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Radiators

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Definition

RADIATORS are heat distribution units that are typically exposed to view that circulate steam, water or another liquid using pipes that may have fins or other means of increasing surface area.

Boiler to radiator: Designs for heat transfer

1. Drawing of a radiator array for a staircase

1. Radiator array for a staircase.
Click the image for more information.


Early on in the development of boilers, radiators were like them — sheets of cast iron, iron or steel, bolted, welded or riveted together to form a “sealed box” to transfer either hot water or steam heat to the indoor air. Then, in the mid to late 1800s, the same flair that gave stoves and cooking ranges of the period their elegant and artistic designs, began to be reflected in the radiator.

One of the Canadian foundries that specialized in radiators and boilers was Taylor-Forbes Co., Ltd., of Guelph, Ontario. By 1912, it produced an extensive line of plain and ornamental radiators, which together provide a good example of the evolution of the “rad” in direct hot water and steam heating systems.

Radiators came in a dizzying array of shapes and sizes: There were half or full circle models; corner, angle, curved, and semi-circular variants; the Carpet Foot (“L”-shaped), extra high legs, and other leg shapes. Custom stairway and window designs which, when installed, matched a stair or window, could be ordered, as could horizontal and vertical sections that connected to make two or six section wall installations. Another variation transferred the heat for blower and ducted ventilation systems.

Most radiators were two-column “0” designs, with a hollow centre often seen still in use in residences today. There were also three and four column models, more often found in commercial buildings. Ten loop sections were most common for transferring heat to indoor air, but other choices existed.

Whenever or whatever the design selected, radiators or baseboards are still an essential component in many of today's residential hot water heating or steam systems.

Section Gallery

2. Drawing of a semi-circular radiator array3. Drawing of a radiator array for surrounding a column4. Drawing of a 1950s “Multifin” radiator cabinet and heating element5. Drawing of a  “hygienic” radiator from the 1950s6. Image of a circular, vertical tube, steam radiator

Factually Speaking

Franz San Galli, a Russian businessman, is credited with inventing the radiator in the mid-1850s.

Eliminating air blocks keeps heat
flowing in hot water/steam systems

1. Photo of a radiator bleed valve

1. Radiator bleed valve.
Click the image for more information.


Hot water heating has been around as far back as the Roman times when only the very rich got to experience that sort of home comfort. Of course, the scope of hot water heating includes steam — the higher temperature sibling to hot water. In both hot water and steam boiler systems, air collects in high places (piping, radiators) as a non-condensable preventing steam and water flow and heat transfer. This phenomena has the effect of reducing indoor temperatures, which gives both customers and installers a headache.

Early air vents were simply manual customer-activated valves opened periodically to allow air to leave the system. Steam has a bad habit of drawing air into the system because water expands 1,500 times to become steam. When steam condenses and collapses back into water it creates a huge vacuum, and air is sucked into the system through the slightest pinhole or loose connection. Today’s automatic steam air vents or “air eliminators” are actuated by heat. They are normally open, until the steam warms them up causing valve closure — one more step toward automated heating systems and less customer unhappiness.

Hot water systems don“t draw in air as easily as steam systems, but it still happens on cool-down. More air is dissolved in the water itself, and it can be driven out when temperatures near the boiling point. Hot water systems that are full of air have no heat, but plenty of angry customers, so as with steam systems, air has to be removed to let water take its place to heat the radiators and warm the indoor space.

To compound the air problem, early systems did not include an expansion tank. Air-laden fresh water always had to be drawn in through the make-up valve and expelled through the safety valve with every heat-up and cool-down cycle. At first, expansion tanks were plain vessels positioned at the top of the system and kept half full of water to maintain pressure. They worked fine except that over the summer when the system was cool, air was dissolved into the water and the tank became “water-logged,” full of water, leaving nowhere for the air to collect where it was useful. Then it was back to the old “in-the-make-up valve” and “out-the-safety” again. The solution was a barrier between the water and air, so the bladder expansion tank was born.

Step-by-step these boiler accessories were invented by necessity and included in the design for efficient automated operation — and more happy customers.

Section Gallery

2. Diagram of a automatic air vent on low-loss header3. Image showing the bleeding of air from a radiator4. Image of an expansion tank

Factually Speaking

Because steam must circulate at high temperatures in steam heating systems, more energy is lost than is the case with hot water systems.

Radiant floor heating:
Bringing Roman comfort back to your feet

1. Image showing radiant system plumbing

1. Radiant system plumbing.
Click the image for more information.


A boiler, all the accessories, and the radiator or baseboard — for much of the past century, that was what was installed for automated hot water heating as it evolved. And then a blast from the past! In-floor radiant heating was introduced in the 1970s, resurrecting a technology with its roots in Roman times. The boiler was still essential — but the radiator was gone, replaced by rows of tubing moving hot water in the floor, under the floor, or on the floor.

For in-floor slab, tubing is installed on the wood floor, or in panel tracks, before the concrete floor (slab) for the basement and/or the main floor is poured over them. For under-floor, tubing is installed in the ceiling joists, when they are open, often with aluminum “plates” to deflect the heat from the tubing up through the floor. On-floor or over-pour is a technique used to install tubing on an existing floor base, or when panels with space for tubing are laid down. Once the tubing is in place, a new floor — slab, hardwood, carpet, tile, linoleum, whatever the homeowner desires — is installed over the tubing arrays.

What makes it all work is plastic “PEX” tubing with an oxygen barrier. Wirsbo was the first to unveil Polyethylene cross-linked tubing (PEX) in Germany, first for potable water systems in the late 1960s, followed by “PEX-a” for cooler radiant heating. Worldwide, an estimated 12 billion feet of PEX have been installed.

Back in 1992, Rob Waters, C.E.T., told a heating conference in Halifax, Nova Scotia: “The rebirth in radiant under-floor heating was fueled by technological advances in specialized plastic tubing, flexible, durable, continuous length and not subject to corrosion. High tech controls, with anticipating thermostats, individual zone (room) controls, and water temperature controls precisely control these systems,” he explained. “However, the real benefits are comfort and energy efficiency. Warm floors produce warm feet, no cold spots or drafts....”

The re-birth in hot water space heating was well underway.

Section Gallery

2. Image of a radiant heat manifold assembly with flow meters3. Diagram comparing forced-air heat to radiant heat4. Photo showing tubing laid out on the floor surface

5. Photo shwoing tubing that is installed under the floor6. Photo shows installers laying out the tubing7. In this photo, self-leveling flooring compound is poured on the tubing


Article Sources

Boiler to radiator: Designs for heat transfer

  • Research from the archives of the HVACR Heritage Centre Canada (DCSB #34, HD1005V and DCSB #45, HD1005HH)
  • Hand Book of Sovereign Radiators and Boilers, Catalogue No. 55R, 1912, Taylor-Forbes Co. Ltd., Guelph, Ontario, 108 pages, hard bound.
  • The Dunham Hand Book, No. 514, C.A. Dunham Co., Ltd., Toronto, Ontario, 432 pages, mid-1930s. HHCC Collections.
  • American Radiator Co., The Ideal Fitter, 21st Edition (New York, NY:n.p.,1925), 348 pages, hard bound. HHCC Collections.
  • “Of Roughing-In Dimensions for Boilers, Radiators Pocket Portfolio,” Warden King Ltd., Montreal, Quebec, undated (before 1923), HVACR Heritage Centre.
  • “Canada Collections,” Lewin-Langsner Archival Collection, Montreal, Quebec, 2010.

Eliminating air blocks keeps heat flowing in hot water/steam systems

  • Research from the archives of the HVACR Heritage Centre Canada (DCSB #12, HD1002E).

Radiant floor heating: Bringing Roman comfort back to your feet

  • Research from the archives of the HVACR Heritage Centre Canada (DCSB #100).
  • “Radiant heating,” via http://www.pexsupply.com.
  • “Radiant Floor Heating, Upnor Inc.,” via http://www.uponor-usa.com/Misc/Applications/Radiant-Floor-Heating.aspx.
  • “Underfloor on comeback,” Mechanical Buyer and Specifier magazine, Plumbing, Piping and Heating, September 1992, p 12.

SIDEBAR

  • Research from the archives of the HVACR Heritage Centre Canada.
  • “Uponor,” via http://www.uponorpro.com)

Factually Speaking

  • Research from the archives of the HVACR Heritage Centre Canada.

Image Credits

Boiler to radiator: Designs for heat transfer

  • Taylor-Forbes Co., Ltd., Catalogue No. 55R (Guelph, ON: n.p., 1912).
  • Ibid.
  • Ibid.
  • Dominion Radiator Limited, Dominion Ideal Fitter (Toronto, ON: n.p., 1951), c/o Lewis-Langsner Archive Collection, Montreal, Quebec, HVACR Heritage Centre Canada .
  • Ibid.
  • James Morrison Co., Illustrated Catalogue and Price List ... (Toronto: R.G. Mclean, 1888).

Eliminating air blocks keeps heat flowing in hot water/steam systems

  • “Bookshelf Boyfriend,” via http://www.flickr.com/photos/bookshelfboyfriend/2531458818/.
  • “Magic Foundry,” [Attribution-NonCommercial-ShareAlike 2.0 Generic (CC BY-NC-SA 2.0)], via http://www.flickr.com/photos/magicfoundry/1764196037/.
  • “Incurable hippie,” [Attribution-NonCommercial-ShareAlike 2.0 Generic (CC BY-NC-SA 2.0)], via http://www.flickr.com/photos/hippie/4312157774/.
  • By Jaho (Own work) [CC-BY-SA-3.0 (www.creativecommons.org/licenses/by-sa/3.0) or GFDL (www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons.

Radiant floor heating: Bringing Roman comfort back to your feet

  • David Wuertele [CC-BY-2.0 (www.creativecommons.org/licenses/by/2.0)], via http://www.flickr.com/photos/51357668@N00/2829192461#.
  • Ron Shuker, HHCC.
  • “Uponor,” via http://www.uponor-usa.com/Misc/Applications/Radiant-Floor-Heating.aspx.
  • Ron Shuker, HHCC.
  • Ibid.
  • Ibid.
  • Ibid.