(e) The internal heat gain due to equipment and lights should be estimated
to 3000 W (10,000 BTUH), when actual heat loads are not available.
(f) The rooms are generally planned in two different sizes, 16 Sq M (180
Sq Ft) and 28 Sq M (300 Sq. Ft).
(g) Depending upon the room size, the space internal heat gain, including
light load, should be estimated as follows:
16 Sq M (180 Sq. Ft) room size = 1,800 W (6,000 BTUH).
28 Sq M (300 Sq. Ft) room size = 2,400 W (8,000 BTUH).
(h) The internal heat gain due to equipment should be coordinated with the
architectural equipment drawings.
3.17 MAGNETIC RESONANCE IMAGING (MRI), UNITS AND CT SCANNERS
3.17.1 GENERAL
3.17.1.1 HVAC requirements for the MRI suite vary widely with the capacity
and make of the imaging unit. Information pertaining to indoor design
conditions, internal heat gain, and shielding against the Radio Frequency
(RF) and EMI (Electro-Magnetic Interference) etc. shall be obtained from
the equipment manufacturer during design development phase of the design
project.
3.17.2 INDOOR DESIGN CONDITIONS
Summer: 24 degrees C (76 degrees F) Db, 50 percent RH
Winter: 25 degrees C (78 degrees F) Db, 30 percent RH
3.17.3 EMERGENCY POWER REQUIREMENTS
HVAC equipment for MRI Suites shall be on emergency power.
3.17.4 HVAC SYSTEMS
3.17.2.1 ENVIRONMENTAL UNITS: Provide a dedicated, air-handling unit to
serve the examination room and other spaces associated with the MRI suite.
Depending upon the specific needs of various spaces, conditioned air shall
be supplied by either constant or variable air volume terminal units
serving as temperature control zones. Note the following guidelines:
(a) Provide an automatic emergency 100 percent exhaust system, in the
gantry room, to remove helium gas during an accidental spill. The minimum
capacity of the exhaust system shall be 12 air changes per hour or 33.6 Cu
M/Min (1200 CFM). The gas shall be discharged at the highest point in the
building. The oxygen sensors shall activate the exhaust system when the
level of oxygen drops below a predetermined level. It is usually 18
percent.
(b) Provide separate vents to remove helium gas produced during boil-off
and quench of the magnet. While the boil-off is a normal venting
phenomenon, the quench occurs when a super conductive magnet becomes
resistive. Coordinate sizes of HVAC equipment, including pressure drops
with the magnet manufacturer. Helium liquid turns into gas and tends to
occupy enormously high volume.
HVAC DESIGN MANUAL
3-18
HVAC REQUIREMENTS FOR OCCUPIED AREAS
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