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AGE of WATER HEATERS
AIRBOUND HEAT SYSTEM REPAIR by WATER FEED VALVE
ALTERNATIVE HOT WATER SOURCES
ANODES & DIP TUBES on WATER HEATERS
ANTIFREEZE for BOILERS
ANTI SCALD VALVES
APPLIANCE EFFICIENCY RATINGS
AQUASTAT CONTROL Functions
BACKDRAFTING HEATING EQUIPMENT
BACKFLOW PREVENTER VALVE, HEATING SYS
BACKFLOW PREVENTER, HEATER WATER FEEDER
BACKUP HEAT for HEAT PUMPS
CARBON MONOXIDE - CO
CHECK VALVES, WATER SUPPLY
CHEMICAL CONTAMINANTS in WATER
CHIMNEY INSPECTION DIAGNOSIS REPAIR
CLOGGED DRAIN DIAGNOSIS & REPAIR
CLOGGED SUPPLY PIPING
CROSS CONNECTIONS, PLUMBING
DEBRIS in WATER SUPPLY, Water Heater
DRAIN a WATER HEATER TANK
ELECTRIC WATER HEATERS
FLOODED HEATING EQUIPMENT REPAIR
FLOODED WATER HEATER REPAIR
FREEZE-PROOF A BUILDING
FROST HEAVES, FOUNDATION, SLAB
GALVANIC SCALE & METAL CORROSION
GAS BURNER Flame & Noise Defects
GAS FIRED WATER HEATERS
GAS PIPING, VALVES, CONTROLS
HEAT TAPES, Heat, Insulation prevent Freeze-Up
HEATING COST FUEL & BTU Cost Table
HEATING COST SAVINGS METHODS
HOT WATER SUPPLY
HOT WATER IMPROVEMENTS
HOT WATER DELIVERY SPEED UP
HOT WATER EFFICIENCY IMPROVEMENT
HOT WATER PRESSURE EXPANSION RATE
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 / SOUND DIAGNOSIS & CURE
NOISE CONTROL for HEATING SYSTEMS
NOISE, PLUMBING CHECKLIST
NOISE, WATER HEATER
ODORS GASES SMELLS, DIAGNOSIS & CURE
ODORS IN WATER
PIPING IN buildings, Clogs Leaks Types
PLASTIC HEATER VENT
PLUMBING FIXTURES, KITCHEN, BATH
PLUMBING VENT DEFECTS & NOISES
PUMPS, HEAT PUMPS
PUMPS, OIL BURNER
PUMPS, PONY PUMPS
PUMPS, SEPTIC PUMPS
PUMPS, SEWAGE EJECTOR / GRINDER PUMPS
PUMPS, SUMP PUMPS
PUMPS, WATER PUMPS
PUMPS, WATER REPAIR
RELIEF VALVE LEAKS
RELIEF VALVES - TP Valves on Boilers
RELIEF VALVES - STEAM TP VALVES
RELIEF VALVES - Water Heaters
RELIEF VALVES - Water Tanks
SAFETY, HEATING INSPECTION
SCALE REMOVAL, WATER HEATERS
SEWER GAS ODORS
SOLAR HOT WATER HEATERS
SOOT on OIL FIRED HEATING EQUIPMENT
SPILL SWITCHES - Flue Gas Detection
TANKLESS WATER HEATERS
THERMOSTATS, HEATING / COOLING
THERMOSTATS, WATER HEATER
TIMERS for ELECTRIC WATER HEATERS
WATER CONTAMINANT LEVELS
WATER HAMMER NOISE DIAGNOSE & CURE
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 PROPERTIES
WATER HEATER SCALE - De-Liming Procedure
WATER HEATER SCALE PREVENTION
WATER HEATER SAFETY
WATER HEATERS for HOME HEATING USE?
WATER ODORS, CAUSE CURE
WATER PIPES, Clogs Leaks Types
WATER PRESSURE & FLOW MEASUREMENT
WATER PRESSURE GAUGE ACCURACY
WATER PRESSURE LOSS DIAGNOSIS & REPAIR
WATER PRESSURE REDUCER / REGULATOR
WATER PRESSURE PUMP REPAIR GUIDE
WATER PUMPS, TANKS, TESTS, WELLS, REPAIRS
WATER PUMP REPAIR GUIDE
WATER QUALITY TESTS, CONTAMINANTS, TREATMENT
WATER QUANTITY IMPROVEMENT
WATER SOFTENERS & CONDITIONERS
WINTERIZE A BUILDING
Hot Water Heating Capacity of Tankless Water Heaters: this article explains the hot water heating capacity of tankless water heaters, also called instant water heaters or "on demand" water heaters. The quantity hot water is delivered can be expressed in gallons per minute of hot water at a particular temperature rise over the incoming water temperature. We also discuss the question of what "endless hot water" really means.Our page top photo illustrates three Bosch instant water heaters for sale in a Home Depot in Celaya, Mexico in 2012.
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A larger electric tankless water heater may be able to increase incoming water temperature by about
Some tankless water heaters are rated at 9.8 GPM but be sure to check the temperature rise that the heater can provide at that flow rate (35 deg.F.).
We haven't seen a tankless water heater providing more than 5 gpm flow rate at high temperature rise (over 65 degF) rating.
If your building needs higher hot water flow rates you may need to use a conventional hot water tank or a gang of tankless water heaters.
If you're trying to provide 100° water, a 35 deg.F. temperature rise assumes an inlet water temperature of 65°F - not something you can count on in cold climates.
In our OPINION, even 100° temperature rise may not be high enough if the system is being used with a mixing valve or on long piping runs that we described earlier.
Limitations on Hot Water Production Rate of Tankless Water Heaters
Each model of tankless water heater is rated to provide a specific water temperature rise, for a given water flow rate.
[Sketch of a point of use tankless water heater courtesy of Carson Dunlop Associates]
Typically a tankless water heater can provide 2 – 5 gallons (7.6 – 15.2 liters) of hot water per minute.
For example, a heater may be capable of increasing the temperature of incoming water 60 deg. F. at 3 gallons per minute flow rate.
The temperature rise that a tankless water heater can provide and the water flow rate that it can support depend on the heater's BTU output capacity which in turn is a function of the fuel used (gas-fired or electric) and the efficiency and the size of the heater.
Also see tankless water heater Problems & Defects where we describe the Tankless Water Heater Cold Water Sandwich Effect. Readers should also see ALTERNATIVE HOT WATER SOURCES to distinguish among these types of hot water producing systems.
The original text of this article was provided courtesy of Carson Dunlop - that text has been edited and may not entirely reflect CD's views.
Our OPINION is that readers looking for plenty of hot water heated efficiently should also consider the heater we describe at Indirect-fired Water Heaters.
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Questions & answers out the hot water heating capacities & flow rates for tankless or demand hot water heaters.
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Technical Reviewers & References
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