Air Con. Volt Drop

[RobFurn]

This is what Im working on I think you will get the point I am trying to verify

Compressor is rated 7A (Max) running current 3A Fan is rated at 1A. toatal load is 8A but more loke 4A when running

2.5mm cable from DB to Compressor

1.5mm cable from Compressor to Fan

D.B is fitted with a 10A C type breaker.

After doing the V.D calcs the drop is far less then 4%
As you can see I have used a slightly derated cable from Compressor to Fan (I could have used less) so the breaker at the D.B will protect all the cable in the circuit.

Everyone agree? I bet you dont

 

[Space cat]

What voltage drop do you get if you wire the whole lot with 1.5 sq mm?

 

[tim west]

This is what Im working on I think you will get the point I am trying to verify

Compressor is rated 7A (Max) running current 3A Fan is rated at 1A. toatal load is 8A but more loke 4A when running

2.5mm cable from DB to Compressor

1.5mm cable from Compressor to Fan

D.B is fitted with a 10A C type breaker.

After doing the V.D calcs the drop is far less then 4%
As you can see I have used a slightly derated cable from Compressor to Fan (I could have used less) so the breaker at the D.B will protect all the cable in the circuit.

Everyone agree? I bet you dont

You have to choose the fuse protection from more than one angle ie the fuse must be of sufficient rating for the uninteruppted operation of the equipment but sufficient low rating to protect the smallest or lowest current carrying capacity cable.
as Space Cat inquires what is the Vd of the run, how long is the run?

 

[RobFurn]

I know I know Iknow

its Bout 7V so it would have been fine.

I had just enough 2.5 SWA from a previous job so I used that From D.B to Compressor. That part of the the install needed mechanical protection.

From Compressor to Fan I have used 1.5mm 3 core and earth (no need for mechanical protection).

My point is that both cables are protected by the main breaker.

 

[tim west]

Without the aid of a regs book at hand i'll have to wait until i get back to work to help you answer any further unless someone else pops in with an answer beforehand?