Wall mount or floor mount, there are times when a specific boiler best fits the bill. Wall-mount boilers may be selected for a project over usually larger floor mounts because space is limited or they can be easier to install.

If you’re comparing wall-mount condensing boilers to older, conventional non-condensing boilers, the basic advantage is weight, says Bronwyn Planasch, the technical service and training manager, dales division, Noritz America Corp. “A wall mount is not going to be as heavy. You can install it with one person, versus having to have multiple people do an installation.”

“In a residential setting, users will experience many different advantages from wall-mounted boilers, such as efficiency, comfort and compact dimensions,” says Dan Moffroid, director of product management at Bosch Thermotechnology.

Generally, floor-mounted boilers are either non-condensing, standard efficiency boilers or condensing models that are too heavy to hang on a wall, says Chad Sanborn, product marketing manager at Bradford White Water Heaters.

“Modulating condensing boilers are inherently lighter because of their low mass and stainless-steel construction. Conventional boilers are generally constructed with either steel or cast-iron heat exchangers and have much larger water volumes. This simply makes them too heavy to mount on the wall. In much the same way that conventional boilers are heavier, they also are typically larger.”

An obvious benefit of a wall-mount boiler is that it is off the ground and potentially at less risk of damage due to flooding issues, says Mike Boyd, product manager with Weil-McLain. “But floor-standing units also can be protected to an extent as well, if placed on non-combustible blocks or an elevated pad/structure. In most instances, wall-mounted boilers minimize the time a contactor needs to kneel during servicing and/or repair events — most components are at chest level.”

Wall-mount boilers allow the versatility of being placed in areas that may get it out of the way, which may free up valuable usable space, agrees Brian Fenske, specialty channel sales manager, Navien. Most often the wall-hung boilers are smaller in size and constructed more compact, which is a large part of the attraction for residential use. Size and weight of all boilers is dictated by Btu, heat exchanger type and material, flow rate design and application purpose.

Wall-mount boilers are intended to be installed in very confined spaces, which allows for optimal use of space in a home or commercial space, says Steve Thurlkill, national sales manager/commercial products, Raypak. “Mounting the unit on the wall above the piping also affords easy access to install the vent system, which is typically the most important part of the installation.”

Chuck O’ Donnell, director of marketing for Laars, says wall-mount boilers can make for a tidier installation, with all piping coming directly from the unit to a series of wall-mounted zoning manifolds. In cases of flooding, the boiler may avoid damage because of its height above the floor.


Check these applications

Wall-hung boilers are a good choice for all hydronic heating applications, Sanborn says, including in-floor radiant, fan-coils and low-temperature baseboard or panels. “Almost without exception, wall-mounted boilers are modulating units, which mean they can alter their Btu input or change supply water temperature, making them ideal for homes that have different water temperature needs for different applications, such as radiant and domestic hot water production.”

Yes, virtually all boilers, wall-mount or floor, may be used in all types of situations including hydronic, radiant and domestic water heating, Fenske says. “With condensing boilers typically offering the best potential efficiencies, wall-hung boilers have two main application choices for producing domestic hot water. One is using an indirect water heater as an add-on zone, or the increasing popularity and fast growing use of the all-in-one combi boiler.”

Wall-mount boilers, like the floor mount versions, can be used for radiant heating, snow melt, indirect domestic hot water or a combination of all of these system types Thurlkill says. “Most all wall-mount boilers shipping today include controls to allow a combination of heating systems to operate from the one appliance with relative ease.”

Almost exclusively high-efficiency boilers, wall-hung boilers are ideal for use with in-floor radiant heating systems, which typically have colder water returning to the boiler, O’Donnell says.


Common installation mistakes

What are the most common mistakes contractors make when installing wall-mount boilers? In replacement situations, some installers simply install the same capacity boiler as the previous model, O’Donnell says. “More times than not, older boilers are oversized, sometimes drastically. Whether new construction or retrofit, a thorough heat loss calculation should always be completed before selecting a boiler size.”

 With domestic hot water production, the opposite problem can exist, O’Donnell notes. “It’s easy to underestimate a home’s domestic load. Always do a walkthrough of all the kitchens, baths and utility spaces to account for water capacities of fixtures, shower heads. Ask the homeowner if they plan to build an addition, put in a multi-head, high flow shower or a roman tub. That needs to factor into the selection of the domestic water delivery.”

“Using a ‘rule-of-thumb’ sizing method is where we see most mistakes, since it seems there are a wide variety of these criteria,” Thurlkill says. “Installers don’t want a callback for not enough heat, so most systems we see are oversized for the application. Having a calculation run by a local engineer for a residential or light commercial application is well worth the fee and provides peace of mind for both the installer and their customer.”

Performing a heat loss to determine boiler size is definitely the preferred method vs. replacing with the same capacity boiler as the one that is being removed.

“You would be surprised on how different the actual heating loss of the house might be,” Boyd says. “The heat loss calculation could have been done incorrectly 20 to 30 years ago, if not longer, and the tendency to oversize a boiler could have been used for the last couple of replacements.

“Even if the heat loss calculation was done properly for the last boiler, what has changed since then? New windows, insulation, built an addition? What type of heat emitters are in the house and at what temperature do they need to operate? Properly evaluating the overall cost if a change in vent configuration is required — some contractors fail to do this.”

The same applies to the hot water side. The contractor needs to know how it’s currently produced, if it’s adequate, current and future demand expectations, the condition of the current appliance, how it’s vented, if it’s common with the boiler and will work with a new boiler, Boyd says.

A big factor in sizing a boiler is doing your heat load calculations, Planasch says. “There are computer programs for that, asking questions such as: What type of installation do you have; What kind of windows do you have; and How many walls are facing the outside vs. internal walls. The answers can change your heat load calculations dramatically, so doing an actual heat load for the house and finding the actual Btu load you need is most important.”

The most common mistake during residential boiler installations is improper sizing,” Sanborn says. “Efficiency and boiler life are maximized when the boiler is sized correctly for the home. A manual heat load calculation should always be completed before a boiler is selected.”

Another mistake specific to condensing boiler installations is failure to properly set the outdoor reset control, Sanborn says. “A lot of efficiency is sacrificed if the boiler doesn’t ‘know’ what temperature water to supply to the connected radiation at specific outdoor temperatures. The unit should be supplying a different water temperature to the home when the outdoor temperature is 40 F, for example, than when it’s 7° outside. On the same token, the outdoor reset sensor should be installed outside the home in order to get an accurate air temperature reading. The sensor should be mounted out of the sun, on the north side of the building, away from windows, doors and vents.” 


Contributed by Noritz

Stanwood, Wash., resident Brian Fleming [Brother of Jason Fleming, senior marketing and customer care manager for Noritz. — Ed.] had a serious heating problem in his two-story home. The 10-year-old, split-level structure had lacked effective space heating since day one.

“The builders had not designed my forced-air heating system to handle two floors, and, as a result, the downstairs portion was always cold,” Fleming says, who used his furnace system for less than 25 cycles annually, instead relying on a gas-powered fireplace to heat his upper floor. “I was spending a significant amount on my electricity bill to heat this space.”

Water heating, though less of a problem was still noticeably difficult whenever he and his family needed to run multiple fixtures simultaneously. “We had a 40-gal. tank water heater, so whenever somebody tried to shower while the laundry was running, the warm water would run out very quickly,” Fleming says.


A two-in-one solution

Although his heating problems had persisted for 10 years, Fleming previously had not the time or resources to fix them until the opportunity to beta-test the new combination boiler/tankless water heater (Combi) from Noritz allowed him to kill two birds with one stone.

The CB Combi, which meets “Energy Star Most Efficient” standards, is a year-round, whole-home solution that uses condensing technology to deliver hot water to both domestic hot water and hydronic space-heating applications. It made the forced-air furnace system and tank water heater completely unnecessary.

Whidbey Island Plumbing in Oak Harbor, Wash., undertook the installation, situating the 90-lb. wall-hung Combi CB unit in Fleming’s garage.

“The most challenging part was setting up the hydronic system,” says Fleming, who opted for in-floor radiant heating on the lower floor. Radiant tubing was stapled up underneath in a serpentine fashion between stud bays. Venting the unit was accomplished through the garage wall, using concentric PVC pipe that handled both intake and exhaust. The installation lasted two days.


Chasing out the cold

Since then, Fleming has observed a marked improvement in energy savings and indoor comfort.

“The new boiler, in conjunction with the radiant system, is providing the best heat I have experienced in my life,” he says, adding he also has seen a total cost reduction of around $60 on his monthly gas and electricity bills. “Not having to run the space heaters all the time saves a lot of energy.”

On the water heating side, Fleming and his family can now take showers and do the dishes for as long as they like, because the condensing tankless technology provides as much hot water as needed for as long as needed with an efficiency of 95%.

“Once that tankless unit fires up, it provides endless hot water and a consistently enjoyable heating experience,” he affirms.

The combination boiler proved to be a highly workable heating solution for Fleming, who no longer needs to deal with cold spots in his room space or shower.

“I see no reason to ever go back to forced air or tank water heaters,” he says.


Contributed by SaniFlo

The problem: Condensing technology saves energy by maximizing the amount of heat energy transferred to the water during the combustion process. A by-product of this process is water, or condensate, that tends to be acidic because of the chemical reaction caused by the heat of the gas burner. Indeed, the higher the efficiency rating, the higher the acid level in the water runoff.If you are a plumber who actively promotes the use of high-efficiency, condensing water heaters, boilers or furnaces, you should be equally energetic in treating this equipment with some sort of neutralization. That’s the only way to protect your customers’ plumbing from the potentially harmful side effects of the condensation process. As the popularity of high-efficiency condensing products grows, so too will the problem of acidic condensate.

If this runoff is disposed of through a home’s or a building’s plumbing system, the piping could corrode over time. Pumping the waste outdoors or into sanitary sewers could contaminate the groundwater or degrade the local water infrastructure. For homes with septic tanks, condensate waste might also destroy the good bacteria essential to keeping the system operating properly.

The higher, front-end costs of high-efficiency equipment are typically justified by lower energy consumption and the resulting lower monthly fuel bills.

“But those savings could be wiped out and then some if the plumber must return in a just a few years to tear out and redo all the plumbing,” says Chris Peterson, West Coast sales director for Saniflo USA. “The smart, long-term solution is to neutralize the acidic content in the condensate waste before it ever enters any piping.”

Peterson notes the International Plumbing Codes require condensate waste-neutralization, but enforcement is spotty. Some sections of the country, such as New England, strictly enforce the code requirements; others — including the far West — tend to be lax.

Ways to neutralize

  1. Manually, by cutting a bed of limestone into the floor where the condensing water heater, boiler, etc., is located, and letting the condensate drip into it;
  2. Positioning a limestone-filled cartridge inside of the condensing unit to neutralize the water internally; and
  3. Hooking a neutralization kit — essentially, a piece of pipe filled with limestone — to the exterior of the condensing equipment and letting the condensate flow through it.

Enforcement of the condensate-neutralization codes will likely increase as the problem — and its potential toll on plumbing systems — become more widely recognized, but Peterson urges plumbers who install condensing equipment not to wait, if only for the sake of their customers.


"This article was originally posted on ww.reevesjournal.com."