Solar at Home

Solar at Home

The trials, tribulations and rewards of going solar

How I saved money quickly and easily by adjusting our pressuretrol


Editor's Note: Scientific American's George Musser will be chronicling his experiences installing solar panels in 60-Second Solar. Read his introduction here and see all posts here.

Monday’s New York Times had an op-ed piece about our house. Well, at least it felt like it was about our house. The author, Richard Moe of the National Trust for Historic Preservation, discussed how pre–World War II houses use 50 percent more energy than newer ones, but can be brought up to modern standards by insulating the attic and basement, plugging air leaks, and sealing (but not necessarily replacing) old windows -- just what my wife and I have been backbreakingly doing over the five and a half years since we moved in.

I dug out our first utility bills and found that our gas usage has gone down by a third. In other words, our house used to consume 50 percent more gas than it does now. So Moe’s claims seem plausible. In fact, our weatherizing has probably done more to reduce our carbon footprint than our solar panels ever will.

Before I pat myself on the back too much, though, I need to come clean: the single biggest step we took to save energy wasn’t some elaborate and expensive project, but a simple adjustment that took about five seconds. Our Victorian-era house has a single-pipe steam heating system, which is regulated not just by a thermostat but also by a device called a pressuretrol (see photo). The thermostat tells the boiler when to fire up. The pressuretrol tells the boiler when there's enough steam in the system and it can shut down.

The pressuretrol works by keeping the pressure in the steam pipes within a certain range. When the device detects that the pressure exceeds some threshold, it turns off the boiler. As the steam gives up its heat to the house and condenses back into liquid, the pressure drops and eventually falls below the desired range. At that point, if the thermostat still indicates that the house is too cold, the boiler fires up again and refills the pipes and radiators with steam. The cycle continues until my feet are finally warm.

What I noticed is that the plumber who had installed the boiler had set the threshold way too high -- about 5 psi. The result was that the boiler overproduced steam, which not only wasted gas but also overshot our thermostat setting and turned our bedroom into an oven. Using a screwdriver, I cranked the pressuretrol down to a cut-in pressure of 1/2 psi and we started noticing the savings (as much as 10 percent) on our very next gas bill. Unlike turning down the thermostat, this measure didn't involve any tradeoff in comfort; to the contrary, our house temperature is now much more stable.

Although it took a few seconds to do, it took a year to realize the problem, and I can thank steam guru Dan Holohan's must-read (not to mention entertaining, in a gruff plumber sort of way) website and book, The Lost Art of Steam Heating. Another easy repair that conserved gas and improved livability was to replace the air vents on the main steam pipe loop in the basement. With these and other tweaks, I’ve come to like steam heat. It’s elegant, quiet, and reliable.

The moral is that a lot of energy is wasted because of ignorance, which is a shame, but relatively easy to fix.

Pressuretrol on George’s boiler, courtesy of George Musser

The views expressed are those of the author and are not necessarily those of Scientific American.

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