Power Supply to Auto Transfer Switches

[DTR]

Hi all,

Hope you can help me, I have clients engineer who I need to convince that we have to have a dedicated and separated power supply to our Auto Change Over Switches from the Alternate Supply, I know this and I have provided the details in figure A.10.8, question is:

Does it clearly state anywhere in NFPA 20 that Auto Transfer Switches have to have a dedicated supply direct from the Alternate Power Source?

I have looked but I can not find it!

Believe it or not this guy is trying supply normal power and alternate power down the same cables!!

The Project is UK so we are not as familiar with NFPA requirements as we are BS/EN, but this is the standard for the Fire Pumps on the job.

Help please!

Cheers

DTR

 

[gouveia]

No sure I understand your question exactly. However, you are only allowed to have one disconnect between the source and controller. I think you want to look in the National Electrical Code. Couple references below.

NFPA 70 - National Electrical Code® - 2005 Edition

695.3 Power Source(s) for Electric Motor-Driven Fire Pumps.
695.4 Continuity of Power.
Circuits that supply electric motor-driven fire pumps shall be supervised from inadvertent disconnection as covered in 695.4(A) or 695.4(B).
(A) Direct Connection. The supply conductors shall directly connect the power source to either a listed fire pump controller or listed combination fire pump controller and power transfer switch. [NFPA 20:9.3.2.2.2]
(B) Supervised Connection. A single disconnecting means and associated overcurrent protective device(s) shall be permitted to be installed between a remote power source and one of the following:
(1) A listed fire pump controller
(2) A listed fire pump power transfer switch
(3) A listed combination fire pump controller and power transfer switch

 

[hbendillo]

Believe it or not this guy is trying supply normal power and alternate power down the same cables!!

Explain this more for me please. Is he bringing one feeder to the transfer switch and then splitting it off?

 

[DTR]

They are bringing one feeder from the Utility with the changeover from normal to alternate power taking place at the Generator rather than the Fire Pump Room. So we have 1 No. Cable per Electric Pump Controller and the Transfer Switch will sit there doing nothing!!

I have told them it is not compliant with NFPA 20 and they are seeking a dispensation from the Insurer. So we will see....I think they have no chance.

Cheers

DTR