York DM 180 Refrigerant Components, Unit Controls, YTG-B-0107, Gas Heating Section Dm***N Models

bearings, internally protected against overload conditions and staged independently.

REFRIGERANT COMPONENTS

Compressors:

a.Shall be Scroll (25T only) compressors internally protected with internal high-pressure relief and over temperature protection.

b.Shall have internal spring isolation and sound muf- fling to minimize vibration and noise, and be exter- nally isolated on a dedicated, independent mounting.

Coils:

a.Evaporator and condenser coils shall have alumi- num plate fins mechanically bonded to seamless internally enhanced copper tubes with all joints brazed. Special Phenolic coating shall be available as a factory option.

b.Evaporator and Condenser coils shall be of the direct expansion, draw-thru, design.

Refrigerant Circuit and Refrigerant Safety Components shall include:

a.Balance-port thermostatic expansion valve with independent circuit feed system.

b.Filter drier/strainer to eliminate any moisture or for- eign matter.

c.Accessible service gage connections on both suc- tion and discharge lines to charge, evacuate, and measure refrigerant pressure during any necessary servicing or troubleshooting, without losing charge.

d.The refrigeration system shall provide at least 15° F of sub-cooling at design conditions.

e.All models shall have two independent circuits.

f.Hot gas bypass option shall be factory-installed on compressor #1 discharge line to provide cooling in low-load applications. HGBP shall be a standard feature on VAV models and an optional feature on CV models.

UNIT CONTROLS

a.Unit shall be complete with self-contained low-volt- age control circuit protected by a resettable circuit breaker on the 24-volt transformer side.

b.Unit shall incorporate a lockout circuit which pro- vides reset capability at the space thermostat or base unit, should any of the following standard safety devices trip and shut off compressor.

c.Loss-of-charge/Low-pressure switch.

1.High-pressure switch.

2.Freeze-protection thermostat, evaporator coil. If any of the above safety devices trip, a LED (light-emitting diode) indicator shall flash a

262259-YTG-B-0107

diagnostic code that indicates which safety switch has tripped.

d.Unit shall incorporate "AUTO RESET" compressor over temperature, over current protection.

e.Unit shall operate with conventional thermostat designs and have a low voltage terminal strip for easy hook-up.

f.Unit control board shall have on-board diagnostics and fault code display.

g.Standard controls shall include anti-short cycle and low voltage protection, and permit cooling operation down to 0 °F.

h.Control board shall monitor each refrigerant safety switch independently.

i.Control board shall retain last 5 fault codes in non volatile memory, which will not be lost in the event of a power loss.

GAS HEATING SECTION (DM***N MODELS)

Shall be designed with induced draft combustion with post purge logic and energy saving direct spark ignition, redun- dant main gas valve. Ventor wheel shall be constructed of stainless steel for corrosion resistance. The heat exchanger shall be of the tubular type, constructed of T1-40 aluminized steel for corrosion resistance and allowing minimum mixed air entering temperature of 25° F. Burners shall be of the in- shot type, constructed of aluminum coated steel and contain air mixture adjustments. All gas piping shall enter the unit cabinet at a single location through either the side or curb, without any field modifications. An integrated control board shall provide timed control of evaporator fan functioning and burner ignition. Heating section shall be provided with the fol- lowing minimum protection:

a. Primary and auxiliary high-temperature limit switches.

b.Induced draft motor speed sensor.

c.Flame roll out switch (automatic reset).

d.Flame proving controls. Unit shall have two inde- pendent stages of capacity.

ELECTRIC HEATING (DM***C/E MODELS)

Nickel chromium electric heating elements shall be provided as required by the application with 1 or 2 stage control, as required, from 13.5 KW to 72 KW capacities. The heating section shall have a primary limit control(s) and automatic reset to prevent the heating element system from operating at an excessive temperature. Units with Electric Heating shall be wired for a single point power supply with branch circuit fusing (where required).

UNIT OPERATING CHARACTERISTICS

Unit shall be capable of starting and running at 125° F outdoor temperature, exceeding maximum load criteria of ARI Standard 340/360. The compressor, with standard controls, shall be capable of operation down to 0° F outdoor

38 Unitary Products Group