

Apartment Radiator Temperature - krschultz
http://terg.is/?p=228

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jws
_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>

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theterg
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)

~~~
jws
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.

~~~
bingaling
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.

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HeyLaughingBoy
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.

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theterg
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)

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lutorm
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...](http://www.heatinghelp.com/products/Steam-Heating-
Books/25/61/We-Got-Steam-Heat-A-Homeowners-Guide-to-Peaceful-Coexistence)). 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.

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

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

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jrockway
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.)

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theterg
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...

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

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cmurphycode
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?

~~~
Someone
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.

~~~
theterg
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)

~~~
lutorm
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.

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CptMauli
Why wouldn't something like this
[http://www.armstronginternational.com/thermostatic-valves-
rv...](http://www.armstronginternational.com/thermostatic-valves-rv-4-one-
pipe) work in your case?

~~~
theterg
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.

~~~
bobjenkins359
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-013G0140-Thermostatic-Rad-Valve-w-
Vac-Breaker-1-Pipe-Steam-5551000-p)
[http://www.pexsupply.com/Danfoss-013G8250-Direct-Mount-
Opera...](http://www.pexsupply.com/Danfoss-013G8250-Direct-Mount-
Operator-5558000-p) [http://www.pexsupply.com/Danfoss-013L8011-1-Pipe-Steam-
Air-V...](http://www.pexsupply.com/Danfoss-013L8011-1-Pipe-Steam-Air-Vent)

