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Mobile View HEATING SYSTEMS PLUMBING TOPICS HOT WATER HEATERS AGE of WATER HEATERS ALTERNATIVE HOT WATER SOURCES Electric Shower Heaters High Efficiency Water Heaters Indirect-fired Water Heaters Instantaneous Water Heaters Multiple water heaters in parallel Multiple water heaters in series Range Boiler Water Heaters Side Arm Coil Water Heaters Solar Water Heaters Tankless Coil for Hot Water Tankless Water Heaters Guide to Tankless Water Heaters Operation & Characteristics Problems & Defects Hot Water Delivery Speedup Installation Requirements & Costs Should I Convert to a Tankless Heater? Calculate Water Heater Requirements Capacities of Tankless Water Heaters Life Expectancy & Applications ANODES & DIP TUBES on WATER HEATERS ANTI SCALD VALVES CARBON MONOXIDE/DIOXIDE CHIMNEY INSPECTION DIAGNOSIS REPAIR CLOGGED PIPING & Hot Water Flow ELECTRIC WATER HEATERS GAS FIRED WATER HEATERS DRAFT HOODS - gas fired Gas BTUH & Cubic Feet Gas Conversion LP Natural Gas GAS PIPING, VALVES, CONTROLS SOOT on OIL FIRED HEATING EQUIPMENT SPILL SWITCHES - Flue Gas Detection HOT WATER IMPROVEMENTS HOT WATER DELIVERY SPEED UP HOT WATER QUANTITY IMPROVEMENT Alternative Hot Water Sources & Methods Anti-Scald Valves & Hot Water Quantity CLOGGED PIPING & Hot Water Flow Extra Tanks to Increase Hot Water Insulate Hot Water Piping Insulate Hot Water Tank? Larger Diameter Water Supply Piping Temperature of Hot Water is Too Low INDIRECT FIRED WATER HEATERS NO HEAT - NO HOT WATER: HEATER DIAGNOSIS NOISES COMING FROM WATER HEATER ODORS IN WATER OIL FIRED WATER HEATERS DRAFT REGULATORS - barometric dampers OIL BURNERS OIL BURNER NOISE SMOKE ODORS OIL PIPING OIL TANKS MIXING VALVES PLASTIC HEATER VENT RANGE BOILERS RELIEF VALVES - TP Valves on Boilers Relief Valves - Water Heaters SAFETY DURING HEATING INSPECTION SEWER GAS ODORS SEWER LINE REPLACEMENT SOLAR HOT WATER HEATERS SOOT on OIL FIRED HEATING EQUIPMENT SPILL SWITCHES - Flue Gas Detection TANKLESS COILS Clogged Piping / Tankless Coil & Hot Water Flow Mixing Valves Tankless Coil Leaks Tankless Coil Hot Water Increase TANKLESS WATER HEATERS Temperature Pressure Relief Valves - Water Heaters Water Heater Noises WATER HEATER PROPERTIES Electric, Gas, Oil Water Heater Efficiency Water Heater Life Expectancy Comparisons Water Heater Operating Cost Comparisons Water Heater Purchase & Maintenance Costs Water Heater Water Quantity Comparisons Water Heater Recovery Speed Comparisons Water Heater Safety Comparisons Water Heater Scale - De-Liming Procedures WATER QUALITY TESTS, CONTAMINANTS, TREATMENT WATER QUANTITY IMPROVEMENT WATER QUANTITY USAGE GUIDE WATER SOFTENERS More Information InspectAPedia Blog - News Updates Air Conditioning & Heat Pumps Bookstore Electrical Environment Exteriors Heating Home Inspection Insulate Ventilate Interiors Mold Inspect/Test Plumbing Water Septic Roofing Structure Accuracy & Privacy Policies Contact Us |
Here we discuss 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. Page top sketch of a point of use tankless water heater courtesy of Carson Dunlop. Also see tankless water heater Problems & Defects where we discuss 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. © Copyright 2009 Daniel Friedman & Carson Dunlop Associates, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use the links at page left to navigate this document or to go to Other Website Topics. Green links at left show where you are in our document & website. Typical Tankless Water Heater CapacitiesA typical small point of use electric tankless water heater may be able to increase incoming water temperature by about
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. Does a Tankless Water Heater Provide Endless Hot Water?Well yes, no, and sort-of. Limitations on Hot Water Production Rate of Tankless Water HeatersEach model of tankless water heater is rated to provide a specific water temperature rise, for a given water flow rate. 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. ... Technical Reviewers & References
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