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INSTALLATION
Considerations for Elevation
The standard ratings are certified for elevations up to 2000 feet
above sea level. Operation at elevations above 2,000 feet
requires ratings be reduced 4% for each 1000 feet above sea
level per ANSI Z223.1. The exception is for units in Canada, CSA
requires that ratings be reduced 10% for elevations between
2,001 and 4500 feet. The following instructions are for units that
will be installed over 2,000 feet elevation. If this does not apply,
you may skip ahead to the Electrical Connections section on
page 10.
Manifold Pressure Adjustment
The unit manifold pressure is factory set for operation at
elevations up to 2000 feet as follows:
• For Natural Gas units, 3.5" W.C. based on a gas heating value
of 1,050 BTU/ft3.
• For Propane Gas units, 10.0" W.C. based on a gas heating
value of 2,500 BTU/ft3.
For higher elevations, some utility companies may derate the
BTU content (heating value) of the gas provided at altitude to a
lower value to allow certain heating appliances to be used with
no manifold pressure adjustments. For this reason it is necessary
that the supplying utility be contacted for detailed information
about the gas type and BTU content (heating value) before
operating any heater. Table 9.1 shows the standard derated
heating values of natural and propane gases at various
elevations.
Table 9.1
Gas Heating Values at Altitude (Btu/ft
Altitude (ft)
Natural Gas
0-2,000
2,001-3,000
3,001-4,000
4,001-4,500
4,501-5,000
5,001-6,000
6,001-7,000
7,001-8,000
8,001-9,000
9,001-10,000
j Values shown are for 3.5" W.C. manifold pressure for Natural Gas and 10.0"
W.C. for Propane Gas. If the local utility supplies gas with a different Btu/ft
value, use Equation 9.1 to calculate the required manifold pressure.
k Gas heating values shown are derated 4% per 1,000' of elevation (10%
between 2,000' and 4,500' elevation in Canada) in accordance with ANSI
Z223.1 and CSA-B149, respectively.
l 945 Btu/ft
for Canada
3
m 2,250 Btu/ft
for Canada
3
n When installed at altitudes above 2,000', a pressure switch may need to be
changed. Refer to Tables 9.2 and 9.3 to determine if a switch change is
required.
If the utility is supplying gas with heating values SAME as shown
in Table 9.1, the manifold pressure should remain set to 3.5"
W.C. for natural gas and 10.0" W.C. for propane gas and you
may proceed to the section on this page titled "Selection of the
Proper High Altitude Kit".
If the utility is supplying gas with heating values DIFFERENT
than shown in Table 9.1, use Equation 9.1 to determine the
appropriate manifold pressure for the elevation and gas heating
value being supplied. Note what that value is, as it will be
needed later for Start-Up. Proceed to the section on this page
titled "Selection of the Proper High Altitude Kit".
) jkln
3
Propane
1,050
2,500
929 l
2,212 m
892 l
2,123 m
874 l
2,080 m
856
2,038
822
1,957
789
1,879
757
1,803
727
1,731
698
1,662
Equation 9.1 - Manifold Pressure for Gas Heating
Values Different Than Shown in Table 9.1
Where:
MP ELEV = Manifold Pressure (" W.C.) at installed
elevation
BTU TBL = BTU/ft
BTU ACT = BTU/ft
utility company
MP SL
= Manifold Pressure (" W.C.), at Sea Level
(use 3.5" W.C. for natural gas and
10.0" W.C. for propane)
NOTE: For units equipped with two-stage or modulating gas
controls, only the high fire manifold pressure needs to be
adjusted. No adjustments to the low fire manifold pressure are
necessary on these units.
Selection of the Proper High Altitude Kit
All units installed at elevations greater than 2000 feet above sea
level require a kit, in addition to potential manifold pressure
adjustment outlined in the previous step. To determine the proper
kit to use, refer to Table 9.2.
Table 9.3 shows the contents of the kit. For more information,
refer to the latest revision of Modine Bulletin 75-530.
Table 9.2 - High Altitude Kit Selection Table jk
Model
Model
Digit 3
Size
G
All
Item Code
75-350 Item Code
P
400
Item Code
j Applies to both installations in the U.S. and Canada.
k Applies to both natural and propane gas.
3
Table 9.3 - High Altitude Kit Contents
Item
High Altitude
Code
Conversion Label
67248
68409
68411
If a unit is to be installed at higher elevations AND converted from
natural gas to propane gas operation, a propane conversion kit
must be used in conjunction with the manifold pressure
adjustment and high altitude kit listed above. For the Selection
and Installation Instructions for propane conversion kits, please
see the latest revision of Modine Bulletin 75-511.
5-564.4
content of gas from Table 9.1
3
content of gas obtained from the
3
Elevation Above Sea Level (ft)
2,001-5,500 5,501-6,500 6,501-7,500
67248
67248
67248
67248
67248
68409
Kit Contents
Pressure
Switch
Yes
No
Yes
Yes
Yes
Yes
67248
67248
68411
Installation
Instructions
Yes
Yes
Yes
9
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