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Engine Room Ventilation Designand RequirementsEngine Room Ventilation DesignEngine Room Ventilation Designand Requirementsand Requirements
University of Wisconsin-Madison
Todd B. Jekel, Ph.D.Research ScientistIndustrial Refrigeration ConsortiumUniversity of Wisconsin-Madison
ASHRAE 2002 Winter Meeting ASHRAE 2002 Winter Meeting Atlantic City, NJ Atlantic City, NJ
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DisclaimerTHIS INFORMATION WAS PRESENTED AT AN ASHRAE SEMINARHELD IN CINCINNATI, OH. THE SEMINAR FORMAT IS TO PRESENTINFORMATION OF CURRENT INTEREST AND TO PROVIDE A VENUEFOR INTERACTION BETWEEN ASHRAE MEMBERS. THESESEMINARS SHOULD NOT BE CONSIDERED PEER-REVIEWED (ORTHE FINAL WORD ON ANY SUBJECT). ASHRAE HAS NOTINVESTIGATED, AND ASHRAE EXPRESSLY DISCLAIMS ANY DUTYTO INVESTIGATE ANY PRODUCT, SERVICE, PROCESS, PROCEDURE,DESIGN, OR THE LIKE WHICH MAY BE DESCRIBED HEREIN. THEAPPEARANCE OF ANY TECHNICAL DATA OR EDITORIALMATERIAL IN THIS PRESENTATION DOES NOT CONSTITUTEENDORSEMENT, WARRANTY, OR GUARANTY BY ASHRAE OF ANYPRODUCT, SERVICE, PROCESS, PROCEDURE, DESIGN, OR THELIKE. NEITHER ASHRAE, THE AUTHORS OR THEIR EMPLOYERSWARRANT THAT THE INFORMATION IN THIS PRESENTATION ISFREE OF ERRORS. THE ENTIRE RISK OF THE USE OF ANYINFORMATION IN THIS PRESENTATION IS ASSUMED BY THE USER.BEFORE MAKING ANY DECISION OR TAKING ANY ACTION ON THIS
SUBJECT, YOU SHOULD CONSULT A QUALIFIED PROFESSIONALADVISOR.
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Introduction
Codes and StandardsDefinition of machinery (engine) room
Purpose of machinery room ventilationCode required ventilation amountsExampleOther considerations
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Codes and Standards
ASHRAE 15-1994 Safety Code for Mechanical Refrigeration
IIAR 2-1999
Equipment, Design, and Installation of Ammonia MechanicalRefrigerating Systems
International Mechanical Code (2000)Uniform Mechanical Code (1997)
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Machinery Room Definitions
ASHRAE 15 - 1994
Space that is designedto safely housecompressors andpressure vessels
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Machinery Room VentilationFunctions
Limit excessive temperature risedue to equipment-generated heat
Provides fresh air for machineryroom occupants
Purges refrigerant vapor fromthe machinery room inemergency situations
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Ammonia as a Refrigerant
Toxic and flammableNIOSH IDLH 300 ppmLFL ~ 16% (by volume), UFL ~ 25% (by volume)
Odor perceptible at very low concentrations (5-15 ppm) Ventilation is essential to purge vapor in leak scenario
ammonia vapor is lighter than air
attempts to prevent the concentration from reaching LFL tominimize the probability of a deflagrationNFPA requires sufficient ventilation to maintain concentrations below25% of the LFL (or 4% for ammonia)
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Emergency VentilationRequirements
Other codes/standards:IMC (2000), UMC (1997)
Same as ASHRAE 15
IIAR 2-1999 (ammonia) ASHRAE 15 amount, or 12 ACH, whichever is greater
Other checkslocal code requirement(s)insurance carrier requirements (if applicable)
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Non-emergency VentilationRequirements
Other codes/standards:IMC (2000), IIAR 2-1999
Same as ASHRAE 15
UMC (1997)Negative pressure of 0.05 in H 2O relative to adjacentspaces
Room temperature must be less than 104 oF
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Other guidance
IIAR Bulletin 111-1991 (ammonia)Recommends
EmergencyRecommends 10 cfm/ft 2 with a minimum of 20,000 cfm
Continuous1-2 cfm/ft 2
Considered industry best practice for ammonia
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ASHRAE 15 Design Ventilation Rates
EmergencyNon-emergency
Intermittent1,095 hp of 93% efficient motors = 195,000 Btu/hrHigh-stage oil separators and discharge gas piping heat gainestimate = 10,000 Btu/hrMiscellaneous = 20,000 Btu/hr
Continuous †
0.5 cfm/ft 2 = 1,250 cfm
cfm200,14000,20100 ==emergencyCFM
( ) ( ) cfm800,111808.1
000,225
08.1 ==∆=−
ER
equipment emergencynon T
qCFM
† May require heat depending on location.
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Other Checks
EmergencyIIAR 2-1999: Check 12 ACH12,500 cfm
IIAR Bulletin 111-1991 : (10 cfm/ft 2)25,000 cfm
Non-emergency (continuous)IIAR Bulletin 111-1991 : 1-2 cfm/ft 2
2,500-5,000 cfm
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Ventilation Placement
Inlet location for exhaust fans shouldconsider where vapors will concentrateExhaust fan location should considerprevailing weather conditions andsurrounding buildings
Avoid recirculation between inlets and outlets
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Ventilation Control
Refrigerant detectorsSet to initiate emergency ventilation at:
50% of IDLH ( UMC )150 ppm ammonia
80% of cardiac sensitization level ( ASHRAE 15 †)42,000 ppm R-2260,000 ppm R-134a
† From Table 1 of allowable refrigerant quantities.
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Recap
ASHRAE 15 is widely referenced by codeauthorities and local jurisdictionsKeep in mind that code values for emergencyventilation are minimums
Always double check proposed design for
compliance with local code requirement(s)insurance underwriter
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Ammonia Ventilation Rule-of-thumb
Ventilating ammonia to keep concentrationbelow 4% (25% of LFL) requires:24 volumes of fresh air for each volume of
ammonia vapor generated in the engine roomtotal exhaust volume is 25
generated vapor ammoniaexhaust CFM CFM = 25
Source: IIAR Bulletin 111, 1991
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Halocarbon Ventilation Rule-of-thumb
Ventilating halocarbon to keep concentrationbelow 7% (19.5% oxygen) requires:13 volumes of fresh air for each volume of
ammonia vapor generated in the engine roomtotal exhaust volume is 14
generated vapor halocarbonexhaust CFM CFM = 14