Carrier 58MVP 170 Series Troubleshooting Manual page 41

EXAMPLE 1:
Furnace ran for 16 minutes in low heat and 5 minutes in high heat during previous call for heat.
LH = 16
HH = 5
Calculate: (228 x 16) + (350 x 5) = 5398
3648 < 5398 < 5600 ⇒ Calculate low heat run time for next cycle.
= (5600 - 5398) / 122 = 1.6 ⇒Next cycle, furnace will run for 2 minutes in low heat and then switch to high heat, if heat
LH
run time
call is still present.
EXAMPLE 2:
Furnace ran for 16 minutes in low heat and 10 minutes in high heat during previous call for heat.
LH = 16
HH = 10
Calculate: (228 x 16) + (350 x 10) = 7148
7148 5600 ⇒ Next cycle furnace will only run in high heat, low heat run time is 0 min.
EXAMPLE 3:
Furnace ran for 13 minutes in low heat and 5 minutes in high heat during previous call for heat. This can happen if the furnace staging
algorithm calculated 13 minutes based on previous call for heat.
LH = 13
HH = 5
Calculate: (228 x 13) + (350 x 5) = 4714
3648 < 4714 < 5600 ⇒ Calculate low heat run time for next cycle.
= (5600 - 4714) / 122 = 7.26 ⇒ Next cycle, furnace will run for 7 minutes in low heat and then switch to high heat, if
LH
run time
heat call is still present.
EXAMPLE 4:
Furnace ran for 0 minutes in low heat and 10 minutes in high heat during previous call for heat.
LH = 0
HH = 10
Calculate: (228 x 0) + (350 x 10) = 3500
3500 < 3648 ⇒ Next cycle furnace will only run in low heat for 16 minutes maximum, then switch to high heat, if heat call is still
present.
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