ECR International MPL-B, Operation And Maintenance Manual

30318 R4 9/9/2005 

9

trunk ducts. These systems may require 
modification to provide some resistance 
to the airflow to prevent over-amping of 
the direct drive blower motor. Selecting a 
lower blower speed may correct this 
problem. 

Direct drive blower speeds are adjusted 
by changing the "hot" wires to the motor 
winding connections. Please refer to 
wiring diagram in Appendix B or the 
wiring diagram label affixed to the 
furnace. 

THE NEUTRAL WIRE 

(normally the white wire) IS NEVER 
MOVED TO ADJUST THE BLOWER 
SPEED

. 

DO NOT CONNECT POWER LEADS 
BETWEEN MOTOR SPEEDS. THE 
NEUTRAL WIRE MUST ALWAYS BE 
CONNECTED TO THE MOTOR'S 
DESIGNATED NEUTRAL TERMINAL. 

It is possible and acceptable to use a 
single blower speed for both heating and 
cooling modes. The simplest method to 
connect the wiring from both modes is to 
use a "piggy-back connector" 
accommodating both wires on a single 
motor tap. It is also acceptable to 
connect the selected motor speed with a 
pigtail joined to both heating and cooling 
speed wires with a wire nut. As a safety 
precaution against accidental 
disconnection of the wires by vibration, it 
is advisable to secure the wire nut and 
wires with a few wraps of electricians 
tape. 

If the joining of the blower speed 
wiring is done in the furnace junction 

box, tape 

off both ends of the unused 

wire. 

DISCONNECT THE POWER SUPPLY 
TO THE FURNACE BEFORE 
OPENING THE BLOWER ACCESS 
DOOR TO SERVICE THE AIR FILTER, 
FAN AND MOTOR. FAILURE TO 
SHUT OFF POWER COULD ALLOW 
THE BLOWER TO START 
UNEXPECTEDLY, CREATING A RISK 
OF DEATH OR PERSONAL INJURY. 

Do not use the blower speed wires as 
a source of power to accessories as 
electronic air cleaners and humidifier 
transformers. The unused motor taps 
auto-generate sufficiently high 
voltages to damage accessory 
equipment. Use the terminals 
provided on the electronic fan timer.  

Do not start the burner or blower fan 
unless the blower access door is 
securely in place. 

Additional ST9103 Fan Timer Control 
information is in Appendix A, Tables, and 
in Appendix B, Wiring Diagrams. 

HUMIDIFIER

A humidifier is an optional accessory 
available through most heating supplies 
outlets. Installation should be carried out 
in accordance with the humidifier 
manufacturer's installation instructions. 
Water or water droplets from the 
humidifier should not be allowed to come 

into contact with the furnace heat 
exchanger. Do not use direct drive motor 
connections as a source of power for 
120 VAC humidifiers and humidifier 
transformers. 

OIL BURNER 

The oil burner must align properly with 
the cerafelt fiber chamber (firepot). The 
cerafelt fiber chamber is initially quite 
soft, but hardens and becomes quite 
brittle after the first firing. The firepot is 
held in place by a retaining bracket; 
however, it is possible for the firepot to 
shift if subjected to rough handling during 
transit. 

BEFORE OPERATING THE 
FURNACE CHECK BURNER 
ALIGNMENT WITH COMBUSTION 
CHAMBER. THE END CONE OF THE 
AIR TUBE MUST BE CENTRED TO 
THE ACCOMODATING RING 
PROVIDED IN THE DESIGN OF THE 
COMBUSTION CHAMBER. ADJUST 
ALIGNMENT AS NECESSARY 
BEFORE THE FIRST FIRING. 

OIL BURNER NOZZLES 

WML-C AND MPL-B furnaces are 
certified for multiple firing rates, ranging 
from approximately 58,000 to 85,600 
BTU/hr. on the WML-C and 85,500 to 
123,000 BTU/Hr. on the MPL-B By 
changing the oil burner nozzle within the 
specific model range, and temperature 
rise, the furnace may be fired at an ideal 
rate for a wide range of structures. 

Figure 4: Horizontal Smoke Test Port Location 

Figure 5: Vertical Smoke Test Port Location