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SI (METRIC) CONVERSION FACTORS / UNIT LOCATION
SI (METRIC) CONVERSION FACTORS
Table 3.1
To Convert
Multiply By To Obtain
"W.C.
0.24
kPa
psig
6.893
kPa
°F
(°F-32) x 0.555
°C
inches
25.4
mm
feet
0.305
meters
m 3 /min
CFM
0.028
UNIT LOCATION
DANGER
Appliances must not be installed where they may be exposed
to a potentially explosive or flammable atmosphere.
IMPORTANT
To prevent premature heat exchanger failure, do not locate
ANY gas-fired appliances in areas where corrosive vapors (i.e.
chlorinated, halogenated or acid) are present in the atmosphere.
Location Recommendations
1. When locating the furnace, consider general space and
heating requirements, availability of gas and electrical
supply, and proximity to vent locations.
2. Unit must be installed on the positive pressure side of the
circulating blower.
3. Be sure the structural support at the unit location site is
adequate to support the weight of the unit. For proper
operation the unit must be installed in a level horizontal
position.
4. Do not install units in locations where the flue products
can be drawn into the adjacent building openings such as
windows, fresh air intakes, etc.
5. Be sure that the minimum clearances to combustible
materials and recommended service clearances are
maintained. Units are designed for installation on non-
combustible surfaces with the minimum clearances shown
in Figure 3.1 and Tables 3.2 and 3.3.
6. Units installed downstream of refrigeration systems, or
exposed to inlet air temperatures of 40°F or less, may
experience condensation, therefore, provisions should
be made for disposal of condensate. Means have been
provided in the bottom pan of the unit to accommodate a
condensate drain line connection flange.
7. When locating units, it is important to consider that the
exhaust vent piping must be connected to the outside
atmosphere.
8. In garages or other sections of aircraft hangars such as
offices and shops which communicate with areas used for
servicing or storage, keep the bottom of the unit at least 7"
above the floor. In public garages, the unit must be installed
in accordance with the Standard for Parking Structures
NFPA #88A and the Standard for Repair Garages NFPA
#88B. In Canada, installation of unit heaters in airplane
hangars must be in accordance with the requirements of
the enforcing authority, and in public garages in accordance
with the current CAN/CGA-B149 codes.
9. Do not install units in locations where gas ignition system is
exposed to water spray, rain, or dripping water.
To Convert Multiply By To Obtain
m 3 /min
CFH
1.699
Btu/ft 3
mJ/m 3
0.0374
pound
0.453
kg
Btu/hr
0.000293
kW/hr
gallons
3.785
liters
psig
27.7
"W.C.
5-564
Figure 3.1 - Combustible Material and Service
Clearances
Access
Slide
A
➀ A 3'' minimum clearance to combustible material is required from the vent collar.
Table 3.2 - Combustible Material Clearances
Combustible Materials
Model
Access
Non-Access
Size
Side
(A)
75
12"
100/125
12"
150/175
12"
200/225
12"
250/300
12"
350/400
12"
Table 3.3 - Service Clearances
Model
Access
Non-Access
Size
Side
(A)
75
18"
100/125
20"
150/175
25"
200/225
27"
250/300
30"
350/400
41"
Combustion Air Requirements
Units installed in tightly sealed buildings or confined spaces
must be provided with two permanent openings, one near
the top of the confined space and one near the bottom. Each
opening should have a free area of not less than one square
inch per 1,000 BTU per hour of the total input rating off all
units in the enclosure, freely communicating with interior areas
having, in turn adequate infiltration from the outside.
For further details on supplying combustion air to a confined
(tightly sealed) space or unconfined space, see the National
Fuel Gas Code ANSI Z223.1 of CAN/CGA B149.1 or .2
Installation Code, latest edition.
C
B
D"
Clearance to
Top
Bottom
Side
(C)
(D)
(B)
1"
3"
2"
1"
3"
2"
1"
3"
2"
2"
3"
2"
2"
3"
2"
2"
3"
2"
Recommended
Service
Clearance
Top
Bottom
Side
(C)
(D)
(B)
6"
10"
0"
6"
10"
0"
6"
10"
0"
6"
10"
0"
6"
10"
0"
6"
10"
0"
3 3
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