Vertical Radiators

With only 2.6" depth maybe can't get appropriate size fittings for one pipe supply???

I'll be interested to see what @Nick_Castrads has to say on this one — and, if he says it will work, what the dynamics of steam and air travel within the radiator are.

I have to admit that I honestly can't see how air can get out of it, or at least enough air to allow it to work, unless there is a way to put a vent on the top header (for one pipe) or put the steam inlet on the top header (for two pipe).

Explanation, please?

Hi team, we don't recommend steel column radiators for steam because we've seen other manufacturers' steel radiators fail at the welds many times over. We've never sold steel column for steam so I can't say whether ours (which are made by IRSAP in Italy) fare any better. For clarity, we do manufacture our cast iron radiators but not the steel ones.

That said, I had a really good conversation with Gennady Tsakh of Absolute Mechanical many years ago about the failing weld issue (this was on a job where we were replacing radiators on a one-pipe steam system). He said (perhaps in agreement with @delcrossv) that he thought it was linked to uneven expansion and contraction linked to the air vent being at the top. He suggested adding a C-shaped piece of pipework to link the top and bottom end openings, allowing the air vent to sit centrally (as it would with a cast iron radiator with its steam boss in the usual position).

Long story short, I'm afraid we don't guarantee steel column radiators for steam, but I think it'd be absolutely fine if you added a vent in the middle by linking the top and bottom bushings with some pipe and using a tee in the middle to add your air vent (see below).

There is another issue in that the 1/2" bushings are normally welded on, but that can be overcome by special order. The manufacturer can put a threaded insert in that would allow us to add a 1" bushing (but no bigger, so again would be an issue if the radiator output is > 4500 BTUs…)

To @ethicalpaul's point about two-pipe steam, in theory it's the same as a cast iron radiator - we have the same four bushings available to play with. I'd pipe it up TBOE with a ¾" supply at the top one side and and a ½" trap bottom opposite side, I don't see any issue with air escaping.

To @Jamie Hall's point about air escaping, again I don't see an issue here. If it was a one-pipe install, I'd perhaps add a master vent at the floor level to vent the pipes before the radiator, minimizing the air that needs to escape through the radiator vent.

If the height of the cast iron radiators is limited you could wall hang a second radiator above the first.

This design is questionable. There is nothing to ensure that the air escapes out of the top rather than out of the bottom. It could have the same behavior as a vent simply attached at the bottom.

That's a reasonable argument! (unless this thing isn't connected across the top—although it appears to be)

Maybe it will. There are a lot of variables here, including the inside diameter of these pipes and the length of them.

A vent in the top opposite the valve will only fill like half of it. A vent at the bottom or on the gauge glass sort of arrangement will let it fill most of the way. A straight vent on the bottom opposite tapping on an ell and 8" or so riser would probably work just fine too.

So do I read @Nick_Castrads right and steel radiators are likely fine (but perhaps not guaranteed) for two-pipe steam?

If you mix steel and cast iron on the same zone they will heat and cool differently and be difficult to impossible to balance. If it is just to make a space you pass through briefly more comfortable this probably isn't an issue.