3.Caulking or sealants are applied to areas such as joints around window and door frames; between sole plates and floors; between wall-ceiling joints; between wall panels; at penetrations for plumbing, electrical, and fuel lines; and at other openings.
If combustion and ventilation air must be supplied to an uncon- fined space from outside, an opening with a FREE AREA of not less than 1 sq in. per 1000 Btuh of total input of all appliances within unconfined space (but not less than 100 sq in.) must be provided. This opening must be located such that it can not be blocked at any time.
When furnace is installed in a closet or enclosure, 2 ventilation openings, with OPEN AREA as dimensioned in example below are required for combustion air. The openings should be located about 6 in. from top and bottom of enclosure at front of furnace.
→For Example:
UNIT | LENGTH | HEIGHT |
SIZE | (IN.) | (IN.) |
036105 | 18 | 9 |
048125 | 20 | 10 |
060155 | 20 | 10 |
| | |
For a confined space, where air is taken from an interior space, 2 permanent openings of equal area are required. One opening must be within 12 in. of ceiling and the other within 12 in. of floor. Each opening must have a free area of at least 1 sq in. per 1000 Btuh of total input rating but not less than 100 sq in.
If outside air is supplied to a confined space, then the 2 openings must be equal and located as above. The free area of each must be:
1.One sq in. per 4000 Btuh of total input rating when air is directly communicated from outdoors.
2.One sq in. per 4000 Btuh of total input rating when air is brought in through vertical ducts.
3.One sq in. per 2000 Btuh of total input rating when air is transferred through horizontal ducts.
When ducts are used to supply air, they must be of the same cross sectional area as free area of openings to which they connect.
The minimum dimension of rectangular air ducts must not be less than 3 in.
In calculating free area, consideration shall be given to blocking effect of louvers, grilles, or screens protecting openings. Screens used shall not be smaller than 1/4-in. mesh and shall be readily accessible for cleaning. If free area through a design of louver or grille is known, it shall be used in calculating size design and free area specified. If design and free area are not known, it may be assumed that wood louvers have 20 percent free area and metal louvers and grilles have 60 percent free area. Louvers shall be fixed in open position or interlocked with furnace so they open automatically at furnace start-up and remain open during furnace operation.
WARNING: Do not block combustion-air openings in the furnace. Any blockage will result in improper com- bustion which may result in a fire hazard and/or cause bodily harm.
→The lack of a proper amount of combustion air can lead to serious furnace operational problems. Some of these problems are:
1.Excessive oil burner after drip and oil fumes.
2.Sooting.
3.Melted oil burner couplings and/or ignitor/relay control.
4.A condition where air band or air shutter settings must be more open than normal to achieve proper combustion.
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5.Lockouts on start-up.
II. DUCT WORK RECOMMENDATIONS
The proper sizing of warm air ducts is necessary to ensure satisfactory furnace operation. Duct work should be in accordance with the latest editions of NFPA-90A (Installation of Air Condi- tioning and Ventilating Systems) and NFPA-90B (Warm Air Heating and Air Conditioning Systems) or Canadian equivalent.
The supply duct work should be attached to flanged opening provided at discharge end of furnace. See Fig. 5 for dimensions of this opening.
The following recommendations should be followed when install- ing duct work:
1.Install locking-type dampers in all branches of individual ducts to balance out system. Dampers should be adjusted to impose proper static at outlet of furnace.
2.A flexible duct connector of noncombustible material should be installed at unit on both supply- and return-air systems. In applications where extremely quiet operation is necessary, the first 10 ft (if possible) of supply and return ducts should be internally lined with acoustical material.
3.In cases where return-air grille is located close to fan inlet, there should be at least one 90° air turn between fan inlet and grille. Further reduction in sound level can be accom- plished by installing acoustical air turning vanes or lining duct as described in item 2 above.
4.When a single air grille is used, duct between grille and furnace must be the same size as return opening in furnace.
CAUTION: Return-air grilles and warm air registers MUST not be obstructed.
WARNING: When supply ducts carry air circulated by furnace to areas outside spaces containing furnace, return air MUST also be handled by a duct sealed to furnace casing and terminating outside space containing furnace. Incorrect duct work termination and sealing will create a hazardous condition which could lead to bodily harm.
When installing furnace with cooling equipment for year-round operation, the following recommendations must be followed for series or parallel airflow:
1.In series airflow applications, coil is mounted after furnace in an enclosure in supply-air stream. The furnace blower is used for both heating and cooling airflow.
WARNING: The coil MUST be installed on air dis- charge side of furnace. Under no circumstances should airflow be such that cooled, conditioned air can pass over furnace heat exchanger. This will cause condensation in heat exchanger and possible failure of heat exchanger which could lead to a fire hazard and/or a hazardous condition which may lead to bodily harm. Heat exchanger failure due to improper installation may not be covered by warranty.
2.In parallel airflow applications, dampers must be provided to direct air over furnace heat exchanger when heat is desired and over cooling coil when cooling is desired.
IMPORTANT: The dampers should be adequate to prevent cooled air from entering furnace. If manually operated, dampers must be equipped with a means to prevent operation of either cooling unit or furnace unless damper is in full cool or heat position.
