Customizable Convection Heating

Offices, hotels, schools, retail stores, sports facilities and other building types typically have rooms that can be efficiently heated by the use of electric heaters, such as convectors, radiant ceiling panels or infrared radiant heaters.

For these applications, the “appearance” of the heating unit is just as important as its performance.

Architects spend countless hours on interior design creating a desired atmosphere in these spaces. Think about how the use of light and the choice of color, furnishings and materials affect the ambiance in a hotel lobby or office boardroom. Consequently, heating units need to “blend in with” or “complement” their surrounding environment.

At the same time, these units must help specifying architects and engineers solve heating problems such as counteracting cold drafty areas near windows, reducing condensation of the glass and aiding in the de-stratification of the air in the space.

With all these factors to consider, there is no one-size-fits-all heating solution for every building. Rather, specifying architects and engineers must solve their distinct heating problems with customizable solutions to ensure optimal cost-efficiency and overall functionality.

For the right combination of customization and performance, convectors may be an ideal solution for buildings with complex heating needs.

Why Choose Convectors
Convectors are non-fan forced heaters that use natural convection to move the heated air back into the conditioned space – making them much quieter than fan heaters. Without the use of a fan to blow air, the convector is a great choice for minimizing the circulation of dust and pollens, making for a better work environment.

Convectors are ideal for use in areas with large spans of windows, such as offices, schools and hotel lobbies. Typically mounted at floor level on exterior walls and under windows, convectors provide an upward movement of air to counteract cold downdrafts and minimize condensation.

Available in a variety of sizes, configurations and colors, convectors also offer design and installation versatility. Architects and engineers can leverage customizable features to develop convectors that fit the custom design specifications of a project as well as solve heating problems without wasting energy or space. Models are available that can be located in a trench, housed in custom enclosures or mounted in a variety of other ways.
Convectors have a wide array of control options from built-in thermostats for controlling individual units to silicon controlled rectifier (SCR) controls that can integrate into Building Management Systems (BMS).

How Convectors Work
Tapping into a natural phenomenon known as “convection,” air inside a convector is heated becoming less dense than the surrounding cool air, enabling it to rise due to buoyancy. As the heated air rises, the cooler air on the floor is drawn into the convector, creating a constant flow. By placing convectors under a window, the heated air rises and blocks the down draft of cold air, creating a heated air curtain.

All convectors contain two components that work together to safely deliver heated air to the space: the element and an over temperature limit.

The element converts electrical energy to heat by passing an electrical current through a specifically designed resistance wire. The elements used in convectors are metal sheathed, and constructed of a spiral wound resistance wire encapsulated in an insulating powder (Magnesium Oxide, MgO) encased in a metal sheath.

Fins are added to the element rod to improve heat transfer by creating a chimney effect, directing air to flow over the element and the larger fin surface to heat the air passing through the unit. Most convection heaters have aluminum fins pressure bonded to the rod. However, heavy-duty and explosion-proof convectors have customized steel fins brazed to the rod to better handle higher demands.

Over-temperature limits are temperature-sensing devices located on or near the element that interrupt the flow of electricity to the element if an abnormally hot condition occurs. In convectors, the over temperature limit device is most commonly activated when an air inlet or discharge opening is blocked by drapery or furniture, causing heat to build up.
Convector Use: When, Where and How

Convectors are typically installed along the perimeter of rooms to block the downdrafts caused by the cold outside wall cooling the air next to it, and to counteract transmission losses. In most cases, convectors are mounted at the floor level along an outside wall and under windows, allowing heated air to rise from the top of the unit and block the cold “down draft” air.

Convectors will draw colder air from the floor area, heat it up and then release it toward the ceiling where it cools, falling back to the floor to complete the cycle. This cycling or rotating effect works best with low to medium ceilings of 8- to 10-foot heights.
To efficiently heat buildings with large expanses of multi-story windows, a second series of convectors can be included at every floor level to prevent the cascading effect of the downdraft. While the rising heated air is blocking the downdraft, it also provides a warm air curtain that acts as a buffer to prevent the heat loss from the space to the cold wall.

For well-insulated buildings with small amounts of glass, the use of more compact convectors may be sufficient. These heaters would only be mounted under the window area, allowing for fewer heaters to be installed and reducing the initial cost. These units, however, would still provide the dual function of counter-acting the downdraft and the transmission effect.

A Warm Place of Work
Commercial buildings run the gamut from hospitals and assisted-living facilities to schools, hotels and retail stores. To accommodate the very different environments in these facilities, many manufacturers of convectors offer a variety of styles and configurations including:
• Front- and bottom-inlet convectors
• Recess-mounted cabinet convectors
• Sill-line convectors
• Architectural convectors, which feature design elements that help them blend into or complement most interior spaces

Similar to residential applications, convectors in commercial applications should be installed on the exterior wall. Within individual office or conference areas, heavy-duty baseboards, draft-barrier convectors or sill-line commercial convectors are the best choice. The decor of the room as well as its heat loss will determine which style best suits the application.

Large open, multi-person, perimeter offices are ideal spaces for heavy-duty baseboards, draft barrier or sill-line commercial convectors and architectural convectors if the window area does not reach the floor. Placing the convector along the entire length of exterior wall eliminates the discomfort of the cold wall effect for people located nearby.
The use of convectors in lobbies is similar to large open offices except additional consideration must be given to the fact that people move around more in lobbies.

Likewise, in lobbies with multi-story windows and atriums, the amount of heated air necessary to block the downdraft of this large expanse of window, and keep the moisture from forming on the top portion of the window, cannot be generated from floor level convection equipment alone. In these cases, sill or pedestal-mounted convectors installed at floor level, working in conjunction with convectors mounted approximately every 10 to 15 feet up the window, will provide sufficient heated air.

Regardless of the office or lobby size, if floor-to-ceiling glass is present, pedestal convectors should be considered.

Keeping A Cozy Home
Since convectors have no moving parts and use natural air flow rather than forced air flow, they are ideally suited to quiet living spaces. This includes bedrooms and home offices where convectors can be installed along exterior walls under windows to provide silent, gentle heat.

However, when installing a convector, specifiers and engineers must ensure there is adequate wall space for placement of furniture and drapery, and the location of electrical receptacles is taken into account to avoid dangerous hazards. Convectors with electronic hydronic elements have a lower surface temperature than standard convectors, making them safe choices for a nursery or child’s bedroom.

For basements, standard convectors should be installed along the above-ground walls to eliminate the cold downdraft, as well as under windows along other walls. Basements with interior divisions should have a heater and thermostat in each area. In large open basements, several smaller heaters will produce a better heated air distribution than a singular large heater. If the area is only occasionally occupied, portable baseboards may be the better choice. Heating the basement has the additional benefit of warming the floor of the rooms above adding to the main floor comfort level.

Industrial, No-Hassle Heat
Factories, warehouses, sports complexes and similar facilities require heaters that can withstand a great deal of abuse but still function properly with little maintenance.
For restrooms, lunchrooms, small to medium workshops and assembly areas with low to medium ceilings, slope top or cabinet-style heavy-duty convectors provide even heating, yet are constructed to withstand normal daily industrial abuse.

Used on exterior walls, the sloped design of slope top convectors prevent them from being used as shelves or step stools. Cabinet convectors can be recessed when space is limited and the wall that the heater is recessed into is a non-exterior wall. In some industrial applications, there is the potential of hazardous gasses being present, and explosion-proof convectors may be better suited for these spaces.

Convection heaters can meet the heating demands of virtually any building without sacrificing aesthetics or efficiency. Easily customized, made-to-order convection solutions enable specifiers and engineers to blend heaters into their designs without wasting energy or budget.

About the author: Jim Herring is the supervisor of Total Custom Solutions & Technical Services at Marley Engineered Products®, a leading North American designer and manufacturer of reliable comfort heating and ventilation solutions for residential, commercial and institutional buildings. Recognized by contractors, architects, engineers and HVAC professionals for providing a wide range of high-performance, reliable heating and ventilation solutions, Marley Engineered Products’ brands include QMark®, Berko®, Fahrenheat® and Leading Edge®.

Marley Engineered Products’ manufacturing operations are based in Bennettsville, S.C., with regional sales representatives located throughout the U.S. and an administrative office in Burr Ridge, Ill.