Product manual

McQuay IM 782-4 19
Installation Guidelines
Electric Heat Operation
The sampling probe is suitable for left-hand or right-hand
airflow and in positive pressure applications may require field
adjustment so the probe faces upstream. This is normally done
during installation by removing two screws, rotating the probe
180° and replacing the screws. Removing the heater from the
duct is not necessary.
The electric heater is designed to operate while installed and
connected to the unit at the supply air fan discharge, to heat air
passing through the heating elements.
Temperature rise is very important and can be obtained using
the following calculation:
Temperature Rise = (KW)(3159)
CFM
Note: Maximum leaving air temperature = 120°F
Field Power Wiring
Wiring must comply with all applicable codes and ordinances.
The warranty is voided if wiring is not in accordance with
these specifications. An open fuse or starter indicates a short,
ground, or overload. Before replacing a fuse or resetting a
starter, identify the trouble and correct.
According to the National Electrical Code, a disconnecting
means shall be located within sight of and readily accessible
from the air conditioning equipment. Power leads must be
over-current protected at the point of distribution. The
maximum allowable overcurrent protection (MROPD) appears
on the unit nameplate.
Supply Power Wiring
1 Allowable voltage tolerances:
a 60 Hertz
– Nameplate 208V: Min. 187V, Max. 229V
– Nameplate 230V: Min. 207V, Max. 253V
– Nameplate 460V: Min. 414V, Max. 506V
– Nameplate 575V: Min. 518V, Max. 633V
b 50 Hertz
– Nameplate 380V: Min. 360V, Max. 418V
2 Minimum Circuit Ampacity (MCA) Calculation is based
on the following formulas:
– Electric heat less than or equal to 50 kW
MCA = 1.25 (heater FLA + largest motor loads) +
(the rest of the loads)
– Electric heat greater than or equal to 50 kW
MCA = 1.25 (largest motor load) + (the rest of the
loads) + heater FLA
3 Size wires in accordance with Table 310-16 or 310-19 of
the National Electrical Code.
4 Wires should be sized for a maximum of 3% voltage
drop.
Electrical Installation
1 Electrical service to the fan must correspond to the rated
voltage on the motor nameplate and be in conformance
with the National Electric Code and local restrictions.
2 The fan section metal frame must be connected to the
building electrical ground.
3 A door electrical interlock is not provided as standard.
4 Thermal motor protection is external to the unit. Unless
the unit is provided with a unit mounted starter, thermal
protection and a disconnect switch provision per electric
codes are provided by others.
5 When the unit is factory provided with a junction box,
disconnect switch, starter, or a variable frequency drive
(VFD), the components are mounted on the outside of
the unit cabinet. Factory wiring is provided from the
device to the unit internal motor.
NOTICE
Heaters are furnished for zero clearance between the duct and
combustible surfaces. However, it is not recommended that
any combustible material be allowed to touch any electric duct
heater or immediate surrounding areas.
NOTICE
Heaters are not intended to be installed with less than 20” of
straight duct at the outlet of the heater.
NOTICE
Field wiring necessary temperatures are:
1) 194°F for dry weather.
2) 167°F for humid weather.
WARNING
Improper grounding may result in severe injury or death.
Check grounding nut tightness before connecting power to the
external junction box.
AVERTISSEMENT
Une mise à la terre défaillante peut causer des blessures
graves ou la mort. Vérifiez l’étanchéité des vis de mise à terre
avant d’alimenter la boite de jonction externe.
WARNING
Hazardous voltage. Can cause severe injury or death.
Disconnect electric power before servicing equipment. More
than one disconnect may be required to de-energize the unit.
AVERTISSEMENT
Haut voltage. Peut causer des blessures sévères ou la mort.
Déconnectez la puissance électrique avant tous travaux de
maintenance. Plus d’une déconnection peut être requis pour
éteindre complètement l’unité.