Pressure Switch - International comfort products N9MP1 Service Manual

Service Manual
In the USA, for furnaces fired on standard rate, the input rating for
altitudes above 2000' (5,0004 for 80,000 BTUH and alternate in-
put) must be derated by 4% for each 1000' above sea level (see
Table 3 and Table 5)
In Canada, the input rating for altitudes above 2000' (5,0004 for
80,000 BTUH) must be reduced by 10% for altitudes of 2000' to
4500' above sea level. Use the 2001 to 3000 column in Table 3
and Table 5.
Alternate BTUH Input Ratings (USA Only)
The input rating of these furnaces can be changed from the stan-
dard input rating to the alternate input rating shown in Table 6, by
changing the main burner orifices. Changing of burner orifices
MUST be done by a qualified service technician. See section on
changing orifices.
CAUTION:
See unit instructions to determine if model may be
converted to alternate input.
MANIFOLD PRESSURE AND ORIFICE SIZE FOR HIGH ALTITUDE APPLICATIONS
LPG or PROPANE GAS MANIFOLD PRESSURE (, w.c.)
Table 7
EXCEPT FOR THE 90% 80,000 BTUH MODEL AND ALTERNATE INPUT RATINGS
HEATING VALUE
at ALTITUDE
BTU/CU. FT.
2500
Orifice Size
LPG or PROPANE GAS MANIFOLD PRESSURE (, w.c.)
Table 8
FOR THE 90% 80,000 BTUH MODEL AND ALTERNATE INPUT RATINGS
HEATING VALUE
at ALTITUDE
BTU/CU. FT.
2500
Orifice Size
NOTE: Propane data is based on 1.53 specific gravity. For fuels with different specific gravity consult the National Fuel Gas Code ANSI Z223.1−2002/NFPA
54−2002 or National Standard Of Canada, Natural Gas And Propane Installation Code CSA B149.1−05.
NOTE: In the USA, for furnaces fired on standard rate, the input rating for altitudes above 2000' (5,0004 for 80,000 BTUH and alternate
input) must be derated by 4% for each 1000' above sea level (see Table 3 and Table 5)
In Canada, the input rating for altitudes above 2000' (5,0004 for 80,000 BTUH) must be reduced by 10% for altitudes of 2000' to 4500'
above sea level. Use the 2001 to 3000 column in Table 3 and Table 5.
Models equipped for or converted to operate on LP Gas will
be equipped with an LP Pressure Switch. If so equipped,
the switch will be located in the gas supply line (in a "Tee"
fitting), just ahead of the gas valve.
The purpose of this switch is to prevent furnace operating
under low line (Supply) pressure conditions. Operating un-
der low line pressure conditions, can create problems such
as incomplete combustion, flashback, sooting, etc.
The switch is a "Normally Open" pressure operated switch
that is wired in series with the furnace (air proving) pressure
switch. The L.P. Pressure Switch closes when line (Supply)
pressure is 8.0" W.C. or higher. the L.P. Pressure Switch
Opens if line pressure falls below 6.0" + 0.6" W.C. inter-
rupting power to the gas valve.
12
MEAN ELEVATION FEET ABOVE SEA LEVEL
0 to 2001 to
2000 3000
10.0 10.0
#54 #54
MEAN ELEVATION FEET ABOVE SEA LEVEL
0 to 2001 to
2000 3000
10.0 10.0
#55 #55
L.P. PRESSURE SWITCH
Single Stage Multi Position Furnace
Table 6 Alternate Input Ratings, USA ONLY.
BTUH
Standard
Rating
50,000
75,000
100,000
125,000
* See Table 5 for High Altitude
3001 to 4001 to
4000 5000
9.0 10.0
#54 #55
3001 to 4001 to
4000 5000
10.0 10.0
#55 #55
Figure 8
BTUH
Alternate
Rating Orifice*
40,000
60,000
80,000
100,000
5001 to 6001 to
6000 7000
9.4 8.5
#55 #55
5001 to 6001 to
6000 7000
9.4 8.5
#55 #55
Typical L.P. Pressure Switch
440 08 2011 00
LP
Gas
#55
#55
#55
#55
7001 to
8000
10.0
#56
7001 to
8000
10.0
#56