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Continuous Air Reduction Jumper
During continuous fan mode with no heating or cooling de-
mand, the blower runs at the total percentage of the CFM
jumpers which cannot exceed 100% of blower capacity.
The continuous air reduction
jumper enables the blower speed
to be reduced by a percentage of
the blower speed during continu-
ous fan mode.
The selections are 75%, 50%, and 0%. The factory places
the jumper on 0%. See figure 12.
Heating Air Reduction Jumper
The heating air reduction jump-
er enables the blower speed,
during heating, to be reduced by
a percentage of the cooling
blower speed.
The selections are 40%, 20% and 0%. Jumper is placed on
0% from the factory. See figure 13.
NOTE − For heat pump applications Option 2 or Option
3, you MUST ALWAYS set the jumper on 0%. High head
pressures may result if air during heating mode is re-
duced. High head pressures may result if air is reduced
during heating mode.
Determine Actual Air Delivered By Blower
The actual CFM delivered to each zone will be deter-
mined by the control center settings, blower motor con-
trol board settings, zone thermostat demand status
[calling for heating, cooling, continuous fan, or no de-
mand (zone damper closed)], and the air distribution
system's duct size.
When the zone control system is set for a particular
zone jumper, heating reduction jumper, and/or continu-
ous air reduction jumper, determine the total CFM avail-
able from the unit as follows:
1. Determine total unit % air selection Total unit %
air selection = (% air of zone 1 + zone 2 + zone 3+
zone 4)
The % air for each zone is the zone jumper setting on the
zone control system board as determined in the preced-
ing section entitled A − CFM Air Selection Jumpers."
NOTE − The % air of each zone is increased by 10%
if the zone is calling for emergency or auxiliary heat.
If total unit % air is calculated as greater than 100%
use 100% in step b.
2. Determine total unit PWM Multiplier using chart
(example 2 in figure 11)
and heat reduction jumper is set for 20%, enter the
horizontal axis at 60 % air, proceed vertically to the
20% reduction heating line, then go horizontally
across to the vertical axis and read 0.31 PWM Multi-
plier.
CONTINUOUS
75%
AIR
50%
REDUCTION
0%
Figure 12
HEATING
40%
AIR
20%
REDUCTION
0%
Figure 13
If total unit % air is 60%
3. Determine total unit available CFM Total unit
available CFM = PWM Multiplier x (Max CFM − Min.
CFM) + Min. CFM.
Again, the maximum and minimum CFM values used in
the formula should correspond to the jumper settings on
the blower control board (PWM Multiplier is as deter-
mined in 2" above).
Example 2
Given − % air of zone 1 = 35; zone 2 = 50; zone 3 = 25;
there is no zone 4; Max CFM = 2220; Min. CFM = 720.
Part 1 − Find total unit available CFM if zones 1 and 3
are calling for heating with heat reduction jumper set
at 20%.
Part 2 − Find total unit available CFM if zones 1 and 3
are calling for cooling (0% reduction).
Solution to part 1
A
Total unit % air selection = (% air of zone 1 +
zone 2 + zone 3+ zone 4) = 35 + 25 = 60.
B
In figure 11 enter the horizontal axis at 60 % air,
proceed vertically to the 20% reduction heating
line, then go horizontally across to the vertical
axis and read 0.31 PWM Multiplier.
C
Total unit available CFM = PWM Multiplier x (Max
CFM − Min. CFM) + Min. CFM = 0.31 x (2220−720)
+ 720 = 1185
Solution to part 2
A
Total unit % air selection = (% air of zone 1 +
zone 2 + zone 3+ zone 4) = 35 + 25 = 60.
B
In figure 11 enter the horizontal axis at 60 % air,
proceed vertically to the 0% reduction cooling
line, then go horizontally across to the vertical
axis and read 0.47 PWM Multiplier.
C
Total unit available CFM = PWM Multiplier x (Max
CFM − Min. CFM) + Min. CFM = 0.47 x (2220−720)
+ 720 = 1425
Indoor Unit Jumper
The indoor unit jumper must be in place to select the
type of heating system that has been installed. For Op-
tion 1, place the jumper on G21V (or GAS). For Option 2,
place jumper on the set of pins which reflect the number
of stages of auxiliary heat; HP1 for one stage, HP2 for
two stages, and HP3 for three stages of auxiliary heat. If
no auxiliary heat is used with Option 2, place the jumper
on HP1. See figure 14.
For Option 3 with the FM21, DO
NOT place the jumper on any
set of pins. Store the jumper by
placing it on one pin only so that
electrical contact cannot be
made. See figure 9.
Page 17
INDOOR UNIT
HP3
HP2
HP1
G21V or Gas
Figure 14
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