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Standby Generator Sizing - BS8519 and LPC Sprinkler Rules

Matt Jarvis

I am currently working on an office refurbishment project, in which I am sizing a Standby Generator for life safety to BS8519. 

There is a Mist Sprinkler System (to BS8489) being installed to cover the commercial spaces. The sprinkler pumpset Locked rotor current is confirmed as 378A. Taking the LPC Sprinkler rules TB210 into account, stating that the current used to select the cable should not be less than 150% of the largest possible full load current, this equates to 378*1.5= 567A = 392.8kVA.

If we allow an additional load of 100A for the rest of the life safety equipment (to be confirmed once we have all the life safety equipment details):

Sub-total – 100A / 69kVA

Grand Total (Sprinkler + other life safety supplies) – 461.8kVA

Generator Load acceptance @ 60% - 646.52kVA

 This would require a generator set at 650kVA. 

 

HOWEVER, if we do not take into account the 150% LPC rule within the sizing of the generator (and only include for the sizing of the supply cable and protective device), the generator set could be reduced to 550kVA. 

Does anyone know if the 150% rule from the LPC Sprinkler Rules needs to be included in the sizing of the generator set, or just the sizing of the cable and protective device for locked rotor states?

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    Hi Matt - the TB210 rule is only used for sizing the cable, and as I understand it this is to factor in the cable being subject to higher operating temperatures under a fire scenario. It doesn’t extend to the generator sizing.

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