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Level 2 > S1, N1, U1 & U2 > Flashcards

S1, N1, U1 & U2 Flashcards

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1
Q

What is the usual “watts per unit length” rating of standard density baseboard heaters?

A

820W per meter

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2
Q

Where in a room should baseboard heaters be mounted?

A

At floor level, centred along a wall and preferably under a window

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3
Q

What type of heater is installed at ceiling height?

A

A Unit heater

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4
Q

Residential electric furnaces are usually available in both single-phase and three-phase ratings from ______ kw to _____ kw

A

4kw to 50kw

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5
Q

What type of heater unit can be used with certain oil-fired, force air furnaces?

A

A Plenum Heater

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6
Q

Residential water heaters are commonly available in ____ kW and ____ kW

A

3kW and 4.5kW

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7
Q

What are three types of thermostats commonly used is residential space heating applications?

A

Line Voltage
Low Voltage
Electronic

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8
Q

If a heat lamp using a medium-base lampholder is installed in a residential bathroom, does it have to be on a separate heating branch circuit? Y or N

A

No

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9
Q

Where are the supply registers of force-air furnace normally located?

A

Around the perimeter of each room

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10
Q

What is the purpose of the heat exchanger in a gas-fired furnace?

A

To separate the products of combustion from the air

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11
Q

The typical efficiency of a gas-fired furnace is between ____ % - ___ %

A

70%-80%

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12
Q

How many conductors are commonly needed between the furnace and the room thermostat? And what is the magnitude of the voltage that they carry?

A

2 or 3c
24v

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13
Q

Which does the room thermostat control directly, the gas valve or the blower motor?

A

Gas Valve

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14
Q

After the thermostat opens, which shuts off first, the blower motor or the gas burner?

A

The gas burner

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15
Q

What is the purpose of the anticipator resistor in the room thermostat?

A

To limit the set point overshoot to an acceptable value

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16
Q

What is the purpose of the thermocouple? Is it necessary?

A

It uses thermoelectric generation to create a small voltage when heated.
No.

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17
Q

List three conditions that may cause overheating of the heat exchanger

A

Room thermostat contacts stuck
Blower does not run
Insufficient air flow

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18
Q

What prevents the heat exchanger from overheating?

A

The high limit over heat safety thermostat will close the gas valve

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19
Q

What are the Typical settings for the blower control/overheat safety thermostat?

A
  1. Blower off 90 degrees
  2. Blower on 130 degrees
  3. High limit off 104 degrees
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20
Q

Where should an electronic air cleaner be installed on a furnace?

A

In the return air duct

21
Q

Describe how an electronic air cleaner filters the air?

A

The ionizing section charges the dust particles which are then attracted to the charges collection plates

22
Q

Why should the electronic air cleaner be interlocked with the blower motor?

A

To prevent the accumulation of ozone

23
Q

What is the purpose of a damper?

A

To regulate air flow

24
Q

Wiring for HVAC control components is usually ____v

A

24v

25
Q

To double the airflow rate, the fan hp should be increased ____ times

A

8 times

26
Q

What are the failsafe positions for the outside, exhaust and return air dampers?

A

Outside exhaust damper (Normally Closed)

Air damper (Normally Open)

27
Q

How does the damper actuator achieve its failsafe position?

A

When power fails

28
Q

What are two methods of providing mechanical cooling in an HVAC system?

A

Chilling cooler tower
Refrigeration

29
Q

What is the typical set point for a mixed air controller?

A

13 degrees

30
Q

The purpose of the minimum position device

A

Prevents the outside air damper from closing

31
Q

What does the term economizer control mean?

A

When the outside air is warmer than the return air

32
Q

What are the typical fail safe positions for the hot and chilled water valves?

A

Hot water Valve Normally Open
Chilled water valve Normally Closed

33
Q

Describe the function of a duty cycle function?

A

Switches equipment off for short intervals during occupied periods, saving electrical energy.

34
Q

Functions of an optimal start/stop program?

A

Adjusts the warm up and cool down timing

35
Q

A programmable thermostat combines the features of?

A

A standard thermostat and a electronic time clock

36
Q

What is demand limiting?

A

Reduces peak electrical demands of the building by turning off non essential loads during peak hours

37
Q

Three problems that can cause a pilot light to go out

A

Backdrafts
Insufficient gas flow
Thermocouple not fully flamed

38
Q

Two problems that could prevent a DSU system from lighting

A

Short electrode or conductor
Spark path not crossing the gas burner

39
Q

A photovoltaic cell is made up of?

A

A semiconductor material such as silicon

40
Q

Domestic electric water heaters are mostly rated at?

A

3kW

41
Q

MI cables are mostly used as resistance elements in?

A

Heating cables

42
Q

The control transformer in a gas fired furnace is typically rated at ____v

A

120/24V

43
Q

What is the correct sequence of control for a complete heating cycle of a low efficiency gas fired furnace?

A

Fan On
Burner On
Burner Off
Fan Off

44
Q

Purpose of a thermocouple in a gas furnace?

A

Indicates the presence of a pilot flame

45
Q

The anticipator in a thermostat is used to?

A

Prevent the room temperature from rising too far above set point

46
Q

A heat pump is used to?

A

Provide both heating and cooling in the same unit

47
Q

Which type of water heater is the most common in homes?

A

Storage tank water heaters

48
Q

What type of water heater that must have a large electrical capacity is?

A

Indirect water heaters

Level 2 (3 decks)

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