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A couple months, glass block, a lot of white paint, makes for a different boiler room.

I installed an RD 1400 microprocessor control system, been fiddling with the vents, and I'm discovering the miracle of steam heat.

I know a few guys that wax all crazy about how incredibly efficient it is, they don't know why it went out of style, and how delightfully warm and cozy it makes an apartment. Well, I'm now one of those guys.

I'm heating a 5 unit, (approx.) 6600+sf 1929 apartment building for less money than I spend to heat my bungalow, and I keep the apartments @ 72.5degF, and my bungalow is kept @ 65 to keep it from being too expensive.

For the apartments that had cool or cold radiators, I've been fiddling with orifice sizing, and I got it so every radiator in the place heats quickly, evenly, and wonderfully. When you get it right, it's like magic.

The control kicks on the boiler, it fires for about 7 minutes, there's a "sigh" from all the vents on the condensate returns for about 5 seconds, then there's what I call "the flash". Suddenly, in the space of a few seconds, all those 20 & 30 pound iron fittings on the boiler go from being room temp to too hot to touch, and in an instant every radiator is warm and toasty. In an instant. With no pressure; the gauge never bumps off 0. OK, maybe it's .01 psi, but the gauge doesn't move. (yes, it works, I installed a new one.)

It's freaky. In an instant.

My building is solid masonry, 14" thick walls, cast concrete coffered 1st fl. platforms with structural terra cotta infill, 2nd fl. platforms are wood frame, wood lath plaster, double hung single panes, storm windows, and not a speck of insulation anywhere. Nothing. It's the poster child for what should be a completely inefficient costly mess of a masonry building. And it heats in cold Chicago weather for surprisingly less than <$300 a month, while maintaining >72degF average temps in all apartments.

How? Why? This isn't supposed to work this way. But it does. I can't figure it out.

Is there some magic thermodynamic principle I'm missing?

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A couple months, glass block, a lot of white paint, makes for a different boiler room.

I installed an RD 1440 microprocessor control system, been fiddling with the vents, and I'm discovering the miracle of steam heat.

I know a few guys that wax all crazy about how incredibly efficient it is, they don't know why it went out of style, and how delightfully warm and cozy it makes an apartment. Well, I'm now one of those guys.

I'm heating a 5 unit, (approx.) 6600+sf 1929 apartment building for less money than I spend to heat my bungalow, and I keep the apartments @ 72.5degF, and my bungalow is kept @ 65 to keep it from being too expensive.

For the apartments that had cool or cold radiators, I've been fiddling with orifice sizing, and I got it so every radiator in the place heats quickly, evenly, and wonderfully. When you get it right, it's like magic.

The control kicks on the boiler, it fires for about 7 minutes, there's a "sigh" from all the vents on the condensate returns for about 5 seconds, then there's what I call "the flash". Suddenly, in the space of a few seconds, all those 20 & 30 pound iron fittings on the boiler go from being room temp to too hot to touch, and in an instant every radiator is warm and toasty. In an instant. With no pressure; the gauge never bumps off 0. OK, maybe it's .01 psi, but the gauge doesn't move. (yes, it works, I installed a new one.)

It's freaky. In an instant.

My building is solid masonry, 14" thick walls, cast concrete coffered 1st fl. platforms with structural terra cotta infill, 2nd fl. platforms are wood frame, wood lath plaster, double hung single panes, storm windows, and not a speck of insulation anywhere. Nothing. It's the poster child for what should be a completely inefficient costly mess of a masonry building. And it heats in cold Chicago weather for surprisingly less than <$300 a month, while maintaining >72degF average temps in all apartments.

How? Why? This isn't supposed to work this way. But it does. I can't figure it out.

Is there some magic thermodynamic principle I'm missing?

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Only David Copperfield knows for sure. [;)]
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. . . How? Why? This isn't supposed to work this way. But it does. I can't figure it out.

Is there some magic thermodynamic principle I'm missing? . . .

It's probably, at least in part, due to the magic of radiant heat. A hot object in a room makes people feel comfortable.

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The only reason to insulate those pipes is to lower the boiler room temps.

or to have more steam condense in the radiators rather than in the pipes before reaching the radiators. I think that's the intent behind the design of steam heating systems.

Kurt, it might be Karma. You pleased your tenants (rare for landlords) and low heating costs is your reward. Or, maybe the utility just read the meter wrong. [:-bigeyes

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I think Lamb has something close to it. The boiler room is nice and toasty, and the entire 1st fl. platform is like a big radiant heat sink. After that, I have no idea.

Yes, I always thought insulation was intended to keep the condensing happening in the radiators and not in the long lateral runs. But this one doesn't have any insulation...never did, and the radiators all heat up at the same time, and there's not a single clank, ting, ping, or rattle. Ever. It just gets hot. Quietly.

Which I've never experienced before with any steam system. There's almost always a little ping or ghost rattle in every other system I've operated.

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Which I've never experienced before with any steam system. There's almost always a little ping or ghost rattle in every other system I've operated.

Yeah, Dylan had that problem in 1965. In his room, the heat pipes did cough, the light flickered in the opposite loft, the country music station played soft but there was nothing, really nothing to turn off.

Can your lucky tenants control the heat fairly well at the radiators?

Can those valves have thermostat controls added?

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Kurt, I assume it is a two-pipe system. Much better than single pipe. As for efficiency, I think it says more about how leaky your bungalow is or how inefficient that heating system is. Steam may be an efficient way to distribute heat, but steam does not change combustion efficiency.

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Steam radiators only have one pipe. The steam escapes through the valve on the left. When the boiler shuts down the steam condenses and drips back down to the boiler through the same pipe it came from. It's why the radiator has to tip back towards the supply pipe.

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Can your lucky tenants control the heat fairly well at the radiators?

Yes, but it's done with correct orifice sizing. There's 37 or more sizes; depends on mfg.

Thermostatic valves are used when some other portion of the system is unbalanced.

The idea is balancing it. This isn't always possible with all systems; some aren't engineered or installed as well as others.

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Kurt, I assume it is a two-pipe system. Much better than single pipe. As for efficiency, I think it says more about how leaky your bungalow is or how inefficient that heating system is. Steam may be an efficient way to distribute heat, but steam does not change combustion efficiency.

A common fallacy I once shared. Two pipe is not inherently better. It was attempted because there were totally screwed up single pipe systems. Some folks managed to screw up the two pipes also.

Part of my amazement is how incredibly well single pipe systems operate when set up correctly. Instant heat distribution at minimal cost with nice toasty temps and nicely humidified air for the extremely dry plaster lath construction.

I've made no claims whatsoever that the system is efficient. I said the package is cheap to operate.

The bungalow is a leaky, but not horrible for the age, but it's old forced air, with lousy register placement.

I think you're misreading my entire post.

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Steam radiators only have one pipe. The steam escapes through the valve on the left.

Surprisingly, very little steam escapes when you get the orifice right. The steam pushes out the air which is nicely humid, but it's not steam or excessively wet.

There's the fire, the flash, then it's hot all of a sudden. It's a timing thing. It's freaky. I think I lucked onto a good system. Well, not all luck. I could tell by the pipe it was probably OK.

The pipefitting and distribution lengths are impeccable. The radiators are really nice castings; clean lines, not huge and clunky, lotta fins but not the heavy bulbous type. It's beautiful iron, one coat of heat resistant paint.

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Mike, radiators for two pipe steam systems have...two pipes. The radiator vents for one pipes systems are for air, not steam.

Thanks. I just did some Googling.

Maybe I am not paying attention but I don't recall ever seeing a two pipe steam radiator. I might only see about 2-3 steam systems a year.

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A common fallacy I once shared. Two pipe is not inherently better. It was attempted because there were totally screwed up single pipe systems. Some folks managed to screw up the two pipes also.

I've made no claims whatsoever that the system is efficient. I said the package is cheap to operate.

I think you're misreading my entire post.

Almost all of the one pipe systems I have inspected take a long time to heat the radiators. I see two-pipe systems mostly in larger buildings and they generally heat up much faster.

Maybe I did not understand your point, but I thought that being cheap to operate means it must be efficient.

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Steam radiators only have one pipe. The steam escapes through the valve on the left. When the boiler shuts down the steam condenses and drips back down to the boiler through the same pipe it came from. It's why the radiator has to tip back towards the supply pipe.

Mike,

The steam condenses in the radiator and the condensate can flow back while the steam is still entering the radiator. When condensate gets trapped in a radiator because it does not slope properly that can create the banging sound associated with steam heat. The sound is water flashing back into steam.

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Almost all of the one pipe systems I have inspected take a long time to heat the radiators. I see two-pipe systems mostly in larger buildings and they generally heat up much faster.

Maybe I did not understand your point, but I thought that being cheap to operate means it must be efficient.

At some point yes, but I think it's much more involved than simple combustion efficiency. Everyone's talking combustion efficiency. There's efficiency of the "package"; heating system efficiency isn't independent of the building it's in, is it?

I'm trying to understand why this large building can be heated so cheaply with a system most of us (me, at least) used to think of as inefficient.

I knew that vents were a component of the system that allowed it to work. What I didn't understand until I had the chance to tinker on my own without intervention of building owners/realtors/occupants was how delicately intertwined vents are in getting the system to heat quick and evenly.

Changing an orifice from a 5 to a 9 (the difference of about 1/32-3/64 of an inch in diameter) means the difference between a radiator being cold and it heating up instantly.

What are the conditions that allow an approximately 400 lb. chunk of cast iron to go from cold to really damn hot in 10-15 seconds?

Why does such a small change in vent size mean so much in performance?

FTR, I see my share of steam. Two pipe, one pipe, doesn't matter. Most of them are totally screwed up and work for shit. I think the problems come from the same things we see on a lesser scale in single family work....lousy design, no calc's, guys winging it, etc., and those same problems are wildly exacerbated by incompetent trades doing stuff like painting vents and radiators, or never cleaning out the traps on the two pipe jobs, or taking radiators out which throws everything off, or some other combination of things.

Also, the line vents are more important than the radiator vents. If the main vents aren't working right, then the radiator vents are having to do the job of both. There should also be vents on the mains where they make the downward drop to become the return. Often, there are main line vents stuck in overheads or walls where you can't even see them; if they're blocked or screwed up, it can totally mess up everything. I think this is a major problem in all those old buildings we see that seem messed up; they've never been maintained like they should be; vents are shot, and no one even knows where they are.

All of these systems were originally coal fired monsters. Stoke the boiler, work the coal bed, and just make the thing crank til it whistles. If it got too hot, open a window. Heck, they even piped steam out to my garage for these monster 300 lb. ceiling mount radiators in each garage bay. They must have had this building blasting heat.

Shifting to a gas fired model with an entirely different firing and steam cycle, and that probably messes up distribution too.

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The condensation of steam to water on the inside surface of the radiator moves massive amounts of heat, much more than conduction. If you size the vent properly it will utilize all the radiator surface with no waste. The same principle applies to loading an evaporator coil only in reverse. If you look up the heating degree days (HDD) and the therms of gas used during the same period,you can figure an approximation of what to expect. An average Chicago heating season will require about 6000-6400 HDD. Here is a linkto the Peoples Gas rate page to calculate your cost. Boiler room is beautiful, looks cleaner than my kitchen!

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The condensation of steam to water on the inside surface of the radiator moves massive amounts of heat, much more than conduction. If you size the vent properly it will utilize all the radiator surface with no waste.

That's what I'm trying to grasp. I can read the formula, but have no intuitive sense of what it means. Moving heat around as steam.....what's it mean?

Thermodynamics is not my strong suit.

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