Va Capacity; Thermostat To Hvac Equipment Wiring - Bosch QV Series Installation, Operation And Maintenance Manual

16 | Electrical—Low-Voltage Wiring
thermostats on an interior wall away from supply
ducts.
Avoid external walls and locations subject to direct
sunlight and drafts. Thermostat wiring must be
18AWG (American Wire Gauge). Refer to the
installation instructions of the thermostats for
further details.
Refer to the installation instructions for the
thermostat for further details.
NOTICE: To prevent voltage drops in the
control circuit,
recommended thermostat wire lengths
detailed in Table 3.
Connection
Y1
First-Stage Compressor Operation
G
Fan
O
Reversing Valve (energized in
cooling)
W1 Auxiliary Electric Heat (runs in
conjunction with compressor)
NC
Transformer 24 VAC Common
(extra
connection)
C1
Transformer 24 VAC Common
(primary
connection)
R Transformer 24 VAC Hot
H Dehumidification Mode
Table 1 Thermostat Connections Options
8733829041 (2021/07)
do not exceed the
Function
Subject to change without prior notice

VA Capacity

Unit heat pumps are supplied with a 50VA control
transformer as a standard. Models with DDC, hot
gas reheat or an economizer are supplied with a 75
VA transformer. The 75 VA and 100 VA
transformers are available as optional components
for most models (size 018 and larger for 100 VA).
The VA capacity of the transformer must be
considered when connecting low-voltage
accessories to the heat pump such as thermostats
or solenoid valves. Table 2 shows the VA draw of
factory-mounted components in the low-voltage
heat pump. The total VA draw of the heat pump
internal components plus attached accessories
must be lower than the VA capacity of the unit
control transformer.
WARNING: Exceeding
capacity will result in low control voltage,
erratic unit operation, or damage to the
heat pump.
Standard Construction
Component VA
Reversing Valve Solenoid 8–9
Compressor Contactor 6-8
UPM Board 2
Total VA Draw 22–26
Table 2 Low-Voltage VA Draw —Standard Construction, Hot Gas
Reheat or Economizer, and Optional Components

Thermostat to HVAC Equipment Wiring

The thermostat may not function properly if the
total resistance of any of the thermostat to HVAC
equipment wires exceeds 2.5 ohms. To ensure that
wire length does not cause excess resistance, refer
to Table 3 and ensure that the wires from the
thermostat to the HVAC equipment are not too
long.
QV Series Heat Pumps
the transformer
Optional Components
Component VA
Monitor Relay (VA draw 6–7
per relay)
Internal 7
Two-Way
Motorized Valve
LED Annunciator 1
QV Series Heat Pumps