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46 Cards in this Set
- Front
- Back
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What is a flow switch classified as? |
Limit and safety controller |
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What are examples of operating controls? |
Thermostat Aquastat Pressure control Draft fan switch |
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Most common type of sensing element? |
Liquid bulb |
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What does a fluid temperature controller do when used with hot wster heating or boiler |
Opens on temperature rise |
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Standard indoor/outdoor capillary tube length? |
10 feet indoor. 30 feet outdoor |
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Where do you want to install an outdoor bulb/bulb gaurd? |
North facing wall/ not in direct sunlight |
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What happens to the circuit of a temp controller on Temperature rise? |
Switch opens and shuts off gas to burner R and b terminals break the circuit |
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What can a low pressure limit control signal? |
Loss of main gas pressure Branch line shut off valve closed |
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Where is the low limit pressure control located? |
Low pressure side of appliance reg, close to combustion chamber |
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What is the set point °c/°f for low limit switch? |
4°c/40°f |
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What position are fan control contacts in? |
Normally open |
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Where are fan controls located? |
Burner plenum chamber |
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What can cause a roll out switch to shut down the appliance burner? |
Physical blockage Dirty combustion air blower |
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What is an example of an operating control for a forced air furnace |
Thermostat |
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What would a 115/24 vac-40va step down transformer be classified as? |
Class 2 power supply |
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What is the maximum temp setting of a high temp limit control in a forced air furnace by code? |
250°f |
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How many temperature set points are found on a combo fan/limit control? |
3 |
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What is the main purpose for a high temp limit control? |
Prevent appliance from overheating |
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What device closes its contacts on temp drop? |
Heating thermostat |
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What device prevents temperature overshoot? |
Heat anticipator |
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What device would not be found in a 120 volt control system? |
Transformer |
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What are some components on a 24v system? |
Thermostat Gas valve High limit control Fan control switch Fan motor Transformer Thermocouple |
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Three circuits in typical domestic heating system? |
120v power circuit 24v control circuit 17-32mv flame proving circuit |
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Who sets the thermostat ? |
The choice of the occupants |
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What temperature is the thermostats set point? |
70°f (20°c) |
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How is the fan control switch connected? |
Series with the motor |
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What happens when a heat exchanger gets too hot? |
High limit opens and gas valve closes |
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What are some variables a fan control and high limit settings depend upon? |
Type of heating appliance Location of control thermostat Temp rise through heat exchanger Sensitivity of the control |
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What is the purpose of a thermostat? |
Maintain area temp at a set value |
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What improvs the comfort and economy of the system? |
Properly installed thermostat |
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What are the 4 categories of a mid- efficiency furnace? |
Combustion air components Burner assembly Fan blower assembly Electronic control board |
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4 combustion air components? |
Combustion air blower Combustion air proving switch Heat exchanger Primary high limit safety switch |
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What moves air through the burners and heat exchangers during a heat cycle? |
Combustion air blower |
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What type of high limit safety switches are in mid efficiency furnaces? |
Disc type bi metal Bimetal strip |
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How is a rollout switch wired? |
In series with the ignition control |
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Common type of flame sensing device? |
Flame rod |
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How is a remote bulb connected? |
To a sealed bellow tube or diaphragm by a capillary tube |
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What input for boilers must automatic low water cut offs be installed at? |
400000btu |
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Max length of capillary tube on aquastat? |
30ft |
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How does a final control element get power? |
From a primary control like a gas valve or fan assist furnace |
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How do you determine the max amperage in electrical controls? |
Using watt's law |
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What switch can sense gas,water vapor or fluid pressures? |
Pressure controller |
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What terminals initiate a call for heat wired on an aquastat? |
Terminals R and B |
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What is located on the vent terminal(outlet) |
Induced draft fan |
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What two switches are required by asme to control operations of a steam boiler |
Operating control High pressure limit control |
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Where would you expect to find a liquid pressure switch |
Private water system |
