Common Types of Residential Heating and Cooling Systems Flashcards
What are three advantages of electric space heating?
- Clean
- Efficient
- Self-contained
- Long life
- Low maintenance
What is the usual “watts per unit length” rating of standard density baseboard heaters?
820 W/m (250W/ft)
Where in a room should baseboard heaters be mounted?
at floor level, centred along the walls, and near areas of high heat loss (such as under windows)
What type of heater is normally installed at ceiling height?
Unit heaters (either vertical or horizontal air projection types)
Residential electric furnaces are usually available in both single-phase and three-phase ratings from _____kW to _____kW
5kW, 40kW
What type of electric heater unit can be used with certain oil-fired, forced-air furnaces?
Plenum heaters
What are two applications for heating cable sets?
- Radiant space heating (floor or ceiling)
- Driveway/sidewalk ice melting
- Freeze protection on pipes
Residential water heaters are commonly available in _____kW and ______kW ratings
3kW, 4.5kW
What are the three types of thermostats commonly used in residential space heating applications?
- Line-voltage
- Low-voltage
- Electronic
If a heat lamp using a medium-base lamp holder is installed in a residential bathroom, does it have to be on a separate heating branch circuit?
No; CEC Rule 62-108(3)
What size conductor would you need to supply a 3kW baseboard heater fed by a 240V circuit?
AWG #12. The calculated load requires a 20A overcorrect device. Therefore, the wire size must be increased from #14 AWG
What is the maximum setting of overcorrect device allowed to protect branch circuit wiring supplying two or more residential baseboard heaters?
30A; CEC Rule 62-114(2)
Is it necessary that a thermostat with a marked OFF position disconnect all ungrounded conductors in the circuit?
Yes; CEC Rule 62-118(2)
Why is it not permissible to shorten the heating portion of a series heating cable set?
The series resistance would be reduced, resulting in increased current and possible overheating (fire hazard); CEC Rule 62-122(1)
Indoor heating cable sets that are to be embedded in concrete shall beat the designation Type _______
1B; CEC Rule 62-124(1) and Table 60
Where are the supply registers of a forced-air furnace normally located?
Around the perimeter of each room, preferably in front of areas of high heat loss
What is the purpose of the heat exchanger in a gas-fired furnace?
To separate the products of combustion from the circulated air
The typical efficiency of a gas-fired furnace is between ___% and ___%
70%, 80%
How many conductors are commonly needed between the furnace and the room thermostat? What is the magnitude of the voltage that they carry?
Two or three; 24V
Which does the room thermostat control directly, the gas valve or the blower motor?
The gas valve
After the thermostat contacts open, which shuts off first, the blower motor or the gas burner?
The gas burner
What is the purpose of the anticipator resistor in the room thermostat?
To limit the set-point overshoot to an acceptable level
What is the purpose of the thermocouple? Is one always necessary?
When heated, the thermocouple generates a small current that holds the gas safety valve open. A thermocouple is not required on units equipped with electronic spark ignition
List two conditions that may cause overheating of the heat exchanger
- Room thermostat contacts stuck closed
- Blower does not run
- Insufficient air flow
What prevents the heat exchanger from overheating?
The high limit overheat safety thermostat will close the main gas valve
What are the typical settings for the blower control/overheat safety thermostat?
- Blower OFF at 32°C (90°F)
- Blower ON at 54°C (130°F)
- High limit OFF at 104°C (220°F)
Where should an electronic air cleaner be installed on a furnace?
In the return air duct, preferably downstream of the standard filter
Describe how an electronic air cleaner filters the air
The ionizing section charges the dust particles which are then attracted to the charged collection plates
Why should the electronic air cleaner be interlocked with the blower motor?
To prevent the accumulation of ozone that can occur if the cleaner is energized and has no air flowing through it
