York Y33 User Manual download pdf (Page 91)

246653-YTG-E-0108

Johnson Controls Unitary Products 91

through each tube, to expel the flue gas and to maintain a

negative pressure within the heat exchanger relative to the

conditioned space. Induced draft fans shall be direct-drive.

One (1) high limit controller per heating module, with auto-

matic reset to prevent the heat exchanger from operating at

an excessive temperature will be installed. A pressure switch

on the combustion section must be provided to prevent igni-

tion until sufficient air flow is established through the heat

exchanger. Secondary airflow safety shall be provided by roll-

out switch protection. The rollout switch shall discontinue fur-

nace operation if the flue becomes restricted. Units shall ship

with an external flue to be shipped in the unit and mounted on

the job site. The flue shall discharge products of combustion

above the unit, preventing recycling of corrosive combustion

gases back through the heat exchanger. Gas heating sec-

tions shall be both ETL and CSA approved to both US and

Canadian safety standards.

Optional Modulating Furnace control or Single Stage control

available.

Electric Heating Section

An electric slip-in heater shall be installed within the rooftop

unit to provide the heating requirements per the schedule

shown on the plans. The electric heater shall be wired in such

a manner as to provide two equal steps of capacity (80 and

108 kW) or a single step of capacity (40 kW). The furnace

shall be an industrial grade design using an open coil(s)

made of the highest grade resistance wire containing 80%

nickel and 20% chromium. The resistance coil(s) shall be

adequately supported in the air stream using ceramic bush-

ings in the supporting framework. Terminals of the coil(s)

shall be stainless steel with high temperature ceramic bush-

ings. The primary high temperature protection shall be an

automatic reset type thermal cut out. Secondary protection

shall be an automatic reset type thermal cut out. Secondary

protection shall be a replaceable thermal link. The operation

of the electric heater shall be an integral part of the roof top

control system. Power connection to the strip heater shall be

through the single power point connection for the entire unit.

Electric heat shall be ETL certified to both US and Canadian

safety standards.

Hot Water Heating Coil

The manufacturer shall furnish and factory install a hot water

coil in the rooftop units, as described in the following specifi-

cations. Water coil capacities and pressure drops shall be

certified in accordance with ARI Standard 410. The hot water

coil shall have eight fins per inch, 2 tubes per circuit, and 2"

inlet and outlet connection. Primary surface shall be 1/2" OD

copper tube, staggered in direction of airflow. Tubes shall be

mandrel expanded to form fin bond and provide burnished,

work-hardened interior surface. Return bends shall be die

formed and silver-brazed to tubes. Headers shall be of heavy

seamless copper tubing, silver-brazed to tubes. Connections

shall be of red brass, with male pipe threads, silver brazed to

headers. Connections also have 1/4" FPT drain plug on each

connection. Extended surface shall consist of die-formed,

continuous, aluminum fins with formed channels, and surface

treatment to minimize moisture carry-over. Fins shall have

fully drawn collars to accurately space fins, and to form a pro-

tective sheath for the primary surface. A structural galvanized

steel casing shall protect the coil. Tube sheets on each end

shall have drawn collars to support tubes. An intermediate

coil support shall be provided. The coil shall be circuited to

provide free draining and venting, through one vent and

drain. Completed coil, including headers, connections and

return bends shall be tested with 325 pounds compressed air

under water. Coils shall be designed for operation at 250 psig

design working pressure.

Steam Heating Coil

The manufacturer shall furnish and factory install a steam

heating coil in the rooftop units, as described in the following

specifications. Steam coil capacities and pressure drops shall

be certified in accordance with ARI standard 410. The steam

coil shall be constructed in the non-freeze style. The steam

coil shall have six fins per inch, and 2" inlet, and 1 1/2" outlet

connection. Tubes shall be 1" OD seamless copper tubing

with a minimum wall thickness of 0.035" and expanded into

the fin collars for maximum fin-tube bond. Inner distributing

tubes shall be 5/8" OD seamless copper tubing with a mini-

mum wall thickness of 1/4". The copper to copper joints shall

be joined with high temperature, silver solder. Corrugated fins

with integral spacing collars shall cover the entire tube sur-

face. Headers shall be constructed of seamless copper. The

header tube holes shall be extruded providing better tube to

header contact for a stronger braze connection. All header

connections shall be of red brass or steel, with male pipe

threads and silver braze to headers. Casing shall be 16

gauge galvanized steel. Chafing shall be prevented by

extruding and flaring the holes in the tube sheet and interme-

diate tube sheet. The core shall be pitched in the direction of

the condensate connection for proper drainage. The com-

pleted coil (including headers and connections) shall be

tested underwater with 325 lbs. compressed air to ensure a

leak free coil.

REFRIGERATION SYSTEM

Units shall have two (25 ton), three (30 ton) or four (40 ton)

independent refrigerant circuits for maximum load-matching

capability. Each refrigerant circuit shall be controlled with a

balance-port thermal expansion valve for maximum control at

low load conditions.

Evaporator Coils

Evaporator coils shall be direct expansion type with inter-

twined circuiting to assure complete coil face activity during

part load operation. Coil fins shall be enhanced aluminum

type. Coil types shall be 3/8” OD copper, internally enhanced

and mechanically expanded to bond with the fins. Coil casing

shall be fabricated from heavy gauge galvanized steel. All

coils shall be pressure tested at a minimum of 450 PSIG. A

galvanized powder painted steel drain pan shall be provided

under the entire length and width of the evaporator coil,

including all return bends. The main drain pan shall be sloped

a total of 1/4” per foot towards the drainage point. Main drain

pan shall be easily cleanable in the field. The condensate

drain opening shall be flush with the bottom of the drain pan

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York Y33 User Manual Page 91

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