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Home > Archive > Electrical Engineering > May 2006 > Question about copper conductor size.
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| Author |
Question about copper conductor size.
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| Peter Jason 2006-05-08, 12:21 am |
| I have a large electric oven rated at 15KW
resistive load, plus another 3KW for 3-phase
induction motors.
Say 18KW total continuous running.
All this has to be connected to a 3-phase
supply in delta.
How can I determine the conductor size for
each of the 3-phase connections in Amps?
Please help, Peter.
| |
| Peter Jason 2006-05-08, 12:21 am |
|
"Peter Jason" <td@jostle.com> wrote in
message
news:e3mabg$2f5p$1@otis.netspace.net.au...
>I have a large electric oven rated at 15KW
>resistive load, plus another 3KW for 3-phase
>induction motors.
>
> Say 18KW total continuous running.
>
> All this has to be connected to a 3-phase
> supply in delta.
>
> How can I determine the conductor size for
> each of the 3-phase connections in Amps?
>
> Please help, Peter.
>
PS the 3-phase is 415V
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| Peter Jason 2006-05-08, 2:21 am |
|
"TimPerry" <timperry@noaspamadelphia.net>
wrote in message
news:Q6KdnVkxxMGiKsPZnZ2dneKdnZydnZ2d@adelphia.com...
>
> "Peter Jason" <td@jostle.com> wrote in
> message
> news:e3mabg$2f5p$1@otis.netspace.net.au...
>
> Peter, although there are several online
> calculators, charts, and tables, i
> would recommend you consult a local master
> electrician to get the correct
> size and type for your situation.
>
> http://www.powerstream.com/Wire_Size.htm
> here is one chart to referance.
>
>
> for 3 phase: AMPS = WATTS / (1.732 X VOLTS
> X PF)
>
> if i assume a PF OF .90 and a voltage of
> 240 i get 48.1 amps.... but you
> need to read the label on the oven to know.
>
Many thanks; The electrician left out the
SqRt3=1.732 in the denominator.
I get Amps = 18000/(1.732 x 415) = 25amps /
conductor
Regards
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| gfretwell@aol.com 2006-05-08, 2:21 am |
| On Mon, 8 May 2006 12:27:55 +1000, "Peter Jason" <td@jostle.com>
wrote:
>I have a large electric oven rated at 15KW
>resistive load, plus another 3KW for 3-phase
>induction motors.
>
>Say 18KW total continuous running.
>
>All this has to be connected to a 3-phase
>supply in delta.
>
>How can I determine the conductor size for
>each of the 3-phase connections in Amps?
>
>Please help, Peter.
>
>
>
>
I get 8ga copper. 31.3a
(using the 1.73 factor to account for 3p, and 125% of computed load)
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| electrician@electrician2.com 2006-05-09, 2:21 am |
| <<Peter, although there are several online calculators, charts, and
tables, i
would recommend you consult a local master electrician to get the
correct
size and type for your situation.
http://www.powerstream.com/Wire_Size.htm here is one chart to
referance.
for 3 phase: AMPS = WATTS / (1.732 X VOLTS X PF)
if i assume a PF OF .90 and a voltage of 240 i get 48.1 amps.... but
you
need to read the label on the oven to know. >>
I wrote the voltage drop calculator being used at powerstream.com,
however, I do not subscribe to the ampacity table. Where did they get
that? It has no resemblance to Table 310.16 ampacity table in the
National Electrical Code Book. FYI I have moved all my calculators to
electrician2.com. electrician.com domain name was sold to a click for
cash group.
As far as the oven is concerned, a demand factor may be applicable.
What is the oven being used for and in what type of occupancy?
| |
| mark@ems-fife.co.uk 2006-05-09, 6:21 pm |
|
Peter Jason wrote:
> I have a large electric oven rated at 15KW
> resistive load, plus another 3KW for 3-phase
> induction motors.
>
> Say 18KW total continuous running.
>
> All this has to be connected to a 3-phase
> supply in delta.
>
> How can I determine the conductor size for
> each of the 3-phase connections in Amps?
>
> Please help, Peter.
Load is 34 amps a phase.Depending on length of cable run I would use
anything from 6mm sq to 10mm sq.Assuming you are in the UK.
regards Mark.
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| billb@abc.net 2006-05-10, 5:21 pm |
| If this is for use within Europe refer to EN 60204-1 or if it is for
installation in the USA have a look at NFPA 79.
This will give you the size of the cables to be used, you may need derate
them dependent on the installation and the type of cable used.
Unfortunately I do not have up todate copies of the standards at home so I
cannot give you sizes today. I will try and post the info on cable sizes
tomorrow. Also ensure that the fuses/circuit breakers are correctly sized to
protect the cable.
BillB
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| Peter Jason 2006-05-11, 10:21 pm |
|
<electrician@electrician2.com> wrote in
message
news:1147149370.600354.246220@g10g2000cwb.googlegroups.com...
> <<Peter, although there are several online
> calculators, charts, and
> tables, i
> would recommend you consult a local master
> electrician to get the
> correct
> size and type for your situation.
> http://www.powerstream.com/Wire_Size.htm
> here is one chart to
> referance.
> for 3 phase: AMPS = WATTS / (1.732 X VOLTS
> X PF)
> if i assume a PF OF .90 and a voltage of
> 240 i get 48.1 amps.... but
> you
> need to read the label on the oven to know.
>
>
>
> I wrote the voltage drop calculator being
> used at powerstream.com,
> however, I do not subscribe to the ampacity
> table. Where did they get
> that? It has no resemblance to Table
> 310.16 ampacity table in the
> National Electrical Code Book. FYI I have
> moved all my calculators to
> electrician2.com. electrician.com domain
> name was sold to a click for
> cash group.
>
> As far as the oven is concerned, a demand
> factor may be applicable.
> What is the oven being used for and in what
> type of occupancy?
>
It runs continuously and unattended during
the off-peak tariff times at night.
It is used for the melting the contents of 4
x 200L (55usg) drums on standard pallets.
It has forced-air circulation directing hot
air to the underside of each drum via air
injectors, by means of a hot-air blower.
It operates at up to 110degC.
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| gfretwell@aol.com 2006-05-12, 12:21 am |
| On Fri, 12 May 2006 07:54:03 +1000, "Peter Jason" <td@jostle.com>
wrote:
>t runs continuously and unattended during
>the off-peak tariff times at night.
>
>It is used for the melting the contents of 4
>x 200L (55usg) drums on standard pallets.
>
>It has forced-air circulation directing hot
>air to the underside of each drum via air
>injectors, by means of a hot-air blower.
>
>It operates at up to 110degC.
>
>
You are looking at MI cable now. How is your wallet ;-)
6ga MI will be plenty, you still might be able to get away with 8 but
it is shaky
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| billb@abc.net 2006-05-14, 4:21 pm |
| If the product is for use in the UK the National Electrical Code does not
apply, it is only applicable in the USA.
In the UK you should refer to EN 60204 for the wiring within the control
cabinet and BS 7671 for the electrical supply to the equipment.
BillB
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