25
Single Point Boxes and Supplementary Fuses
When the unit MOCP device value exceeds 60-A, unit-mounted
supplementary fuses are required for each heater circuit. These
fuses are included in accessory single point box, with power distri
-
bution and fuse blocks. The single point kit fuse holder and termi
-
nal block will be installed into the unit control box-back wall, bot
-
tom left corner. See Fig. 37. The single point box also includes a
set of power taps to complete the wiring between the single point
box and the unit’s main control box terminals. Refer to accessory
heater and single point box installation instructions for details on
tap connections.
On 50TCQ units, all fuses are 60-A. Single point boxes containing
fuses for 208/230-v applications use UL Class RK5 250-v fuses
(Bussman FRNR 60 or Shawmut TR 60R). Single point boxes for
460-v and 575-v applications use UL Class T 600-v fuses
(Bussman JJS 60 or Shawmut A6T 60). (Note that all heaters are
qualified for use with a 60-A fuse, regardless of actual heater am
-
pacity, so only 60-A fuses are necessary.)
Unit heater applications not requiring supplemental fuses require a
special single point box without any fuses. Connect power supply
conductors to heater conductors and field-supplied base unit pow
-
er tap leads (see “Completing Heater Installation”) inside the emp
-
ty single point box using UL-approved connectors.
SAFETY DEVICES
Electric heater applications use a combination of line-break/auto-
reset limit switches and a pilot-circuit/manual reset limit switch to
protect the unit against over-temperature situations.
Line-break/auto-reset limit switches are mounted on the base plate
of each heater module. See Fig. 38. These are accessed through
the indoor access panel. Remove the switch by removing two
screws into the base plate and extracting the existing switch.
Pilot-circuit/manual reset limit switch is located in the side plate of
the indoor (supply) fan housing. See Fig. 38.
Fig. 37 —
Typical Single Point Installation
Fig. 38 —
Typical Location of Heater Limit Switches (3-phase heater shown)
Fuse
Holder
Terminal
Block
RED (HI-TEMP)
FEED WIRES THRU
STRAIN RELIEF BUSHING
IN CONTROL PANEL
INSULATED
TERMINALS
AT LIMITS
HTR 1
BLUE
12 GA.
BLUE
12 GA.
YELLOW
12 GA.
YELLOW
12 GA.
BLACK
12 GA.
RED (HI-TEMP)
BLACK
12 GA.
BLACK 12 GA.
BLACK
12 GA.
18 GA.
HTR 2
Summary of Contents for WeatherMaker 50TCQ 17-24 Series
Page 35: ...35 Fig 53 RTU Open Overlay for Economizer Wiring ...
Page 36: ...36 Fig 54 VFD Overlay for W2770 Controller Wiring ...
Page 68: ...68 Fig B 50TCQD17 24 Control Wiring Diagram APPENDIX D WIRING DIAGRAMS ...
Page 69: ...69 Fig C 50TCQD17 24 Power Wiring Diagram 208 230 3 60 Units APPENDIX D WIRING DIAGRAMS ...
Page 70: ...70 Fig D 50TCQD17 24 Power Wiring Diagram 460 3 60 575 3 60 Units APPENDIX D WIRING DIAGRAMS ...
Page 71: ...71 Fig E RTU Open Overlay APPENDIX D WIRING DIAGRAMS ...
Page 72: ...72 Fig F PremierLink Overlay APPENDIX D WIRING DIAGRAMS ...