Arizona ROC R-4R Boilers (Residential) Examination

A residential hydronic boiler system has a design heat load of 120,000 BTU/h and is designed for a standard 20°F system temperature drop (Delta T). What is the required system water flow rate in gallons per minute (GPM)?

• A6.0 GPM
• B12.0 GPM
• C18.0 GPM
• D24.0 GPM

Where should a diaphragm expansion tank be connected relative to the system circulator pump in a closed residential hydronic heating system?

• AOn the suction (inlet) side of the circulator pump at the point of no pressure change.
• BOn the discharge (outlet) side of the circulator pump to maximize system pressure.
• CAt the lowest return line header point immediately before entering the boiler drain valve.
• DOn the cold water makeup supply line downstream of the backflow preventer only.

Prior to installing a diaphragm expansion tank on a 2-story residential hydronic heating system with a cold fill pressure of 12 psig, what should the air pre-charge pressure of the tank be set to while unpressurized on the water side?

• A0 psig
• B12 psig
• C25 psig
• D30 psig

In a primary-secondary hydronic piping system, what is the maximum recommended center-to-center distance between the closely spaced tees connecting the secondary loop to the primary loop?

• A2 pipe diameters
• B4 pipe diameters
• C8 pipe diameters
• D12 pipe diameters

Where is the most effective location to install a microbubble air separator in a hydronic heating loop?

• AOn the boiler supply pipe where water is at its highest temperature and lowest static pre…
• BOn the return main pipe right before the water enters the boiler bottom drain connection.
• CAt the furthest terminal baseboard heater unit at the highest floor level.
• DOn the cold water makeup feed line immediately upstream of the pressure reducing valve.

Why must PEX tubing used in closed-loop hydronic heating systems feature an oxygen barrier (such as EVOH coating per DIN 4726)?

• ATo prevent oxygen molecules from permeating the pipe wall and causing corrosion of ferrou…
• BTo prevent water leaks caused by high-pressure thermal shock.
• CTo reduce heat loss through the plastic pipe wall in slab-on-grade applications.
• DTo satisfy EPA drinking water requirements for potability.

What is the primary function of a thermostatic mixing valve (ASSE 1017 / ASSE 1070) installed on a radiant floor heating zone connected to a high-temperature cast iron boiler?

• ATo reduce supply water temperature from 180°F to 100°F–120°F to protect floor coverings a…
• BTo increase system water pressure to overcome radiant loop friction loss.
• CTo eliminate the need for an expansion tank on the radiant manifold.
• DTo automatically bleed air from the PEX tubing during high-demand heating cycles.

Per the International Plumbing Code (IPC) and International Residential Code (IRC), what is the maximum allowable lead content for solder and flux used in joining copper water piping?

• A0.2 percent
• B2.0 percent
• C8.0 percent
• D50.0 percent

When calculating total equivalent pipe length for hydronic pump head loss, a 1-inch copper 90-degree standard elbow adds approximately how many equivalent feet of straight pipe?

• A1.0 foot
• B2.5 to 3.0 feet
• C7.5 to 10.0 feet
• D15.0 feet

What is the key hydraulic advantage of a reverse-return piping arrangement compared to a direct-return piping arrangement in a multi-zone hydronic system?

• AIt inherently balances water flow through all radiator circuits because total supply plus…
• BIt eliminates the need for a system circulator pump.
• CIt reduces total piping material requirements by 50%.
• DIt allows low-pressure steam boilers to operate without pigtail siphons.

A closed-loop residential hydronic system has a total equivalent pipe length of 200 feet in its longest circuit. If the pipe friction loss rate is 3 feet of head per 100 feet of pipe, what is the required circulator pump head?

• A3.0 feet of head
• B6.0 feet of head
• C12.0 feet of head
• D25.0 feet of head

What piping accessory must be installed when connecting copper hydronic distribution pipe directly to a black iron boiler tapping to prevent galvanic corrosion?

• AA dielectric union or dielectric flange.
• BA brass gate valve without PTFE tape.
• CA schedule 80 PVC nipple.
• DA flexible rubber vibration isolator rated for 60°F.

According to standard hydronic installation practices and the IMC, horizontal hydronic supply and return mains should be sloped upward toward air vents at what minimum pitch?

• A1/4 inch per 10 feet
• B1/2 inch per 1 foot
• C1 inch per 10 feet
• D2 inches per 10 feet

Which type of heat transfer fluid additive is required for freeze protection in residential hydronic systems connected to potable makeup water lines?

• APropylene glycol containing inhibitors approved for hydronic use.
• BEthylene glycol automotive antifreeze.
• CMethanol windshield washer fluid.
• DSodium chloride brine solution.

When installing gas-fired hydronic boilers at elevations above 2,000 feet in Arizona (e.g. Flagstaff at ~7,000 ft), at what rate must the boiler fuel BTUH input rating be de-rated unless specified otherwise by the manufacturer?

• A1% per 1,000 feet above sea level
• B4% per 1,000 feet above sea level starting at sea level
• C4% per 1,000 feet above 2,000 feet elevation
• D10% per 1,000 feet above 5,000 feet elevation

What is the standard recommended range for pipe friction head loss per 100 feet of pipe when sizing hydronic supply and return distribution loops?

• A1 to 4 feet of head per 100 feet of pipe
• B8 to 12 feet of head per 100 feet of pipe
• C15 to 20 feet of head per 100 feet of pipe
• D25 to 30 feet of head per 100 feet of pipe

What is the purpose of installing a differential pressure bypass valve across the supply and return headers in a multi-zone hydronic system using two-way zone valves and a single-speed circulator?

• ATo maintain minimum water flow through the boiler and prevent pump dead-heading when most…
• BTo increase system pressure to 30 psig to open the relief valve.
• CTo automatically dump excess hot water to the house sewer system.
• DTo bypass the expansion tank during summer shutdown periods.

Per IMC Chapter 3 and IRC Chapter 13, what minimum working clearance must be provided in front of boiler controls, pumps, and service panels for inspection and maintenance?

• A12 inches
• B18 inches
• C30 inches
• D48 inches

To prevent erosion-corrosion in copper hydronic heating pipes operating with water temperatures above 140°F, what is the maximum recommended fluid velocity?

• A2 feet per second
• B4 feet per second
• C8 feet per second
• D12 feet per second

What is the industry standard maximum recommended single circuit loop length for 1/2-inch nominal PEX tubing in a residential radiant floor heating system?

• A150 feet
• B300 feet
• C500 feet
• D1,000 feet

What is the typical factory pressure setting for an automatic pressure reducing (fill) valve installed on a standard two-story residential hydronic heating system?

• A5 psig
• B12 to 15 psig
• C30 psig
• D50 psig

Why must a newly installed residential hydronic heating loop be thoroughly flushed with clean water and trisodium phosphate (TSP) or hydronic cleaner prior to initial firing?

• ATo remove pipe joint flux, oils, metal shavings, and slag that cause foaming and boiler m…
• BTo coat the interior copper walls with a protective lead barrier.
• CTo test the operation of the high-limit thermal switch.
• DTo increase the boiling point of the hydronic fluid above 300°F.

Automatic air vents must be installed at which locations in a residential hydronic heating system?

• AAt all high points in the piping system where air naturally collects.
• BAt the lowest boiler drain point only.
• CInside the combustion chamber near the burner orifice.
• DOn the gas supply manifold downstream of the main regulator.

When water in a 50-gallon hydronic system is heated from 60°F to 180°F, its volume expands by approximately what percentage?

• A0.5%
• B3.0% to 3.5%
• C10.0%
• D20.0%

Per IMC Section 1004.3, water boilers installed with forced circulation that can be damaged by low flow must be equipped with what safety interlock?

• AA flow prove switch or differential pressure switch that prevents burner operation when w…
• BAn automatic high-pressure water blowdown valve.
• CA secondary gas pressure regulator.
• DA flue gas recirculation damper.

Which ASME Code symbol stamp designates a low-pressure heating boiler constructed in accordance with ASME Boiler and Pressure Vessel Code Section IV?

• AS Stamp
• BH Stamp
• CU Stamp
• DU2 Stamp

Under ASME Section IV rules for low-pressure heating boilers, what are the maximum allowable working pressure (MAWP) and temperature limits for a hot water heating boiler?

• A15 psig pressure and 212°F temperature
• B30 psig pressure and 200°F temperature
• C160 psig pressure and 250°F temperature
• D250 psig pressure and 350°F temperature

What is the maximum operating pressure allowed for a low-pressure steam heating boiler governed by ASME Section IV and IRC Chapter 20?

• A5 psig
• B15 psig
• C30 psig
• D100 psig

What is the standard factory set pressure of the pressure relief valve supplied on standard residential cast iron hot water heating boilers?

• A15 psig
• B30 psig
• C75 psig
• D125 psig

Per IMC Section 1006 and IRC Section M2002, which of the following is prohibited when installing the discharge piping from a boiler safety relief valve?

• AInstalling threaded fittings or a shutoff valve in the discharge pipe line.
• BDischarging through an air gap into a floor drain receptor.
• CPiping the discharge line downward to prevent water traps.
• DUsing full nominal pipe size equal to the valve outlet.

According to IMC Section 1007 and IRC Section M2002.5, when is a low-water cut-off (LWCO) control mandatory on a residential hot water boiler?

• AWhen the boiler is installed above radiation levels or where specified by the manufacture…
• BOnly when the boiler operates on propane gas instead of natural gas.
• COnly on steam boilers; hot water boilers never require low-water cut-offs.
• DOnly when boiler water volume exceeds 500 gallons.

How should a float-type low-water cut-off (LWCO) on a low-pressure steam boiler be routinely tested during the heating season?

• ABy opening the LWCO blowdown valve while the burner is firing to flush sediment and verif…
• BBy turning off the main electrical breaker and measuring resistance across the coil.
• CBy increasing boiler operating pressure until the high limit trips.
• DBy adding cold water through the manual bypass until the pressure relief valve opens.

How are an operating aquastat and a high-limit safety aquastat wired relative to each other in a gas boiler control circuit?

• AIn series with the automatic gas valve control circuit.
• BIn parallel with the 120V circulator pump motor circuit.
• CDirectly across the 24V transformer secondary terminals as a dead short.
• DIn series with the outdoor temperature sensor loop.

High-efficiency condensing boilers extract latent heat of vaporization from flue gas by maintaining return water temperatures below approximately what threshold?

• A100°F
• B130°F
• C180°F
• D212°F

Why does flue gas condensate produced by high-efficiency condensing boilers require neutralization before discharge into domestic building plumbing drains?

• ACondensate is acidic (pH 3.0 to 5.0) and will corrode metal drain pipes, cast iron soil p…
• BCondensate contains flammable dissolved propane gas.
• CCondensate is highly alkaline (pH 12.0+) and scales PVC drain piping.
• DCondensate contains toxic glycol antifreeze additives.

What is the purpose of installing a pigtail (syphon) loop tube between a steam boiler shell and its steam pressure gauge or pressuretrol control?

• ATo trap condensed water in the loop, preventing high-temperature live steam from contacti…
• BTo drain excess water from the steam chest back into the return line.
• CTo increase the sensitivity of the low water cut-off probe.
• DTo vent trapped air directly to atmosphere during startup.

Per ASME Section IV, the minimum relief valve discharge BTU/h capacity stamped on a boiler safety valve must equal or exceed what boiler specification?

• AThe gross heat output rating (or maximum burner input rating) of the boiler.
• B50% of the net I=B=R rating of the boiler.
• CThe circulator pump GPM capacity.
• DThe domestic water heater input rating.

What is the main operating advantage of installing multiple small modular boilers in parallel instead of a single large boiler for residential hydronic heating?

• AImproved seasonal efficiency through step-staging and built-in system redundancy if one b…
• BLower initial piping installation material costs.
• CElimination of the need for backflow preventers on makeup water lines.
• DElimination of expansion tanks and safety relief valves.

Unless labeled otherwise by the manufacturer testing listing, what is the standard minimum required clearance from an unlisted gas-fired boiler shell to combustible walls?

• A1 inch
• B6 inches
• C18 inches
• D36 inches

How does an outdoor reset control curve optimize hydronic heating system operation?

• AIt automatically lowers boiler supply water temperature as outdoor temperature rises, mat…
• BIt shuts off the circulator pump when outdoor air temperature drops below 32°F.
• CIt maintains boiler water at a constant 200°F regardless of weather conditions.
• DIt increases gas manifold pressure during sub-zero outdoor weather.

What causes thermal shock in a cast iron sectional heating boiler, and how is it prevented?

• ASudden entry of cold return water into hot cast iron sections; prevented by installing a…
• BExceeding 15 psig steam pressure; prevented by blowing down the LWCO.
• CHigh electrical voltage spikes; prevented by installing a surge protector.
• DExcessive air velocity through the chimney; prevented by a barometric draft regulator.

During a service call on a gas boiler that fails to fire, a technician measures 24 VAC across the R and C control terminals, but 0 VAC across the gas valve solenoid terminals when the thermostat calls for heat. Which condition would cause this symptom?

• AAn open safety limit switch (such as a high limit, LWCO, or spill switch) in the control…
• BA shorted 24V transformer secondary winding.
• CExcessive gas manifold pressure.
• DA tripped 120V circulator pump breaker.

Per ASME Section IV HG-402, what information must be permanently stamped on the metal nameplate of an approved boiler safety relief valve?

• AManufacturer name, set pressure (psi), steam or hot water relieving capacity (BTU/h or lb…
• BInstalling contractor license number, pipe size, and gas meter serial number.
• CCirculator pump horsepower rating and impeller diameter.
• DMaximum system glycol concentration and expansion tank pre-charge pressure.

What is the function of the bottom blowdown valve on a low-pressure residential steam boiler?

• ATo drain accumulated sediment, mud, and heavy sludge from the mud ring at the bottom of t…
• BTo add chemical rust inhibitors during firing.
• CTo automatically adjust steam pressure based on outdoor temperature.
• DTo divert steam to domestic hot water coils during peak demand.

What is the recommended target pH range for circulating water in cast iron and steel residential hydronic boilers to minimize internal corrosion?

• A4.0 to 5.5 (Acidic)
• B6.0 to 6.5 (Slightly Acidic)
• C8.0 to 10.0 (Slightly Alkaline)
• D12.5 to 14.0 (Strongly Caustic)