We have variable/modulating everything else but...

the_donut

steam radiators. I know heat output can be modulated with vacuum or on off by TRV and zone valves. Why not have column radiators that zone sections or columns with serviceable actuators? You could precisely match room heat loss with radiative output by effectively changing edr on the fly. The boiler could modulate to match output and never turn off, no pickup loss. I understand, more moving parts, more issues. Most systems already have radiators. Sometimes radiators have to be added or replaced. Why not make it a modulating one?

SeymourCates

CI rads, by definition, are already modulating. Give them less steam and they produce less output. There is absolutely no need to vary the EDR.

the_donut

When CI are full of steam and at temp they will have a certain btu/hr value. Sure at start up steam will favor colder and closer radiator due to vacuum and less steam will condense when radiators come up to temp. I am thinking steady state, constant on condition. Not start and stop.

Gordy

How often in a heating cycle if room set point is steady state do rads, or any other emitter completely come up to steady state temps across their entire surface before room set point is reached? I’ll assume properly sized radiation, and over sized.

Knowing little about steam you size the boiler to the installed radiation. What happens when you decrease the amount of radiation?

Eastman

Steady state variable EDR can be accomplished with TRVs.

SeymourCates

the_donut said:

When CI are full of steam and at temp they will have a certain btu/hr value. Sure at start up steam will favor colder and closer radiator due to vacuum and less steam will condense when radiators come up to temp. I am thinking steady state, constant on condition. Not start and stop.

If you modulate the burner, or cycle the burner for that matter, the rads will never be full of steam therefore rendering an "EDR modulating device" superfluous.