IN LAST MONTH’S article, we looked at the evolution of heat sources and distribution piping. This month, we’ll look at the heat emitters.
Some of the original steam heat emitters had the appearance of a metallic mattress. In fact, they were called mattress radiators. They were relatively easy to manufacture, being made out of tin, and provided the steam a place to give up its heat and condense back into a liquid.
As the industrial revolution marched on, the heavier, more dependable, longer-life cast-iron column radiators worked their way onto the heating scene. There were many manufacturers of different types of heavy-duty radiators on the market. Some were made for steam only, while some were made for either steam or hot water. Some were one-pipe, some were two-pipe and many could be used with either steam or hot water. These grand old guardians of comfort stood sentry for many years, keeping the occupants warm and comfy and protecting them from the ills and chills of the night.
Many of these radiators are still in operation today. In fact, a resurgence has occurred in recent years with people restoring historic buildings. Certain market-savvy manufacturers have begun manufacturing antique-looking radiators to fulfill the needs of this growing market segment. God protect the backs of the men who move these behemoths.
As time went on, the large amount of space these guardians of comfort took up became more valuable, and they were eventually phased out, replaced by more compact baseboard convectors, as well as radiant floors, walls and radiant ceilings.
All these leaps in technology owed their existence to the availability of the circulator. This allowed the designer the flexibility to squeeze lots of Btu out of a small box, or even no box at all in the case of radiant floors, walls and ceilings.
Some of the earlier radiant floor heating systems used steel pipe. This worked quite well under ideal circumstances. The definition of ideal circumstances would be with the tubing completely surrounded with cement, and the operating temperatures kept as low as possible while satisfying human comfort needs. That’s the ideal for steel tube in cementitious materials.
I’ve also come across steel pipe imbedded into the tops of floor joists with the tubing 16 in. on center. Although it is different than tube in cementitious materials, it requires a higher operating temperature to deliver the goods.
Another ideal requirement was the need to keep the length of the tubing run as short as possible to avoid continuous expansion and contraction as a result of warm up and cool down.
As time went on, and production of soft copper tubing became less expensive, use of steel pipe gave way to copper. Copper is more conductive than steel, and it can resist external and internal corrosion better than its steel cousin. It could also be manufactured in small diameters more easily. With the advent of the pump, it allowed use of what we’d consider microtubes, compared with its gravity-circulated brethren. The use of 38-in. copper tubing in radiant ceiling hot water heating systems was prevalent back in the 1950s.
Not only was hot water heat using a smaller tube, but steam was also following suit. The steam men had been holding their ground, continuing to profess the virtues of steam heating over that of its wetter cousin. They introduced the Iron Fireman steam heating system, which by any standard was an engineering marvel. Not only did steam provide the thermal portion of the equation, but it also provided the mechanical energy necessary to turn a fan in the convector to quickly heat a room using forced convection. Quite the trick when you think about it. Some of these gems are still out there working.
The problem with these systems was that they required a lot of maintenance compared to hot water, and the knowledge to maintain them was dying along with the designers and installers who had put them together in the first place. These guys are on the other side of the lawn now, laughing at those of us who come across their mechanical marvels and try to figure out what exactly was going through their heads and their systems.
More recently, the radiant revolution had a renaissance of sorts, thanks in part to television shows like “This Old House” and the likes of Richard Trethewey. It was a step forward from the copper and steel tubing days to the plastic tubing of today.
Even today, some types of tubing require more attention than others due to the need for, or lack of, oxygen barriers. Between the oxygen barrier debate and the application discussions (above the floor vs. below the floor), this conversation could go on forever.
Suffice it to say that the tubing we’re using today should last long past the life expectancy of the original designers and installers, and a couple of generations of the families that live in these homes.
Tune in next month as we continue our journey. Until then, Happy Hydronicing!
Mark Eatherton is a Denver-based hydronics contractor. He can be reached via e-mail at [email protected] or by phone at 303/778-7772.