Question 1 A well-built single-story residential bungalow is shown below. Lay ou

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Question 1 A well-built single-story residential bungalow is shown below. Lay out schematically a constant-volume (CV) system and all its associated ductwork and equipment on the floor plan. The bungalow has a 2-ft crawl space below the floor. The bungalow is considered to be a single zone. The ductwork runs in the crawl space with "Group C" outlets (which are shown in Fig. -2 in the text on page 369). The outlets are usually placed near windows, as shown in Fig. 11-9) on page 386. Explain the logic of placing a thermostat and humidistat. Describe a general operation of the system during occupied and unoccupied periods. Note: The thin lines at walls are windows Main Bedroom ashroom entranceKitchen lo Equipment room Bedroom Bedroom Living and dining room

Explanation / Answer

Thermostat is placed inside a room in order to maintain the room temeperature at the desired point which is set by the occupant.It comes in various forms like analog,digital and pneumatic.A thermostat consists of a sensor and a controller.The sensor will measure the temperature and the controller would operate HVAC equipment.There are thermostats with additional and advanced features that would give maximum amount of comfort to the occupant and also will optimize energy cost.

A conventional thermostat consists of two pieces of metals connected by bolts and forms a bimetallic strip.The strip,being a conductor of electricity operates the circuit and maintains heating the room.Once,the strip gets overheated and then it will bend and breaks open the circuit and the electricity switches off automatically.

As a result,the room cools and the strip also cools and regains its original shape.In the above one story building plan shown,thermostats can be placed in three bedrooms ,living and dining rooms which are used for long by the occupants during winter season.

During occupied periods,the thermostat output is connected with the occupied signal terminal that will provide 24 vac,allowing the thermostat to operate normally.The thermostat automatically cools according to outside climate.During unoccupied periods,the thermostat output is connected with unoccupied signal terminal.During the unoccupied period,the thermostat output will stop its operation.

A humidistat is a device that controls the relative humidity in the air and can be adjusted by the occupant to the desired set point.It indicates the current humidity level in %.It should be adjusted to higher or lower levels according to the room space.The humiditats work on a power of 24 v or 110 v.Normally the humidity level of a home is 45 % to 60%.In the above one story building plan shown, humidistat can be placed in kitchen where some amount of humidity is needed.Also,humidistat can be placed in equipment room during summer season where humidity level should be maintained.

During unoccupied periods,humidistat requires a level of control according to environmental conditions that could result in moisture related issues.Generally,humidistat is to set to maintain a relative humidity level between 20% and 60 % irrespective of whether the room is occupied or not.

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