Technical Requirements -
Computer Room
adjustable Transfer Switches shall be provided to preclude sending the start
signal for power outages of less than 10 seconds.
3. Generator Sizin
g
Where generators are determined essential, they should be sized based on
UPS and generator manufacturers' recommendation and to ensure a minimum
of 30% additional capacity over design attached load (whichever is greater).
This will minimize adverse harmonic feedback from the UPS system and allow
for reasonable expansion for future requirements.
4. Branch Circuits to UPS loads
Individual branch circuits shall be installed in liquidtight conduit to associated
subfloor "isolated ground" type (IG) receptacles. Preferably these receptacles as
well as the Liquidtight whips shall be attached to the access floor pedestals. All
isolated circuits feeding ADP equipment shall be installed with oversized
neutrals to reduce neutral heating. Neutrals shall have current ratings of at least
1.7 x phase rating to achieve these results. A ground wire should be pulled for
each circuit along with a dedicated neutral (for each 3 phase feed.) Branch
circuits shall be sized per NEC and ADP equipment nameplate rating for all
UPS loads.
Air Conditioning/Humidification
For redundancy and serviceability, two identical computer room air conditioning
units are required. Temperature shall be adjustable and maintained between a
minimum of 68 and a maximum of 75 Fahrenheit dry bulb with no more than 1
degree/hour change allowable. Humidity must be maintained in the range of 40%-
60% RH. The units shall be positioned at opposite ends of the computer room,
preferably diagonally opposite, to ensure even distribution of conditioned air from
both units. The units shall have programmable microprocessor controls with local
monitoring and alarm indicators/enunciators. Air filters shall be computer room
grade high efficiency. Both units shall be operating at all times and sharing the load
unless one fails or is undergoing maintenance.
These units should be
independently supported on factory supplied stands of the same height as the
raised floor.
To assure continuity of cooling, two separate computer room air conditioning
(CRAC) units including dual refrigerant systems and glycol or DX cooling is required
in the event of mechanical malfunction in one system. Cooling capacity of each
CRAC unit must be adequate to remove all the sensible heat from the computer
Page 4-8
VBA Design Guide
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