Test 1 Flashcards
Developed Length and Max Developed Length:
Developed Length: is the actual length of pipe between the source of water supply and the most remote fixture plus the developed length of fittings
Max. Developed Length = 1.2 x actual pipe length to the remote fixture
Hot-water system
Hot-water system: is a subsystem of the domestic water system.
The demand of hot water is included in that for domestic water.
Hot-water temperature
For residential use: 130 - 140 F
Water for washing dishes and clothing: 140 F
Commercial applications: 180 F
Tempered Water: is a blend of hot and cold water that is mixed at a thermostatic (mixing) valve.
The temperature ranges 100 – 110 F
There are three types of water heaters
● Storage tank water heaters
● Instantaneous on-demand (tank-less) water heaters
● Circulating water heaters
Storage tank water heater consists of a storage tank and a heating medium.
There are available in natural gas, fuel oil, and electric
models.
They are the most popular type residential houses.
Street pressure drives water flow.
A thermostat controls the heating medium.
The storage tank is insulated to reduce losses.
There is a temperature and pressure (T/P)
relief valve.
A vent runs vertically through the center of
the tank to vent the product of combustion
Instantaneous on-demand (tank-less) water heaters: supply hot water on demand.
They do not have a storage tank.
They have a heating device that is activated by the flow of water when a hot water valve is open.
Circulating water heaters consist of a separate storage tank that stores water heated by heat exchanger.
The heat exchanger may be a separate unit that is heated by stream or hot water from a boiler or may be contained in a boiler
Heat Pump Water Heaters
Heat pump water heaters extract energy from outdoor air and use it to produce hot water very efficiently.
To remove heat from air, the heat pump does both cools and dehumidifies the air.
This means that the heat pump is helping to meet cooling needs.
It is economical in hot humid regions where natural gas is
unavailable, the cost of electric energy is high, and there is
need for dehumidification.
Solar Water Heaters
Solar water heaters include collectors mounted on the roof, a separate storage tank, connecting pipes, and an electronic controller
For energy conservations:
- Control the use of hot water (better management)
- Select the proper water heating equipment.
- Select the proper flow control devices
Hot Water Recirculating System
The hot water in the piping system tends to cool off when is not used constantly,
even if the pipes are insulated.
This is because water temperature is 140 F and room temperature is 60 – 70F
lower.
To maintain the desired water temperature;
Use a second pipe as a hot-water circulation line (re-circ)
When the water is cooled off, it drops down the second pipe, and creates a
natural circulation
Sizing Storage Tank Water Heaters
The sizing of a storage tank heater is based on the First Hour Rating (FHR).
First Hour Rating (FHR). is the maximum output of the water heater over an hour, in gallons of hot water in a 100o F temperature rise.
FHR (in gallons) = 70% of tank capacity (gallons) + recovery rate (gallons per hour)
