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AGE of WATER HEATERS
ALTERNATIVE HOT WATER SOURCES
ANODES & DIP TUBES on WATER HEATERS
ANTI SCALD VALVES
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 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, WATER HEATER
ODORS IN WATER
PIPING IN buildings, Clogs Leaks Types
RELIEF VALVE LEAKS
RELIEF VALVES - Water Heaters
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 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
How & why to install a tankless or demand water heater. This article describes the conversion from a conventional LP-gas fired hot water tank & heater to a Bosch Confort 13BP N low-pressure system tankless water heater. With text & photos we illustrate both the old and new water heating systems and the steps required to install the tankless water heater. The article reports on why the owners decided to convert to a tankless water heating system, and on both their satisfaction and their disappointments in the results.
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Tankless water heater installation details: conversion from a conventional hot water tank to a demand-type Bosch instant water heater
New Water Heater Hookup Prep: check water heater flue vent diameter, routing, length, clearances for combustion gas venting
The original LP gas water heater (above left) vented through a 4-inch metal flue (green arrow in our photo). We measured the diameter of the flue vent connector on the new Bosch instant water heater (above right), confirming that it wanted a 5-inch flue vent or chimney.
At below left you'll notice that we chipped away some concrete where the LP gas pipe penetrates the masonry wall. We confirmed that the LP gas line to this point was 1/2-inch in diameter, meeting the manufacturer's confusing specifications on this point.
We say confusing because while the instant water heater installation instructions recommend feeding a 1/2-inch LP gas line to the tankless heater, the actual gas pipe fittings, valve, and flexible gas line provided by the manufacturer in an installation kit named as intended for this Bosch heater were all 3/8-inch diameter. We decided to connect a new gas shutoff valve to the existing 1/2-inch gas line at the wall and use the kit's 3/8-inch flexible gas line & fittings for the remainder of the connection.
Check water heater installation location clearances, spaces, safety, protection from elements, wind, etc.
1. Turn on water supply to the unit and check for water leaks
2. Turn on the gas supply to the unit and check for gas leaks (see GAS LEAK DETECTION, LP / NG)
3. Install batteries in the heater's battery compartment (above left, shown empty of batteries), making sure that the batteries are new, of the proper type and rating, and installed with their + and - ends in the proper position.
4. Turn the heater's ON-OFF switch to the ON position (above right) - our photo shows the switch in the ON position.
The burners of an instant or tankless water heater are triggered by sensors that detect the flow of water. If the flow of water is too low, typically less than ½ gallon per minute, the burners will not turn on and no hot water will be delivered.
Watch out: water-saving shower heads, for example, may not allow enough flow to turn the water heater on, especially when the water heater has a high minimum flow rate. Rheem and Bosch (table above), for example, requires a .66 GPM flow rate to ignite the burner on smaller capacity units and a higher flow rate on higher capacity units. (This is probably to avoid overheating in & damage to the tankless water heater's heat exchanger.)
For example, all Rheem tankless water heaters can be programmed to operate at elevations up to 9,840 feet. Our photo (left) illustrates a Rheem Eco-Sense instant water heater for sale in a Home Depot store in Phoenix, Arizona (2012).
The temperature/pressure relief valve lets water escape if the temperature or pressure is too high. This valve should be connected to a tube that discharges no more than six inches above floor level so hot water won't scald anyone nearby.
Some codes require that the tube discharge outside the building. The tube should be as large as the tank fitting and the tube end should never be threaded, capped or plugged.
The tube should be able to withstand 250°F temperatures, should have no shut-off valve, and should be as short and as straight as possible.
In response to complaints of combustion gas odors, CO alarms sounding, and intermittent loss of hot water where tankless water heaters were installed we inspected several rental properties owned by the same landlord [B.P., SMdA, MX]. We found that the plumber she used to install tankless water heaters at multiple apartments didn't realize that each gas fired unit needed combustion air for safe and continuous operation..
Each tankless water heater had been installed on an exterior wall and to avoid tenants fooling with the heater, the plumber enclosed each unit in a steel box with a lock.
The tenants complained of gas odors and of constant loss of hot water. Because the units were installed outdoors the dangerous carbon monoxide that was being produced had not resulted in a catastrophe.
How did the new tankless water heater perform compared to the conventional hot water tank & heater that was removed
At TANKLESS WATER HEATER REPAIR GUIDE we explain 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
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.
How to Get the Most from Your Tankless Instant Water Heater & How to Avoid Sudden Cold Water Bursts or Complete Loss of Hot Water from a Tankless or Instant Water Heater System
Watch out: most tankless or demand water heaters (such as those made by Bosch & by Rheem) are sold in models designed for a specific fuel such as Natural gas OR LP Gas.
Some instant water heaters such among the Rheem units cannot be converted from LP to Natural Gas or vice versa. So be sure you are specifying the proper model and fuel type when buying a tankless water heater.
Bosch and some other tankless or point of use water heaters provide a conversion kit to change a natural gas model water heater to a propane or butane fuel source, or vice versa.
Other tankless water heater accessories & kits include
TANKLESS WATER HEATERS - separate article
Frequently Asked Questions (FAQs) about how to choose and install an instant or tankless water heater
Questions & answers or comments about about how to install a demand or instant or tankless hot water heating system: installation details, problems, solutions.
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