InspectAPedia ® | ||||||||||||||||||||||||||
| Building & Environmental Inspection, Testing, Diagnosis, Repair, & Problem Prevention Advice |
| |||||||||||||||||||||||||
| InspectAPedia Home |
| | Air Conditioning |
| | Electrical | | | Indoor Environment |
| | Exteriors | | | Heating | | | Home Inspection |
| | Insulate Ventilate |
| | Interiors | | | Mold Inspect/Test |
| | Plumbing Water Septic |
| | Roofing | | | Structure | | | Contact Us |
| Directory of Professionals to Inspect or Test a Building | ||||||||||||||||||||||||||
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 operating characteristics of tankless water heaters, also called instant water heaters or "on demand" water heaters. Readers should also see ALTERNATIVE HOT WATER SOURCES to distinguish among these types of hot water producing systems and see Electric Shower Heaters for a discussion of point of use heaters at shower heads. 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. Page top sketch of a point of use tankless water heater courtesy of Carson Dunlop. 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. A Guide to Tankless Water HeatersA tankless water heater saves energy by turning off completely when no hot water is being drawn - there are no standby losses - no tank of hot water needs to be kept hot when hot water is not being used. Although some instantaneous water heaters can provide up to 9 GPM (and use 200,000 BTUH), smaller units cannot provide very large hot water flow rates in gallons per minute.If the hot water usage rate is expected to be high, a very high BTUH unit (efficient but not necessarily economical) or multiple smaller point of use tankless water heaters may be needed to satisfy all building occupants and uses. Consumer Reports points out that a tankless water heater may be efficient but not necessarily economical to operate. What they mean is that it is certainly efficient to avoid heating water when no one is using it. But if water usage is high, a high-BTU tankless water heater may consume more total energy than a large but more conventional oil or gas fired hot water tank and burner. Tankless Water Heater Operation & CharacteristicsAs the name suggests, tankless water heaters have no tank, and therefore no storage capacity at all. Tankless heaters include a burner, heat exchanger, venting system, and the necessary controls. When the faucets and fixtures in the home are idle, the water heater is dormant. When a hot water faucet is opened or the dishwasher or clothes washing machine calls for hot water, the tankless heater detects the water flow and ignites the burners. These powerful burners quickly heat the water inside the small diameter heat exchanger. As hot water is drawn out, fresh cold water is drawn in and the cycle continues. A significant advantage of this system is that you can't empty all of the hot water out of the tank because there is no tank - just continuous hot water. No Stored WaterThe other major advantage over conventional water heaters is energy savings. Tankless water heaters have no large reservoir of water that has to be kept hot around the clock in case hot water is needed. One side effect of the lack of storage is that all of the water in the system is cold when the system has not been in operation recently. When a hot water faucet is operated, it may take more time for hot water to be delivered than in a conventional system. Small SizeTankless water heaters are much smaller than conventional waters with storage tanks, and are usually wall-mounted. However the burner on a tankless or demand water heater must be much larger than on a conventional heater since it has to instantly heat incoming cold water to its target hot temperature. Tankless Water Heater Fuel and VentingMost tankless water heaters are either electric, or they are fueled by natural gas or propane and are vented through a side wall of the house. As Rheem points out, "The venting must be Category III, Stainless steel, and it applies to the adapter, the vent pipe, all elbows, and terminal vent. This is important because the flue gases and by-products of combustion can cause condensation. Stainless steel will not deteriorate like type B venting under these conditions." Tankless Water Heater EfficiencyTankless water heaters are often much more efficient than conventional water heaters, using modulating burners, direct venting and/or condensing combustion systems. Mixing Valve use on Tankless Water HeatersMost systems include a mixing (tempering) valve and a means of setting a maximum water temperature to avoid scalding. This tempering valve mixes some cold water with the hot water leaving the unit to reduce the temperature. In one sense, there should be no need for a tempering valve, since we do not need to keep the reservoir water at 140° to prevent Legionnaires Disease. On the other hand, since we don't know the flow rate of the water through the heater, the tempering valve may be needed since the burner cannot modulate to deliver exactly the temperature we want due to the infinitely variable water flow. If the flow rate is low, the water moves more slowly through the heater, and picks up more heat from the burner. Tankless Water Heater Remote ControlSome tankless systems include a remote control, which can be used to monitor the performance of the system, display error codes or change the desired water temperature. ... Technical Reviewers & References
Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website. ALTERNATIVE HOT WATER SOURCES
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
| ||||||
|
HEATING SYSTEMS PLUMBING TOPICS HOT WATER HEATERS More Information InspectAPedia® Home & Site Map 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 |
More Information on Building Diagnostic Inspections and Repairs
|
03/26/2009 - 02/02/2009 - InspectAPedia.com/plumbing/Tankless_Water_Heaters.htm - © 2009 - 1988 Copyright Daniel Friedman All Rights Reserved - InspectAPedia® is a Registered U.S. Trademark