MPS Master
SECTION 23 54 16.13
GAS-FIRED FURNACES
PART 1 - GENERAL
1.01 SUMMARY
A.Section Includes:
1.Provide indirect fired gas fired units for heating makeup air as shown on Drawings and described in this Specification.
1.02 QUALITY ASSURANCE
A.General Requirements:
1.Fans shall bear the AMCA Certified Ratings Seal for air and sound performance.
2.All products furnished under this Specifications shall be UL or ETL listed and shall meet requirements of all applicable codes.
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MPS Master
SECTION 23 54 16.13
3.All gas fired equipment furnished under this Specification shall be AGA approved and shall meet requirements of all applicable codes.
4.Provide indirect fired, factory assembled air handling units that are the products of a manufacturer regularly engaged in manufacturing units of the size and type specified. Any manufacturer submitting proposals for indirect fired units shall include published catalog data demonstration ongoing manufacture of these products. To be approved, a manufacturer or its representative shall have a qualified, local parts and service organization.
5.The manufacturer shall review the selection of all components furnished under this Specification. Manufacturer shall provide written notification to the Engineer about any related components not furnished by them and that will not be compatible with manufacturer’s products.
1.03 SUBMITTALS
A.General: Provide submittals in accordance with Section 013300.
B.Shop Drawings: Furnish Shop Drawings for all equipment provided under this Section.
PART 2 - PRODUCTS
2.01 MANUFACTURERS
A.Acceptable Manufacturers For Indirect Fired Units: Subject to compliance with requirements of the Contract Documents, acceptable manufacturers are as follows or Owner approved equal:
1.Greenheck
2.Rheem
3.Tital
4.Reznor
2.02 UNIT HOUSING
A.Configuration: Provide indirect gasfired heating air handling system as shown on Drawings. Include air filters, an indirect fired gas furnace, and centrifugal fan with each unit. Components may be delivered to the job site unassembled to facilitate shipping and permit the Contractor to move them into place with in the building, but the manufacturer shall clearly state in the proposal, the amount of assembly required with each unit.
B.Materials:
1.Construct unit housing from galvanized or bonderized furniture steel with a bake enamel finish.
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Gas-Fired Furnaces
MPS Master
SECTION 23 54 16.13
2.Line the fan section and filter section with double wall construction, at least2inch thick fiberglass insulation. Use only insulation that meets NFPA and UL Standards and the requirements of Section 230700, HVAC Insulation. Interior walls of 22 gauge galvanized steel; external wall of 18 gauge galvanized steel.
3.Provide double wall, insulated, gasketed, and hinged doors for access to sections and components that require service. Locate the doors where required and equip them with latches on both sides.
2.03 FANS
A.General:
1.Provide centrifugal blowers with belt drives and multiblade, air foil or forward curved wheels as noted in Schedule on the Drawings. Statically and dynamically balance fan wheels at the factory and then rebalance in the field, if necessary. Provide fans capable of delivering the air flows (cfm) and external static pressures (inches of water, gauge) listed in Schedule on the Drawings while requiring no more than the brake horsepower (BHP) shown. Provide selfaligning ball bearings rated for at least 200,000 hours. Extend lubrication fittings to the exterior of the fan housing. Refer to Section 233400, HVAC Fan, for further requirements for centrifugal fans. Lubrication lines shall be copper tubing; plastic not acceptable.
2.Provide motors, drives, and power factor correction capacitors as required in Section 230513, Common Motor Requirements for HVAC Equipment. Provide an adjustable motor base. Factory mount and adjust motors and drives. Prewire motors to an external junction box.
3.Select fan assemblies so they operate without passing through the first critical speed.
2.04 HEATING SECTIONS
A.General: Provide a direct fired, modulating natural gas burner with low-fire start. Provide an electronic burner control equal to the “Maxitrol” Electronic Gas Flame Modulation System capable of at least 25:1 turns down ration. Include controls to ensure that the burner will not fire unless the fan is operating and all housing doors are closed. Provide all pilot and ignition systems, and all other controls and accessories required by codes, local authorities, and the gas utility.
B.Gas Burner: Provide an induced draft burner with stainless steel baffles that will direct the correct amount of combustion air to the flame at any firing rate. Provide gaselectric ignition and controls to shut down the burner in the event of an ignition, pilot, or main flame failure. Provide an electronic detector to prevent primary fuel valves. From opening until pilot flame is established,
C.Natural Gas Manifold Arrangement: Include with each unit a complete gas train approved by Factory Mutual for indoor applications with filters. Include at least the following:
1.Main Gas, Hand Pressure ShutOff Valve
2.Main Gas Pressure Regulator
3.Low Gas Pressure Switch
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Gas-Fired Furnaces
MPS Master
SECTION 23 54 16.13
4.(2) Main Gas Valves
5.FIA or FM Leakage Test Valve
6.FIA or FM Vent Valve
7.Modulating Gas Valve
8.High Pressure Switch
9.Pilot Hand ShutOff Valve
10.Pilot Gas Pressure Regulator
11.Pilot Adjustment Valve
12.Pilot Gas Valve
2.05 FILTERS
A.General: Provide an internally insulated filter section to accommodate 2inch flat prefilters and 4inch pleated 65percent main filters. Provide full size access doors on both sides of the unit of easy access for replacement of filters.
1.Furnish filters as described in Section 234000, HVAC Air Cleaning Devices.
2.06 CONTROLS
A.General:
1.Mount all unit controls within a NEMA 1 (or better) enclosure included as part of the unit housing. Furnish the enclosure with hinged metal doors and a key lock. Arrange the enclosure to contain the gas train, the blower motor starter, and all relays and controls. Provide a “Hand/Off/Auto” switch for the supply fan and indicating lights to show flame failure and fuel valve open. Mount indicating lights and manual switches on the outside of the unit in a hinged panel for access to wiring. Lights shall be pushed-to-test type.
2.Provide a magnetic starter and a main disconnect switch for the supply fan motor. In the starter cabinet, provide a transformer to supply low voltage power for controls. Provide the airflow proving sail switch and a sensor to determine when the cabinet doors are open. Provide discharge temperature probe mounted in the air stream, downstream of the burner.
3.Provide a motorized outside air damper, wired complete to open on fan start and close on fan stop. Refer to Section 230913, Instrumentation and Control Devices for HVAC, for damper quality.
4.Provide inlet air duct sensor at setting of 62degreesF (adjustable). During winter setting, pilot shall be shutoff if outside temperature is above setting.
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Gas-Fired Furnaces
MPS Master
SECTION 23 54 16.13
B.Sequence of Operation: On a call for start from the BAS, the exhaust fan and the directfired makeup air unit will operate simultaneously. The furnace shall fire as needed to maintain the discharge sensor set point within the limits set at an electronic thermostat provided by the Temperature Control Contractor. The modulating burner shall respond directly to a discharge temperature controller provided with the unit. The furnace shall be locked out whenever the sail switch in the duct indicates the fan is not running. The furnace shall also lock out whenever the access doors on the unit are open.
2.07 INDIRECT FIRED UNIT
A.General:
1.Provide unit housing, fans, and filters.
2.Provide heating section of stainless steel heat exchanger for indirect fired unit.
PART 3 - EXECUTION
3.01 INSTALLATION
A.General: Install each unit with vibration isolators as described in Section 230548, Vibration and Seismic Controls for HVAC Piping and Equipment. Assemble components and place the unit in accordance with manufacturer’s written recommendations.
1.Isolate fan section from other components using flexible duct connections.
3.02 WIRING
A.General:
1.Temperature Control Contractor will provide any control wiring required between the space thermostat, the BAS, and the unit cabinet.
2.The unit supplier shall provide all safety controls and lockouts, including the wiring, to meet the requirements of this Specification and those of FM, the gas company, and local authorities.
3.Power ring will be provided under Section 26.
END OF SECTION
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Gas-Fired Furnaces