The Past and Future of Hydronic Heating

WITH THE DAWNING of the New Year, I hope this column finds you and yours in good health and looking forward to a prosperous 2004. I’ve decided to look into my crystal ball and tell you what I see looming on the horizon for futuristic hydronic heating systems. During the next series of columns, we’ll look at what has been and what is to be for the hydronic heating contractor. So, sit back, buckle your seat belts and let’s go back to the future!

A little more than 100 years ago, the hydronic heating contractor was making the switch from steam-based systems to much safer hot water heating systems. He was struggling with the concept that hot water heating required two pipes to work effectively, as opposed to the one-pipe steam systems he’d been accustomed to installing. Granted, there was the “safety factor” of hot water vs. steam, but at what expense to the end user?

He attempted to replicate the one-pipe steam system with some limited success. There was the Oliver Schlemmer fitting, which was used in one-pipe hot water heating systems. It allowed the hotter, less dense water to flow through the top half of the pipe, which then flowed into the cast-iron radiator, giving up its heat, causing the water to become cooler and more dense and falling to the bottom of the one-pipe main. I’ve seen one-pipe hot water systems that were parallel in flow, as well as counterflow in design.

These dead men were much smarter than they were given credit for. It causes you to stand there in amazement, looking at the piping configurations, shaking your head and thinking to yourself, “What the ...?”

I know, because I’ve been there and done that. How, I think to myself, can hot and cold water travel in opposing directions through the same pipe? I have gotten close to seeing it in my mind’s eye, but never clearly. And there were obviously some snags with the technology because, if there weren’t, the technology would still be with us!

I’m not sure, but I think that the introduction of the electric circulator was the demise of the one-pipe hot water heating system. At just about the same time, steam was still king, and the engineers had designed a two-pipe system that allowed individual control of radiators that had never been possible.

Now, instead of leaving the steam valve open and controlling the room temperature with the double-hung thermostat (window), it was possible to throttle the steam flow down enough to actually match the heating demands of the room in which the radiator sat. Room zoning capabilities.

The hot water heating guys, not wanting to be left behind, jumped quickly onto the two-pipe bandwagon and offered the same energy-efficient results without the cataclysmic explosive potential for which steam systems were notorious. Comfort with safety. What a concept.

Many of the early gravity circulation hot water heating systems (pre-electricity) are still operating today. Many of them operate without electrical power due to power-pile thermocouples generating the electricity necessary to operate the gas valve. These systems still shine today, especially during lengthy power outages.

The dead men who designed and installed these systems took advantage of the laws of nature whenever they could. The piping was pitched upward from the heat source at a specific pitch that had to be maintained for its entire length. This meant that the basements of hydronically heated homes were basically off limits to all but vertically impaired people and children.

Time moved on, electricity became available, circulation pumps began hitting the market, and hot water heating men latched onto the concept of almost instantaneous heat. Keep the boiler idling and start a circulator to cause water movement and almost immediate reaction to a call for heat. The two-pipe systems they had been installing were conducive to this idea.

The fuel sources for the boilers gradually moved from the slower, more labor-intensive solid fuels to the cleaner, labor-free, fast-reacting natural gas when and where it was available. This was the focus of many potential labor battles.

The coal miners didn’t want to give up their livelihood to natural gas. Natural gas eventually won out over the dirtier alternative fuel. Oil was also thrown into the mix where natural gas was not readily available. That’s a whole other story that this hydronician is not qualified to address (I’ve seen three oil boilers in my lifetime).

As time went on, and families grew, the basement was no longer considered off limits and became a part of the home. To use all the headroom available, hot water heating contractors made their pipes much smaller than the gravity circulation systems. With a circulator, you could move the same amount of energy through a 34-in. pipe as you could with a 2-in. gravity main.

With the introduction of gas and oil, the size of the boiler decreased substantially too. Remember, the solid fuel appliances were sized so that they would only need to be stoked and the ash hauled off twice a day. This meant they were much larger than was necessary for burning oil or gas.

Tune in next month as we continue our journey through time from the past to the future.

Happy New Year 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.