FURNACE ORiFiCE SIZE AND ALTITUDE=FEET
SEA
MODEL OUTPUT CAPACITY LEVEL 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000
Orifice Size - Nat. Gas 29 29 30 30 30 30 31 31 31 32
M1M/M1G OiiiiceSize- [P 45 46 47 47 47 48 48 49 49 50
- 056
Orifice Size - Nat. Gas 24 25 26 27 27 28 28 29 29 30
M1 M/M1G Oiifice Size [[P 42 42 43 43 43 44 44 45 46 47
-070 Oyt£_tzMBTLI _ 56.7 52.3 50.2 48.2 46.2 44.4 42.6 40.9 39.3 37.7
Orifice Size - Nat. Gas 21 23 23 24 25 26 27 28 28 29
M1M - 077 Orifice Size - LP 40 41 42 42 42 43 43 44 44 45
Oytput: IVIB!UU 61.7 56,9 54.6 52.4 50.3 48.3 46.4 44.5 42.7 41.0
Orifice Size - Nat. Gas 21 23 23 24 25 26 27 28 28 29
M1G - 077 Orifice Size - LP 40 41 42 42 42 43 43 44 44 45
Oytput: [VIBTUH 59.9 55.2 53.0 50.9 48.9 46.9 45.0 43.2 41.5 39.8
Orifice Size - Nat. Gas 17 18 19 19 20 21 22 23 24 26
M1M - 090 Orifice Size - LP 36 37 38 38 39 40 41 41 42 43
QytpNt: [VIBTUH 71.7 66,] 63.5 60.9 58.5 56.1 53.9 51.7 49.7 47.7
Orifice Size - Nat. Gas 17 18 19 19 20 21 22 23 24 26
M1G - 090 Orifice Size - LP 36 37 38 38 39 40 41 41 42 43
Out_)ut-MBTUH 69.7 64.2 61.7 59.2 56.8 54.6 52.4 50.3 48.3 46.3
Orifice Size - Nat. Gas 26 27 28 28 28 29 29 30 30 30
M1B - 066 Orifice Size - LP 43 44 44 44 45 45 46 47 47 48
Output-MBTUH 52.6 48.5 46.6 44.7 42.9 41.2 39.6 38.0 36.5 35.0
Orifice Size - Nat. Gas 18 19 19 20 21 22 23 24 26 27
M1B - 086 Orifice Size - LP 37 38 39 39 40 41 42 42 43 43
Output-MBTUH 68.2 62.9 60.3 57.9 55.6 53.4 51.2 49.2 47.2 45.3
NOTES: For Canadian high altitude (2,000 - 4,500'), reduce gas manifold pressure to 3.0" W.C. for
natural gas and 9" W.C. for LP gas. (Includes 4% Input Reduction for Each 1,000 Feet). These specs
do not apply to oil furnace installations. Reference Sources: ANSI Z233.1 & NFPA 54, National Fuel
Gas Code.
Table 11. Equivalent Orifice Sizes for High Altitude Installations
MI/M5*B Models and for use with Blower Kit No. 903773 114 Hp 3 Speed
Furance Input Heating Speed Cooling Speed/Evap Coil
Setting 2 Ton 2-1/2 Ton 3 Ton
086, 090 H L M H
066, 070, 077 M L M H
56 L L M H
32
MI/M5*C Models and for use with Blower Kit No. 903413 112 Hp 4 Speed
Heating Cooling Speed/Evap Coil
Furance Input Speed 2Ton 2-1/2 Ton & 3Ton 3-1/2 Ton 4Ton
Setting
077, 086, 090 ML L ML MH H
056, 066, 070 L L ML MH H
MI/M5*D Models & for use with Blower Kit No. 903890 314 Hp 4 Speed
Heating Cooling Speed/Evap Coil
Furance Input Speed 2Ton 2-1/2Ton & 3Ton 3-1/2Ton & 4Ton
Setting
077, 086, 090 ML L ML MH
056, 066, 070 L L ML MH
5Ton
H
H
Table 12. A/C Blower Speed Selection Chart