McQuay UH108 Installation Manual

Solid-State Speed Controller

CAUTION

!

Steam/Hot Water Unit Heaters

Installation Instructions 698-1

Group: Fan Coil
Date: March 2002

Application

For remote control of air delivery, a solid-state speed controller is
available for McQuay steam/hot water unit heaters. Models UH­18 through 108 with 115/60/1 motors (Power Code A).
A solid-state module in the controller controls motor input volt­age to maintain steady-state speed regulation at any setting be­tween “High” and “Low”. Controllers are packed separately and
must be connected according to wiring diagram, Figure 1 or 2.

NOTE: These controllers are not interchangeable with different
motor sizes or motor manufacturers. Before installation, check
unit heater model number, motor manufacturer and speed con­troller size (listed in Amps on back of controller), to verify compat­ibility. If not matched correctly and failure occurs, warranty will be
nullified. For UH86 and UH108 the speed control cannot be used
to turn unit on/off for 3-lead motors. A thermostat or disconnect
switch must be used.

Figure 1
Wiring Diagram - 2 wire motors (UH18 – UH63)

Wiring Connections

1. Disconnect line voltage supply from service at the main
electrical panel. Bring power supply leads into junction box.

2. Remove speed controller cover and make wiring connections
as per the appropriate wiring diagram.

Failure to wire this device according to the appropriate
diagram may result in failure of the equipment or injury to the
installer or user.

Operation Check

Set thermostat to lowest possible position. Turn controller to mini­mum speed. Turn on power to the system. Adjust thermostat above
room temperature. Motor will then start on lowest speed. Adjust
the controller to select the desired fan speed.

If motor does not start on lowest setting, the minimum control
speed may be adjusted. This can be accomplished by removing
the cover plate to the controller and turning the screw labeled
MIN SPEED ADJ with a small screw driver. Turn as indicated to
increase or decrease minimum set point. If the motor still does not
start, check power supply and wiring. On new motors, bearings
may be slightly tight until motor is “broken-in”. Do not adjust speed
controller below minimum speed level until motor has experienced
some running time. Periodically repeat above procedure if lower
speeds are desired.

Figure 2
Wiring Diagram - 3 wire motors (UH86 & UH108)

Installation

1. Controllers are furnished assembled and must be connected
between the fan motor and the thermostat; see Figure 1 or 2.

2. Install thermostat at desired location, (see instructions
packed with thermostat).

3. Install speed controller in a suitable location that will not
invite tampering.

ALL WIRING MUST COMPLY WITH NATIONAL ELECTRIC CODE AND
ALL LOCAL CODES. ALL COMPONENTS MUST AGREE WITH THEIR

®

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