Two-Pipe Third Floor Radiator Slow to Heat

109A_5

KarlW said:

But I haven't fully confirmed that - they do still kind of heat and they haven't been opened all winter (i.e. they'd be filled to the brim with water by now).

Hello @KarlW,
This is the second time you seem to have stated it like this above. Almost like you expect the steam trap valve to be normally closed.

A normally operating steam trap valve should only close with the presents of steam. Any water (condensate) should simply drain out when the steam is absent. If when closed they leak steam, or do not close properly (and modulate or have abnormal oscillations) due to incorrect installation, it causes other system problems, since excessive steam will enter the returns.

They can fail either way, closed or open.

KarlW

Fair enough, I guess I’d say the behavior is what I’d expect if it failed closed or if the capsules don’t allow the water to escape in the horizontal configuration.

This was true on my first floor radiator.

I’m also quite sure based on my temperature of the dry return steam isn’t entering (I used to have that problem)

mattmia2

Condensate can probably drain once it reaches a certain level in the trap but that is keeping the bottom of the radiator full of water. The same thing will happen when the steam hits that water as if water is trapped in but not occluding a main, the water will cool and collapse the steam until the steam heats the water to steam temp and it won't heat until that happens.