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Prestige® 2-Wire IAQ Equipment Interface Module
Prestige® 2-Wire IAQ Equipment Interface Module


Prestige® 2-Wire IAQ Equipment Interface Module

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Equipment Interface Module controls up to 4-stages of heat and 2-stages of cool in a heat pump system and up to 3-stages of heat and 2-stages of cool in a conventional system. Three sets of Universal IAQ contacts to control humidification, dehumidification, and ventilation. Four sensor inputs for wired sensors or dry contact devices.

Product Specifications

Gas, oil, electric, heat pump, forced warm air, hot water, steam or gravity
Dimensions (in.)
9 5/16 in. High, 4 13/16 in. Wide, 1 5/8 in. Deep
Dimensions (mm)
237.4 mm High, 122.5 mm Wide, 40.6 mm Deep
THM5421R1021 Equipment Interface Module
Used With
All THX9421R5021 Prestige® 2-Wire IAQ Thermostats and all versions of Prestige® IAQ Thermostats and the VisionPRO® Thermostats with RedLINK™ technology.
Item Type
Electrical Ratings
18 to 30 Vac
50 Hz; 60 Hz
Up to 4 Heat / 2 Cool Heat Pump or Up to 3 Heat / 2 Cool Conventional
Electrical Connections
Screw terminals
Operating Humidity Range (% RH)
5 to 95% RH, non-condensing
Supply Voltage
18 to 30 Vac
Operating Temperature Range (F)
-40 F to 165 F
Operating Temperature Range (C)
-40 C to 73.9 C
Power Method
Terminal Designations
R, RC, RH, C, W-O/B, W2-AUX1, W3-AUX2, Y, Y2, G, A-L/A, U1, U1, U2, U2, U3, U3, S1, S1, S2, S2, S3, S3, S4, S4, A, B, C, D
Cool Current
1.0 A running
Heat Current
1.0 A running
Fan Current
0.5A running