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3 phase supply size

Discussion in 'Electrical Forum' started by James sparks, Apr 13, 2014.

Discuss 3 phase supply size in the Electrical Forum area at ElectrciansForums.co.uk.

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Offline
James sparks Active EF Member

Hi all,

I need to put in a 3 phase supply for a piece of equipment in a commercial unit. They've sent the spec sheet for the item over and all it says is

Current type (Ph/V/Hz): 3/420/50
Power rating (kW): 7.8

I just want to clarify if it's 7.8kW per phase or 7.8kW total over all 3 phases.

Thanks!!

James sparks, Apr 13, 2014

#1
Offline
uksparks Electrician's Arms

Location:

Market Harborough

I would imagine it's in total not per phase.

uksparks, Apr 13, 2014

#2
Offline
darkwood Super Moderator Staff Member Super Moderator

Location:

West Yorkshire

usually if you use a kw rating in the same spec as 3ph its per phase ...

darkwood, Apr 13, 2014

#3
Offline
uksparks Electrician's Arms

Location:

Market Harborough

I suppose the best thing would be to get more data from the device

uksparks, Apr 13, 2014

#4
Offline
micknew Electrician's Arms

Location:

Kent

uksparks said: ↑

I would imagine it's in total not per phase.
Click to expand...

I agree with you.
If not it should have said 'per phase.

micknew, Apr 13, 2014

#5
Offline
James sparks Active EF Member

[TABLE="width: 100%"]
[TR="class: tecdata_title"]
[TD][h=3]Technical data[/h][/TD]
[TD] [/TD]
[TD] [/TD]
[/TR]
[TR="class: tecdata_row"]
[TD="class: bodysmall lineundertd"][TABLE]
[TR]
[TD]Current type Ph/V/Hz[/TD]
[/TR]
[/TABLE]
[/TD]
[TD="class: bodysmall lineundertd"] [/TD]
[TD="class: bodysmall lineundertd"][TABLE]
[TR]
[TD="class: tecdataval"]3[/TD]
[TD]/[/TD]
[TD="class: tecdataval"]420[/TD]
[TD]/[/TD]
[TD="class: tecdataval"]50[/TD]
[/TR]
[/TABLE]
[/TD]
[/TR]
[TR="class: tecdata_row"]
[TD="class: bodysmall lineundertd"][TABLE]
[TR]
[TD]Flow rate (l/h)[/TD]
[/TR]
[/TABLE]
[/TD]
[TD="class: bodysmall lineundertd"] [/TD]
[TD="class: bodysmall lineundertd"][TABLE]
[TR]
[TD="class: tecdataval"]500[/TD]
[TD="class: tecdataval"]-[/TD]
[TD="class: tecdataval"]1000[/TD]
[/TR]
[/TABLE]
[/TD]
[/TR]
[TR="class: tecdata_row"]
[TD="class: bodysmall lineundertd"][TABLE]
[TR]
[TD]Pressure (bar/MPa)[/TD]
[/TR]
[/TABLE]
[/TD]
[TD="class: bodysmall lineundertd"] [/TD]
[TD="class: bodysmall lineundertd"][TABLE]
[TR]
[TD="class: tecdataval"]30[/TD]
[TD="class: tecdataval"]-[/TD]
[TD="class: tecdataval"]200[/TD]
[TD]/[/TD]
[TD="class: tecdataval"]3[/TD]
[TD="class: tecdataval"]-[/TD]
[TD="class: tecdataval"]20[/TD]
[/TR]
[/TABLE]
[/TD]
[/TR]
[TR="class: tecdata_row"]
[TD="class: bodysmall lineundertd"][TABLE]
[TR]
[TD]Max. temperature (°C)[/TD]
[/TR]
[/TABLE]
[/TD]
[TD="class: bodysmall lineundertd"] [/TD]
[TD="class: bodysmall lineundertd"][TABLE]
[TR]
[TD="class: tecdataval"]155[/TD]
[TD="class: tecdataval"]-[/TD]
[TD="class: tecdataval"]80[/TD]
[/TR]
[/TABLE]
[/TD]
[/TR]
[TR="class: tecdata_row"]
[TD="class: bodysmall lineundertd"][TABLE]
[TR]
[TD]Power rating (kW)[/TD]
[/TR]
[/TABLE]
[/TD]
[TD="class: bodysmall lineundertd"] [/TD]
[TD="class: bodysmall lineundertd"][TABLE]
[TR]
[TD="class: tecdataval"]7.8[/TD]
[/TR]
[/TABLE]
[/TD]
[/TR]
[TR="class: tecdata_row"]
[TD="class: bodysmall lineundertd"][TABLE]
[TR]
[TD]Consumption fuel oil (kg/h)[/TD]
[/TR]
[/TABLE]
[/TD]
[TD="class: bodysmall lineundertd"] [/TD]
[TD="class: bodysmall lineundertd"][TABLE]
[TR]
[TD="class: tecdataval"]6.4[/TD]
[/TR]
[/TABLE]
[/TD]
[/TR]
[TR="class: tecdata_row"]
[TD="class: bodysmall lineundertd"][TABLE]
[TR]
[TD]Fuel tank (l)[/TD]
[/TR]
[/TABLE]
[/TD]
[TD="class: bodysmall lineundertd"] [/TD]
[TD="class: bodysmall lineundertd"][TABLE]
[TR]
[TD="class: tecdataval"]25[/TD]
[/TR]
[/TABLE]
[/TD]
[/TR]
[TR="class: tecdata_row"]
[TD="class: bodysmall lineundertd"][TABLE]
[TR]
[TD]Fuel tank (cc³)[/TD]
[/TR]
[/TABLE]
[/TD]
[TD="class: bodysmall lineundertd"] [/TD]
[TD="class: bodysmall lineundertd"][TABLE]
[TR]
[TD]-[/TD]
[/TR]
[/TABLE]
[/TD]
[/TR]
[TR="class: tecdata_row"]
[TD="class: bodysmall lineundertd"][TABLE]
[TR]
[TD]Weight (kg)[/TD]
[/TR]
[/TABLE]
[/TD]
[TD="class: bodysmall lineundertd"] [/TD]
[TD="class: bodysmall lineundertd"][TABLE]
[TR]
[TD="class: tecdataval"]171[/TD]
[/TR]
[/TABLE]
[/TD]
[/TR]
[TR="class: tecdata_row"]
[TD="class: bodysmall lineundertd"][TABLE]
[TR]
[TD]Dimensions (L x W x H) (mm)[/TD]
[/TR]
[/TABLE]
[/TD]
[TD="class: bodysmall lineundertd"] [/TD]
[TD="class: bodysmall lineundertd"][TABLE]
[TR]
[TD="class: tecdataval"]1330[/TD]
[TD="class: tecdataval"]x[/TD]
[TD="class: tecdataval"]750[/TD]
[TD="class: tecdataval"]x[/TD]
[TD="class: tecdataval"]1060[/TD]
[/TR]
[/TABLE]
[/TD]
[/TR]
[TR="class: tecdata_row"]
[TD="class: bodysmall lineundertd"][TABLE]
[TR]
[TD]Detergent tank (l)[/TD]
[/TR]
[/TABLE]
[/TD]
[TD="class: bodysmall lineundertd"] [/TD]
[TD="class: bodysmall lineundertd"][TABLE]
[TR]
[TD="class: tecdataval"]20[/TD]
[/TR]
[/TABLE]
[/TD]
[/TR]
[/TABLE]

James sparks, Apr 13, 2014

#6
Offline
micknew Electrician's Arms

Location:

Kent

That is telling you that the total load of the machine is 7.8KW.

Last edited: Apr 13, 2014

micknew, Apr 13, 2014

#7
Offline
uksparks Electrician's Arms

Location:

Market Harborough

So it's 7.8kW split across phases, so not much then, what is it you say? A pump?

uksparks, Apr 13, 2014

#8
Offline
darkwood Super Moderator Staff Member Super Moderator

Location:

West Yorkshire

its per phase 7.8kw per phase otherwise it would have stated single

darkwood, Apr 13, 2014

#9
Offline
micknew Electrician's Arms

Location:

Kent
darkwood said: ↑

its per phase 7.8kw per phase otherwise it would have stated single
Click to expand...

No it wouldn't.
- Like x 2
micknew, Apr 13, 2014

#10
Offline
darkwood Super Moderator Staff Member Super Moderator

Location:

West Yorkshire
If you have a spec asking fot 3ph and a Kw rating its Kw per phase .. . no disrespect to other posters but your guessing and not experienced in 3ph so express this in your post or you may mislead the OP ... I assume a 3ph device is part of the setup like a motor; motors are specd per phase not devided by 3..
- Like x 1
darkwood, Apr 13, 2014

#11
Offline
NickD Regular EF Member

Location:

Vulcan
micknew said: ↑

No it wouldn't.
Click to expand...

I would ask the question of the supplier/manufacturer/whoever. Assumption is the mother of all cock ups.
- Like x 1
NickD, Apr 13, 2014

#12
Offline
micknew Electrician's Arms

Location:

Kent

darkwood said: ↑

If you have a spec asking fot 3ph and a Kw rating its Kw per phase .. . no disrespect to other posters but your guessing and not experienced in 3ph so express this in your post or you may mislead the OP ... I assume a 3ph device is part of the setup like a motor; motors are specd per phase not devided by 3..
Click to expand...

You are wrong and most of my work is industrial 3 phase.

micknew, Apr 13, 2014

#13
Offline
darkwood Super Moderator Staff Member Super Moderator

Location:

West Yorkshire

micknew said: ↑

You are wrong and most of my work is industrial 3 phase.
Click to expand...

If you request a supply from DNO in Kw then its per phase.
If you get a motor and it says 4kw 400v then its per phase.
If you have a machine that asks for a 3ph supply 10kw then thats per phase.

25yrs of industrial intalls design and machine panel building plus several requests to DNO for supplies or upgrades im sure im not wrong....

Only exception is the occasional machine usually from china and 2nd hand that does go over 3ph and checking the wiring plan or load characteristics can usually identify this but other than that ill say your wrong.

Its always good to cross check these values Ive seen architects mess up if a reading is in KVA on a machine or supply then its likely to be a total demand across the phases as dave points out below but the OP spec'd a Kw value.

Last edited: Apr 14, 2014

darkwood, Apr 14, 2014

#14
Offline
davesparks Forum Mentor

Location:

guildford

Consider a 32A three phase mcb, that's 32A per phase. Same goes for KW rating.

Only fly in the ointment I can think of is from UKPN's paperwork where a 100A 3ph supply is described as being a 69KVA 3ph supply.

davesparks, Apr 14, 2014

#15

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