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AGE of WATER HEATERS
ALTERNATIVE HOT WATER SOURCES
ANODES & DIP TUBES on WATER HEATERS
ANTI SCALD VALVES
APPLIANCE DIAGNOSIS & REPAIR
APPLIANCE EFFICIENCY RATINGS
AQUASTAT CONTROL Functions
BACKDRAFTING HEATING EQUIPMENT
BACKFLOW PREVENTER, HEATER WATER FEEDER
CARBON MONOXIDE - CO
CHECK VALVES, WATER SUPPLY
CLOGGED SUPPLY PIPING
CROSS CONNECTIONS, PLUMBING
DEBRIS in WATER SUPPLY, Water Heater
DRAIN a WATER HEATER TANK
ELECTRIC WATER HEATERS
FLOODED WATER HEATER REPAIR
FREEZE-PROOF A BUILDING
GALVANIC SCALE & METAL CORROSION
GAS BURNER FLAME & NOISE DEFECTS
GAS FIRED WATER HEATERS
GAS PIPING, VALVES, CONTROLS
HEATING COST SAVINGS METHODS
HOT WATER EXPANSION TANKS
HOT WATER SUPPLY
HOT WATER IMPROVEMENTS
HOT WATER DELIVERY SPEED UP
HOT WATER EFFICIENCY IMPROVEMENT
HOT WATER PRESSURE EXPANSION RATE
HOT WATER PRESSURE IMPROVEMENT
HOT WATER PRESSURE LOSS
HOT WATER PROBLEM DIAGNOSIS
HOT WATER QUANTITY IMPROVEMENT
HYDROGEN SULFIDE GAS
INDIRECT FIRED WATER HEATERS
MANUALS & PARTS GUIDES - HVAC
MIXING / ANTI-SCALD VALVES
NO HEAT - NO HOT WATER: HEATER DIAGNOSIS
NOISE, WATER HEATER
ODORS IN WATER
PIPING IN buildings, Clogs Leaks Types
RELIEF VALVE LEAKS
RELIEF VALVE, WATER HEATER
SCALE REMOVAL, WATER HEATERS
SEWER GAS ODORS
SOLAR HOT WATER HEATERS
TANKLESS WATER HEATERS
THERMAL EXPANSION of HOT WATER
THERMOSTATS, WATER HEATER
TIMERS for ELECTRIC WATER HEATERS
WATER HEATER ALTERNATIVES
WATER HEATER ANODES, DIP TUBES
WATER HEATER AIR INLET
WATER HEATER DEBRIS FLUSH
WATER HEATER DRAIN PROCEDURE
WATER HEATER EFFICIENCY
WATER HEATER FLUSH PROCEDURE
WATER HEATER NOISES
WATER HEATER PROBLEM DIAGNOSIS
WATER HEATER COMPARISONS, PROPERTIES
WATER HEATER SCALE
WATER HEATER SAFETY
WATER HEATERS for HOME HEATING USE?
WATER ODORS, CAUSE CURE
WATER PIPES, Clogs Leaks Types
WATER PRESSURE TOO HIGH: DANGERS
WATER PRESSURE LOSS DIAGNOSIS & REPAIR
WATER QUANTITY IMPROVEMENT
WATER SOFTENERS & CONDITIONERS
WINTERIZE A BUILDING
Tankless Water Heater Repair Advice: this article explains concerns, problems, & special characteristics of tankless water heaters, also called instant water heaters or "on demand" water heaters.
Page top sketch of a point of use tankless water heater courtesy of Carson Dunlop Associates.
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Conventional water heaters are relatively inexpensive due to their simplicity while tankless water heaters are more expensive to purchase and install. In 2009 in Toronto, Ontario a high capacity instantaneous water heater installation could cost $4000. CDN.
Their complexity also means that maintenance and repairs can be more expensive. Dedicated isolating valves help simplify draining and other regular maintenance.
The water heater must have a continuous fuel supply. Malfunctioning burners, sensors or controls will cause poor operation or may result in the system not working at all, meaning no hot water.
The small diameter of the heat exchangers means that these units are susceptible to clogging with scale, especially in areas with hard water. In hard water areas, annual de-scaling is recommended.
As with tank-type water heaters, some manufacturers recommend regular flushing - a step that removes sediment and debris from the heater, not scale.
If the heater is equipped with a water filter, usually an in-line screen that can be removed, inspected, and cleaned. The demand water heater filter screen should be checked and cleaned monthly, or performance will suffer.
Consumer Reports reports that some tankless water heaters do not heat continuously and constantly. If a particular model has this problem users will find that in the shower the water runs in cold bursts from time to time.
Watch out: In our own tankless water heater installation experience in the U.S. & Mexico we have confirmed that there can be hot water constancy & flow regulation problems, particularly in low-pressure tankless water heater installations.
Depending on exactly how hot and cold water pipes are routed to the tankless water heater and to various plumbing fixtures in a building, low pressure tankless water heater units are sensitive to reductions in water flow rate when additional plumbing fixtures are in operation in the same building.
The result can be complete cessation of hot water (the heater turns off on a too-low-flow-rate condition) or difficulty balancing the proper hot water temperature by attempts to mix cold water in at the shower or sink where hot water is in use.
We suspect that for this reason, after about 2004, Bosch stopped selling low pressure tankless water heaters in the U.S. However as recently as in 2012 these units continue to be sold and installed in other countries including Mexico where some homes depend on low water pressure delivered from a (not very high) rooftop water storage tank.
These low water pressure problems can be addressed by
Depending on how you use your demand hot water heater, an unpleasant jolt of cold water often occurs when water is turned on and off fairly quickly. This can happen at a kitchen sink when rinsing dishes or at the bathroom basin while washing and shaving, for example.
Rinnai™, a maker of tankless water heaters explains the cold water sandwich effect as follows:
The hot water flow rate is not only dependent on the heating capacity of the water heater and the output water temperature, but also on the inlet water temperature.
Homes in northern climates draw water from colder water supplies, and since it takes longer to heat up colder water, tankless water heaters installed in these homes will have lower hot water flow rates. The design temperatures for many water heaters is 60 deg. F. but in northern climates (Toronto, Ontario, or Two Harbors MN), the incoming water temperature may be 50 deg. F. or even as low as 40 deg. f.
Portions of this article were provided courtesy of Carson Dunlop - that text has been edited and may not entirely reflect CD's views.
Continue reading at TANKLESS WATER HEATER SIZE REQUIREMENTS or select a topic from the More Reading links shown below.
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