Apartment Radiator Temperature | Hacker News Reader

Apartment Radiator Temperature

terg.is

70 pointskrschultz21 comments

Single Pipe Steam Radiator[1] – what a quaint solution. I see how they got there, cheaper to build and can, in optimal conditions, be made to work within certain limitations.

I think I might try a no-moving-parts solution and attach an electric heating element to my bleed valve. By heating it just before the steam cycle starts you could prevent steam from entering your radiator, then after a suitable interval, stop heating it, let the air out, and begin your personal, abbreviated cycle.

You might also have success with partial air entrapment in the radiator by heating a little early and keeping the bleed valve closed for the rest of the heat cycle, thereby reducing the available power from the radiator but spread over the entire heating cycle.

In any event, you will want to let the air bleed open after each heat cycle to let your water go.

Oh, and incidentally if you don't have thermistors laying about: http://www.maximintegrated.com/datasheet/index.mvp/id/2815 there is Arduino code. One pin, two wires, one resistor, a bunch of probes, all calibrated and 0.5°C accuracy from -55°C to 125°C. A couple bucks each, you mostly save that in ancillary component costs.

EOM

[1] http://en.wikipedia.org/wiki/Hydronics#Single-pipe_steam

Interesting! I was thinking of attaching a small geared DC motor to the main steam valve on the radiator, but controlling via the auto-bleed is a really cool idea. I've been a little worried about damaging the bleed valve, but it's an elegant solution.

EDIT - could you elaborate on how heating the bleed valve is a good way of controlling it? Isn't it moisture based? --Andrew (Terg.is)

My understanding of the bleed valves is that they are normally open devices which close when heated. The cycle goes something like this:

at rest: radiator full of air, valve open

steam begins flowing: steam is displacing air from radiator, bleed valve begins heating up

bleed valve closes: radiator is now full of steam, some of which condenses and ideally runs back down pipe, if your building hasn't shifted too much over the years. any condensed steam is replaced with new steam from pipe

boiler stops: steam is no longer coming up the pipe. As the steam in the radiator condenses we suck air back in through the bleed valve. radiator is cooling.

bleed valve opens: at some point the radiator cools enough that the bleed valve opens. We are now ready to begin the cycle again.

Additionally, I think there is a time delay component in the bleed valve to let it get the air good and purged before it closes.

From the wikipedia page:

The valves close when steam reaches them, due to a small amount of alcohol in them turning into vapor and exerting mechanical force to close the valve.

controlling the bleed valve is definitely the way to go. The commercial solution is a bleed valve that opens and closes based on the temperature in the room.

What am I missing here? Thermistors are inherently nonlinear. Using a Wheatstone bridge or a current mirror won't change that. The reason Wheatstone bridges were so popular is that they made differential measurements easier in an age where dynamic range was limited and subtraction had to be done by analog means.

Configuring your thermistor with a precision resistor in a voltage divider, driven from the same reference voltage as the Arduino (or whatever) will give you equally good performance. If you want linearity, apply the Steinhart-Hart equation.

I don't think you're missing anything. Dude needs a measurement, and he's on his way to getting it done.

The Wheatstone bridge is timeless. In a precision measurement context we use it and related bridges all the time.

I had some issues correctly biasing (selecting the divider) for the voltage divider circuit on a previous project, so this was just an experiment with a different technique. But that project had other issues (resistive load sensors that were out of their load range), and reading into it now I agree that the voltage divider should be just as fine. I glanced at the Steinhart-Hart equation, and i'll give a shot at implementing it when I try to calibrate the sensors, thanks! --Andrew (Terg.is)

Heh, this looks a lot like my steam radiator plots! I used 1-wire DS18B20 probes on radiators, the risers, and on the boiler itself.

Your radiator valves may be adjustable, which makes it possible to set how fast they let the air out. That way you can heat up rads in cold rooms faster than in hot rooms and do a rough temperature balancing.

Btw, if you want to learn more about steam systems and how they work, I can recommend the book "We've got steam heat" (http://www.heatinghelp.com/products/Steam-Heating-Books/25/6...). It explains how things are supposed to work and what can cause problems, I found it very helpful when I first moved to a place with steam heat.

Thanks for the tip! I'd love to see your plots.

Unfortunately I don't live there anymore so the high-res plots have expired from the RRD, I just have the daily averages.

I was just thinking about doing this. I always find it weird that the riser pipes in my apartment heat up at times unrelated to when my radiators are on. The time-of-day temperature fluctuations also annoy me (because if I open a window to cool off and then the heat turns off for the night, I can never get warm again).

All in all, HVAC was my biggest surprise when moving to NYC. I lived in Chicago before where every structure I ever lived in had central heating and air conditioning. Set the thermostat, enjoy. Moving to NYC, I have to screw around with steam heating and window AC units. (The corollary is that nobody in NYC has anything nice because NYC is the thing that's nice. If only I cared in the slightest.)

Exactly! I'm also working with an old NYC apartment building. Once I get radiator control working, I also would love to automate opening and closing my window, but actuators to do that can get pricey...

How about a fan that normally exhausts, but when you want it colder, changes direction?

Looking forward to seeing the additional measurements.

Can anyone explain why "I can’t leave it partially open or the radiator will fill with water and start spitting it out of the auto-bleed valve."? Why is partially open different from completely closed?

The way I understand http://en.wikipedia.org/wiki/Hydronics#Single-pipe_steam, he has a system where the heater pumps water vapor into his radiator, the vapor condenses, producing heat, and the water flows back through the same pipe that pumps in the vapor.

If the valve is closed, no steam enters the radiator, so no heat is produced, and no water is produced in the radiator.

If the valve is half-open, I guess the steam flows in fine (in reduced quantities), but the water does not flow back (looks like a design error in the radiator, or maybe it wasn't installed correctly; I guess that such radiators are fairly sensitive to being installed level)

With ever more water in the radiator, the water eventually exits through an overflow valve.

Yeah, this is my read on it as well. I don't have a lot of experience with steam heating systems, but I noticed that I had some issues with water dribbling out of the auto-bleed valve when the main steam valve was half closed. For all I know, my observations could also be caused by maintenance issues with the radiator... --Andrew (Terg.is)

No, it's standard. The pipe needs to have room for both the steam to come in and the water to flow back. If you partially obstruct it, the steam comes in (because it has higher pressure), but the water can't flow back down and fills the radiator.

Why wouldn't something like this http://www.armstronginternational.com/thermostatic-valves-rv... work in your case?

Neat, that would probably work really well. Now that i've gotten my mind set on electronic control, though, i'd love something that I can also put on a timer. The idea of controlling the radiator via the bleed valve seems to be a solid one though... Duly noted.

Your website seems to have died, FYI. I tried at some point to post this as a comment there some of which is redundant given this thread, but the hazards I believe are still a new contribution:

For one pipe steam you can control the radiator by controlling the air vent on the non-steam side. This prevents steam from entering the radiator in order to disable it for some cycles. I was lazy and used the parts below in my apartment, which is a mechanical thermostatic regulator. In my experience, by cutting off the airflow manually part way through, you can have some measure of control over the amount of steam the radiator allows in. I imagine that if you placed thermistors at several points along the length of the radiator, and had the valve portion below, you might be able to cut the steam at 1/3 2/3 full on heat. Keep in mind that when a real cold snap hits, heat is a safety issue and a possible cause of lots of damage if pipes freeze. There is something to be said for old designs of reliable mechanical systems like those below, especially if you go on vacations.

http://www.pexsupply.com/Danfoss-013G0140-Thermostatic-Rad-V... http://www.pexsupply.com/Danfoss-013G8250-Direct-Mount-Opera... http://www.pexsupply.com/Danfoss-013L8011-1-Pipe-Steam-Air-V...

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