Carrier 50BK - Manual (Page 15)

START-UP
General — The 50BJ,BK. units are designed for use
in Modu-Vac Variable Air Volume Systems using
Carrier 37A Moduline® and 35B Modubox Air
Terminals. For air terminal installation and adjust­
ment, refer to 37 A or 35B literature as required.
CAPACITY CONTROL — The units are equipped
with electrie unloaders on the lead compressor
(Fig. 17) and hot gas bypass on the no. 1 refrigerant
system. (Size 016 units have only one refrigerant
system.)
Unit capacity is monitored and controlled by a
Honeywell W7100 microprocessor (Fig. 20). This
controller provides the number of capacity control
steps as shown in Table 8.
Table 8 — Capacity Control Steps
UNITS I CAPACITY CONTROL
50BJ.BK I (No. Steps)
016 I 3
024,028,034 6
044 4
054,064 6
Fig. 20 — Honeywell Microprocessor
TIMER CONTROL — Carrier strongly recom­
mends use of an accessory timer control panel with
the 50BJ,BK units. Installation and adjustment of
this device (Fig. 21) is covered in separate Installa­
tion, Start-Up and Service Instructions included in
the accessory package.
If accessory timer is not used, install field-installed
manual switch between TB3 terminals [~T~| and
in the variable volume eontrol box for the 016-034
units. Switeh is factory-installed on the 044-064
units.
Fig. 21 — Accessory Timer Control Panel
MOISTURE INDICATORS are located ahead of
thermal expansion valves. They must be full of
liquid
to properly indicate moisture content.
Operate system for 30 minutes before determining
moisture content.
SERVICE VALVES (50BK) — Valves use teflon
seat washers to ensure position seal with minimum
stem torque (10 Ib-ft max). Do not overtighten valve
stem. Use wet rag on valve when soldering. If refrig­
erant has been lost, midseat valve. Always replace
stem cap.
Prior to Unit Start
1. Clean and inspect the unit.
2. Open (backseat) compressor service valves and
liquid line shutoff valves. Replace and tighten
valve caps to prevent leakage.
3. On 50BK (air-cooled condenser) units, turn on
indoor fan motor circuit breaker. Check that
compressor crankease heaters are energized and
crankcase oil level is half full.
4. Leave crankcase heaters energized for 24 hours
to ensure safe oil/ refrigerant mixture in crank­
cases for unit start-up.
Control Sequence Checkout
1. Perform all applicable steps described above
under Prior to Unit Start.
2. Turn on unit main power supply.
^3. Set the control band knob on microprocessor
(Fig. 20) at 2.
4. Turn on indoor fan motor circuit breaker.
5. If unit is equipped with accessory timer control
panel and 7-day clock is not calling for cooling,
turn on unit by overriding clock with manual
bypass
switch (see Start-Up General section
entitled, TIMER CONTROL).
6. Close compressor circuit breakers.
7. Check for cooling by turning microprocessor
SETPOINT knob to 40 F. Light-emitting diodes
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