publication

Single Stage Equipment

Compressor Relay

SINGLESTAGEHVAC CONNECTIONS

MMZ3

HVAC EQUIPMENT

R 24V. Transformer C

Heat Relay

EQUIPMENT

C W R Y G

OPEN

COM

DAMPER

ZONE THERMOSTAT

Power Closed

Power Open

24VAC Common

To Damper Motor

See Damper Wiring

Instructions

SINGLE STAGE THERMOSTAT

TRANSFORMER CONNECTIONS

WIRING DIAGRAM 3 – 24 Volt AC, 40 VA Transformer

WIRING DIAGRAM 1 – Zone Thermostat and Damper

MMZ3

24VAC

CMM-3

LEAVING AIR SENSOR (CLAS)

The Leaving Air Sensor, Model CLAS, is a remote sensor that is lo-

cated in the supply air duct to sense the leaving air temperature of the

HVAC Unit. The CLAS is a high limit protection for the heating and a

low limit protection for the cooling. When zoning, the airflow through

the HVAC Unit is critical. The CLAS protects the equipment in low air

flow situations as well as when by-pass air is being directed back into

the return air duct.

The heating limit is fixed at 180°F. The cooling limit is fixed at 40°F.

When the CLAS senses heating above its set point, or cooling below

its set point, the CMM3 will drop both stages of heating or cooling. The

CLAS must sense a 10°F fall for heating or rise for cooling before re-

activating the first stages of heating or cooling. If two stage heating or

cooling is being used the second stage timer will start again once the

first stage is re-activated.

The CLAS requires 2 wires from the sensor to the LAT terminals on

the CMM3 panel. The CLAS probe can also be adjusted for length by

loosening the end nut and sliding the probe thru the mounting plate in

order for the probe to pass through any duct insulation.

LAT1

Leaving Air Sensor

Mounted in Supply Air Plenum

End Nut

Adjustable Length by loosening end

nut, adjusting length and re-tightening

LAT2

NOTE: If the CLAS is not used, the NO SENSOR jumper located

just above the LAT terminals must be on the pins.

TROUBLESHOOTING

The CMM-3 is a very simple control to troubleshoot, especially with

the LED indicators. The only other device needed is a simple Volt/

Ohm meter.

The first check is for 24VAC Power to the panel. When there is power

the Green Power LED will be lit. If not check the transformer and the

power supply to it.

Almost all problems can be traded to an external component or wiring

to the CMM-3. While the CMM-3 has been designed to operate under

extreme voltage conditions and is fuse protected, like any computer

the micro-processor can hang up and not operate properly. For these

instances a BOOT button has been installed that re-boots the micro-

processor just like your computer. Pressing this button for a few seconds

and then release it will allow the micro-processor to re-boot and in most

all cases eliminate the problem. If not the following procedure can help

isolate the problem.

Zone(s) Not Calling

Each zone has a Green LED next to the zone relay when it is calling.

The LED being lit shows that the call is being recognized by the CMM-3.

If a zone is supposed to be calling and the Zone LED is not on, check

for 24VAC across the thermostat terminal C and the Y, if a Cool call, W

if a Heat Call, or G if a Fan call. If there is no voltage here at the panel

the panel is not getting the signal from the thermostat. The problem is

mis-wiring, a broken wire or a problem in the thermostat. To check the

zone on the panel, place jumper from R to Y to simulate a Cool call, R to

W to simulate a Heat call, or R to G to simulate a Fan call. By jumpering

these terminals the zone call LED will activate.

Zone(s) Will Not Shut Off

If a zone will not stop calling, the Zone LED should still be on. Depend-

ing on the call disconnect the Y, W or G wire from the terminal strip.

The zone will drop out. Check the thermostat wiring for a mis-wiring or

short that keeps the zone calling.

Damper Motor Checkout

To checkout the dampers, the panel provides 24VAC to the COM and

OPEN terminal when the damper is to be open and 24VAC to COM and

CLOSE when the damper is to be CLOSED. When any zone is calling

and its Green LED is ON, there is 24VAC across COM and OPEN. The

only time a damper will close is when another zone is calling and its

zone is not calling. In this instance there will be 24VAC across COM

and CLOSE terminals. Refer to the instructions with each damper for

their individual checkout.

CMM-3

CMM-3K

ZONE PANELS

www.white-rodgers.com

217

TECHNICAL HELP