Using SWA cables in parallel

[Ian1981]

Was going to say are you installing a separate cpc (half the line conductor using table 54.7) or using armour as cpc?

 

[bigspark17]

What is this supplying? With the info above id lean twoards 2x 95mm 4c

 

[Ian1981]

What is this supplying? With the info above id lean twoards 2x 95mm 4c

Each cable needs the appropriate correction factors applying first before adding together if using in parallel. volt drop and making sure zs is low enough for the protective device needs considering also.

 

[Perci]

There will be a separate cpc installed to achieve the maximum Zs for the mccb. The supply is for a unit that will be effectively rented so no idea what sort of load it will be.

 

[Ian1981]

There will be a separate cpc installed to achieve the maximum Zs for the mccb. The supply is for a unit that will be effectively rented so no idea what sort of load it will be.

Do you know the mccb max zs from manufacturer, as this may be the big influencing factor to what size cable(s) you need to install as 100meter run and 300 amp supply is rather large.

 

[bigspark17]

Have you already taken a Ze at mccb panel board.? What is the max zs you need to meet.?

 

[Perci]

The Ze was 0.09 I'll have a look when I get in the office buts it's a 400A Square D MCCB set at around 0.8 mulitiplyer to give 300A I have a feeling it was 0.37

 

[Ian1981]

The Ze was 0.09 I'll have a look when I get in the office buts it's a 400A Square D MCCB set at around 0.8 mulitiplyer to give 300A I have a feeling it was 0.37

You need to apply a tolerance of +20% using a mccb for max zs giving a multiplier of 1.2
See beama guide to low voltage circuit breaker standards.
It's a good download to give good guidance.

 

[Perci]

What's the tolerance of 20% for? I'm really thinking the 2x 95mm are going to be a lot easier than a 300mm2

 

[Ian1981]

What's the tolerance of 20% for? I'm really thinking the 2x 95mm are going to be a lot easier than a 300mm2

It's the tripping characteristic of the device.
Manufacturers may state lower tolerances that's why it's best just to ask the manufacturer

 

[Perci]

I have found on their website what they state the maximum Zs at max- 0.968 min- 0.052

 

[Ian1981]

I have found on their website what they state the maximum Zs at max- 0.968 min- 0.052

Is it a nsx 400 micro logic 2.3?
I have zs times from Schneider which is square D now anyway.
You need the isd short time setting which will be on the device.
For example an (isd)Im short time setting of 1.5 is o.33 ohms.
Isd of 10 is 0.050 ohms.
If you've got your info from an old Square D site it maybe more accurate tho as mine is Schneider.