Arizona ROC C-58/CR-58 Evaporative Cooling and Ventilating Examination

What is the primary operational mechanism of a direct evaporative cooling system operating in dry desert climates?

• APassing outdoor air over wetted media, causing water to evaporate into sensible heat, red…
• BCirculating chilled water through a sealed closed coil without adding moisture to the sup…
• CCompressing vapor refrigerant to absorb latent heat from outdoor air before discharging i…
• DUtilizing chemical desiccants to absorb air moisture before passing the air through a sec…

When installing 12-inch thick rigid cellulose evaporative cooling media (CelDek), what is the maximum recommended face velocity to prevent water droplets from being entrained into the supply ductwork?

• A550 to 600 feet per minute (FPM)
• B250 to 300 feet per minute (FPM)
• C850 to 900 feet per minute (FPM)
• D1100 to 1200 feet per minute (FPM)

How does an indirect evaporative cooling stage differ from a direct evaporative cooling stage in a two-stage (IDEC) HVAC system?

• AThe indirect stage cools primary supply air sensibly through a heat exchanger without add…
• BThe indirect stage adds moisture directly to the supply air to achieve 100% relative humi…
• CThe indirect stage uses electric heating elements to pre-warm outdoor air before passing…
• DThe indirect stage relies on a mechanical compressor to chill water inside the sump basin.

Why is a continuous water bleed-off assembly required on commercial evaporative cooler sumps operating in Arizona?

• ATo drain mineral-concentrated water continuously, preventing dissolved scale (calcium/mag…
• BTo maintain constant high water pressure inside the distribution spider header.
• CTo prevent the circulation pump motor from overheating by dumping excess water into the d…
• DTo dilute the incoming electrical charge of the water pump motor.

A commercial evaporative cooler delivers 10,000 CFM across 12-inch rigid cellulose media. Assuming a design requirement of 1.5 GPM of water flow per 1,000 CFM for thorough media flushing, what total pump flow rate is required?

• A15.0 GPM
• B7.5 GPM
• C22.5 GPM
• D30.0 GPM

What is the correct water level setting for a mechanical float valve inside an evaporative cooler sump basin?

• A1/2 inch to 1 inch below the top of the overflow pipe standpipe.
• BFlush with the top edge of the sump basin rim.
• C1/2 inch above the overflow pipe standpipe to ensure continuous overflow.
• DCompletely covering the blower pulley and drive belt.

Which sequence of steps represents the proper end-of-season winterization procedure for an outdoor evaporative cooler in northern Arizona?

• AShut off supply water valve, drain water supply line and sump, clean sump basin, disconne…
• BLeave water supply on, add chemical antifreeze to the sump basin, and run the pump contin…
• CClose supply air dampers, seal the float valve open, and turn off only the blower breaker.
• DDisconnect the belt, fill the sump basin to the rim with oil, and cover the unit.

What condition occurs if aspen wood fiber media pads sag or slump inside an evaporative cooler pad frame?

• AAir bypasses through un-wetted voids at the top of the frame, delivering warm un-cooled o…
• BThe static pressure drop across the media increases by 300%.
• CThe water distribution spider header clogs automatically.
• DThe blower wheel reverses rotation due to reduced drag.

Why are rigid structured cellulose media blocks manufactured with unequal flute angles (such as 45-degree / 15-degree cross-fluted configurations)?

• ATo direct water flow toward the air entering side, washing away dirt particles while dire…
• BTo prevent water from trickling down into the sump basin during operation.
• CTo allow air to pass through at supersonic velocities without creating noise.
• DTo eliminate the need for water distribution headers across the top of the media.

What is the operating principle of a timed automatic sump dump valve / purge pump installed in a commercial evaporative cooler?

• AIt periodically evacuates the entire mineral-laden sump basin every few hours of operatio…
• BIt injects liquid chlorine into the water distribution line every 15 minutes.
• CIt pumps water out of the sump into the building supply ductwork during peak heat hours.
• DIt reverses blower wheel rotation to blow scale off the media pads.

According to standard mechanical design practices and IMC guidelines, what is the minimum required distance between an evaporative cooler outdoor air intake and a wet cooling tower discharge or plumbing vent terminal?

• A10 feet
• B3 feet
• C1 foot
• D25 feet

Which type of evaporative cooler cabinet configuration is specifically designed for mounting on a sloped residential or commercial roof curb where supply air enters straight down into the roof plenum?

• ADown-discharge cooler
• BSide-discharge cooler
• CTop-discharge cooler
• DHorizontal inline duct fan

Compared to standard aspen wood fiber pads, what is an advantage and disadvantage of synthetic woven polyester evaporative cooler pads?

• ASynthetic pads resist biological rot and lasting physical degradation, but generally hold…
• BSynthetic pads provide 99% wet-bulb efficiency, but dissolve rapidly in hard water.
• CSynthetic pads require oil soaking prior to installation, but last 50 years.
• DSynthetic pads increase blower motor amperage draw by 400%, but eliminate scale.

Why are magnesium or zinc sacrificial anodes installed in the bottom sump basin of metallic evaporative coolers?

• ATo protect galvanized steel cabinet sumps from galvanic corrosion by corroding preferenti…
• BTo absorb excess chlorine from municipal tap water.
• CTo soften hard water by neutralizing calcium carbonate ions.
• DTo prevent water pumps from tripping internal thermal overloads.

When operating a two-speed commercial evaporative cooler in Low Speed mode, approximately what percentage of High Speed CFM airflow is typically delivered?

• A65% to 70%
• B25% to 30%
• C85% to 90%
• D10% to 15%

What component is responsible for metering water equally from the pump discharge tubing into each individual pad section of a traditional side-draft evaporative cooler?

• ASpider water distributor manifold
• BThermostatic expansion valve
• CAtmospheric vacuum breaker
• DCentrifugal blower scroll

What is the immediate symptom and effect of clogged orifices in a water distribution spider tube on an evaporative cooler?

• ADry spots form on the media pads, allowing uncooled hot air to pass into the cabinet and…
• BSump water level rises above the overflow pipe.
• CBlower motor voltage drops by 50%.
• DThe water pump motor draws double its full load amperage.

In a two-stage indirect-direct evaporative cooling system (IDEC), what is the typical overall dry-bulb cooling effectiveness achievable relative to outdoor wet-bulb depression?

• A100% to 115% (supplying air below entering outdoor wet-bulb temperature)
• B40% to 50%
• C60% to 65%
• D140% to 150%

How does increasing the media depth from 8 inches to 12 inches of rigid cellulose media affect direct evaporative cooler performance?

• AIt increases saturation efficiency (from ~85% to ~95%) while slightly increasing static p…
• BIt decreases saturation efficiency by 50% while reducing air pressure drop.
• CIt doubles water consumption while reducing supply airflow to zero.
• DIt eliminates the requirement for a sump pump.

What maximum Total Dissolved Solids (TDS) concentration is recommended in evaporative cooler sump water before aggressive scaling occurs on media pads?

• A1,000 to 1,500 ppm
• B5,000 to 10,000 ppm
• C50 to 100 ppm
• D50,000 ppm

What causes a small submersible evaporative cooler pump motor to trip on its internal thermal overload protector repeatedly?

• ADebris or mineral scale binding the pump impeller, or operating out of water without liqu…
• BHigh water level in the sump basin.
• CLow outdoor relative humidity.
• DExcessive water pressure from the city water supply line.

What is the purpose of a pre-wetting pump delay feature on an automated evaporative cooler thermostat control?

• ATo energize the water pump for 2 to 4 minutes before starting the supply blower, ensuring…
• BTo run the supply blower for 10 minutes before turning on the water pump to dry out the d…
• CTo pump all sump water into the building sewer before starting the blower.
• DTo bypass the high limit switch during compressor startup.

Why are premium commercial evaporative cooler sumps often fabricated from 304/316 stainless steel or heavy composite polymers instead of standard galvanized sheet steel?

• ATo eliminate rusting and premature sump basin failure caused by continuous contact with o…
• BTo allow the sump basin to expand under 500 PSI internal water pressure.
• CTo reduce the weight of the cooler cabinet by 95% for manual lifting without cranes.
• DTo prevent electrical current from flowing to the blower motor frame.

Where should pre-filters be installed relative to evaporative media pads when treating outdoor air in areas subject to heavy dust storms (haboobs)?

• AUpstream (on the air entering face) of the wet media pads to capture airborne dust before…
• BDownstream of the blower wheel inside the supply drop duct.
• CSubmerged inside the sump basin water under the pump intake strainer.
• DDirectly in the overflow drain line.

A commercial evaporative cooling system has an evaporation rate of 30 GPH. If water hardness requires a bleed ratio of 50% of the evaporation rate, what total makeup water flow rate must the float valve supply?

• A45 GPH
• B15 GPH
• C60 GPH
• D30 GPH

A blower motor turning at 1725 RPM has a 3.5-inch pitch diameter motor pulley connected to an 8.0-inch pitch diameter blower pulley. What is the operational RPM of the blower wheel?

• A755 RPM
• B3943 RPM
• C1725 RPM
• D1200 RPM

If a ventilation blower currently delivering 4,000 CFM at 600 RPM is sped up to 750 RPM by adjusting the motor pulley, what will be the new airflow volume (CFM)?

• A5,000 CFM
• B6,250 CFM
• C4,800 CFM
• D7,812 CFM

A centrifugal fan requires 2.0 Brake Horsepower (BHP) at 800 RPM. If the fan speed is increased by 20% to 960 RPM, what is the new required Brake Horsepower?

• A3.46 BHP
• B2.40 BHP
• C2.88 BHP
• D4.80 BHP

What design friction rate in inches water gauge (in. w.g.) per 100 feet of duct is standard for sizing commercial ventilation ductwork using the Equal Friction method?

• A0.08 to 0.10 in. w.g. per 100 ft
• B0.50 to 0.75 in. w.g. per 100 ft
• C1.50 to 2.00 in. w.g. per 100 ft
• D0.001 to 0.005 in. w.g. per 100 ft

Per the International Mechanical Code (IMC) and SMACNA installation standards, what is the maximum permitted sag and maximum support hanger spacing for flexible air ducts?

• AMaximum sag of 1/2 inch per foot of hanger spacing; supported at intervals not exceeding…
• BMaximum sag of 3 inches per foot; supported at intervals not exceeding 12 feet.
• CNo sag allowed; supported continuously on solid wood planks.
• DMaximum sag of 6 inches per foot; supported only at connections to metal trunks.

What is the standard rating temperature of a fusible link installed in a standard UL 555 fire damper protecting a 2-hour fire-resistance rated wall assembly?

• A165°F (74°C)
• B350°F (177°C)
• C500°F (260°C)
• D100°F (38°C)

What type of commercial kitchen exhaust hood is required by NFPA 96 and IMC Chapter 5 over equipment that produces grease vapors and smoke?

• AType I Hood
• BType II Hood
• CResidential recirculation hood
• DGravity relief hood

Per IMC Section 506.3.11, what is the minimum required clearance between an uninsulated single-wall commercial kitchen grease duct and combustible construction materials?

• A18 inches
• B6 inches
• C1 inch
• D24 inches

What are the minimum material thickness and joint welding requirements for a field-fabricated steel kitchen grease exhaust duct per IMC 506.3.2?

• AMinimum 16-gauge carbon steel or 18-gauge stainless steel, with continuous liquid-tight e…
• BMinimum 26-gauge galvanized sheet steel with snap-lock longitudinal seams sealed with duc…
• CMinimum 22-gauge aluminum sheet metal with pop-riveted lap joints and silicone sealant.
• DMinimum 10-gauge structural steel plate with spot-welded seams every 12 inches.

What is the minimum required slope for a horizontal commercial kitchen grease exhaust duct that is less than 75 feet in total length per IMC 506.3.7?

• AMinimum 1/4 inch per foot (2%) sloping toward the hood or an approved grease reservoir.
• BMinimum 1 inch per foot (8.3%) sloping away from the hood.
• CMust be perfectly level to prevent oil from pooling.
• DMinimum 1/16 inch per foot sloping upward toward the roof fan.

According to IMC 506.3.13 and NFPA 96, how far above the roof surface must a commercial kitchen upblast exhaust fan discharge air?

• AMinimum 40 inches above the roof surface
• BMinimum 12 inches above the roof surface
• CMinimum 6 feet above the roof surface
• DFlush with the roof surface curb

Why must dedicated replacement make-up air (MUA) systems be electrically interlocked with commercial kitchen exhaust hoods?

• ATo ensure the make-up air fan operates whenever the exhaust fan runs, preventing severe n…
• BTo increase the speed of the exhaust fan when kitchen doors are opened.
• CTo shut down building electrical power if kitchen temperature exceeds 80°F.
• DTo prevent water from entering the evaporative cooler sump.

What operational characteristic distinguishes a forward-curved centrifugal fan blade (squirrel cage) from a backward-inclined fan blade in HVAC ventilation?

• AForward-curved fans operate quietly at low speeds but can overload the motor if system st…
• BForward-curved fans are non-overloading under all static pressure conditions.
• CBackward-inclined fans require 10 times more horsepower for the same CFM.
• DForward-curved fans can only handle high-temperature kitchen grease exhaust.

What controls the actuation of a UL 555S rated smoke damper installed in an engineered smoke control ventilation duct?

• AAn electric or pneumatic actuator commanded by a smoke detector or fire alarm control pan…
• BA 165°F fusible link melting under heat.
• CA manual hand crank mounted on the outside of the duct.
• DGravity weight dropping when water pressure drops.

Where should manual volume balancing dampers be installed in a multi-branch air distribution duct system?

• AIn each branch duct takeoff close to the main trunk duct, allowing total airflow balancin…
• BDirectly behind the face of supply diffusers only.
• CInside the return air plenum cabinet.
• DAt the outdoor air intake louver hood.

Per SMACNA HVAC Duct Construction Standards, what standard sheet steel gauge is required for a 30-inch wide rectangular galvanized supply duct operating at 1-inch water gauge static pressure?

• A24 gauge
• B30 gauge
• C14 gauge
• D10 gauge

Per the International Energy Conservation Code (IECC) and IMC, what minimum thermal insulation performance (R-value) is required for supply air ducts passing through an unconditioned residential attic in Arizona?

• AR-8
• BR-2
• CR-19
• DUninsulated

An outdoor air intake louver has a gross frame dimension of 48 inches by 48 inches (16 sq ft). If the louver design has a 50% free area ratio, what is the maximum airflow (CFM) it can handle without exceeding 500 FPM face velocity through the free area?

• A4,000 CFM
• B8,000 CFM
• C2,000 CFM
• D16,000 CFM

What is the function of a automatic gravity backdraft damper installed on a rooftop ventilation exhaust fan outlet?

• ATo allow exhaust air to blow outward when the fan runs, while automatically closing by gr…
• BTo regulate water flow into the evaporative cooler pump.
• CTo prevent electrical line voltage surges from reaching the motor windings.
• DTo trap grease vapors before they reach the fan wheel.