Lose the tank, save the energy
BY JOSEPH SANCHEZ
Special to The Wholesaler
Tankless water heaters or hot water on demand water heaters provide hot water only as it is needed, reducing the standby energy losses associated with typical storage water heaters. As one might expect, and as the U.S. Department of Energy has indicated, this energy savings will help a facility or dwelling save money.
Among the most popular benefits of tankless water heaters are the constant supply of hot water that reduces consumption and lowers water bills, and the significant energy savings that puts money back in the end user’s pocket while qualifying the purchaser for Federal tax credits under Section 25C of the Federal Internal Revenue Code for the tax years of 2009 and 2010.
For homes that use 41 gallons or less of hot water daily, tankless water heaters can be 24% to 34% more energy efficient than conventional storage tank water heaters. They can be 8% to14% more energy efficient for homes that use a lot of hot water — classified at around 86 gallons per day by the U.S. Department of Energy.
The average efficiency of the available tankless water heaters on the market is between 82% and 93%. And in fact, the Navien condensing tankless water heater is 98% efficient, one of the highest rated in the industry.
Navien America Inc., based in Irvine, Calif., achieves this tremendous efficiency thanks to its stainless-steel primary and secondary condensing heat exchangers, which are able to recover the thermal energy in the condensation that would otherwise be lost. The use of stainless steel primary and condensing (secondary) heat exchangers allows up to 20 times more resistance to erosion and condensate corrosion than the typical copper heat exchanger.
Navien units are able to provide instantaneous hot water because of the built-in hot water recirculation pump and buffer tank, which puts hot water at the faucet the moment it is turned on. This neat feature saves water and reduces water bills since a homeowner won’t be waiting for the hot water to arrive to faucet. Navien units also include dual-redundant microprocessors to ensure uninterrupted operation. A fingertip Intelligent Remote Control System is supplied with every unit, allowing the owner to easily make any needed adjustment to the water heater from the inside comfort of their home.
Navien’s contractor-friendly design allows the use of PVC venting up to 100 feet, reducing the costs of installation dramatically by eliminating the need for stainless steel venting. Another benefit of PVC venting is that it allows the end-user to install the unit right next to the old tank water heater — eliminating the need to move the unit to an outside wall. And each of these units comes with peace of mind in the form of a 15-year warranty, one of the best in the industry.
Metropolitan Industries is the authorized representative of Navien tankless water heaters for the entire state of Illinois, Northern Indiana and half of Missouri. Two recent installations by them demonstrate both the commercial and residential application capabilities that incorporate energy-savings for the end-user.
President’s Mansion - University of Illinois
The University of Illinois President’s Mansion in Champaign, Ill. was an interesting application requiring the muscle and efficiency of a Navien solution.
Built in the 1800s, the 8,000-square-foot mansion is occupied by the University President and sits on 10 acres of land. Such amenities include over a half-dozen bathrooms, eight bedrooms, servant quarters and executive kitchen.
The President’s Mansion is a tool used to entertain dignitaries, donors and other very important people. During these events, hot water or the lack of it was a constant issue — especially during graduation, sporting events and meetings. If more than three people showered at the same time, the hot water supply would run out.
The existing hot water heating system consisted of two 100-gallon natural gas tank water heaters that were only 60% efficient when new, and lacked sufficient hot water even when the house was only partially occupied.
Given the existing system was a tank system, heating the water when the mansion was vacant was an expensive issue as well. Tank systems have an eternally lit pilot flame and will turn on to heat the water periodically even when demand is at its lowest, unlike a tankless system that only uses energy on demand. Also, as minerals are prone to build-up in the tank over time, the heaters sometimes become less and less efficient thereby adding to the energy costs.
Metropolitan Industries replaced the old tank water heaters with three Navien NR240A natural gas tankless water heaters, each with a Btu rating of 199,000. These new water heaters — installed in June 2010 — provide an endless supply of continuous hot water and with 98% efficiency, reduces energy costs associated with the Mansion. The systems are on a recirculation loop that saves an average of 12,000 gallons of water per year because the need to “wait” for hot water to arrive at the tap is eliminated.
Since the installation, supply issues have been eliminated and the costs of heating the water were drastically reduced.
Sunny Hill Nursing Home
After reading an article written by Metropolitan released in a trade magazine and also attending a seminar conducted by Metropolitan Industries, the Maintenance Director of Will County approached HVAC Division manager Matt Brickey for his input regarding replacing existing commercial hydronic boilers with a skid-mounted Navien package.
The nursing home used their massive hydronic boilers to supply heat to their domestic hot water storage tank through an internal shell and tube heat exchanger. The problem with this configuration is inefficiency because the huge boilers would short cycle 24/7 due to satisfying the load quickly, turning off, and then turning back on again shortly thereafter due to a drop in domestic water temperature.
Short cycling causes numerous issues for a heating system. One, it causes more stress on the boiler components by constant expansion and contraction. Boiler parts will wear and fail quicker than their intended life cycle. The second issue is the amount of wasted heat energy that is thrown up the stack. Each time a boiler turns on, or off, it goes through a purging process. During this process, a substantial amount of energy is lost in the form of wasted heat when the boilers short cycle.
Metropolitan’s solution was designing a heating system that can directly heat the domestic water more efficiently and allow the maintenance staff to shut down their existing boiler plant in the warmer months. Metropolitan supplied a skid-mounted 98% efficient Navien condensing domestic heating system that modulates and heats the existing domestic tank without any short cycling. A unique feature of these units is the ability to cascade them for high-Btu applications.
The system included eight tankless water heaters, a variable speed supply pump that circulates domestic water from the tank to the heaters, a control system that monitors tank temperature and adjusts pump speed accordingly by sensing the flow and all the necessary piping and valves manufactured on a prefabricated skid for a complete functional system. This system also allows for ease of installation by the contractor because field work is limited to making piping connections from the tank to the skid, bringing electrical power to a single point connection, and running the CPVC exhaust & intake to the outside wall.
The anticipated natural gas energy savings during the summer months is expected to be a whopping 50% to 75%.
In both project examples, the end user saved money because of reduced energy demand by using Navien condensing tankless water heaters. Metropolitan Industries stocks a large supply of these units in their shop ready for immediate delivery, and can fabricate large custom commercial systems for contractor installation.
For more information, contact Mark Brickey at 815-886-9200 or visit their website at www.metropolitanind.com.