New Commercial Water Heaters
Ask Chuck Appleby, president of Old Lyme, CT-based Appleby Plumbing Co. if he recalls an emergency job. One he quickly remembers began with an urgent, Christmas day plea from a restauranteur who needed half a million BTUs of water heating at the height of their businest season (see sidebar story).
Appleby was there on site within 30 minutes. While studying their need for hot water he discovered that the old, leaking beast was sized for peak load, making it at least 20 percent too large 90 percent of the time. The big, atmospheric system could be replaced by a 400 MBH condensing unit that would be smaller in size, a whole lot less expensive to operate and – if need be – could be coupled with a smaller indirect water heater to meet peak loads.
The new water heater, which offered a much greater recovery rate, was also a lot less burdensome to install than the old one, not requiring the large, ducted air vent. The new system, a condensing water heater, would require only a 3-inch PVC air intake and a 3-inch PVC flue gas discharge. “A piece of cake,” said Appleby while marveling the extraordinary efforts taken (and expense) to install the intricate air passageway for the unit that would soon be replaced.
“The new unit’s sealed combustion is a huge benefit for restaurant jobs, eliminating all concern about one of the trickiest challenges with commercial facilities where food is prepared,” added Appleby. “Large ventilation hoods are notoriusly adept at stealing combustion air from atmospherically-fired systems. Those days – thanks to new, sealed combustion technology – may soon be gone.”
Appleby’s experience with the system he replaced is illustrative of the way water heating technology has changed in just the past couple of years. Not long ago, contractors, engineers and building owners were routinely challenged by an inability to easily place and locate commercial water heaters. The limitations of atmospherically-vented systems, facility design, aesthetics and close proximity to other buildings all factored-in.
Today it’s not uncommon for facility managers, late in the game, to express an aversion to visible venting, based purely on aesthetic reasons. This is especially true in historic districts.
Fortunately, many of the obstacles to easy placement of water heaters – at least those tied to building design and construction – are overcome with the emergence of new water heater systems, making it much easier to achieve manufacturer-specified combustion air or venting runs.
The arsenal of commercial water heater products and associated technology has grown considerably, availing a wide range of fuel, venting and combustion air options. There are also many new application-friendly components and techniques to enable trouble-free specification and installation, though – with the new, green systems – a few new needs emerge.
Higher efficiency, condensing systems are great for end-users in terms of energy consumed, chiefly because they harvest heat from waste condensate. The energy advantage requires modest design and installation changes to meet the need for condensate treatment and drainage. This may translate to an inability to use existing venting if the original water heater was atmospherically vented, and the availability of electricity. Some systems require hard-wiring; other commercial systems need only a simple wall plug-in.
Condensate drainage is a likely necessity. Often, fluids to be drained are too acidic for metal drain lines. Routing the condensate through a simple, lime-bed acid neutralizer may solve the problem easily. Better yet: CPVC or PVC drain lines can handle the acidity. Condensate typically has a pH of 4.0, about that of Coka-Cola – just enough to attack any metal it connects with. Over time, the cumulative effect of exposure to acidic runoff threatens the integrity of the drain lines.
Venting. If new, high-efficiency water heaters are planned as a retrofit, existing, single-wall B-vent must be replaced in favor of PVC, CPVC or ABS plastic. The majority of venting lines are three or four inches in diameter, precisely matched to the design requirements of new blower motor assemblies that discharge from the top of water heaters.
Plastic vent materials are inexpensive and easy to work with, and yet present no compromise in safety or performance. Some new water heater systems have the ability to vent through the roof and pull air in for combustion through the wall; this is a big advantage. The need to improve flexibility of installation and placement has driven the development of power, power direct vent; through-roof and side-wall venting options.
Finally, if the application offers abundant atmospheric combustion air, some water heater models require only one pipe: for venting.
Multi-story and high-rise installations challenge traditional venting. High efficiency water heaters often can accommodate to long venting runs. Often, there’s no need to run vertical venting all the way to the roof, requiring a roof penetration. Many systems are now just as well served with side-wall venting.
New codes are forcing all of us to be attentive to a broad range of emerging requirements. National, state and local codes are changing in the wake of the green movement’s more stringent environmental policies and initiatives. Among the applicable national codes is the need for water heater system over 199,999 MBH to be ASME-certified.
Historic settings are commonly guarded by restrictions that regulate the presence and appearance of modern building systems and attachments (i.e., wire, regulators, transformers and venting). In fact, the presence of old and unsightly or loud venting systems has actually encouraged the replacement of aging atmospheric water heaters.
Case in point: New system shaves cost of operation
Recently, Appleby received an emergency replacement call from the 232-year-old Griswold Inn, founded in 1776 near the banks of the Connecticut River and nestled among many other old and beautifully preserved buildings.
The Inn needed a substantial overhaul brought on by the sudden death of an eight year-old, half million BTU commercial water heater, the only source of domestic hot water for the Gris’ award-winning kitchen.
“Of course, the old Inn wasn’t built to accommodate modern mechanical systems,” said Appleby. “He specified a new, 400 MBH, LP-fired, high-efficiency eF water heater by Bradford White to replace the quickly deteriorating system installed by another firm.
The water heater they replaced had required a 12-inch stainless steel draft hood and chimney. “Too bad they had to spend that kind of money on a water heater with such a short life span,” said Appleby. “The new system we installed requires only a simple, four-inch PVC stack, and at 98% efficiency, would cost them a whole lot less to operate. The key advantage was the new, condensing unit’s super-high recovery rate. Because we could heat so much more water, we were able to size it at 100,000 fewer BTUs, a move that also had a huge impact in their fuel consumption.”
Another attribute is that there are no stack losses because the new system is equipped with sealed combustion and uses both PVC exhaust and combustion air lines. The water heater also offered several venting options, electronic controls, four protective magnesium anode rods, a sediment reduction system and factory-installed dielectric fittings.
Considering the sad waste of resources on the stainless steel stack, which Appleby left in place, he devised a plan that gave it new purpose. “We used it as an intake air ventilation duct to cool the restaurant’s large refrigeration equipment,” he said. “They had a growing problem there because the equipment had been running hot, and this was consuming electricity [highest, by far, of all energy sources in the state] at an alarming rate. Typically, the air around the refrigeration systems was 120 to 130 degrees, year-round. Using the 12-inch duct to bring fresh air in, we were able to get those temperatures down substantially.”
“The biggest benefit of all was in the energy savings,” concluded Appleby. “Today, no one can responsibly afford to waste energy.”
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