In fairness to all, we don't discuss pricing on the Wall. Thanks for your cooperation.
There are a lot of choices for ECM style circs now, depends on what color you like
Alpha is available in a 1 and 2 version now, a basic, or more featured version. I think the 2 comes with an insulation shell. Millions of Alphas in service, built in Fresno, CA.
Wilo probably pioneered the US market, one of the first to offer full function small size ECMs. Looks like the popular Yonos is finally arriving , a small size circ with a few different versions including a PWM model. It's been a very popular OEM circulator in Europe.
Armstrong has some dry rotor style ECM which takes the magnetite issue out of the equation. AquaMotion is another brand making inroads.
First, let's be very sure this is one pipe steam. Each radiator or baseboard unit has one pipe entering it, at the bottom on one end, and a vent?
Now in one pipe steam it is essential that the ends of the mains have ample venting. Are there any vents on the ends of the mains? How big are the mains (length and diameter)? How big are the main vents?
Is this parallel flow or counterflow? In parallel flow, the mains slope down away from the boiler, and have a drip at the distant end which connects back to the boiler through a wet return. In counterflow, the mains slope down towards the boiler, and have a drip quite near the boiler which connects to the wet return to the boiler.
Now -- you mention that you had a return line gunked up and that it was not a wet return. Ah... what is it? What does it connect to at each end? What feeds into it along the way? Dry returns and steam mains do, very occasionally, get "gunked up" but, since water never sits in them to have them do that is very rare indeed.
I think we need some near boiler pictures and a sketch of the whole system.
In the meantime, three things. First, insulate those steam mains. Second, install main vents at or near the ends of them -- as I say, let us know the size and material and we can help size them. Third, slow the vents on the side getting hot faster.
Pictures would be helpful of near boiler, vents, radiators and end of mains. Are you sure the returns aren’t wet?
Main vents on a 1 pipe should be a couple feet behind the end of main near the drop to return. You are only venting the distance from the boiler to the mains above boiler. You are not venting the 60’ of mains past the #1 and #2. Doesn’t matter how fast you vent the few feet by the boiler.
The radiator vents are venting the mains.
Install vents near end of main. Also pipe insulation will help. Stone cold pipes will condense water quickly forming a vacuum pulling more steam. Insulating will reduce heat loss and condensation in main.
How many stories tall is the building?
The floor grills used for return air must have supply air vents somewhere?
Could that 2 x 2 corner been a masonry chimney at one time?
Is there evidence of where the chimney might have been, the basement would maybe tell you.
You use both terms of boiler and furnace.
The best traces of evidence are often in the basement if the ceiling is unfinished.