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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 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
The LP gas fired 30-gallon water heater shown at left was installed around 2001 and was still in working condition. But the building occupants were not happy with their hot water supply for several reasons:
Before starting to work on a water heater or water heater swap-out such as this change from a gas fired conventional water heater and tank to a tankless Bosch instant water heater, don't forget these preparatory steps:
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.
Watch out: some installers opined that the new 5-inch vented tankless heater would work just fine connected to a 4-inch chimney.
We did not agree, nor does the manufacturer who is very clear on this point.
Venting a heating appliance into a flue or chimney smaller than the outlet diameter of the vent connection on the appliance itself is asking for trouble including:
Our photograph at left as well as the above right photo show what was required to install the new 5-inch chimney and vent system for this heater. We had to chop open a concrete wall, remove the 4-inch chimney and install a 5-inch diameter chimney in the same location.
At left you can see the 5-inch flue vent connector and elbows entering the base of the chimney for this appliance.
Water heater Installation tip: because we were working in close quarters we decided to get the entire chimney, elbows and flue vent connector in place before setting the exact mounting position of the heater itself. That was a lot easier than mounting the heater and then wrestling with custom-cut little vent connection pieces to try to match an arbitrary heater mount location to the exact location of the bottom of the metal chimney.
That screened vent shown in the right side of the photo was an add-on exit vent for an indoor gas-log fireplace; we didn't want any interference between those two gas burning appliances and we didn't want any possibility of drawing carbon monoxide gas into the building through the screened vent when the fireplace was not in use.
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.
Before starting to work on a water heater don't forget to locate ahead of time
As we warned in our introduction:
At the photo at below right you can see the new water and gas piping connections at the bottom of this instant water heater.
Yellow arrows point to the LP gas line connections.
Red arrows point to hot water piping connections. Notice that for safety reasons there can be no shutoff valve on the hot water outlet line on the heater.
Blue arrow points to the cold water connection; you will notice that there is a cold water shutoff valve on the inlet end of this line.
Our photo at far left of the original LP gas line and shutoff show black staining around the shutoff valve and flare fitting, with some of the black worn away - previously there had been an LP gas leak at this location.
Check water heater installation location clearances, spaces, safety, protection from elements, wind, etc.
Although in southern climates it is common to install the instant water heater outdoors, the manufacturer, in this case Bosch, requires that the heater be installed under shelter, protected from rain and wind.
You can see that this heater is in a sheltered location.
By placing it as high as we could on the wall under the enclosed masonry stairs, we were avoiding possible wind problems that had plagued the base-located gas burner in the previous water heater installed in this same space.
Indoor installations of tankless water heaters
Watch out: do not install a tankless water heater (nor any other gas or oil fired heating appliance) indoors without providing an approved, properly installed flue vent connector and chimney to vent combustion gases. Otherwise you risk death of building occupants due to potential flue gas and carbon monoxide poisoning.
Watch out: local building codes or water heater manufacturers may require (and we recommend) installation of flue gas spillage sensors and safety controls on all indoor installations of gas fired heating equipment.
Watch out: other installation & safety recommendations from the Bosch installation instructions for the LP gas piping include
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.
Above our photo shows how you can verify that the gas flame is on in this tankless water heater - but it's not easy to see on this model. We listen for flame and we feel the exhaust (be careful about burns!)
5. Turn on hot water at a nearby fixture - you should see the flame indicator lit in the front of the water heater (blue flame showing in horizontal slit in our photo at left) and you should feel hot water delivered at the fixture.
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
Well the bottom line is the owners are pretty happy with their new instant water heater, with "endless" hot water on demand and no LP gas fuel consumption when no one needs hot water. Once the occupants learned how to work with the low pressure instant water heater system the result was the ability to run a single shower with plenty of hot water, on demand, without running out. But there were a few surprises and disappointments to get by first.
In this particular installation, running two showers at the same time at the same building level (the building has baths on three different floor levels) results in delivery of warm but not hot water to both showers. If the occupants want a really hot shower they run just one shower at a time.
The variations are most likely due to peculiarities in individual building water pressure and in the actual routing of existing water piping. Bosch recommends feeding a dedicated cold water line directly to the water heater and carrying separate cold (from the cold source) and hot (from the heater) to the location where hot water will be used. But when installing a tankless water heater at many buildings you may find that the existing piping was not routed by that schema.
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.
Fuel Alternatives for Tankless Water Heaters: Butane, Natural Gas, Propane: proper set-up required
Several readers have asked about the availability of a butane-fueled tankless water heater, and about converting tankless water heaters among fuels using butane (C4H10), propane, or natural gas. Indeed it is possible to convert most gas-fired heating appliances among fuels. But conversion to the proper pressures, combustion air settings, and fuel jets is necessary unless the appliance has been delivered already set up for the fuel you intend to use.
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.
Details about the difference between LPG, Butane, and Propane and Natural Gas are discussed at GAS BTUH, CUBIC FEET & PRESSURES.
Other tankless water heater accessories & kits include
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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