What you don't know about heating can cost you.

It was one of those winter days when the wind snapped off the ocean like an icy bullwhip. The weatherman said we could expect more of the same for at least another week. The people who came into the warmth of the coffee shop were grumbling and stomping the slush off their shoes. "Cold enough for you?' the guy behind the counter asked a young woman. She didn't smile.

I was a bit early for my appointment so I figured I'd duck in there for a hot cup of coffee. It was convenient, right across the street from the building where I was to look at a problem boiler.

I sipped my coffee and looked at that building. It was ten stories tall and looked to be about 60 years old. The windows on the lower floors were half open. Those on the upper floors were shut. Two-pipe steam heat, I thought. Definitely two-pipe steam. It's freezing and the windows are open just right.

That's the funny thing about this business. You look at enough heating systems, they begin to talk to you - even from the outside!

I knew I'd find a leaky boiler in this one. The president of the co-op board had told me that already. I wondered if he also knew his radiator steam traps had failed. I could tell that from across the street as well. That's why the windows on the lower floors were open, in spite of the frigid cold. I also knew I'd find the folks on the upper floors freezing. That's what happens when radiator steam traps fail, you know Some people roast while others freeze. And then there are the spiraling fuel bills.

Radiator steam traps are simple enough. They're little automatic valves that, when working properly, let air and water pass, but close against steam. In the typical New York City apartment building, the traps open and close about 175,000 times a year. Most trap manufacturers say the working parts of a radiator steam trap last about five years. After that, they die a quiet death and begin to pass steam into the return lines. That's when the tenants begin to roast or freeze.

A two-pipe steam system looks like a ladder. The two sides of the ladder are the supply and return lines, the radiators are the rungs. The radiator steam traps stand guard at the outlet of each radiator "rung." Their job is to keep steam pressure out of the return side of the "ladder."

When they're working, steam traps set up an area of high pressure and an area of low pressure. This is important because all steam systems start out completely filled with air. The steam pushes the air our of the pipes and then condenses in the radiators. In condensing, the steam shrinks dramatically and causes the air to come rushing back into the pipes and radiators.

Steam systems actually breath, just like people!

This goes on year after year, and as long as that high-pressure-to-low-pressure relationship remains between the supply and return sides of the system, things work out just fine. The steam moves from the boiler to the radiators, clearing the air ahead of itself, and allowing the condensed steam to flow back to the boiler by gravity. The traps are like tiny heating cops who control the traffic patterns inside the pipes and radiators.

The trouble starts when the radiator traps fail. If they can't close, the steam will zip through the radiators and apply pressure to the return side of the system. If the traps on the lower floors fail first, the steam will pass into the bottom side of the "ladder" before the air can get out of the radiators on the upper floors. The result? The folks on the lower floors have warm radiators while their neighbors on the upper floors freeze. You see, steam simply won't go where air is trapped. These two gasses have different densities. They won't mix.

So the people upstairs complain to the superintendent and he raises the steam pressure. He thinks higher pressure will help. He's wrong.

High steam pressure doesn't make the steam move faster, it just adds more pressure to the trapped air. It also overheats the radiators on the lower floors because high-pressure steam is hotter than low-pressure steam. And that's when the windows fly open and the fuel bills soar.

But that's only the beginning of the troubles. In an attempt to get heat to the upper floors, the superintendent may add air vents to those hard-to-heat radiators. Sure, that gives the people on the upper floors heat because the air suddenly has a way out. But now the condensed steam has no way to get back to the boiler because the return lines are under pressure.

So the boiler begins to take on cold, fresh, make-up water and then overflow on the night-set-back cycle. The makeup water contains a lot of oxygen, which can damage the boiler and cause it to leak. And that, I figured, was why I was there in the first place. The boiler was leaking.

My crew would fix that boiler in no time, I wasn't worried about that. That's our business and we've fixed thousands of similar boilers. I was more concerned that the co-op board would listen to my story of how their boiler probably came to leak in the first place. I hoped they would listen and take my advice, because if they. didn't take care of those steam traps they'd be calling me again real soon. They'd be wasting fuel while their member tenants either roasted or froze. They'd also be living with banging pipes and higher-than-normal repair bills as the years went by.

In short, they had to begin to look at their stem system as a system, a sum of many parts. It was my job to help them see that system, to help them solve their problem by finding and curing the real cause of the problem. That's what a full-service boiler repair company does.