Refrigerators Flashcards
What are the three purposes of the P-trap on the sealed combustion fridges?
Prevent down draft
Prevent moisture from outside
Prevent condensation from dripping on the flame
What is a sealed combustion fridge?
A fridge that draws combustion air from outside and exhausts outside the unit
What is the priority sequence for a norcold fridge?
1st- AC
2nd- propane
3rd- 12vdc
What is the priority sequence for a domestic fridge
1- AC
2- 12VDC
3-propane
What should you do with a fridge door that is cracked or warped?
Replace
What is the advantage of wire shelving in the fridge?
Allows for good air flow and circulation
How do you adjust a fridge door?
Loosen the hinge bracket screw and adjust.
All or remove washers if need to raise or lower the door
How might the light be wired into the fridge?
May be wired into the harness for the thermistor
What turns the fridge light on in low ambient temp.
And what temp should it turn off?
Low ambient temp switch
Should turn off when it’s 50F (10C) outside
What can happen if the door switch is defective?
It can cause inefficient cooling if the bulb remains on
What should be turned on if condensation is noticed
The High humidity switch and heater
What does the High humidity and heater do?
Keeps the surface between the door opening dry during high humidity conditions
What are two purposes of the eyebrow control
Used to select the mode of operation
Displays the mode of operation
What senses refrigerator interior temp.
Thermistor
What will temp do to the thermistor?
It affects the resistance of the thermistor
Temp increases - resistance decreases
Temp decrease- resistance increases
What 3 components will distribute DC Current?
Connecting lead,
Ribbon cables
Wire harnesses
What controls the circuit to the 12vdc heat element?
The 12vdc relay
What completes the circuit through the flame to ground?
The sensor probe
What does the ignition module do?
Ignited and monitors the flame
Powers the gas valve
If flame is out it will spark for a period, the close the gas valve and go into “check” mode
What does the reignitor/relighted do?
- Monitors the flow of micro-amps through the flame.
- If it doesn’t sense micro-amps it will spark indefinitely until flame is established
How far must the igniter probe or electrode be above the burner
Domestic: 3/16 above burner
Norcold: 1/8”-3/16 above burner slots
What is a zip tube?
A perforated aluminum tube with holes that allows the flame to travel down
What should you do if the piezo snaps but there is no spark?
There is a problem with the high tension wire or the electrode
What does the thermocouple do and what does it generate
It energizes the electromagnetic in the safety valve
Generates 14-30 Millivolts
When should you replace the thermocouple?
If the tip is burnt.
What are the two types of electric heating elements?
Pencil type
Cartridge type
How big is the cartridge type heating element?
5/8” or larger
Which T-stat has one capillary tube and bellow that controls both functions?
The combination propane/electric thermostat (manual model)
What is the purpose of the flue baffle?
It’s to concentrated heat from the burner at the boiler/generator
Forces heat to the outside of the flue tube
What is directly under the flue tube?
And what is it’s purpose?
The burner
To apply heat to the boiler/generator
What are the 4 types of orifices?
- Ceramic insert
- drilled brass fitting
- stainless steal insert/ brass fitting
- laser drilled ruby insert/brass fitting
How do you clean all the orifices?
Methal hydrate and tooth pick except the ruby just clean and dry
What is threads on most test ports?
1/8” NTP female threads
What are the two types of thermostat inlet and outlet fittings?
What must be done every time the thermostat is separated?
Threaded type
O-ring deal type
The o-ring must be replaced
What controls the “low flame”?
And what does it consist of?
The bypass screw.
Bypass screw, gasket, o-ring
What is in the capillary tube?
And what does it do?
Where is the sensing side attached too?
Contains refrigerant that expands and contracts
It moves the bellows and controls the propane
It’s attached to the high-temp evaporator fins
On a propane T-stat, what happens when it’s satisfied with the temp.?
The pressure is reduced to 3-5”WC to produce “low flame”
What the AC working range of a fridge?
108-132volt
What are the 3 functions of the lower vent
Fresh air intake
Fresh air for ventilation
Access for service
Where must the lower fridge vent be?
Bottom edge must be at or below the fridge cabinet floor to allow for propane vapour to flow out
What is the “thermo-siphon effect”
Hot air rises and cooler air is drawn in the bottom
What is the side clearance for the fridge?
MAX 1/2” on either side
What is the max clearance for the top of the fridge?
MAX 1/4”
What may may happen to the fridge in low ambient temp
Ammonia/water mixture may gel in the absorber and stop circulating causing the fridge to stop cooling
What do you do when performing a Bypass test?
What should it cool to?
You bypass the thermostatic controls and let run for 24 hrs on 120vac
Water should cool too -10C
What do you do when performing a “run test”
What temp should it cool too
Just let run for 12-24 hours.
Water should cool down too minimum of 6C (43F). (34-38 is better)
What does excess moisture or frost build up in the fridge/freezer indicate?
Air leaks
What is the hydrogen static gas pressure? And when heated?
250 psi and up to 600psi when heated
What are the four main components of the cooling unit
- boiler/generator
- condenser
- evaporator
- absorber vessel/leveling chamber
How far off level can the fridge be?
3 degrees side to side
6 degrees front to back
What can happen if the fridge is run off level?
The sodium chromate can overheat and crystallize and cause a blockage
What are the 4 chemicals in the cooling units
Ammonia
Water
Hydrogen
Sodium chromate
What kinda motor is in the compressor refrigerators?
A “Swing motor”
What kind of power do most compressor fridges need at the compressor?
How is this accomplished?
20VAC!
With step down transformers and inventors
