1What is the main difference between a relay and a contactor?
Relay rated at lower amperage
2Are the contacts in standard contactors normally open or normally closed?
Normally open
3Is the life expectancy of a contactor longer or shorter than that a relay and why?
Shorter, it handles much more current
4What causes the plastic movable contact carrier to warp in contactors?
Heat, and wear from frictions
5What malfunctions result when the movable contact carrier does warp?
The contactor sticks pulling or dropping out
6What is the usual cause for a burned out contactor coil?
Warped movable contact carrier, keeping the armature and magnet from pulling right together
7Why is it not advisable to replace just a coil in a contactor when the coil fails, even if it is available as a separate replacement part?
It will fail again soon
8Contacts that are melted to welded together indicate what?
Short circuit
9What causes carbon build up around the plastic or bakellite body of a contactor?
Electrical arcing
10On what contactors does carbon build up become a major and dangerous condition?
480 volt
11Do contactor contacts that look dark in color necessarily mean that the contactor needs to be replaced?
No
12Do contacts that look like they have a rough surface indicate that the contactor should be replaced?
No
13What will contactors look like in a contactor when the contactor should be replaced?
Worn thin or cratered out
14When contactor coils fail, is it always an immediate process or can the failure happen gradually?
15What often causes pilot circuit fuses to blow in circuits that use contactors?
Shorted contactor coils
16How do you check a contactor coils to ensure that it is alright?
Ohm it with a meter and compare it to a chart, or to an exact duplicate contactor
17When a contactor buzzes when it is energized, what is the problem?
Worn, the armature is not pulling down tightly
18When a contactor chatters when energized, where is the problem?
In the controls
19Will replacing a chattering contactor solve the problem?
No
20What can be used to eliminate a chattering problem in a contactor?
A capacitor across the contactor coil
21 A capacitor used in a contactor circuit should always be connected where?
Across the contactor coil
22Can a capacitor in a contactor circuit be connected across the control operating the coil?
No, if it shorts, it bypasses the control
23What is the danger of connecting a capacitor across the control contacts?
If it shorts, it will bypass the control
24Which is greater, the FLA rating or the resistive rating on a contactor?
Resistive
25The full load rating of a contactor is used to determine its capacity for what kind of load?
Motor load
26What is the advantage of a mercury contactor?
Can cycle millions of times without wear or damage
27How does a mercury contactor operate?
The coil pulls a steel cylinder down in a tube of mercury, displacing the mercury so that it touches both contact points
28Are mercury contactors direction specific?
Yes, they need to be mounted with "Top or Up" at the top
29Why do mercury contactors fail?
Loose connections
30What opens and closes the circuit in a solid state relay?
Triac
31Solid state Relays are very susceptible to what problem in commercial cooking equipment?
Heat
32What must you do when installing a new solid state relay?
Heat sink it, and make sure wire and terminals are in perfect shape
33What is the only way to check the operation of a solid state relay?
Ammeter
34Solid state Relays are most often switched on gut with what type of voltage?
AC
35Solid state Relays usually fail in what mode?
Closed circuit
36What is the difference between an AC and DC relay?
Coil resistance
37Are AC and DC relays interchangeable?
No
38Why are more DC relays being used in hot and cold side equipment today?
Because the output from most solid state controls is DC voltage