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| Photo credit: ©istockphoto.com/Taylor Hinton |
An engineer friend called to ask me some questions about old steam-heating systems, particularly those of the New York City variety.
She was writing a paper on what to watch out for when considering an energy management system for an older building with either one- or two-pipe steam heat. She mentioned there were lots of case studies on newer buildings, mostly provided by the folks selling EMS packages, but she couldn’t find any scientific research on older, steam-heated buildings. You know the sort where they had two identical buildings, each with the same problems, and they put an EMS in one but not in the other.
I told her I didn’t think two such buildings existed with the exact same problems, and knew of no unbiased research.
She told me that she knew of a building where they installed the EMS, watched it for a while, and then turned it off to see what would happen.
“And what happened?” I asked.
“They saw a 3° difference in temperature. Up in some spots, down in others.”
And that made us both wonder if the EMS was worth what it cost to install and maintain. Perhaps they’d be better off spending the money on basic maintenance – good air vents, steam traps, pipe insulation, stuff like that.
Where the thermister goes
There’s a device that’s been around longer than I have that manages steam systems in NYC apartment buildings. You set the control to sense the outdoor temperature, and you place a thermister on a pipe that’s going to tell the control when steam has filled the pipe to that point. That’s supposed to indicate that steam is everywhere in the system. The control will then begin a countdown-to-shutoff cycle based on the current outdoor temperature.
So, imagine it’s 40° outside. The burner comes on and steam travels down the pipe and finds the thermister. The control may then decide to run the burner for another 20 minutes because it’s 40° outside, which is chilly but not freezing. On a colder day, the control will run the burner longer.
OK, let’s introduce people into the mix. Who picks the spot for the thermister? Probably the installer, right? Suppose he places it near the end of the longest steam main. That seems like a grand place to put it, but what if the main vent clogs with debris and won’t let the air escape ahead of the steam. That happens every day, and where there is air, steam will not go. So the end of the main stays cooler than the thermister’s trigger point and the burner runs on and on and on. The boiler is burning lots of fuel and the tenants are cold. Happens every day, and the price of a new main vent will solve it, but who’s noticing this?
Now let’s install an EMS in the building. It will tell us that we’re burning a lot of fuel, which we already know. It might even tell us that some tenants are too hot and others are too cold. We get that news as a computerized report, or perhaps as a Web app, which we access from our iPad anywhere in the world. It will tell us what we could find out by walking to the end of the pipe and looking at that clogged main vent, or by talking to the tenants.
Oh, and I’ve seen thermisters installed on wet-return lines, which will never reach the temperature of steam because those pipes are always filled with liquid water. I’ve seen them installed on sewage lines, which probably won’t get that hot either. Why did the guy do that? Because he could.
I once saw a thermister installed on a cold-water pipe. Hey, a pipe is a pipe, right? And I even saw one installed on the gas main.
“Why did you move that thermister to the gas main?” I asked.
“We’re trying to save gas,” the superintendent explained.
Supers can be so creative.
Modern electronics and monitoring
But back to the modern EMS. Nowadays, everything is about electronics and monitoring and knowing what’s going on in the building and catching people opening windows in the winter so the landlord can toss them out. EMS packages are smart and sexy, but I don’t think they’re the answer to the problems we see in older buildings heated with steam. I think they should be the last step, and only if you think it’s worth it at that point.
For instance, consider a two-pipe-steam riser in an apartment building. It goes up, say, 20 stories. The steam supply is on the right; the condensate return is on the left; the radiators are the rungs of the “ladder,” and at the outlet of each radiator we have a thermostatic radiator trap. That’s typical.
OK, one day the trap that serves the radiator on the first floor fails in the open position, sending steam into the condensate return line, which is way too small to handle steam. We now have steam pressure in both the supply and the return lines, and this happens before the air can move through the radiators on the 19 floors above the failed radiator trap and exit the system through the vent on the boiler-feed-pump’s receiver. Keep in mind that where there is air, steam will not go.
Now let’s bring in the people again. The guy with the bad trap will always have heat. Everyone above him will be cold. They’ll call you; the guy on the first floor won’t. He’s happy.
A knucklehead shows up and installs one-pipe-steam air vents on all the two-pipe steam radiators. That allows air to escape the radiators so the steam can enter. The radiators get hot and the tenants praise the knucklehead.
But now the condensate won’t drain from the radiators because there’s steam pressure in the return from the failed trap on the first floor. The water builds up within the radiators, gurgles and squirts from the brand-new air vents. The boiler goes off on low-water. The boiler-feed pump comes on and does its job.
Later, when the boiler finally shuts down, the water comes cascading from the radiators and overflows the feed-pump’s receiver, leaving the super with a big mess and the building owner with a need for expensive water-treatment chemicals.
And you say you want an EMS?
I’d fix the traps first. I’d also make sure any main vents are the right size and in the right place. I’d check the near-boiler piping to see if the boiler can produce dry steam. I’d made sure the asbestos that came off the pipes gets replaced with fiberglass so the steam doesn’t die on its way to the furthest radiators. Without insulation, the boiler will run a lot longer and that inspires tenants to open windows. The EMS can let you know that the tenants are doing that, but you could also learn that on your own by stepping outside and looking up.
Unless you get an older steam system working as it should be working, sensors and software will just let you know that something is wrong, which you already know.
The Lovely Marianne asked me about the weather the other day. I started to look at The Weather Channel app on my iPad, but then a novel thought struck me. I put down the iPad, opened the door and stepped outside. I looked up and got hit in the puss with rain. “It’s raining,” I shouted. “Thanks!” she shouted back.
Point being, you don’t need a weatherman to know which way the wind blows. When it comes to older heating systems, what you do need is knowledge of the quirks of those systems and a willingness to care for those old systems.
That’s not sexy. But it is smart.
