Thermo Pride Air Handler MA User Manual

Page 25

External Relay Outputs

The control includes two outputs to drive external relays having 24 VAC

coils. The outputs have a maximum rating of 1.0 Amp pilot duty at 24

VAC.
HUM OUT
The HUM OUT output can be used to drive an external relay or solenoid

(24 VAC coil) to control a humidifier. The output is energized when the

HUM input is energized, the HUM STAT is in the YES position, and the

control has a thermostat call for heating (heat pump or electric heat).
EAC
The EAC output can be used to drive an external relay (24 VAC coil) to

control an electronic air cleaner. The output is energized whenever the

blower relay on the control is energized.

Heat Output and Limit Connections

The control is connected to the heater relays and limit switch using the

6-pin connector. The relay outputs and the limit switch signal are 24

VDC.
The control energizes the heat relays and senses the limit switch input

as shown in Table 4 when the HEAT ENABLE jumper is in the HEAT

position.

The control energizes the first stage of electric heat immediately, the

second stage 10 seconds after the call for second stage heat, and the

third stage 20 seconds after the call for third stage heat.

Depending on the heat kit installed in the air handler, the control pro-

vides the flexibility to configure the amount of heat delivered with the

first stage heating call. As an example, when the control’s W1 input is

connected to the room thermostat’s first stage heat signal, a call for first

stage heat will energize one heating element (HT1). If the control’s W2

input is connected to the room thermostat’s first stage heat signal, a call

for first stage heat will energize two heating elements (HT1 and HT2).

With either configuration, the control will energize three heating ele-

ments (HT1, HT2, and HT3) when it receives a first and second stage

heat input from the thermostat.

Limit Switch and Lockout Operation

Limit Switch Operation
If the HEAT ENABLE jumper is in the HEAT position and the limit switch

opens (fault code 1), the control will immediately de-energize all electric

heat relay outputs and energize the blower (if it wasn’t already ener-

gized). When the limit switch closes, the control will re-energize electric

heat according to the thermostat inputs using normal timings.
Fan On Lock Condition
If the limit switch opens multiple times during a single call for electric

heat (fault code 3) or if the limit switch opens for a long duration (fault

code 4), the control will energize the blower until power is removed from

the control. The control will cycle the heat outputs on and off as the limit

re-closes and opens. The constant fan operation will signal the home-

owner that a problem has occurred and a service call is required.
Soft Lockout
If the limit switch opens for a second long duration period during a sin-

gle call for heat (fault code 5), the control will keep the blower locked on

and lock out the heat outputs for one hour. The control will only reset

this one hour lockout when the power is removed from the control. After

the one hour period has passed, the control will re-energize electric

heat according to the thermostat inputs using normal timings. The

blower will remain locked on from the first long duration limit opening.
Hard Lockout
The control has a hard lockout condition during which the control will

keep all heat outputs de-energized until power is removed from the con-

trol. The control de-energizes the blower five minutes after entering the

hard lockout condition.

If the limit switch closes and re-opens during the one hour soft lockout

period, the control will enter a hard lockout condition and continue to

indicate a fault code 5.

If the limit switch opens twice when no call for electric heat is present

(fault code 2), the control will enter a hard lockout condition.

If the limit switch opens multiple times soon after a soft lockout reset

(fault code 6), the control will enter a hard lockout condition.
Wiring Related Faults
If the control receives a simultaneous call for heating and cooling (fault

code 7), the control will perform both heating and cooling operations.

SECTION VII: LINE POWER CONNECTIONS

Power may be brought into the unit through the supply air end of the

unit (top when unit is vertical) or the left side panel. Use the hole appro-

priate to the unit’s orientation in each installation to bring conduit from

the disconnect. The power lead conduit should be terminated at the

electrical control box. Refer to Tables 10, 11, 13 or 14 to determine

proper wire sizing. Also see Figure 3. To minimize air leakage, seal the

wiring entry point at the outside of the unit.

TABLE 3: Fault Codes

Fault or Status Condition

LED1 (RED)

Flash Code

Status
No power to control

OFF

Normal operation

2s ON / 2s OFF

Control in test mode

Rapid Flash

Control failure

Limit Faults
Limit switch currently open (not in lockout)

Multiple limit openings with no call for heat

Multiple limit openings during one call for heat

Single long duration limit opening

Multiple long duration limit openings

Fan failure

Wiring Related Faults
Simultaneous call for heating and cooling

Internal Control Faults
Control recovered from internal event

TABLE 4: Heat Relays

Input

Heat Relay Output

HT1

HT1 and HT2

W1 and W2

HT1 and HT2 and HT3

This manual is related to the following products:

Air Handler MV