Thermo Products OHFA199DV5B, OHFA199DV5R C. Draft Regulators, D. Duct Work/Air Conditioning

C. DRAFT REGULATORS:

Note: Do not use with Direct Vent application.

A draft regulator is supplied with the furnace and should be installed according to the regulator manufacturers recommendations. With the burner operating, use a draft gauge to adjust the regulator to the proper setting. (refer to the instructions enclosed with draft regulator to adjust to the proper setting). When the burner air supply and draft are properly adjusted, the over fire draft should be a negative (-).01" to (-).02" WC, as measured at the 5/16" over fire air tap (See Fig. 12). This tap is provided in the upper burner mounting plate. To measure the flue draft, punch a small hole in the vent connector pipe as close to the furnace as possible and always before the draft regulator.

Note: Draft over fire may be positive for high fire applications but not to exceed (+).02" WC.

D. DUCT WORK/AIR CONDITIONING:

If the furnace is used in connection with summer air conditioning (cooling), the furnace should be installed parallel with or on the upstream side of the evaporator coil to avoid condensation in the furnace heat exchanger. If the cooling unit is installed with a parallel flow arrangement, dampers or other means used to control flow of air should be provided to prevent chilled air from entering the furnace. If such a damper is manually operated, it must be equipped with a means to prevent operation of either unit, unless the damper is in the full heat or cool position.

The duct system should again follow the current design standard of Air Conditioning Contractors of America (ACCA) or ASHRAE Fundamentals volume. The most common location for the A-shaped coil (A style) is shown in Fig. 8.

Fig 8: Acceptable locations for the air conditioner evaporator coil.

NOTICE: The minimum coil pan clearance for a sectional or drum type heat exchanger is three inches unless specified otherwise by the individual coil manufacturer.

NOTICE: The minimum return air temperature is 55° F.

Airflow Requirements and Sizing of Duct Work:

The duct system must be sized and installed by a qualified installer or service person, following the design standards of the Air Conditioning Contractors of America (ACCA) or the American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE). This furnace has been designed to operate against a maximum external static pressure of 0.5 in. W.G. This is equivalent to 0.1 in. W.G. supply, and 0.1 in. W.G. return, and 0.3 in. W.G. for evaporator coil.

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