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How I saved money quickly and easily by adjusting our pressuretrol


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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





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  1. 1. Hillbilly 4:49 pm 04/9/2009

    I no nada about steam heat.
    We live in a 15 year old modular in North Central North Carolina. It was built a couple years before Palm Harbor went to Energy Star standard and had a lot of air leaks, big ones.
    Palm Harbor makes a sturdy house, this same model survived Hurricane Andrew (I was there to witness, concrete houses next to the Palm Harbor development that were flattened). The structure is sound, but first owners went CHEAP on everything, windows, insulation, not even weather strip on the doors.
    We have been doing small things to save on energy, until we cut enough to go for the bigger things. Foam insulation in the holes where wires and pipes penetrate, pipe insulation, double jacket the electric water heater, we have a solar water heater body and need the supports and the balance of system, it is big enough to add radiant in floor heat. When we add the radiant floor heat we will add insulation and new heavier plastic sheeting on the dirt floor down there. We have insulated curtain liners, during sunny days even when it its only 30 -40 degrees out I can open the drape during the day and do not have to run the heatpump, kero, or fire place at all. I cook in covered pots, use a toaster oven for smaller meals, slow steam veggies(don’t like how they come out of microwave).We plan to put a recirc on the hot water system to save the wait and waste of well water to get to the hot. We plan to put solar panels up for the well pump, solar water heater pumps and eventually for the house power. I am painting the dark shingles with Kool Seal, to cut the heat gain and to preserve the shingles until we can afford a new metal roof and decking and foam in place insulation in the ceiling/roof voil(no attic), the vinyl siding is about to expire, that will be recycle metal and extra insulation too. I want to replace the windows because the vinyl frames are coming apart. We will put in induction cook top and I plan to build a solar cooking oven /dehydrator too.
    So far we have knocked down our high energy power use by about 45%. We have also used all CFLS, but replaced 12 of those so far with LEDS, puter screens are now LCDS. Our low energy use times went from 2500kwhrs to 1200, our feb 2 years ago was 3200kwhrs this feb was 1300kwhrs, we did use the fireplace and kero heater a lot it was very cold. The firewood was deadfall from our property and relatives so it was not freshcut for the purpose. We hope we can do without the kero heater next year. The heat pump only works down to 25 so it was mainly useless (needs replaced)

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  2. 2. Joe Beanfish 1:32 pm 04/10/2009

    Cool savings. One seemingly unintuitive thing to note though. LCD screens actually use more energy that comparable CRTs. Plasmas are even worse. At least that’s what I’ve found by reading the specs on a number of them.

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  3. 3. airking1 4:57 pm 07/18/2009

    Good for you George.First of all you should have had a qualified HVAC tech work on your boiler,not a plumber.A half psi is typically too low as most systems are designed to operate between 2-5 psi.If you were overheating that could have been due to faulty traps,undersized orifices on your vents or boiler oversizing.The latter sounds like the most logical,as your house is being heated by such a low pressure.Many unaware contractors (and plumbers) make the mistake of sizing a new boiler by matching the plate rating to the old boiler.New steam boilers should always,repeat always be matched to the heating surfaces of the existing radiators.Also,your boiler,if older,may have been designed with a safety factor of a third which means your boiler could be oversized by as much as 33%Typically,steam would not be able to reach most radiators before condensing back to water,at a half psi,causing underheating and water hammer.While this adjustment of the operating control may have worked for you,your posting suggests this is a cure-all for anyone with similar problems.It is not! I would suggest to any and all readers not to tamper with operating controls as there is a degree of danger involved in doing such.It is always better to contact a qualified HVAC company and consult with them.Chris Justin,Air King A/C & Heating,Zion,IL

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  4. 4. bn 10:38 pm 11/29/2009

    please do yousef a favor and read dan holohans book "lost art of steam heating". in it he explains why almost no building with steam heat needs more then 2psi. if you work in the heating business this book will pay for itself hundreds of times over. also please vist his website heatinghelp.com

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  5. 5. Chrispy 11:56 pm 11/29/2009

    Great article. I’ve been doing green building and retrofitting for over 25 years. Even had a project featured on Discovery Channel’s Greenovate Show. There are so many small and affordable steps folks can take before going solar. One analogy I use is that just replacing four 75 watt incanadescent lights with 25 watt CFL’s or LED’s can save 200 watts – the same amount of energy made by one typical solar electric module. So, spend $20 for CFL’s or under $200 for LED’s that will last 20 years and you have the same impact as a $1,000 solar panel. The absolute first step I recommend for everyone is replace ALL incandescent lighting and kill all of the power vampires. Shameless plug: New Leaf America.com has a great selection fo hard to find dimmable and 3 way CFL’s and LED’s along with Smart Power strips, showerheads, etc. Keep up the great work.

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  6. 6. ddrescher 2:24 pm 03/21/2011

    I installed a Vaporstat by Honeywell to replace the Pressuretrol. I set it to cut in at 2 ounces and cut out at 8 ounces.

    The new oil burner has a water level monitoring system that shuts down the burner for 2 minutes ever 9 minutes. Even after the burner shut off, the controller continued to track the same 11 minute cycle. The burner would come on for a minute to 8 minutes and then was shut down for 2 minutes while the water level was measured.

    I installed a wire from the burner to the controller to reset the controller back to zero. Now I get a full 9 minute burn and the house heats more quickly without 2 minutes of boiler heat going up the chimney.

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  7. 7. BadgerBoilerMN 10:33 am 08/3/2012

    Not all “plumbers” are hot water/steam qualified. Here in Minnapolis/St.Paul we have to be licensed for hot water and steam, plumbing, warm air, etc.

    It is all well to “adjust” you own steam boiler but a qualified professional should have a look at safety controls and water quality on a regular basis. A steam boiler can hurt you if you neglect it.

    Your point is a good one. When we look at an old house in need of a new boiler we always ask about insulation and window upgrades. Sizing the boiler to radiation is the key in steam but if you have a 2 pipe and convert to a condensing boiler sizing the boiler to the heat load is the only proper procedure.

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