1. DAY 17 CHAPTER 28 OVERCURRENT PROTECTION FUSES AND CIRCUIT BREAKERS

2. FIVE CIRCUIT CONDITIONS
1. NORMAL LOADING
2. OVERLOAD
3. SHORT CIRCUIT
4. GROUND FAULT
5. OPEN

3. NORMAL CIRCUIT
THE CONDUCTORS CAN SAFELY CARRY THE CURRENT. THEY DO NOT GET HOT. THE 15A FUSES DO NOT OPEN.
CONDUCTORS RATED AT15A
CONDUCTOR RESISTANCE=0.001Ω
15A FUSE A
240V SOURCE
SOURCE R=1mΩ
24Ω
LOAD RESISTANCE
15A FUSE

4. THE CONDUCTORS BEGIN TO GET HOT, BUT THE 15A FUSES
OVERLOADED CIRCUIT
THE CONDUCTORS BEGIN TO GET HOT, BUT THE 15A FUSES
WILL OPEN BEFORE THE CONDUCTORS ARE DAMAGED.
CONDUCTORS RATED 15A
CONDUCTOR RESISTANCE=0.001Ω
15A FUSE
19.995A
240V SOURCE
SOURCE R=1mΩ
24Ω
24Ω
15A FUSE

5. SHORT CIRCUIT THE CONDUCTORS GET EXTREMELY HOT. THE INSULATION AND THE
CONDUCTORS WILL MELT UNLESS THE FUSE OPENS QUICKLY.
LOAD RESISTANCE
CONDUCTORS RATED 15A
CONDUCTOR RESISTANCE=0.001Ω
15A FUSE
80,000A
240V SOURCE
SOURCE R=1mΩ
24Ω
15A FUSE
SHORT CIRCUIT PATH

6. GROUND FAULT
WHEN A HOT CONDUCTOR COMES IN CONTACT WITH METAL AND THE RETURN PATH HAS HIGH RESISTANCE THE BREAKER WILL NOT TRIP. THE METAL WILL HAVE THE SAME VOLTAGE AS THE HOT.THE VAULE OF RESISTANCE CAN VARY GREATLY DUE TO THE DIFFERENCE COMPOENTS ALONG THE CIRCUIT PATH, MAKING IT HARD TO FIND THE GROUND FAULT CURRENT VALUE.
HOT CONDUCTOR
SOURCE
GROUNDED CONDUCTOR

7. X OPEN CIRCUIT THE CIRCUIT HAS AN OPEN, NO CURRENT WILL FLOW.
CONDUCTORS RATED 15A
CONDUCTOR RESISTANCE=0.001Ω X
15A FUSE
OPEN
240V SOURCE
SOURCE R=1mΩ
24Ω
LOAD RESISTANCE
15A FUSE 0A
ANY OPEN HAS INFINITE RESISTANCE

8. FUSES/CIRCUIT BREAKERS: PROTECT CIRCUIT FROM CURRENT OVERLOAD.
SHORT : UNWANTED PATH THAT CURRENT TAKES.
PARTIAL SHORT :ONLY PART OF LOAD IS SHORTED OUT.
DEAD SHORT : ALL OF THE LOAD IS SHORTED OUT.

9. SCREW BASE FUSES HAVE RATINGS FROM 0 TO 30AMPS

10. Fuses have two types of bases, the Edison Base (Type T fuses) and the Rejection Base (Type S fuses), also known as a "tamper-proof base".
The Edison Base Type T fuse works with the typical socket used in the fuse box seen in older homes and the fuse base looks like a light bulb base.
A Rejection Base Type S fuse actually consists of two components, an adapter base that screws and locks into the Edison socket in the fuse box, and the fuse itself. Each different amperage rating of a Type S fuse has a matching socket base adapter with a different sized thread that prevents mismatching (rejection base). It stops a person from putting a 20 Amp rated fuse in a 15 Amp circuit.

11. REJECTION BASE, TYPE S FUSE

13. DUAL ELEMENT FUSE
The Bussmann S Series Plug Fuse is for all-purpose applications. It's like two fuses in one. Features include a simple link element for short-circuits and dangerous overloads, plus a series-connected element which lets the harmless overload starting currents of motors pass without opening. It uses less energy, operates cooler, and provides superior protection.

16. CARTRIDGE FUSES ARE RATED FROM 1/8 T0 600 AMPS IN BOTH 250V AND 600V

18. CARTRIGE FUSES CAN BE USED AS THE MAIN DICONNECT MEANS

22. 115KV FUSE

23. FUSES

24. CIRCUIT BREAKERS: TWO TYPES: THERMAL,MAGNETIC
THERMAL:CAN BE RESET MANUALLY OR AUTOMATIC. AUTOMATIC RESET OCCURS AFTER BREAKER HAS COOLED.

25. Circuit Breaker: A device designed to open and close a circuit by nonautomatic means and to open the circuit automatically on a predetermined overcurrent without damage to itself when properly applied within its rating.

26. DUAL POLE
SINGLE POLE

27. THREE POLE BREAKER WITH HANDLE TIE
TWO POLE

29. MAGNETIC CB: WHEN A OVERLOAD OCCURS A BIMETALLIC ELEMENTS UNLATCHES THE INNER TRIP MECHANISM. A MOMENTARY OVERLOAD DOES NOT CAUSE THE BREAKER TO TRIP. IF THE OVERLOAD IS HEAVY, A MAGNETIC COIL CAUSES IT TO TRIP.

32.
Circuit Breaker Animation & Working

33. MULTI WIRE BRANCH CIRCUITS MUST HAVE HANDLE TIES
ON CIRCUIT BREAKER FOR SIMULTANEOUS TRIPPING.

34. OCPD (OVERCURRENT PROTECTION DEVICES) LOCATIONS
Location in or on Premises.
Accessibility. Overcurrent devices shall be readily accessible and shall be installed so that the center of the grip of the operating handle of the switch or circuit breaker.
(D) Not in Vicinity of Easily Ignitible Material. Overcurrent
devices shall not be located in the vicinity of easily
ignitible material, such as in clothes closets.
(E) Not Located in Bathrooms. In dwelling units and
guest rooms or guest suites of hotels and motels, overcurrent
devices, other than supplementary overcurrent protection,
shall not be located in bathrooms.
(F) Not Located over Steps. Overcurrent devices shall not
be located over steps of a stairway.
230.79(C) One-Family Dwellings. For a one-family dwelling,
the service disconnecting means shall have a rating of not
less than 100 amperes, 3-wire.

36. Noalox Anti-Oxidant Compound
Reduces galling and seizing on aluminum conduit joints
Suspended zinc particles penetrate and cut aluminum oxide
Carrier material excludes air to prevent further oxidation
Improves service life of aluminum electrical applications