Qmark MUH - Horizontal / Downflow Unit Heaters - Manual (Page 3)

Horizontal Discharge (Rod-mount from Ceiling)
1. Install four threaded mounting rods in the threaded holes and
secure in place using lock nuts. (See Table 2).
2. Securely attach the four mounting rods to the ceiling. (Refer
to Table 1 for wall and ceiling clearances, and Table 2 for
mounting rod spacing).
Vertical Discharge (Rod-Mount from Ceiling)
1. Remove bolts from the threaded holes in the back of the
heater.
2. Install four threaded mounting rods in the threaded holes and
and secure in place using lock nuts.
3. Securely attach the four mounting rods to the ceiling. (Refer
to Table 1 for wall and ceiling clearances, and Table 3 for
mounting rod spacing dimensions.)
WIRING
Branch Circuit (Power)
1. Connect heater only to the voltage, amperage and frequency
specified on the nameplate.
2. Field wiring must be properly sized to carry the amperage in
accordance with the NEC.
3. The access door is hinged. There are either one or two
screws accessible from the side that must be loosened to
gain access. These screws are the captive type; do not try
to remove them.
4. A knockout is provided in the back of the heater close to the
power terminal block and the control terminal board. The
control terminal board knockout is 1/2 inch (12.7 mm) conduit
size. The power terminal block knockout is multiple diame-
ter. Use the diameter that fits the required conduit size.
5. A ground terminal is provided near the power terminal board.
The ground wire should be connected before other connec-
tions are made.
6. The power terminal block is equipped with box terminals sized
to accept the correct size power supply wire. Branch circuit
wire rated min 600V, 60° C is acceptable for heaters rated up
to 80 amps. For heaters rated more than 80 amps, branch
circuit wire must be rated at least 75°C. Either aluminum or
copper wire is satisfactory for connection to the heater power
terminal block box terminal. Copper wire is recommended
and must be used with built-in disconnect switch.
7. Each heater has a wiring diagram affixed to the inside of the
access door. Consult this diagram before making any field
connections.
Important Note - Installation Screw Lug Torque:
During transportation it is possible screw lug connections can
loosen. After installation, before power is turned on to the
heater, check all screw lug connections for tightness to a recom-
mended minimum torque of 35 in-lbs. (3.9 N-m).
8. Single or three-phase power connections may be used with
heater models MUH0521, MUH0581, MUH072, MUH078,
MUH102, MUH108, and MUH158. These units are factory
wired for single-phase operation. If these heaters are for
use with three-phased power, reconnect the wires as indi-
cated in the wiring diagram attached to the heater.
Additional information can be found by looking at the wiring
illustrations in Figures 3a and 3b and following the directions
shown below.
On models MUH0521,MUH0581, MUH072, MUH078, MUH102,
and MUH108 (Figure 3a), move only the two wires marked “A1”
and marked “B1”; do not move or change any other wiring. The
element lead wire marked “B1” which is factory connected to the
power terminal block (terminal located closest to the elements)
must be moved to terminal “B” on the three-phase terminal
block.
The relay (contactor) lead wire “A1” must be moved from the
end terminal of the power terminal block (terminal closest to the
contactor or control terminal board) to the “A” terminal of the
lower terminal block (center terminal).
Model MUH158 (Figure 3b) has two three-phase terminal blocks
located adjacent to the relays (contactors). Move only the two
wires marked “C1” and “D1” on each of these two three-phase
terminal blocks to terminal “B”. Do not move or change any
other wires.
9. Electrical Accessories, either kits or factory-installed
options, are shown connected by a dash line on the heater
wiring diagram.
10. 208/240 VOLT HEATER: The heaters are wired for 240V
from factory. When heater is to be connected to 208V sup-
ply, the transformer leads have to be interchanged. For units
rated 30/40kW or higher, interchange ORANGE and RED
primary leads. The black colored lead is the COMMON for
the transformer (50VA) provided with the high wattage units.
For lower kW rated heaters, interchange BLACK and RED
primary leads. The WHITE colored lead is the COMMON for
the control transformer provided with these heaters. Always
refer to the wiring diagram on the cover of the heater before
making this reconnection of tranformer primary leads.
Control Wiring
1. Use min. 600 volts, NEC Class 1 insulated wire for all control
circuit wiring.
2. Use a crimp-on type fork terminal on the wire ends that attach
to the control terminal board if more than one connection is to
be made under the terminal screw.
3. On units not provided with internal contactor (3 & 5 KW), refer
to Figure 4 for wiring diagram.
Note: Thermostat and control circuit wiring must be suitable to
handle the full load of the heater (example MUH0581 is rated 24
amps)
4. On units provided with internal contactor (units rated 7 KW and
higher) refer to Figure 5 for wiring diagram. Control wiring
must be rated minimum 18 AWG.
LINE VOLTAGE IS PRESENT ON SOME OF THE TERMI-
NALS ON THE CONTROL TERMINAL BOARD. ALWAYS
DISCONNECT THE POWER FROM THE HEATER BEFORE
MAKING ANY CONNECTIONS TO THE CONTROL BOARD
TO PREVENT ELECTRIC SHOCK HAZARD.
3
Figure 2. Vertical Discharge Mounting and Rod Spacing
CEILING
B
A
C
K
W
A
L
L
S
I
D
E
W
A
L
L
ACCESS
DOOR
MOUNTING
ROD (4)
THREADED
MOUNTING
HOLES
CLEARANCE EQUAL TO WIDTH
OF HEATER TO PERMIT FULL
OPENING OF THE ACCESS DOOR
LOCK NUT
BACK WALL
E
H
F
G
(TOP VIEW)
Table 3. Rod Thread and Spacing Dimensions, inches (mm)
for Vertical Discharge
Rod Thread
Unit Type E F G H
3 - 5 kW
6 9 3 /
4
2 4 1 /
16
5 /
16
- 18
(152.4) 247.7) (50.8) (103.1)
7.5 - 20 kW
8 7 / 8 14 5 / 8 2 5 1 / 8
(225.6) (371.6) (50.8) (130.3)
25 - 30 kW 3 / 8 - 16
14 1 /
2
21 1 /
4
2 3 /
16
6 3 /
16
(368.3) (539.8) (56.0) (157.2)