Aprilaire 1953 & 1972 - Manual (Page 7)

7
INSTALLATION OF INTERNAL MOUNT ROOFTOP UNITS (MODEL 1972)
Wiring Access Cover
Mounting Brackets
Lamp Socket
Lamp
FIGURE 5 – Model 1972
90-744
CHECK LAMP OPERATION
The preferred method for checking lamp operation is to measure the current draw of the lamp using a clamp-on ammeter. To detect
the low current of the UV lamp, the ammeter must be capable of measuring 100 mA and above. To prevent accidental exposure to
harmful UV germicidal light during this procedure, the location where the amperage measurement is taken must be in a
separate compartment from where the UV lamp is installed. To measure the current draw of the lamp:
a. First, shut off power to the HVAC equipment.
b. Next, in the control panel for the HVAC equipment, locate the hot and neutral wires that were installed to provide power to the lamp.
c. Place the clamp-on ammeter around either the hot or neutral wire. Make sure the ammeter is set to read amps in the mA range.
Again, make sure that the UV lamp – or light from it, if it were on – is not visible from where the ammeter is placed.
d. Next, turn the power to the HVAC equipment back on.
e. If the lamp has been installed correctly and is drawing power, the amp reading will be a minimum of 150 mA. For multiple lamps,
the reading would be a multiple of this value, i.e., with two lamps installed, the amp reading will be at least 300 mA.
f. If the lamp is operating correctly, remove the ammeter from the wiring and put back any access panels that were removed during
this procedure. If the lamp is not operating correctly, refer to the ‘Troubleshooting’ section of this manual.
Note: If other electrical components or accessories share the same circuit as the UV lamp(s), the current draw will be higher and the
above method may not be an accurate indication of lamp operation.