In a three-heat switch, how are the elements connected at a low level of heat at 25% of power consumption?
Both elements are connected in series
In a three-heat switch, how are the elements connected at a medium level of heat at 50% of power consumption?
Only one element is connected
In a three-heat switch, how are the elements connected at a high level of heat at 100% of power consumption?
Both elements are connected in parallel
How does a thermostat work?
By sensing temperature and regulating the temperature by closing or opening contacts to control the load
What controls can be used for auto temperature control?
Thermostat
Electronic control
Simmerstat
What type of thermostats do ovens and metal plating mostly use?
Simmerstat control thermostats
What type of thermostats do cooktops and stoves mostly use?
Bulb and capillary thermostats
What type of thermostats does the industrial sector and instrumentation mostly use?
Strut and tube thermostats
What type of thermostats do irons and grills mostly use?
Bi-metal thermostats
The OTC (Over Temperature Cut-out) is used to ensure cut-out in the event of thermostat failure. What temperature should it be set to?
95°C
What is the valve that prevents water within the water heater from exceeding 99°C by discharging the water to the drain line?
Pressure and Temperature Relief Valves (PRV)
What is the name of the device that's installed to protect the steel, brass or copper of the tank, element or valves from the corrosive effects of galvanic action?
A Sacraficial Anode
What is the method for checking a sacraficial anode in a water heater?
a Visual inspection of the sacrificial anode
If a thermostat of an air conditioner working in cool mode was working on a 4⁰C differential and it "cuts out" at 21 ⁰C when would it "cut in"?
25 ⁰C
TRUE or FALSE
A Device with a small differential will have a higher cyclic rate of switching whereas a device with a larger differential will switch less often
True
Where should the thermometer be located to test the correct operation of a thermostat using a thermometer?
Near the probe of the thermostat
TRUE or FALSE
In electronic heat control, Zero voltage switching (ZVS) is a method of controlling the applied voltage to heating elements by which thyristors are used to regulate the supply voltage
True
TRUE or FALSE
For instantaneous water heater, the turning on of the kitchen tap allows the mains pressure water to be introduced into the unit, engaging the operation of a water flow switch. Flow switch controls the energy to the electric heating
True
What temperature should the thermostat be set at to deliver an acceptable temperature for mains-pressure water heaters?
65°C
What is a simmerstat?
A simmerstat is a proportional device that does not use the temperature at the load for control
What is an instantaneous water heater?
A tankless water heater
What water heater is most commonly used in domestic settings?
Mains pressure water heaters
What device/s must be installed to keep pressurised water heaters safe?
OTC's and PRV's
Which techniques may be used for testing of over-temperature cut-out of a thermostat?
Dipping the probe of OTC in Boiling water (100°C) to confirm it cuts out with a sound
TRUE or FALSE
A switchboard requires a time clock, a ‘frequency injection control, or an off-peak relay to supply a controlled load water heater
True
TRUE or FALSE
The wire size connecting a single element water heater or multiple element water heater would always be the same for supply connections
False
TRUE or FALSE
The booster element of a water heater is operational during off-peak supply
False
What are the two most used collectors for solar water heating?
Flat-plate and Evacuated tube
When the temperature of water from the solar water heater is not enough, which component turns on the electrical supply?
The Thermostat
What are the tubes inside the evaporator of a heat pump made from?
Copper
What is the most common “method of control” used for storage water heaters?
Bi-metal thermostats
What is the most commom method of control used for Instantaneous water heaters?
Flow switch operates as a tap is turned on
According to AS/NZS 3000: 2018, what is the minimum allowable insulation resistance for circuits containing heating elements?
10kΩ
What steps should you take to identify and locate faulty components in heating equipment/control?
1. Do a Visual check
2. Do a Polarity check
3. Do a Continuity resistance test
4. Do an IR test
What are the two most common types of fault in heating devices?
Open Circuit Fault & Internal Element Short
What type of heating device is this?
An Instantaneous Water Heater
What type of heating device is this?
A Heat Pump
What type of heating equipment is this?
A Bi-metal Thermostat
What type of heating equipment is this?
A Three-heat Switch (Series)
What type of heating equipment is this?
A Strut and Tube Thermostat
What type of heating equipment is this?
A Vapour Pressure Thermostat
What information must be provided on SDS/MSDS?
First-aid measures
Identification (product identifier & chemical identity)
Hazards identification
Exposure controls & PPE
What class of appliance is this according to AS/NZS 3000?
A Class 2 Appliance
What class of appliance is this according to AS/NZS 3000?
A Class 1 Appliance
An appliance is suspected of tripping the RCD on the circuit it is connected to. What test will be able to confirm if it has a fault that is tripping the RCD?
An Insulation Resistance Test
Other than using a megger, what other ways can an IR test be carried out?
By using a PAT to test insulation resistance
By using a current clamp meter to test leakage current to earth
As soon as any appliance is plugged into a specific socket outlet, the RCD on the circuit trips. The appliances work ok on all other socket outlets. What is the possible reason?
The socket outlet has Neutral and Earth swapped
Why does earth continuity need to be tested on an earthed stove?
If the resistance is too high, the circuit protection may not trip in the event of a fault
If appliances are connected to a final sub-circuit, what test shouldn’t be conducted?
Active to Neutral IR test
An oven is faulty. The indicator light comes on when the thermostat control is turned to high, and the fan in the oven works, but the element doesn’t get hot. What is the possible fault and how would you confirm this?
Open circuit element
Test between element connections with ohmmeter
A continuity test of a cooktop element showed O/L on the meter (infinite resistance). What is the problem with this element?
The element is open circuit
An RCD on a socket outlet circuit is continually tripping. Why is this happening?
A faulty appliance is plugged into the circuit