Carol Brzozowski 2015-04-20 17:34:55
When it’s time to replace a water heater—or put one into a newly constructed building—facility managers can choose between the traditional storage tank heater or tankless. Tankless water heaters, also known as demand-type water heaters, can provide endless hot water only as it is needed and used, points out Brian Fenske, specialty channel sales manager for Navien. To be classified as a tankless water heater, the total volume capacity must be 2 gallons of storage or less, he says. In contrast to storage tank water heaters, “you’re receiving heated water, but installing the unit is different; taking precautions to make sure it’s done correctly is different; the education and how it works in functionality is different; the savings and longevity is different,” notes Jason Fleming, Noritz marketing manager. Tankless water heaters offer reduced heating costs of up to 40% off of a utility bill for the life of the product and 30% more efficiency than a 50-gallon tank water heater, according to Noritz. Also, with tankless water heaters, end users avoid using water that has been stored in a tank with accumulated rust and scale. “A tank-type product has been around since Civil War technology,” says Fleming. “The US market really wants new technology, and the benefit is the fact that it is good for the environment and also good for the natural resources it saves. We’re only heating hot water when it’s required, rather than all the time. A tank-type water heater will heat and reheat water until somebody needs it, and you’re wasting a lot of gas and energy to do that.” Jason Renner, senior product manager for Keltech, a subsidiary of the Bradley Corporation, agrees. “Savings can result from eliminating standby losses—energy that’s wasted when heated water sits unused in a tank. While leaks are rare in tankless water heaters, over time, most storage tanks will eventually spring a leak, which can be a major expense to fix or replace.” Footprint is another difference. A tankless hot water heater, which is mounted on the wall or installed outdoors or indoors, takes up significantly less room than traditional water heaters. “Installation only requires a water and electric supply,” says Renner. “This translates into lower labor and material costs because there is no gas line or venting required, and maintenance is easy because you aren’t dealing with a large tank, anodes, or softeners. Lower energy usage and less maintenance mean lower costs over the life of the product.” Tankless water heaters operate efficiently at the time of usage, he adds. “Inefficient boiler systems waste energy cycling through heating water that might not be used and letting it cool to maintain temperature.” The high-efficiency benefits of tankless water heaters can be applied to countless applications and processes vital to a variety of industries, says Renner. Navien’s Fenske points out that in commercial applications, “due to demand, there might need to be, and often there are, multiple tankless water heaters installed.” Renner states, “Tankless units are available for small to large commercial buildings like schools, hotels, health care, and airports. There are also larger units for commercial and heavy industrial applications such as petrochemical, energy, and mining, as well as safety shower and emergency eyewash applications. In addition, tankless water heaters can be engineered as a complete system solution—recirculation pumps, expansion tanks, heat exchangers—for unique applications.” Common applications for tankless water heaters: • tepid water for use in eyewash and drench shower systems • water temperature boosting • wash down of parts, vehicles, parking lots • equipment sterilization • laboratory testing • commercial dishwashing and food preparation • industrial laundry • chemical process heating Function Noritz features a lineup that offers everything from small- to large-scale natural gas and propane gas installations, such as for a hotel, Fleming says. Mid-efficiencies start at 0.82, and go to 0.95. How it works: A user turns on a hot water valve. Cold water enters the flow sensors to trigger the computer. The computer calculates how hot to set the burners to deliver water at the “perfect” temperature. Water quickly circulates around the heat exchanger to reach the designated temperature and exits the heater. The heater shuts down and stops using energy when there is no more demand for hot water. In 2014, Bradley introduced two new and improved models to its Keltech Tankless Tempering Systems. Its new CNA and SNA Series electric tankless water heaters feature lower pressure drops than the original CN and SN Series. The newly enhanced CNA and SNA models feature larger 1 ¼-inch passageways and a flow sensor designed to significantly reduce pressure drops up to 69%. New O-ring seals improve seal pressure and reliability against water hammer or pressure spikes. Other plumbing and electrical advancements have improved installation and service of the new models, says Renner. The SNA Series delivers on-demand ANSI-required tepid water to emergency safety showers with or without eye/face washes. The unit is armed with TepidGuard, an overshoot purge protection system that ensures compliance to ANSI Z358.1, even in standby mode. Combined with a Bradley safety fixture including an anti-scald valve option, these technologies ensure that even the hottest environments will not drive water temperatures above ANSI standards, Renner says. “Bradley’s Keltech Electric Tankless Water Heaters are specially designed to draw energy only when needed, and are highly efficient and precise in supplying tepid water within seconds—even in the most extreme and challenging work environments,” he says. Navien’s most popular tankless unit is the NPE A-Model series, which incorporates an internal circulator and buffer tank. The advanced tankless water heater allows it to be used with a 0-GPM burner activation flow rate. Additional features include external domestic hot water recirculation capabilities with both internal and external circulation settings. Fenske says, “Most standard tankless water heaters require a minimum flow rate of 0.4 to 0.75 GPM to activate the burner and heat the water. Our NPE-A series with ComfortFlow Technology (internal circulation pump, buffer tank, and control system operation) can create the flow with the pump to move the water through the heat exchanger, sense the temp, and stop the pump when it reaches set point temperature. “This is a feature that can be used and set up to circulate inside the tankless,” he continues—“we call this internal circulation mode. Also, it can be set to recirculate water in the external piping to the fixtures via a return line; we call this external recirculation mode. Thus, either way, with this pump operation option activated on our advanced series tankless the NPE-A, we literally can produce and deliver hot water at a drip zero-GPM cold water flow to activate the burner.” This eliminates the “cold water sandwich” or “cold water stacking” effect, which occurs with flows stopping or starting or dropping below the typical 0.5-GPM flow requirements on standard tankless water heaters, he says Fenske. “Without enough flow or demand of hot water or the fixtures being turned on and off, slugs of cold water may be sent through the pipes as the gas burner cycles on and off.” He adds that the Navien NPE-A is designed to eliminate that during operation. As of April 2015, the lowest efficiency standard allowed to be manufactured by the US Department of Energy for gas-fired tankless water heaters will be a 0.82 EF (Energy Factor), says Fenske. “These were once considered high-efficiency just six years ago, and since then many more models have been introduced with much higher efficiencies,” he says. “Many studies and publications from Energy Star and consumer agencies have stated that a user could gain 20 to 30% efficiency from switching from a standard storage hot water tank to a tankless water heater.” Given that manufacturers have introduced 90+ efficiency condensing gas-fired tankless water heaters, the energy savings that is obtainable is even higher, potentially in the 30–40% range, Fenske adds. Navien’s gas-fired water heating appliance has an Energy Factor and recovery efficiency of 99%. “The tankless water heaters and the condensing type of tankless water heaters offer a higher efficiency than the majority of the other options that have been used in the past,” says Fenske. Rinnai tankless water heaters use up to 40% less energy than tank-style water heaters and produce an endless supply of hot water, says Joe Holliday, director of business and product development at Rinnai. Additionally, tankless units offer a longer lifespan than tank water heaters as well as space savings and are Energy Star qualified. Rinnai’s new Ultra Series Tankless Water Heater RUR Models encompass thermal bypass technology that includes an integrated recirculation pump, an internal bypass line inside the unit, and a thermal bypass valve provided inside the box to send unlimited hot water when and where it is needed, Holliday says. Another new addition to the company’s lineup: the Ultra Series RUC models, offering multiple venting solutions. The new RUC98i, RUC90i, and RUC80i models of the Rinnai Ultra Series Tankless Water Heaters are the only tankless water heaters to offer Concentric Polypropylene or PVC/CPVC venting options on the same unit, he adds. “The dual venting configuration on the top of the new RUC Tankless Water Heaters allows for maximum flexibility—one concentric vent or two PVC/CPVC pipes can be used for venting.” Rinnai’s condensing design delivers up to a 0.96 Energy Factor and incorporates two heat exchangers to achieve optimum water-heating value from every cubic foot of natural gas or propane, notes Holliday. Sizing and Capacity Right-sizing tankless water heaters to a facility’s needs is critical, as there are many variables that affect the correct sizing, such as flow rate, temperature rise, and the available power supply, says Renner. “When calculating temperature rise, it’s important to base this from the annual coldest ground water temperature,” he adds. “Be sure to carefully review the product’s technical data to select the right-sized heater for the application.” One factor that needs to be considered when choosing the appropriate tankless water heater is peak gallons per minute (GPM), says Fenske. “This is the total fixtures expected to be used at one time simultaneously, and knowing their designed flow rates at the desired mixed temperature settings,” he says. “Along with peak GPM, the temperature rise required must be factored. This is the coldest incoming water temperature along with the desired set point.” If the coldest incoming water temperature is 40°F in the winter and the desired hot water temperature setting may be 120°F, selected for safety, the results would be an 80°F temperature rise required, Fenske says. “For example, a Navien tankless model NPE-240S, 199,900 BTU, will produce about five GPM at an 80 degree Fahrenheit temperature rise,” he adds. Most quality tankless water heaters regulate the outlet flow temperatures to within a couple degrees of setpoint, says Fenske. “This assures an endless stream of hot water available 24/7,” he says. “In the event that additional fixtures are used together beyond the tankless maximum flow rate capabilities and additional tankless units were not installed to support the additional demand, the water temperature at the fixture doesn’t drop in temperatures—it will split the flow and may be felt only in lower hot water pressure delivery.” There are many ways to calculate demand on domestic hot water for commercial buildings, Fenske points out. “It tends to follow design principles usually set forth by ASHRAE. The peak GPM requirement is based on the Hunter’s Curve,” he says. That curve considers water flow, flow duration, and probability of use. Fenske points out that one difference between tankless water heaters and storage-type water heaters is that storage water heaters can typically deliver a lot of hot water faster, but then need time to recover. “A lot of times, boilers and storage tanks and gas-burned storage tanks are calculated on one-hour requirements, whereas tankless water heaters are never really counted as one hour,” he says. “Peak 2 p.m. is very important so the highest demand can be met.” A case in point: “Let’s say you wanted to heat 40-degree Fahrenheit water to 140 degrees Fahrenheit for commercial purposes,” he says. “Now we’re talking about a 100-degree Fahrenheit rise, whereas we do about four GPM. “While some fixtures might need that 140-degree Fahrenheit water, there also are some that might be blended with cold water, such as lab faucets and things like that where you’re going to get a higher flow rate at a reduced temperature.” Installation Holliday recommends a tankless water heater be installed by a licensed contractor trained to handle its plumbing, gas, electrical, and venting aspects. “Having a non-licensed professional perform the installation may cause operational and performance issues,” he says. “Rinnai Tankless Water Heaters typically require a three-fourths-inch gas line to provide a sufficient gas supply to the unit’s burner. “However, if there is sufficient pressure and the gas line is short enough, there are some cases where a half-inch gas line can be used, which is the most common size used in the United States and Canada. This can make switching from a tank-style water heater to a tankless water heater faster, easier, and less expensive.” Rinnai Tankless Water Heaters can vent vertically through the roof or horizontally through an exterior wall, Holliday says. They also can be mounted on an exterior wall. For commercial and industrial maintenance personnel, Noritz offers online training as well as in-house training. Training is recommended because tankless water heaters are “fundamentally different from a tank water heater in the way they work and operate,” notes Fleming. The unit should be properly maintained to address scale buildup as would be necessary in a tank water heater, he says. “The big difference is that tankless is maintenance-possible, whereas tanks are not so easily maintained,” he says. “You can definitely work on a tankless water heater because of the modularity of the product. Any part or piece can be taken out, put back in, and you don’t have to replace the entire unit.” “Any facility person can get installation instructions, diagrams, troubleshooting maintenance—anything that they need to have is at their fingertips from an iPad, iPhone, or any other device that they would need,” says Fleming. Maintenance and life expectancy is mainly determined on the amount of usage, water quality, and service and upkeep performed, notes Fenske. “Quality brand gas-fired tankless units have a life expectancy of 20 years on average,” he says. “Many manufacturer warranties support this by offering 10- to 15-year heat exchanger and three to five-year parts warranties. Having an acceptable quality of water or treated water is desired to prolong the life of the unit, which also will reduce the potential service and maintenance required of the tankless unit to maintain its efficiency and output.” Life expectancy can be significantly reduced with poor water quality or lack of typical maintenance, says Fenske. Sediment settling at the bottom is a problem for traditional hot water storage tanks. “Tankless doesn’t have any place for this to settle, so it either gets passed through the tankless water heater or it adheres itself to the heat exchanger, which would reduce the efficiencies and eventually impede the output and potentially cause a problem. There are a lot of boilers heating domestic water commercially that require some sort of annual service and tankless isn’t any different.” Holliday points out that hard water—which contains high concentrations of calcium and magnesium ions—is “the most common enemy of any water heater. These deposits can cause scale buildup on the heating units. Rinnai tankless water heaters can be affected by scale buildup in the heat exchanger.” When that happens, the unit provides a diagnostic code signaling the need for preventative maintenance. Flushing the tankless water heater is the most important maintenance practice for keeping the Rinnai unit in running order, Holliday says. In some cases, that can help a tankless water heater last up to 20 or more years, he adds. Electric tankless water heaters require very little maintenance, Renner says. “To ensure the heater works properly, always keep the inside of the enclosure dry,” he instructs. “Moisture inside an enclosure increases the humidity, which condenses on cooler surfaces. This can cause electrical problems and reduce the efficiency of enclosure insulation. Higher-quality electric tankless water heaters will last for a minimum of 10 to 20 years.” Models, sizes, types, efficiencies, and options all play a part in the cost of a tankless water heater installation, notes Fenske. Additional factors include location, plumbing, gas requirements, combustion venting, and addressing existing appliances that may have once shared the chimney of the removed tank water heater, he adds. An ROI is affected by such variables as usage, standby times, and fuel costs. “However, the average reported paybacks tend to be in the four- to seven-year range,” says Fenske, adding that in reality, the purchase of a tankless water heater considers the cost of replacing a traditional water heater tank so in essence, it is an “upgrade.” “Never running out of hot water, or endless hot water along with space savings, tends to be the bigger factor when considering a gas-fired tankless upgrade,” notes Fenske. For the commercial market, footprint is important. “We find the need for space savings especially true in restaurant-type establishments,” he says. “They appreciate not having the equipment on the floor. It gives them more floor space to park their mop buckets and do cleaning. “Endless hot water is very key to them because if they don’t deliver consistent hot water to certain fixtures, they can get in trouble, especially in the restaurant establishment not having the right temperature of the water at the fixture.” The ROI in hotels, restaurants, health clubs, and other facilities that have a high-water demand can be as fast as a one- or two-year equipment payback, Fenske says. “Typically, tankless water heater installations as a system can cost less money up front than some of the more expensive tank water heaters or the boilers and storage tanks,” he adds. Tankless water heaters are expected to last 15–20 years in commercial-type applications. They can range in cost from a few hundred to thousands of dollars. ROIs are becoming closer to that derived by tank water heater purchases, Fleming notes. “The more water used, the more savings. The more percentage of their water heating is of their overall gas bill, the higher that they’re going to see. We see the largest savings is in commercial applications.” BE Carol Brzozowski specializes in topics related to energy and technology.
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