Operating room ventilation requirements Calif.

[maxcfms]

Greetings,
I recently had an E.M.S. system installed on the air handler/chiller utilized by (4) outpatient operating/recovery area rooms in southern Ca.
It was an upgrade to a previously pneumatically controlled constant volume supply/return/exhaust fan with v.a.v. reheat terminals system with a mixed air damper arrangement. The air distribution system runs 24/7, but the chiller can be scheduled off after hours.
My questions are, can I utilize v.s.d. control of the 25 h.p supply fan, and 10 h.p. return fan motors, if the system is designed as constant volume?
Would this acutally save energy?
Is this 24/7 operation an actual code requirement for Calif?
Also, how should the mixed air dampers be controlled?
By outside air temp, humidity, enthalpy, or building pressue? Maybe all 4?
The previous control was via a pneumatic "logic module", but I never saw the dampers change position, even at 100 degrees o.s.a, they were always in the full o.s.a/exhaust mode.
I'm assuming this was due to air change requirements.
Any help/comments would be appreciated!

 

[EEJaime]

You need to review the CMC for those requirements. 100% outside air I believe is required according to the Mech heads around here and the volume must be such that the pressure relationships are maintained between the OR and adjacent areas- so I would be careful using VAV for the Operating rooms. Humidity and temperature are also regulated. OSHPD has very specific criteria for all these issues. It would probably be a good idea to consult with one of the many OSHPD/CMC savvy Mechanical Engineers around here. (We are in SoCal also).

Good Luck,

 

[maxcfms]

Thanks EE.
I located some info. regarding pressure differential and air change requirements on the OSHPD site, but am still in the dark about having to run the 35 h.p of air handler 24/7.
I also have the P.E. whose company installed the EMS stopping by next week to hopefully shed some light on the v.s.d. issue(s)

 

[Zesti]

VSD on the fans makes sense. You should use the VSD to compensate for the fouling (increased pressure loss) of the filters. That way you can be sure of the correct air volumes going to the various rooms.

I am not familiar with your specific codes/regulations (I am in Europe) but running the system at 100% 24/7 does not make a lot of sense to me if the rooms are not in use.

However, maintaining the right pressure levels seems a likely requirement. But pressures can also be maintained at, say, 50% air volumes.

 

[EEJaime]

If this is in fact an outpatient facility that has no inpatient presence 24 hours per day, (and not one such as that which a client of ours termed a 23 hour-59 minute per day facility get out of inpatient OSHPD rules), then the air handler can be shut down if the facility is totally unoccupied. But in southern California, it does not always make sense to do so as the systems take so long to get the building down to it's steady state conditions that you will be chasing temperatures and humidity control most of the day.

We do a lot of work for one of the large 'Permanent' health care providers here and there MOB's and outpatient care facilities do not completely shut down. They've done studies which show that this actually reduces their operating costs. (No pun intended).

Keep us updated on what your Engineer thinks.

Regards,
EEJaime

 

[maxcfms]

Engineer claims that variable speed control would not be economic with constant volume air handling system without installing minimum air controls on each box, which would allow decreased fan horsepower durning unoccupied hours.
To do so would involve approximately 5 year payback.
Surgery center administrators indicate air handler will run 24/7 irrespective of cost. (even though this is not a code requirement)
So, they will get neither v.s.d. control nor reduced energy savings by shutting down equiptment durning unoccupied hours. Problems solved!