Steam Mini-Tube System Description
The Steam Mini-Tube System or more specifically the original Iron Fireman Select Temp System is a steam system that by design defies all the written rules of a steam system construction. The most glaring feature of the system is the significantly smaller piping employed to create it. Were not just talking a little smaller here, we are talking about tiny. The supply tube to the heat emitters is 3/8th inch OD copper tube. The return tubes from the heat emitters are 1/4'' OD tube.
Dwell on that for awhile the next time your looking at your mamouth sized steam pipes.
The system also is almost entirely copper tube. Why copper when copper can be detrimental to the cast iron boiler? Because there can be no rust in the system piping. It would easily clog the small tubing. So the Iron Fireman system was to my knowledge the only steam system actually designed to use copper. The boiler and its header are cast iron and steel. Yes there is a little give and take on the matter of dissimilar metal corrosion verses the premature clogging of pipes.
These systems also run at much higher pressures than the standard steam systems do. That is because of the need to overcome serious friction losses encurred by the small tubing.
The original Iron Fireman Select Temp System mainly used these little temperature adjustable heaters in each room so that one could set a different temperature at each room or zone. Hence the name 'select temp'. But they were by no means limited to using those heaters. In fact one of my customers has some rooms that have original copper convector heaters instead of select temp heaters in them. Why the mix when the first floor is select temp heaters? Good question, and the answer is noise. The select temp heaters have a little steam driven blower assembly (fan) the would make some sound. The upstairs bedrooms had convectors because they were quieter. Thats why I prefer the name mini-tube over select temp, since your not obligated to use a select temp heater.
These systems are very efficient due to the speed the steam moves thru the small tubing. It is a shame this didn't catch on but these systems came along a little to late in the game. These were really from the 1950's and 60's. The problem was steam installation in new construction was already dead by then. It was Iron Fireman's last ditch effort to keep steam alive. These systems are so efficient they would be every where had they only come along 20 years sooner. But we will try to keep it alive.