Four equally rated heating elements are contained in a forced air-heating unit. These are sometimes called FBUs (Fan Blower Units) because a blower motor forces air over the heating elements to provide heated air for a room.
Figure 115.342 Forced-Air Heating Unit
Your calculations will not include any power requirements for the blower motor in the FBU. The nameplate on the FBU indicates that it will deliver a total of 11.2 kW of heat when the supply circuit is 250 volts.
5. Refer to the illustration of the FBU and the information shown with Figure 115.342. The "hot" resistance of Element 3 (R3) is ____ ohms.
a. 1.2857
b. 1.3951
c. 5.5804
d. 5.1429
e. 4.7246
6. Refer to the illustration of the FBU and the information shown with Figure 115.342. When operated at exactly 240 volts the actual power used by Element 4 (P4) is ____ kW.
a. 10.332
b. 2.580
c. 11.200
d. 2.800
e. 14.064
Figure 116.418
The actual output voltage of the power supply is 472 volts. Hint: This is your applied voltage (Ea or ET). Element 1 (R1) is rated at 4.8 kW @ 250 volts and Element 2 (R2) is rated to put out 5.2 kW @ 240 volts.
7. Refer to Figure 116.418. The fixed resistance of Element 2 is ____ ohms.
a. 21.3056
b. 11.4556
c. 11.0769
d. 22.0339
e. 8.8757