Electric Heat - Daikin PreciseLine Series Installation And Maintenance Manual

Installation

Electric Heat

The factory installed electric heat section (if equipped) consists of an open coil heater rack mounted to the unit's primary coil in the
preheat position for horizontal units or reheat postion for vertical units. Electric heat is designed to operate only when the supply
fan is running, heating the air as it passes through the heating elements. The electric heat section consists of the mounting rack,
electric elements, contactor, optional SCR module and the manual and automatic reset thermal limits. Electric heat comes pre-
wired to the main control box for a single point (or 2-point on sizes 060-100) power connection to the unit.
The temperature of the air leaving the unit (LAT) which is dependent on the entering air temperature (EAT), electric heat capacity
(kW), and the air volume (CFM), must not exceed 125°F. The minimum allowable air volume for various combinations of EAT and
kW are provided beginning on Table 17 on page 31 or may be calculated using the equation below.
LAT = (kW × 3145.622 ÷ CFM) + EAT
Electric Heat Safety
Overcurrent Protection
Optional factory provided over current protection is available on all units with a maximum operating current less than or equal to 48
amps. This protection is provided with fuses located on the unit main power circuit. Units with a maximum operating current greater
than 48 amps will come with factory installed fusing on the electric heat circuit.
Thermal (Over Temperature) Protection
All units with electric heat are provided with at least two thermal protection devices. The primary thermal protection device is
an automatic limit switch. The switch will reset itself when the temperature drops below a certain level. The secondary thermal
protection device is a manual reset thermal cutout. This switch opens at a certain level but must be reset manually after the over
temperature issue has been resolved. Units provided with the SCR type electric heat control have an additional automatic thermal
protection built into the SCR controller.
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