Johnson Controls CM8M/CMLM*MP - Manual (Page 10)

368261-UIM-A-0508
10 Johnson Controls Unitary Products
HIGH ALTITUDE NATURAL GAS ORIFICE
CONVERSION
The National Fuel Gas Code requires that gas appliances installed
above 2,000 feet elevation have their inputs de-rated by 4% per 1,000
feet above sea level. The modulating furnaces automatically de-rate for
altitude by measuring the inducer blower pressure and using that to
determine if there is adequate air to support good combustion. If there
is not enough combustion air to properly support 100% of the furnace
nameplate input rate, the control will reduce the input to the point that
there will be good combustion.
The factory gas orifice sizes are based on a gas heating value of
1030 BTU/Cu.ft., so if your gas value is significantly higher or
lower than that, it may be necessary to change to smaller or larger
gas orifices.
The chart below shows recommended gas orifice sizes to use at vari-
ous altitudes and at various de-ration levels. To use the chart, follow
these instructions:
1. Clock the gas meter and calculate the actual input rate using your
local gas heating value. See "CALCULATING THE FURNACE
INPUT (NATURAL GAS)" in this manual.
2. Divide that input rate by the input rate shown on the furnace rating
plate to get the actual de-ration percent.
3. Read down the left-hand “Actual Rate” column to find the closest
number to your actual de-ration percent.
4. Read across that row to the column for the elevation at your loca-
tion. The number listed there is the orifice size that is proper for
your unit.
Example – You have a 100,000 BTU/H furnace installed at an elevation
of 6,000 feet. You clock the gas meter and find that the furnace is actu-
ally fired at 64,000 BTU/H. Divide 64,000 by 100,000, which gives 0.64
(64%). The closest number to 64% in the left-hand “Actual Rate” col-
umn is 65. Read across that row to the column for 6,000 feet elevation,
which shows “#43”. You should change from the factory #45 orifices to
larger #43 orifices, which will bring the input rate back up to approxi-
mately 76,000 BTU/H, which is what it should be for that furnace at
6,000 feet.
SECTION V: ELECTRICAL POWER
ELECTRICAL POWER CONNECTIONS
Field wiring to the unit must be grounded. Electric wires that are field
installed shall conform to the temperature limitation for 63°F (35°C) rise
wire when installed in accordance with instructions. Refer to Table 6,
"Ratings & Physical / Electrical Data" in these instructions for specific
furnace electrical data.
Annual Fuel Utilization Efficiency (AFUE) numbers are determined in accordance with DOE Test procedures.
Wire size and over current protection must comply with the National Electrical Code (NFPA-70-latest edition) and all local codes.
Table 5: High Altitude Orifices
Actual Rate
(percent of
nameplate)
Elevation in Feet Above Sea Level
4,000 5,000 6,000 7,000 8,000 9,000 10,000
84% 80% 76% 72% 68% 64% 60%
Orifice Drill Size
100 48 49 49 50 51 51 52
95 47 48 49 50 50 50 51
90 46 47 48 49 49 49 50
85 45 46 47 48 49 49 50
80 45 45 46 47 48 48 49
75 44 45 45 45 47 47 49
70 43 44 44 45 45 45 48
65 42 43 43 44 45 45 47
60 41 42 42 43 44 45 46
55 40 41 41 32 43 43 44
50 39 40 40 40 43 42 42
PROPANE KITS
It is very important to choose the correct kit and/or gas orifices for the altitude and the type of gas for which the furnace is being installed.
Only use natural gas in furnaces designed for natural gas. Only use propane (LP) gas for furnaces that have been properly converted to use pro-
pane (LP) gas. Do not use this furnace with butane gas.
Incorrect gas orifices or a furnace that has been improperly converted will create an extremely dangerous condition resulting in premature heat
exchanger failure, excessive sooting, high levels of carbon monoxide, personal injury, property damage, a fire hazard and/or death.
Propane (LP) conversions are required in order for the appliance to satisfactory meet the application.
An authorized distributor or dealer must make all gas conversions.
In Canada, a certified conversion station or other qualified agency, using factory specified and/or approved parts, must perform the conversion.
The installer must take every precaution to insure that the furnace has been converted to the proper gas orifice size when the furnace is installed.
Do not attempt to drill out any orifices to obtain the proper orifice size. Drilling out a gas orifice will cause misalignment of the burner flames,
causing premature heat exchanger burnout, high levels of carbon monoxide, excessive sooting, a fire hazard, personal injury, property damage
and/or death.
Use copper conductors only.
Table 6: Ratings & Physical / Electrical Data
Input
Max/Min
Output
Max/Min
Nominal
Airflow
Total Unit
Amps
AFUE
Air Temp. Rise
Max Input
Air Temp. Rise
Min Input
Max
Over-Current
Protect
Min. wire Size
(awg) @ 75 ft
one way
Max. Outlet
Air Temp
MBH kW MBH kW CFM m 3 /min °F °C °F °C °F °C
60/30 17.6/8.8 48/24 14.1/7.0 1200 34.0 7.0 80.0 35-65 19-36 20-50 11-28 15 14 165 73.9
80/40 23.5/11.8 64/32 18.8/9.4 1200 34.0 7.5 80.0 40-70 22-39 20-50 11-28 15 14 170 76.7
80/40 23.5/11.8 64/32 18.8/9.4 1600 45.3 10.0 80.0 40-70 22-39 20-50 11-28 15 14 170 76.7
100/50 29.3/14.7 80/40 23.4/11.7 1600 45.3 10.0 80.0 40-70 22-39 20-50 11-28 15 14 170 76.7
100/50 29.3/14.7 80/40 23.4/11.7 2000 56.6 17.0 80.0 35-65 19-36 20-50 11-28 20 12 165 73.9
120/60 33.7/16.9 96/48 28.1/14.1 2000 56.6 17.0 80.0 45-75 25-42 25-55 13-31 20 12 175 79.4