Image courtesy of George Marks / Retrofile RF/ Getty Images.

I was, I’m sure, not even in the minds of my someday-to-be parents, but I’ve spent a lot of time in that decade of the Great Depression nonetheless. I like to think of them as teenagers as they wondered what was to be. They truly were the Greatest Generation.

There were a lot of writers then who focused on the art of steam- and hot-water heating back then. I imagine most of the hydronic heating work at the time was going into the homes of those who had managed to escape the worst of the Great Depression. I love this time in heating history because it was a sort of pause, and the writers spent time explaining what was going on, and why. I thought I’d share some of that with you. You can learn a lot by looking back over your shoulder.  

I asked one of the 1930s Dead Men how the various systems compared in terms of cost during his time. He told me that hot-air heating was the cheapest, which I expected it would be because a furnace will always be cheaper than a boiler. He then said that steam heat cost twice what a hot-air system cost, and an ordinary hot-water system cost one-third more than an ordinary steam system. This was interesting. I figure he was taking into consideration gravity-hot-water systems, which were still popular because the circulator had just been invented. Gravity systems used very large pipes on both supply and return.

Finally, he told me that vacuum- and vapor steam systems cost one-third to one-half more than ordinary steam, depending on the system chosen. Those systems were really top of the line. They were fast, quiet and economical.

Then I asked how much fuel each system required on average. Coal was kind in the 1930s, and the Dead Man said that it took 12 tons of coal to heat a typical building with hot air and a cold-air supply. It took nine tons of coal to heat with direct steam radiators, and 8 tons of coal to heat with hot water. And then he said that a vapor or vacuum system would need a bit less than eight tons of coal, and coal averaged about nine bucks a ton. So you spend more going in but much less as the years went by when you chose hydronics.

Next, I asked him what the average life of each system was. He said that hot air would last from 10 to 12 years, with approximately 25% of the original cost spent on repairs. Steam- and hot-water systems would last about 25 years, with an average of 10% of the original cost spent on repairs. Again, it cost more upfront but the long-term savings were significant.

I learned from the U.S. Census that prior to WWII, half of the buildings in the U.S. that had central heating had hydronics. Imagine that. These days, it’s less than 10%. Why? Because a furnace will always be cheaper than a boiler.

I listened to another Dead Man who told me that the early radiators often wound up on inside walls because that required less piping. But they soon realized that a radiator installed on an outer wall would draw the cold air toward it, warm and expand it, and cause it to rise along the cold wall. However, a radiator on an interior wall would draw cold air from across the floor, setting up uncomfortable drafts. So it’s better to spend the money on more piping and keep the customers happy, right?

Oh, and how about this? A radiator doesn’t care whether it’s getting steam or hot water. It’s looking only at temperature, not latent heat. Steam at 215° F will give out the same amount of heat as water at 215° F. That’s important to know. Consider the definition of EDR (Equivalent Direct Radiation). One square foot of steam EDR will give up 240 Btu when there is 70° air on the outside of the radiator and 215° steam (or hot water) on the inside of the radiator. Latent heat means nothing when it comes to sizing radiators; only the temperature of the gas or liquid matters.

Another Dead Man told me that before we had diverter tees (think B&G Monoflo tees, or Taco Venturi tees) they had to make sure they kept at least five feet of main between the supply and return to each radiator. This was for one-pipe systems that didn’t have a circulator. The hotter water would always be at the top of the main with those gravity systems, so they fed each radiator from the top of the horizontal main and returned the water from the radiator into the side of that same main. As you can imagine, this is part of what made diverter tees so popular once they showed up.

Open gravity systems with expansion tanks in the attic called for relatively large pipes, but it you used a closed compression tank you were able to save about 25% on pipe, valves, and fittings because you could run the closed system at a higher pressure than what you could use in an open system (typically 180° F max). The higher temperature of the closed system also caused the water to circulate more quickly.

For a time, there was a patented closed system of hot water that operated the coal-fired damper (by using chains) based on the pressure within the system. It sensed the pressure of the air trapped inside the steel compression tank. But then temperature-responsive dampers showed up and that spelled the last of sensing the air pressure within a compression tank, but I thought it was an interesting way to get the job done back when coal was king.

And did you know this? The early copper fittings had a groove cut into the inside of the fitting. It was set back a bit from each open end. On the outside of the fitting there were marked spots to indicate where the fitter was to drill one hole. He chose the most convenient spot for that fitting, based on its location. Then he’d use a blowtorch to heat the fitting. He’d insert a solder wire into the hole and capillary action would take over from there. The Dead Man said nothing about flux. I wish I could have given him a heads-up.

Hot-water radiator valves of the time had a 1/16th inch hole drilled in the valve seat. This served to protect the radiator from freezing when the radiator was not in use and the valve was closed. The hole allowed enough circulation through the radiator to prevent the water from reaching 32° F. How about that!

And guess what they used to remove boiler scale. Kerosene! They said that it worked much better than prepared compounds, and it was cheap.

Steam boilers have glass tubes that need to be replaced from time to time. You would use a special glass cutter for this nowadays, but back then, the fitters did it a different way. They would wet a three-cornered file. Then they’d take the tube in their left hand (this Dead Man favored righties in his writing). You mark with your thumb and forefinger where you need the cut to be. Then you file quickly and lightly several times to mark the cut on the tube. Then, with the tube in both hands, and each thumb on opposite sides of the mark, you carefully bent the tube. It would either break exactly on the mark, or send you looking for the first-aid kit.

I also learned that hot-water boilers were very similar to steam boilers, the big difference being the hot-water boiler didn’t have to have the spaces reserved for the steam to break loose from the water. That meant a hot-water boiler could have more heating surface than a steam boiler, and the water moved much more slowly through a hot-water boiler than it did through a steam boiler. But they paid more for hot water, and that’s part of the reason why they did.

Another thing that eventually allowed hot water to win out over steam was that you could have radiators at the same level as the boiler when you chose hot water. Not so with steam, where the radiators often found themselves high up on the wall or even on the ceiling. And I suppose many homeowners didn’t like the way that looked.  

So even though hot water heat was the most expensive system at the time, it brought with it enough features to make it win out over steam heat after the Great Depression and WWII ended.

But the furnace ultimately won the war, and you know why. Cheap matters, especially if the person doing the selling doesn’t take the time to learn about the differences between the systems and how to explain those differences in a way that makes the customer see the value of spending a bit more upfront.  

And that still applies today.

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