19 AM

I would give you a GA for having a sense of humor! Very subtle, but it did make some pause at the absurdity of your comments.

Thanks for the chuckle.

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#10

Re: What Size Cable Do You Suggest to Power My House?

07/07/2010 10:40 PM

Hey did the last two responders drop a decimal point somewhere.

I think I see them rolling down the road.

The OP said it was an 11kw service but two responders indicated a 4500 kw hob and a hydraulic press was rated at around 10,000 kw.

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#27
In reply to #10

Re: What Size Cable Do You Suggest to Power My House?

07/08/2010 8:50 AM

Have a look at post #26, please.

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#11

Re: What Size Cable Do You Suggest to Power My House?

07/07/2010 11:13 PM

whatever you do finally . . . do ensure that you comply with the local supply company rules and the national electrical code in toto . . . . in fact if you comply with the code you automatically build in safety and economy together . . .

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#12

Re: What Size Cable Do You Suggest to Power My House?

07/07/2010 11:24 PM

Sizing cables is influenced by the following factors: - Voltage Drop - Current carrying capacity - Earth loop impedance - Short circuit temperature rise Since you are sizing your cable for voltage drop, I doubt the 2nd and 4th factors would be of concern. 95mm2 cable does seem excessive for 11kW, even if it is 75m away. In Australia we use AS3008 as a go-by for sizing cables. It is based on the IEC standard (number escapes me). Generally 2% drop from transformer to distribution point is kept at 2% with 3% allowed from distribution point to final connected load (ie. house hold distribution board to heater). To be safe, total voltage drop (from transformer to final connected load) should not exceed 5% but it is dependent on how the equipment is designed.

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#45
In reply to #12

Re: What Size Cable Do You Suggest to Power My House?

07/10/2010 9:48 AM

Sizing cable could be done by adhering to BS/NEC. Before that one should calculate/assess the current for which the cable to be rated.

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#47
In reply to #12

Re: What Size Cable Do You Suggest to Power My House?

07/10/2010 4:43 PM

The 2% voltage drop mentioned is from the point of connection(metering point) to the consumer unit(power centre) ie in the main cable, as you don't know the voltage at the secondary of the transformer installed by the utility.The utility assumes that the voltage at the metering point to be rated voltage. For big loads a separate transformer will be used for each consumer and for homes a single transformer will be used to feed several homes.

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#14

Re: What Size Cable Do You Suggest to Power My House?

07/08/2010 1:46 AM

Yes, the cable is oversized. I assume you will be using 3 1/2C Al cable to be laid underground from Trf. to main panel of your house. Within the house the entire load of 11 Kw will be equally distributed amongst the three phases. So your total 3-phase load will be about 36A. A 3 1/2C X 50 mm2 Al cable which has CCC of 130A in underground laying configuration should suffice. That will take care of voltage drop as well as future expansion of your house.

BBRaina

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#28
In reply to #14

Re: What Size Cable Do You Suggest to Power My House?

07/08/2010 9:04 AM

No - He said SINGLE Phase!

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#16

Re: What Size Cable Do You Suggest to Power My House?

07/08/2010 2:58 AM

I Think 95mm is too short I will not stretch the 75 Meters.

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#25
In reply to #16

Re: What Size Cable Do You Suggest to Power My House?

07/08/2010 8:10 AM

Guest, you deserve a GA for that answer. It was the funniest thing I have seen posted in a long long time.

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#17

Re: What Size Cable Do You Suggest to Power My House?

07/08/2010 3:22 AM

11kV single phase within a house?

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#23
In reply to #17

Re: What Size Cable Do You Suggest to Power My House?

07/08/2010 8:08 AM

Oi Guru, where the hell did you read 11Kv single phase from? I think if you re-read (assuming of course that you can in fact read) the original post, it stated 11kw and not 11kv (you do know the difference between a v and a w right?) You were probably too busy including that stupid "Danger of Death" sign. Muppett.

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#32
In reply to #23

Re: What Size Cable Do You Suggest to Power My House?

07/08/2010 9:25 AM

Maybe he wants to research some of Tesla's theories?

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#18

Re: What Size Cable Do You Suggest to Power My House?

07/08/2010 4:25 AM

Oh dear, more examples of posters not checking their post or not knowing anything about the subject! There are dangers involved here, guys, so please be careful with your statements and advice. 4500MW cooker? - come on, check what you're saying.

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#19

Re: What Size Cable Do You Suggest to Power My House?

07/08/2010 5:04 AM

Please check:

11kW 240V Single phase ===> ~57A max and including utilisation factor of 70% ==>40A

If the cable is Copper conductor, then a max of 25mm2 will do for the distance and the load. 95mm2 is overkill too high! (unless the utility is going to use it to supply other neighbors on your contribution, they should pay...). Your oven will be arround 4000 Watts and take ~17A when working full. At any one time, you would not be loading the whole 11kW but rather more likely to be on 8kW peak (34A).

If Al conductors, then 50mm2 will do.

You could go for 35mm2 in Cu or 70mm2 in Al at best if for the future you think that you could be increasing your own load...

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#20

Re: What Size Cable Do You Suggest to Power My House?

07/08/2010 5:11 AM

Hi,

nobody seems to have addresed the duct installation specified by the OP.

This will raise temperature and we need duct sizes and anything else that affects the temperature of the cable.

Happy Hunting,

Sleepy

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#21
In reply to #20

Re: What Size Cable Do You Suggest to Power My House?

07/08/2010 6:41 AM

Yes I have. After that only I have arrived at 3 1/2 C X 50 mm2 Al cable. He can save on investment cost by going for Al cable which is pretty okay for the said application. There is lot of room still left in the cable sized.

BB Raina

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#35
In reply to #21

Re: What Size Cable Do You Suggest to Power My House?

07/08/2010 10:54 AM

I have lived through owning a house with some aluminum wiring. I will never again be satisfied with aluminum. When I hit the lottery, and buy a mountain resort, if it has aluminum, I will have it changed.

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#37
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Re: What Size Cable Do You Suggest to Power My House?

07/08/2010 11:18 AM

I too have fought with aluminum; in my case an industrial building whose breaker box had aluminum bus bars and contacts. Although the breakers were rated Cu/Al, the contacts oxidized and were a general PITA! It was a rented building, and we moved to a larger facility, but if we had stayed there, the whole box would have been replaced with a copper-based one. I don't know what happened after we left...

On the other hand, The feed lines from the transformer to the houses in my area have all been aluminum for at least 50 years, and I'm not aware of any problems. These lines are installed and terminated by the utility, not by contractors, if I'm not mistaken. It is these lines that the OP is talking about...

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#43
In reply to #21

Re: What Size Cable Do You Suggest to Power My House?

07/09/2010 6:19 PM

He is talking about single phase supply and your 3 1/2 cores is usually for 3 phase and Neutral ! Also, the current will be less is 11kW , 3phase.... revise and read the question please otherwise you will be wrong.

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#22

Re: What Size Cable Do You Suggest to Power My House?

07/08/2010 8:06 AM

Terminating aluminium cable can be difficult, bare that in mind when choosing aluminium over copper. Also ensure that the main incommer on your house can terminate the cable you're planning to install. This can be found in the circuit breakers manual. There are plenty of cable sizing applications online, a quick google search retrieved this: http://www.kilowatts.com.au/calculator-voltage-drop.php This does not consider current carrying capacity, but I can assure you 50mm2 will be able to deliver 11kW without overheating, especially if it is installed suspended in air.

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#24
In reply to #22

Re: What Size Cable Do You Suggest to Power My House?

07/08/2010 8:09 AM

Terminating aluminium cable can be difficult, bare that in mind when choosing aluminium over copper. Also ensure that the main incommer on your house can terminate the cable you're planning to install. This can be found in the circuit breakers manual. There are plenty of cable sizing applications online, a quick google search retrieved this: http://www.kilowatts.com.au/calculator-voltage-drop.php This does not consider current carrying capacity, but I can assure you 50mm2 will be able to deliver 11kW without overheating, especially if it is installed suspended in air. - sorry posted this without logging in

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#29

Re: What Size Cable Do You Suggest to Power My House?

07/08/2010 9:05 AM

Why not just go to the power company and ask .?? They will help.

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#31

Re: What Size Cable Do You Suggest to Power My House?

07/08/2010 9:20 AM

I will offer this bit of trade information since only one poster has even touched on it.

In the U.S. service entrance conductors are not sized by the home owner or even by a contractor; they are sized by the utility company. The utility company may require the cables to be a standard size for the purpose of tying the service entrance into the grid, so the utility may require cabling for a 100A (4 awg) service even if a house requires only 60A (6 awg).

Throw the book away and forget about online amperage calculators. Call your local utility and ask what size conductors you are required to run. They may even give you a pamphlet complete with other useful information such as height of stub out, distance from the power pole, etc. if you ask nicely.

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#33

Re: What Size Cable Do You Suggest to Power My House?

07/08/2010 9:38 AM

The post seems to indicate that the installation is foreign to the United States.

This being said, The National Electric Code (NEC) requires a minimum 100A service to the main house and a minimum 60A service to outbuildings.

100A service is normally #2[6.544 mm dia; 33.6 cm] (60/75/90C insulation. The ampacity for a run, of max 50 feet, is 95 / 115 / 130 A respectively.) run in 3 1/2 inch underground coduit (Southern California Edison [SCE] required that).

75 Meters is approximately 250 feet. The cable is upped one AWG size for each 50 feet. That would mean an AWG cable size (minimum) 4/0 (107 cm, more than 95) derated for 250 feet. The conduit would also be increased by a factor of 5. There also may be antiscuffing characteristics to consider.

1000 feet (4 cnductors of 4/0; 2 hot legs, 1 neutral, 1 earth-ground) cable is a poderous thing to consider.

Be careful and do not undersize either the wire or the conduit.

Other countries may have different (less stringent) requirements.

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#34
In reply to #33

Re: What Size Cable Do You Suggest to Power My House?

07/08/2010 10:50 AM

I believe that you meant to say that the NEC requires a minimum of a 100A service disconnect for a single family dwelling, and a minimum of a 60A service disconnect for outbuildings.

The NEC says this about overhead service entrance conductors:

230.31 Size and Rating.
(A) General. Service-lateral conductors shall have sufficient ampacity to carry the current for the load as calculated in accordance with Article 220 and shall have adequate mechanical strength.
(B) Minimum Size. The conductors shall not be smaller than 8 AWG copper or 6 AWG aluminum or copper-clad aluminum.
Exception: Conductors supplying only limited loads of a single branch circuit — such as small polyphase power, controlled water heaters, and similar loads — shall not be smaller than 12 AWG copper or 10 AWG aluminum or copper-clad aluminum.
(C) Grounded Conductors. The grounded conductor shall not be less than the minimum size required by 250.24(C).

And more generally:

230.42 Minimum Size and Rating.
(A) General. The ampacity of the service-entrance conductors before the application of any adjustment or correction factors shall not be less than either (A)(1) or (A)(2). Loads shall be determined in accordance with Part III, IV, or V of Article 220, as applicable. Ampacity shall be determined from 310.15. The maximum allowable current of busways shall be that value for which the busway has been listed or labeled.
(1) The sum of the noncontinuous loads plus 125 percent of continuous loads
(2) The sum of the noncontinuous load plus the continuous load if the service-entrance conductors terminate in an overcurrent device where both the overcurrent device and its assembly are listed for operation at 100 percent of their rating

The NEC is to be considered the minimum requirements to reduce the risk of fire hazards. Local utility requirements supercede the NEC.

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#36

Re: What Size Cable Do You Suggest to Power My House?

07/08/2010 11:00 AM

To estimate the size of cable you must give the breakdown of connected load as below: a)light(CFL)13W -05nos b)light(inc)60W -10nos c)TV(...W) -01no c)Fridge(...W) -01no d)Iron(....W) -01no e)microwave(...W) -01no f)Washing machine(.....W) -01no g)cloth dryer(....W) -01no h)computer(...W) -02nos i)printer(...W) -01no j)vacuum cleaner(...W) -01no k)air conditioner(...W) -02nos l)stove(...W) -01no etc etc etc Add any other load to be connected in the future When you calculate the anticipated load one should apply a diversity factor for simultaneous use of items(in the nights lights,stove,washing machine,iron,TV fridge,a/c etc or in day time some machine like press,stove,computer,fridge,tv etc). Some engineers apply a diversity factor for each of the item and take the total as the load. For load calculation kVA is needed and not Wattage ,as pf plays an important role in determining the current flowing. The average consumer won,t have the knowledge to calculate so the supply authority should calculate based on experience. For a new building(home/office/shop/factory) the authorities should give a declaration form to be filled by the consumer and verified by the authorities regarding load to be connected.Regarding type of cable(cu/al/Arm) and method of laying(overhead/underground),location of meter the power authority should take the decision depending on location,safety and economic considerations.

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#38

Re: What Size Cable Do You Suggest to Power My House?

07/08/2010 12:57 PM

Guys I'm disappointed. No one could give a decent answer to this question. Here is what our guest tells us 1- Load: 11kw 2- Voltage: 240v 3- Phase: single phase 4- Distance: 75 meters From these givens I deduce this house is not located in the states. 240v whispers to me its either in UK or some former British colony. Now some very primitive calculation. 11,000 watts divided by 240volts will give us 45.8Amps That is not so huge a load as some guys were joking. I'm not very familiar with British Standards but i will tell you the recommendations of IEC (International Electrical Code) This code is based on supposing the distance is less than 100 meters and an allowed voltage drop of 5%. Of course we can do the calculations ourselves if we know the material used. If we know the Rho (conductivity) of the material , Rho times the length in meters divided by the cross-section area in millimeter square will give you the resistance of the cable in Ohm. For copper the Rho is 0.0225 if I'm not wrong, please check. 5% of 240volts is 12 volts So after doing some arithmetic we get 2.5mm2 15amps 4mm2 20Amps 6mm2 30Amps 10mm2 40Amps 16mm2 50Amps 25mm2 80Amps 35mm2 100Amps 50mm2 125Amps Of course these are the maximum permissible currents, and an automatic circuit breaker or over-current device or fuse must be used to protect the wires from overloading. It should also be taken into consideration the quantity of parallel cables in a trunk or conduit or cable-tray. But these do not make a severe difference. Also it is not clear how did our guest calculate the load as 11kw. What load is this? Is it the maximum load? If yes the above table can be used without getting into trouble if the wires are properly protected from overload and short circuit. So as we see with a maximum load of 45.8 Amps 16mm2 wire would be sufficient. but we have 2 extremes here 75 meters too close to 100 meter limitation and 45.8Amps too close to 50Amps limit. So I would recommend 25mm2. Anyway 25mm2 is far more economical than 95mm2. Hope this will enlighten you.

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#42
In reply to #38

Re: What Size Cable Do You Suggest to Power My House?

07/09/2010 6:14 PM

I think that the Rho you are using is for Aluminium conductor. For Copper = 0.016 Ω per m length per mm2.

It is better to use the cable maker tables when selecting cable sizes for better accuracy. There are factors other than just the voltage drop, like heat dissipation which depends on the insulation material and its thickness...

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#39

Re: What Size Cable Do You Suggest to Power My House?

07/08/2010 1:52 PM

I would never recommend aluminum for a drop or house wiring. Too many problems. The utility co. had to recable the entire residential neighborhood where I lived once because of corrosion (buried cable). The cause seemed to be always at terminations.

Use copper clad, unless your utility says otherwise.

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Join Date: Jun 2010
Posts: 75
#41
In reply to #39

Re: What Size Cable Do You Suggest to Power My House?

07/09/2010 1:04 AM

Al cable was suggested for connection between tranformer and main panel of the house only. For inside house wiring/ cabling it has to be copper cabkle only as rightly pointed out by you. Al wiring inside houses creates nuisance of loose connections which the inhabitant of the house has to suffer interminably with possibility of serious damage to household appliances arising out of loose contacts which aluminium conductor develops over a period of time due to heating effect of current.

BB Raina

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Anonymous Poster
#40

Re: What Size Cable Do You Suggest to Power My House?

07/08/2010 8:42 PM

I live in Pennsylvania, and our electric company will give us a booklet that has all the technical info you need and much more you do not need. Contact you electric supplier, but yiu will need to rquest the manual.

PEbobimm

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#44

Re: What Size Cable Do You Suggest to Power My House?

07/10/2010 4:42 AM

You can use any size of cable as long as it is equal to or exceeds your loading capacity.

When selecting cable sizes, diversity and load factors are taken into consideration that tends to reduce the recommended size when these factors are taken into consideration. In situations where future needs are considered, corresponding cable size is selected and put in place but not when such is not conceived.

There is no way a 16mm2 load cable can be replace with a 95mm2 load cable, it is extremely outrageous and an unnecessary wast of resources. A 16mm2 cable has a maximum current rating of 74 Amps that quite above your rated 62.5 Amps but a 95mm2 cable has a maximum current rating of 230 Amps which is 3 times your required load cable.

If the recommendation is from your electrician when you are not considering having any future loads, it is a wrong prescription that has no bases or facts.

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Anonymous Poster
#46
In reply to #44

Re: What Size Cable Do You Suggest to Power My House?

07/10/2010 12:39 PM

So basicly your saying, if i was wiring a plugin with no intention now or in the future of ever plugging in anything but a 40 watt light bulb, it should be ok to run 20 awg wire to that plug.

Boy, what backwards and dangerous thinking that is,,,,,,,

ie: You might not own or even think about owning a hot tub or central air in the future ,,But you could or the owner behind you could and that has to be taken in to concideration in new contruction.

Electrical codes and rules for homes are there, not only for you and your families safety but also for the safety of people who buy the house when you sell it.

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#48

Re: What Size Cable Do You Suggest to Power My House?

07/11/2010 6:44 PM

No the cable will need to be longer than 95mm as the distance to your house is 75 m.

Is the 95mm the cross sectional area or the diameter and it depends on the voltage.

lower the voltage you up the current so your wire needs to be "fatter".

Where I am at full load you are drawing 50 Amps at 220v RMS.

In the US you have 100 Amps at 110v RMS I think.

So we need more information to help you...but that is the clue.

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Anonymous Poster
#49

Re: What Size Cable Do You Suggest to Power My House?

07/13/2010 3:45 AM

It is depends upon your wife and how many friends she have and how often the late night outings .

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