How that steam boiler got to be so big
There was a time in America when people were afraid of the air that they found inside their homes, and with good reason. Many of these people lived in tenements, and they were stacked upon each other like so much cordwood. There was little ventilation, and, even less medical attention. There was also a widespread belief that the indoor air was poisoned because so many people were breathing their body toxins into it.
In 1918, when central heating was in its infancy, there was a flu pandemic that killed 40 million people. We were afraid of the air in those days - and for good reason.
People were afraid of the air in their homes. They weren’t about to close their windows, so the early engineers who sized those first steam boilers and radiators had to put in units that would warm the building with the windows open.
When the wealthier people who lived in single-family homes made the leap from fireplaces to central heating systems they chose either steam or gravity hot water heat because that was the best that was available. They also chose coal as a fuel because that was the fuel that just about everyone used in those days. When I look in my old engineering texts, I see that the Dead Men were concerned about who was going to make the coal fire. On most days, the woman of the house made the coal fire because the man of the house was out working. The early engineers wrote books in which they warned the installers to put in boilers that would have at least 75% more firebox capacity than necessary to heat the home – just in case the man made a mistake with his fire on the weekend.
So we had boilers that could heat the building on the coldest day of the year with the windows open, and we added 75% to the size of the firebox because of the husbands.
And that’s the way it was until the 1930s. At that time, there was labor strife in the coal-mining regions. There was also a huge oil strike in Texas, and that made the price of oil was very attractive to most Americans. Many, many people decided to convert from coal to oil. And the people who did the conversions were the oil people. They’d take those old coal-fired boilers, remove the grates, and add a burner. The challenge, though, was that there has never been a reliable conversion factor from coal to oil because the heating value of coal varies quite a bit. The rule of thumb was to use so many gallons per hour based on the grate area in square feet. That seemed safe, and it worked. So the oil people did this, and they also oversized a bit - just to be sure.
So we had boilers that could heat the building on the coldest day of the year with the windows open, and to this, we added 75% to size of the firebox to accommodate the husbands, and then we added another 50% or so for the coal-to-oil conversion. And these boilers lasted for many more years.
In 1973, the OPEC Cartel shut off America's oil supply. We sat on long lines at the gas stations, waiting for a few precious gallons and checking the other guy’s license plate number to make sure it wasn’t an odd number if the date on the calendar was an even number. And many of those old boilers served their final days because few could afford to operate those behemoths anymore. A lot of those old coal-to-oil conversions became oil-to-gas conversions.
Now, how do you suppose most contractors sized the boiler for the gas conversion? Right! They used the rating of the oil burner, and then added a bit - just to be sure. And besides, the boilers that came along after 1973 were so much smaller than the boilers of yesteryear, that this made the gas-conversion contractor nervous. He added a section or two to make sure he had enough water volume. He didn’t want to get stung by a boiler that went off on low water.
So we had boilers that could heat the building on the coldest day of the year with the windows open. To this, we added 75% to the size of the firebox for the husbands, another 50% for the oil dealer, and a good 30% on top of that for the gas-conversion contractor
And that’s how we got where we got.
And those boilers are now 25 years old and many of them are failing because they’re attached to ancient and leaky piping systems. Which brings me to you. It’s now your turn to replace those old boilers. So how are you going to size it?
Are you going to read what’s on the label and give ‘em what they’ve got – adding make another 25% or so. Just in case. Think about where that’s going to put you.
Or are you going to do the right thing?