Volt Drop Calculation

[m4tty]

Hi,

A 10kw 230V Shower is supplied using PVC T&E Clipped Direct to surface over distance of 15m. Circuit Protected by BSEN60898 Type C. Ambient Temperature is 25 degrees c.

Reference Method C ?

10000/230 = 43.5A (rounded)

Breaker 45A Type C

Rating Factors 1.03 for 25 degree temperature, therefore 43.5/1.03 gives 42.23

Cable = Could use 6mm but its close so use 10mm for future upgrades.

Volt Drop - 10.0/4.00 is 6.44 (OSG)

This is where im stuck (if not gone wrong already)

6.44x(??43.5??)x15m

1000

=4.20V which is well less than the 5% allowed.

Ive bolded out the bit im mainly stuck on is this supposed to be the design current after or before rating factors have been taken into account

Thanks in advance for any help

Cheers

Matt

 

[revjames]

The Volt drop calculation is done on the Iz figure which is In/Cg or Ca or whatever factor(s) are involved. This is causing me headaches on my asignment at the mo!

In your case the 45a of the protective devive is divided by the factor for the ambient and then included in the Vd x A x M/ 1000 calc

HTH

JR

 

[matt.leung]

4.4 x 42.23a x 15m / 1000 = 2.78 volt drop

10mm T&E volt drop per meter is 4.4.... (BRB page 282 last column) where did u get 6.44 from....?

 

[m4tty]

Nice one thanks

I was looking at the wrong table in OSG for Cable Resistances ffs.

Thanks again

 

[Banjo]

Hi,A 10kw 230V Shower is supplied using PVC T&E Clipped Direct to surface over distance of 15m. Circuit Protected by BSEN60898 Type C. Ambient Temperature is 25 degrees c.

Reference Method C ?

10000/230 = 43.5A (rounded)

Breaker 45A Type C

Rating Factors 1.03 for 25 degree temperature, therefore 43.5/1.03 gives 42.23

Cable = Could use 6mm but its close so use 10mm for future upgrades.

Volt Drop - 10.0/4.00 is 6.44 (OSG)

This is where im stuck (if not gone wrong already)

6.44x(??43.5??)x15m

1000

=4.20V which is well less than the 5% allowed.

Ive bolded out the bit im mainly stuck on is this supposed to be the design current after or before rating factors have been taken into account

Thanks in advance for any help

Cheers

Matt

Ib = 10000/230 = 43.5A

In = 45a Type C BS60898 Circuit Breaker

It = In/rating factors = 45/1.03 = 43.7A

6mm @ 47A

Mv/A/m x Ib x metres / 1000

7.3 x 43.5 x 15 / 1000 = 4.76v

This is what i got...

Stu