Unit Installation
5.11.2 Thermostats with a Malfunction Light
If the unit is being connected to a thermostat with a malfunction
light, this co
nnection is made at the unit malfunction output or
relay.
If the thermostat is provided with a malfunction light powered
by the common (C) side of the transformer, a jumper must be
used between the “R” and “COM” terminals of the “ALR”
contacts.
If the thermostat is provided with a malfunction light powered
by the hot (R) side of the transformer, then the thermostat
malfunction light should be connected directly to the (ALR)
contact on the unit’s UPM board.
5.11.3 Thermostat to HVAC Equipment Wiring
The thermostat may not function properly if the total resistance
of any of the th
ermostat to HVAC equipment wires exceeds 2.5
ohms. To ensure that wire length does not cause excess
resistance, refer to Table 5 and ensure that the wires from the
thermostat to the HVAC equipment are not too long.
Table 5 Length by Wire Gauge for Thermostat to HVAC Equipment
Wiring
Copper Wire Gauge Maximum Wire Length
22 AWG (0,33mm
2
)
150 ft. (46m)
20 AWG (0,50mm
2
)
240 ft. (73m)
18 AWG (0,75mm
2
)
385 ft. (117m)
5.11.4 Remote Sensor to Programmable Thermostat Wiring
Because remote temperature sensors measure resistance, very
long cable
runs can cause slight errors in the measurement. For
the highest temperature reading accuracy, avoid exceeding the
maximum recommended wire lengths show in Table 6.
Table 6 Length by Wire Gauge for Remote Sensor to Programmable
Thermostat Wiring
Copper Wire Gauge Maximum Remote Sensor
Wire Length
22 AWG (0,33mm
2
)
1000 ft. (300m)
20 AWG (0,50mm
2
)
1500 ft. (450m)
18 AWG (0,75mm
2
)
2500 ft. (750m)
5.11.5 VA Capacity
Unit heat pumps are supplied with a 75 VA control transformer as
a standard. M
odels with hot gas reheat, modulating hot gas
reheat, economizer, and DDC are supplied with a 100 VA
transformer. The 100 VA transformers are available as optional
components for all unit sizes. The VA capacity of the transformer
must be considered when connecting low-voltage accessories to
the heat pump such as thermostats or solenoid valves. 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 the transformer capacity will result in low control
voltage, erratic unit operation, or damage to the heat pump.
| 17
EC Series Heat Pumps — 8733841499 (2024/05)
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