Electric Heaters; Connect Power And Control Wires - Carrier Aero 39MN Series Installation, Start-Up And Service Instructions Manual

9 = DRIVE FAULT
10 = DRV NOT FLT
11 = DRIVE ALARM
12 = OVERRIDE
13 = BYPASS HAND
The Start command can come from the bypass control
board terminal block, the ACH550 keypad, the bypass keypad,
or serial communications depending on the operational mode
selected. The System Started relay is ideal for use in damper ac-
tuator circuits, opening the dampers only under those condi-
tions where the system is preparing to run the motor. The Sys-
tem Started relay will de-energize, closing the dampers if the
safeties open, the system faults, or when a Stop command is is-
sued.
Electric heaters are factory installed.
Electric Heaters —
If circumstances require field installation of an electric heater,
it can only be installed in a factory-supplied EHS (Electric
Heat section). Installation of electric heat in a section other than
an EHS section will void the UL listing of the product.
1. Identify ALL electrical power supplies serving the
unit, lock off and tag each before working on the unit.
2. Locate the electric heat section mounted on the unit
and remove the protective shipping cover.
3. Identify the electric heater and verify that the heater
matches the unit. Unit hand and heater hand must also
agree.
4. Properly sized power wiring and control wiring entry
holes are provided in the upstream sidewall of the
heater control box.
For outdoor unit sizes 36-110 only, a narrow, fixed up-
stream panel is provided for electrical power entry
from the outside. Power may also enter the unit from
below, penetrating the floor of the unit. Carefully seal
all entries, weather tight where necessary. Control wir-
ing may enter the same way as electrical wiring.
Take future service requirements into account when lo-
cating field power entry holes in the unit casing.
5. Sleeve these holes and seal around the conduit to pre-
serve the integrity of the casing. In some cases, it
might be preferable for the power to actually enter the
cabinet through an adjacent section, or enter the con-
trol box from another angle, which is acceptable.
6. If the original holes are not used, they must be appro-
priately plugged.
7. Insert the electric heater into the section (the heater el-
ement rack will be located along the leaving air side of
the section).
NOTE: If the heater must be hoisted into position, once the
top panel has been removed to a safe place, the horizontal
top rail may be removed by carefully removing the flat cor-
ner plug from the end corner pieces and extracting the
screw visible within the exposed cavity. (Do not mix these
screws with others, as they are specific for this location.)
The corners may then be separated, lifting the rail and cor-
ner segments away from the unit at approximately a 45-
degree angle, taking care not to damage the double bulb
seal.
8. The heater has lifting hook openings on each end.
When the heater is within 3 in. of its final position, re-
install the crossrail with the box-seal facing down and
the panel seal toward the top.
9. Secure the heater to the section posts and rails with the
furnished screws, drawing it the last
sealed position against the framework, by alternately
cross tightening the screws. The opposite end of the
heater rests on lateral spacers provided on the floor
23 = SYSTEM FLT
24 = SYS FLT/ALM
25 = SYS EXT CTL
26 = SYS OVERLD
27 = CONTACT FLT
3 / in. into final
8
panel, and is retained by a screw through an angle clip
on the last one or by an upright corner flange.
10. Replace the top panel, and proceed to complete the
wiring in accord with all applicable codes and ordi-
nances. The wiring diagram is fastened inside the con-
trol box, with a spare, loose copy provided as a conve-
nience for maintenance manual preparation. Do not
mix the wiring diagrams, as they are specific for each
unit.
11. Connect power and control wiring according to the
wiring diagram supplied (see Fig. 129-131 for typical
wiring details).
CONNECT POWER AND CONTROL WIRES — Heater
wiring schematic is located on control box panel. Verify that
minimum airflow requirement (minimum coil face velocity,
fpm) will be met, especially on applications where variable air
volume is supplied.
Use copper power supply wires rated for 75 C minimum.
On 250 v or greater applications, use 600 v rated wiring. Size
wires to carry 125% of current load on each set of terminals.
Use the following formulas as required:
Single-phase line current =
Three-phase line current =
Note that if the heater is rated at 50 kW (or more) and is
controlled by a cycling device such as a multi-stage thermostat,
or a step controller, conductors may be sized at 100% of load
amperes (see Table 39) per NEC Section 424-22. Heater con-
struction and application information are based upon Space
Heating Standard UL No. 1096 and the requirements of the
NEC. Installer is responsible for observing local code require-
ments.
Install a disconnect switch or main circuit breaker in accor-
dance with NEC and other applicable codes. Locate so that it is
easily accessible and within sight of heater control box (per
NEC Article 424-19 and 424-65).
Weatherproof junction boxes have no knockouts for wire
entrance. Provide knockouts for all wiring using field-supplied
grommets of correct size and type of conduit as required.
Where field-supplied thermostats are used, isolate circuits
to prevent possible interconnection of control circuit wiring.
Where field-supplied step controller is used, connect steps
to terminals as marked on wiring schematic. When connecting
multi-stage heaters, wire stage no. 1 so that it is first stage on,
last stage off.
Provide sufficient clearance for convection cooling of heat-
ers with solid-state controllers. Provide at least 5 in. of free air
space above and below cooling fins extending from heater ter-
minal box. Be sure to connect interlock terminals F1 and F2 to
auxiliary contacts on fan starter.
Each heater has 2 different types of factory-installed ther-
mal cutouts for over temperature protection: an automatic reset
thermal cutout for primary protection, and a manual reset ther-
mal cutout to protect against failure of the primary system.
Also provided is an airflow pressure differential switch to pre-
vent the heater from operating when the fan is not in operation
or airflow is restricted or insufficient. The primary automatic
reset cutout is a bi-metal disk-type cutout. It is wired into the
control circuit which operates the magnetic disconnecting con-
tactors (the same contactors that also switch on and off the var-
ious steps of the coil). The secondary manual reset cutout is a
bi-metal disk-type cutout. This secondary thermal cutout is
load carrying and is installed in each heater subcircuit. The pri-
mary and secondary overtemperature protection systems are
independent of each other. The secondary system is designed to
153
(kW per set of terminals) (1000)
voltage
(kW per set of terminals) (1000)
(voltage) (1.73)