Maintenance; Controlling The System - Price Acutherm THERMA-FUSER SYSTEMS Installation & Operation Manual

Fig 8. Blow patterns
TK-HC THERMA-FUSER diffuser
APPEARANCE PANEL REMOVED
3-Way D3
2-Way Opposite D2
2-Way Corner D2C
1-Way D1
Page 4 of 6

MAINTENANCE

The moving parts of the TK Therma-Fuser diffuser have
no maintenance or lubrication requirements. We are often
asked to recommend periodic maintenance procedures and
a spare parts stock. Recommended maintenance is to clean
the outer surfaces of the Therma-Fuser diffuser—nothing
else. We do not recommend stocking any spare parts. Our
customers also confirm that stocking is unnecessary.

CONTROLLING THE SYSTEM

References:
•
System Design, p 3, TK brochure, Form 051.101.
•
Chapters 2.2, 3.1 and 3.2, pp 6, 7 and 8, Designing
Modular VAV Systems, Form 5.2.
•
Air Handling and Fan Coil Units Subzoned with Therma-
Fuser VAV modules, Form 6.7.
• DX Equipment Zoned with Therma-Fuser VAV Modules,
Form 6.5.
SUPPLY AIR TEMPERATURE
The sources of cooling and heating are controlled from
supply air temperature. As with all VAV systems, the goals
are to achieve a constant supply air temperature (may
be reset to another constant supply air temperature) and
to limit the supply air temperature. Limits for supply air
temperature should be between 50°F/10°C and 68°F/20°C
when cooling and between 80°F/26.5°C and 120°F/49°C
when heating. The heating temperature limit should be
as low as possible. These objectives are best achieved by
modulating chilled water valves, hot water valves and other
variable equipment from supply air temperature. On/off
equipment such as DX compressors and electric heat are
cycled from supply air temperature. Use a discharge air
sensor for the supply air temperature signal.
Mode change between heating, recirculation and cooling
is controlled from room temperature. Signals from one
or more room temperature sensors may be used for
mode change. When using more than one sensor, either
a "majority rules" or a "cooling dominant" approach is
recommended.
STATIC PRESSURE
As with all VAV systems, the fan must run continuously
during occupied times. Goals of static pressure control are
to provide enough static pressure to obtain the required air
volume especially at the diffuser farthest from the fan, to
avoid diffuser noise by limiting static pressure at both full
flow and turndown and to provide pressure independence or
consistent operation as the system flow changes.
These objectives can be achieved with the usual methods
of automatic static pressure control: bypass dampers,
discharge dampers, zone dampers, and fan control (variable
speed drives, inlet dampers, etc.). Locate the static pressure
sensor as far down the duct as possible—at least 2/3 down
the duct from the first takeoff.