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RT-SVX075A-EN
Note:
Single zone VAV is designed to be used with a zone
sensor. If a unit is configured for Single zone VAV
operation but is connected to a thermostat, the
control will revert to multi-speed (2-speed) indoor
fan control and staged compressor control. This
drastically reduces the energy savings available with
this design.
Air Filters
Filters are to be used with this unit. Units ship from the
factory with filters installed.
Figure 65.
Gas unit overview
SUPPLY AIR
RETURN AIR
PRESSURE SWITCH
GAS VALVE
COMPRESSOR
AIR FILTERS
It is very important to keep the central duct system air filters
clean. Be sure to inspect them at least once each month
when the system is in constant operation. (In new homes,
check the filters every week for the first 4 weeks.) See the
following table for the required filter size(s).
If you have disposable type filters, replace them with new
filters of the same type and size. Do not attempt to clean
disposable filters.
Permanent type filters can be cleaned by washing them
with a mild detergent and water. Ensure that the filters are
thoroughly dry before reinstalling them in the unit (or duct
system).
It may be necessary to replace permanent filters annually if
washing fails to clean the filter, be sure to use the same
type and size as was originally installed.
Table 16.
Recommended standard filters
Tons
Unit Model
Number
Qty
Filter Size
(L x W x D)
6
YHJ072A**(0,A)(L,M,H)
2
18 x 24 x 2
3
24 x 16 x 2
7.5
YHJ090A**(0,A)(L,M,H)
2
18 x 24 x 2
3
24 x 16 x 2
8.5
YHJ102A**(0,A)(L,M,H)
2
18 x 24 x 2
3
24 x 16 x 2
Table 16.
Recommended standard filters (continued)
Tons
Unit Model
Number
Qty
Filter Size
(L x W x D)
10
YHJ120A**(0,A)(L,M,H)
2
18 x 24 x 2
3
24 x 16 x 2
12.5
YHJ150A**(0,A)(L,M,H)
3
18 x 18 x 2
3
24 x 18 x 2
15
YHJ180A**(0,A)(L,M,H)
8
20 x 24 x 2
17.5
YHJ210A**(0,A)(L,M,H)
8
20 x 24 x 2
20
YHJ240A**(0,A)(L,M,H)
8
20 x 24 x 2
25
YHJ300A**(0,A)(L,M,H)
8
20 x 24 x 2
Heating System
Heating Cycle Operation
The unit heating system is a solid-state electronic ignition
control that lights the furnace burners each time the
thermostat calls for heat. At the end of each heating cycle
the furnace burners are extinguished. This type of system
is called Direct Spark Ignition (DSI).
A normal heating cycle begins when the air temperature
drops below the thermostat setting. The thermostat then
energizes the heating electrical circuit that starts and
controls the furnace burners. Shortly after the burners
