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3.6 DOMESTIC HOT-WATER SYSTEMS - Coggle Diagram
3.6 DOMESTIC HOT-WATER SYSTEMS
1) REDUCED ENERGY LOSS
Reducing standby losses
Standby loss is heat loss from the water in a domestic water heater and its distribution system when it is not in use.
HOW TO REDUCE THAT:
Place DHW close to the area of use and minimize pipe length.
Place DHW on protected rigid insulation to reduce heat loss from the bottom of the tank.
Heat trap is installed above the water heater to STOP CONVECTION
Level of tank insulation is increased
Hot-water pipes are insulated
HEAT TRAPS
Heat is trap is a simple piping arrangement that prevents hot water from rising up the pipes in the first place, thereby reducing heat loss.
REDUCING PIPE LOSSES
Best way to reduce heat loss from the piping is to maximize the length of hot-water piping required
Insulated pipes for at least the first meter (3 ft) of pipe from tank, the pipe insulation should be at least RSI 0.35(R-2)
2) GAS-FIRED WATER HEATERS
GAS-FIRED WATER HEATERS
with a seasonal energy efficiency in the range of 55%, to high-efficiency condensing units of 90% and above. EF (Energy Factor) is the unit used to gage the efficiency of hot water systems.
Natural draft gas-fired water heaters.
DO NOT HAVE FANS. Naturally aspiring burner and a draft hood. As a result they are more subject to combustion spillage than other gas-fired equipment.
Their overall efficiency is fairly low, with an EF in the low of 50% range.
Induced draft (fan-assisted) gas-fired water heaters
Use fans downstream of the water heater to move combustion by-products through the venting system rather than relying on dilution air to move gases by natural convection.
Most induced-draft fan (fan-assisted) units require combustion air and dilution air from inside of the house.
In a well built house a source of combustion air must be provided near the water heater.
Direct-vent-gas-fired water heaters (sealed combustion)
are designed to bring all of their combustion air from outdoor through a directly connected inlet, and to vent combustion by products outdoors.
Units can achieve efficiency as high as 90%.
INSTANTANEOUS GAS-FIRED WATER HEATERS
Unlimited hot water, energy efficient, conserve space, and declining in price.
Typical features:
Uses natural gas or propane
Vertical or wall-through venting
Minimum 20 PSI water pressure is required
Tankless water heater can be cost effective as they do not have standby losses. Most tankless units provide hot water more slowly than conventional water tank.
GASB BOILERS (WALL HUNG)
Can provide water and space heating with a sign wall-hung unit.
3) ELECTRIC WATER HEATERS
40 gal units, widely used, inexpensive, simple to install
They should have a factory-installed insulation level at least RSI 1.75 (R-10).
The seasonal efficiency of these units is about 93%.
Also, the initial cost is low, it cost of operation is significantly higher.
4)HEAT PUMP WATER HEATERS
Many of heat pumps used for space heating can also be used for water heating.
A heat pump will supply more energy than it uses.
The ratio of energy supplied to energy used is called the Coefficient of Performance (COP).
Heat pump water heaters generally operate with a COP in the range of 2.5 to 3, and can save up to 60% of the energy used by a tactical electric water heating system.
5) SOLAR WATER HEATERS
Systems can provide about 40% to 50% of a houses annual domestic hot water.
6) GREY WATER HEAT RECOVERY
Primarily warm or hot water, it contains heat.
This energy is recaptured and used to preheat incoming cold water to the domestic hot water heating system using simple, passive device.
To do so, grey water must be seperated from toilet water in the home, and it can be sent through the heat recovery unit.