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Operating Room Lighting Replacement
The operating rooms are served by two air handlers (AHU 5 & 7). Air Handler 7 handles 8 of the 12 operating rooms,
and an even higher percentage of the required air; 74%, or 12,637 CFM, based on the May 31, 2009 air balance. This is
57.7% of the 21,900 CFM air handler’s capacity. Air handler 5 is a 21,200 CFM air handler, which distributes a total of
4,435 CFM to the remaining 4 operating rooms. The operating rooms are constant volume, 100% outdoor air units
with hot water reheat. All of the air handlers in the hospital are served by a common chiller and steam boiler plant. Air
is supplied overhead around the patient and onto the surgeons, and returned at floor level at the perimeter of the
operating room. The schedules associated with this equipment are available in Appendix I.
Figure 3: OR Supply Grille
The units are controlled by a Johnson Controls Metasys system.
Local control and thermostats are located in each of the surgical
suites. The operating rooms are maintained in condition appropriate
for surgery at all times. Room temperature is controlled by resetting
the air handler’s supply air temperature to meet the maximum load
on the system, and then incorporating reheat to obtain the required
condition for the operating room, which typically is kept between
65°F and 68°F. No humidity control is currently utilized. This
control strategy has also been utilized at Petaluma Valley Hospital,
although with a Delta Control system.
The chiller plant consists of three water cooled chillers: 2 Centrifugal York chillers at 450 and 250 tons, and 1 150 Ton
York YT screw chiller. These chillers are being utilized at a 43 degree supply temperature and a 20°F delta T. When
load is increased facilities usually lowers the supply temperature. The heating hot water plant consists of 2 Bryan
LMB750 steam boilers. The field readings indicate a supply of 320°F and 10 psi, and a return temperature of 120 F.
Currently the associated air handlers are not meeting the requested setpoint. When plant field readings were taken the
outdoor air temperature was above the limit of the air handlers, and the units were unable to hold the requested
setpoint of 53°F. Air handler 5 was at 57.5°F, and air handler 7 was at 58.6°F. These units have passed their
expected lifespan, and will be replaced. The new design will not be a direct replacement, but a transition to a common
152,000 CFM air handler with a fan motor over 200 HP.
Petaluma Valley Hospital’s surgery center consists of 4 operating suites, the layout of which is available in Appendix
II. The operating rooms are denoted as Operating Rooms 1-3 & ORTHO. The facility is a two story hospital, with the
surgical facilities being on the first floor. These are served by a single two speed air handling unit. Appendix III
contains each OR’s specifications, the metered supply and return air data and the associated economic analysis of the
OR LED replacement. Note that although the surgical suites are only utilized 68 hours a week, they must be
Salas O’Brien Engineers | expect a difference | Project No. 09104
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