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PF100
Adding Air Conditioning to the PF100 furnace.
The PF100 furnace can be fitted with an air condi-
tioning coil mounted in the supply air plenum.
The Harman Stove Co. is not responsable for
sizing,duct placement, or interconnections. However we
have made adding A/C to the furnace easier with the
information listed below.
There is a factory installed junction box ready to
accept your A/C relay. The A/C fan control center with
40 va transformer must have a DPDT relay.
STEVECO # 90-112 - Harman part # 3-20-38056
Other brands are available at local supply houses.
The wiring should be done as per Fig. 34. The low
voltage wiring to the outside condensing unit and the
cooling thermostat are not shown, see condensing unit
diagrams for that information.
This style relay is used to lock out the feeder sys-
tem of the furnace when the A/C unit is calling for cool-
ing. This is a fail-safe against both units operating at the
same time. See the NOTE in the lower left corner.
Recommendations for Supply Air and Return Air
duct sizing.
The speed or velocity of air moving through duct
systems increases as the duct decreases in size with the
same CFM blower. The sound of air flowing through
the duct increases as the velocity increases. Therefore
the largest size duct practial should be used.
The velocity to sound level must be taken into con-
sideration when connecting this furnace into an existing
duct sustem.
As a primary source furnace the duct system can
be installed to fit the customers needs.
These are recommended Supply Air duct sizes (in
square inches)for the different CFM blowers that may
be used with this furnace.
Velocity 500fpm 700fpm 900fpm Static
I.W.C. .3 min. to .6 max.
1000CFM 270sq.in 210sq.in. 160sq.in.
1500CFM 360sq.in. 290sq.in. 220sq.in.
2000CFM 470sq.in. 360sq.in. 290sq.in.
(These duct sizes are only recommendations. )
The Return Air duct system should be sized aprox.
10 percent larger for heating only systems and 20 per-
cent larger if airconditioning is installed.
It is highly recomended that the
furnace control be turned to the
“OFF” position whenever air
conditioning is being used, whether
or not it is interconnected.
An easy rule of thumb for A/C CFM blower size
is, .75 to 1 CFM for each square foot of conditioned
space. (std. 8’ ceiling height )
CAUTION: Regardless of the supply air duct
size installed the Distribution Blower Motor MUST be
checked for running Amperage. Check the motor name
plate for the full load AMPS. If the amperage is running
higher than that listed, a supply air restricting damper
may be required to increase the supply plenum positive
static pressure.
Fig.34
NOTE:
Installing Duct/Air Conditioning
Installing Duct