Crown Boiler CHC68-96 用户手册

 
One way to measure the temperature rise across the furnace is to insert temperature 
measuring devices (e.g. thermometers) into the return air duct and into the supply air 
duct about 12 inches from the furnace. After the furnace has been firing continually for 
over 20 minutes, read the temperature difference between the two (2) thermometers. 
The temperature difference should not exceed 100ºF, nor be less than 70ºF. A 
temperature rise of 85ºF is considered to be optimum for comfort. For better energy 
efficiency, a temperature rise closer to 70ºF is recommended. 
 
The blower (fan) speed fan is adjusted by changing the fan motor winding energized by 
the control system. The furnace is set on the lowest fan speed, “L”, at the factory, refer 
to Table 2. To adjust the fan speed, follow this procedure. 
 

a.  Turn off all electrical power to the furnace at the disconnecting switch. 

 

b.  Remove the blower compartment access door. 

 

c.  Move the orange wire from the low speed terminal block, marked “L”, to the next 

higher fan speed (medium low), marked “ML” on the terminal block, refer to 
Figure 8. Other available higher fan speeds are medium high, marked “MH” and 
high, marked “H”. 

 

 

d.  Replace the blower compartment access door.  
e.  Restore electrical power to the furnace at the disconnecting switch. 

 

With the furnace operating, measure the air temperature rise across the furnace again. 
If the value does not fall in the range of 70 to100ºF, repeat the above procedure. 
 

24