Industrial Boiler Installation

[dazzlaaaaaa]

hi everyone

first post, so please be gentle

Hoping someone can help me out. I have not been involved in very much installation work over the years as my job is more maintenance orientated. Work is currently installing a new industrial boiler and i am trying to work out cables schedules and fusing from distribution board to boiler panel. The boilers normal full load characteristics are 415v 34 amp full load. But the start up current is 134 amps approx. The main rise in start up current is caused by a force draft fan motor, wired in star/delta and a water feed pump. What i am pondering over is should I be sizing the cable and fuses accordingly to allow for start up current as I don't have any information on start up times and how long this start up current will be present for also these motors will be stopping and starting numerous times throughout the day.

Obviously dependent on whether i should be sizing for start up current will greatly affect size of cable I need to install.

Thanks everybody in advance

Hope someone can point me in the right direction

 

[babylonsBurning]

The 34A is per phase

 

[telectrix]

assuming a flc of 34A per phase, 6mm or 10mm, depending on derating factors and VD. the start-up current of 134A is for a very short duration and should be handled by either of those 2 conductor sizes. obviously type II or type III fuses will be required .

 

[MDJ]

if the 34A is across all phases.

EH????

 

[dazzlaaaaaa]

I believe that full load is 34a per phase not across all phases. I am definitely unable to use cb unfortunately as i know this would be ideal for inrush current, i am required to fuse the circuit within the old db that fed the removed boiler

 

[alanl]

34A total, not per phase.
Or, 34A per phase.

Makes a big difference. If this is an electric boiler, then I can see 34A per phase, but if gas, it'd be 34A total

 

[babylonsBurning]

I agree with teletrix!

 

[Sintra]

You could always use the fuses to feed a type d mcb then go to the boiler.

 

[dazzlaaaaaa]

hi thanks for your reply, your thoughts are as mine. So if im correct im looking 63a fused. Appreciate your help

 

[babylonsBurning]

3 phase motors are rated to show FLC &KW per phase

- - - Updated - - -

Do you know what fuse type? I would go for 63A based on info given.

 

[dazzlaaaaaa]

thank you telectrix for your reply. I will finish my calcs tomorrow at work but that seems as per what i was thinking. Was just a little worried about inrush. Thanks

 

[MDJ]

63 AMP? why not a 45 D rated?

 

[babylonsBurning]

Dont think OP can use d rated.

 

[MDJ]

okay C rated

 

[Guest154]

if u use a 63amp u are looking at a 16mm swa

 

[babylonsBurning]

maybe 10mm?