Two steam radiators piped in series

Forget it- it won't work. @DanHolohan covers this in his excellent book "The Lost Art of Steam Heating".

Curious, could there be an arrangement utilizing a single supply valve where they could be joined in parallel so to speak? Basically split at the inlet valve, piped around behind the first radiator with slope to the second radiator which would have to be set on some amount of blocks to maintain pitch on the supply pipe. I have never seen it but if the current supply pipe size is large enough to support the two radiators could it work?

like others have said, you have to look at the sizing of the runout to see if it can handle more capacity, but your options are either to get a bigger single radiator(new radiators are available from a few manufacturers or you can find a used radiator). your other option is a tee at the riser to connect it to 2 radiators that do not exceed the capacity of the runout.

Curious, why wouldn't this work?

I mean I think it looks ridiculous but, it would have to work, no?

It should. It's now one bigger radiator. (assuming there's enough input.)

I'm so happy you volunteered!

I would, but I won't be home until very late.

I would think it would work unless it is too long to pitch correctly

@DanHolohan didn't elaborate because presumable he wanted tlaosh to not be a 10 volume set, he simply says that the condensate in the first radiator keeps the steam from getting in to the second radiator.

I think what is happening if i try to think like steam is when the steam fills the first radiator down to the far outlet where the second radiator is connected, it encounters the condensate in the bottom of the radiator and that for the most part stops the steam there, it doesn't follow the pipe across.

I think that @ChrisJ 's connecting to and bottom would work. the textbook way is to run a lateral that tees up to both radiator between the legs of or behind both radiators with pitch back to the riser.

or just get a bigger radiator.

but once again make sure the piping can support the bigger load.

1 1/2" can handle 81sqft. 1 1/4" 55sqft.

Let's back up a second. Does that radiator get fully hot? If not, adding radiators will accomplish nothing

I wonder why Dan said this?

What Steamhead said.

After @Steamhead said this? "Forget it- it won't work. Dan Holohan covers this in his excellent book "The Lost Art of Steam Heating"."

Maybe they know something from experience. But What do I know. @ethicalpaul could do a video to prove everyone wrong.

We have done it several times. Not good practice, and there are a number of issues that negatively affect this, but it has worked where we've done it.

As some above have said, you need the proper sizing and pitch of the supply pipe. You also must understand that the standing condensate in the first radiator will dramatically condense the steam passing over it into the second. And the condensate will cool both radiators. That can cause hammering, a cold radiator, wet steam or spitting vents.

Like most things steam: You can try it and maybe it will work. Maybe it will work in mild weather only; maybe it will work in cold weather only. Maybe or maybe not it will be balanced. Sometimes. Maybe it won't work at all.

Proper practice assures a consistent, well operating system. Anything less than that invites problems.

So there is already a radiator in the space that isn't connected to anything? That seems a bit odd, but I guess a radiator could have been removed from service and stored there. However it might pay to check for piping that was mothballed for some reason.

As a separate possibility, would a fan on the existing radiator increase it's heat output?

-Jonathan

…and it will look great too.

let me just imagine it