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.
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.