CSA 96MDT SERIES, Руководство по установке

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84
High Altitude
HIGH ALTITUDE
NATURAL GAS AT HIGH ALTITUDES
No high altitude pressure switch changes are required;
only a 4% derate per 1,000 ft. at altitudes above 2000 ft
above sea level.
NATURAL GAS
NOTE: Factory installed orifices are calculated and sized
based on a sea level Natural Gas heating value of 1100
BTU per cubic ft. Regional reduced heating values may
nullify the need to change orifices except at extreme
altitudes.
The following are examples of orifice sizing using the
National Fuel Gas Code Annex E, Tables E1.1(a) and
E1.1(d), 2015 edition
. For a simplified estimation of orifice
size based on heating value and elevation, use Table 14
on the following page. However, calculations as shown
below are the best method.
Example:
Use the formula below to calculate the amount of gas used
per hour based on the Regional Heating Value of
900BTU/ft 3 .
I / H = Q
Where:
I =BTU input of burner at sea level (btu)
H = regional heating value of natural gas at sea level
(btu/ft
3
)
Q = volume of natural gas per hour (ft
3
)
I=14,000 BTU. For this furnace the input per burner is
14,000 BTU.
H=900 BTU/ft 3 . Obtain the natural gas heating value from
your regional natural gas provider. For this example we
will use a Regional Natural Gas Heating Value 900 btu/ft
3
.
Q= Calculate for the volume of natural gas per hour.
14,000 / 900 = Q
15.56 FT
3
=Q
The volume of natural gas used on this furnace at sea
level is 15.56 ft
3
per hour. Use this value to locate the ori-
fice size in table Table E.1.1(a) of National Fuel Gas
Code,2015 edition (3.5” water column) Orifice required at
Sea Level is : #49
Use this orifice size to find derated orifice sizes for eleva-
tions on
Table E.1.1 (d)
of National Fuel Gas Code, 2015
edition.
Orifice required at 5000 ft. elevation (4% de-rate per
thousand ft. above sea level): #51
Orifice required at 8000 ft. elevation (4% de-rate per
thousand ft. above sea level.): #52
!
CAUTION
I
NSTALLATION OF THIS FURNACE AT ALTITUDES
ABOVE 2000 FT. (610 M) SHALL BE IN ACCOR-
DANCE WITH LOCAL CODES, OR IN THE ABSENCE
OF LOCAL CODES, THE NATIONAL FUEL GAS
CODE, ANSI Z223.1/NFPA 54 OR IN CANADA, NATU-
RAL GAS AND PROPANE INSTALLATION CODE,
CSA B149.1.
!
CAUTION
ELEVATIONS ABOVE 2000 FT. REQUIRE THAT THE
FURNACE INPUT RATING BE ADJUSTED AND THAT
THE SIZE OF THE BURNER ORIFICES BE RE-CAL-
CULATED BASED ON ELEVATION AND GAS HEAT-
ING VALUE. THE BURNER ORIFICES MAY (OR MAY
NOT) NEED TO BE CHANGED. THE FOLLOWING EX-
AMPLES SHOW HOW TO DETERMINE IF AN ORI-
FICE CHANGE WILL BE NECESSARY AND HOW TO
DETERMINE THE NEW ORIFICE SIZE.
IN CANADA, AS AN ALTERNATE TO ADJUSTING
THE BURNER ORIFICE SIZE, THE MANIFOLD GAS
PRESSURE MAY BE ADJUSTED. THIS METHOD IS
COVERED LATER IN THIS SECTION. THIS METHOD
OF ADJUSTING MANIFOLD PRESSURE MAY ONLY
BE USED IN CANADIAN INSTALLATIONS.