Unnecessary Drip Traps to Wet Return?

Harry_6

Recently I've come across a number of 1920s two-pipe vapor systems, specifically Trane, that drip the ends of the steam mains into a wet return by way of a thermostatic trap - as if it was going into a dry return. Now there is no question that these wet returns were always below the water line, and the end of the main is vented with an old cast-iron Trane vent, so what's the deal? In older/other systems they always just dripped right into the return and let physics do the work, since the water partly fills the drip line anyway. I can see no reason for or advantage to them, and sometimes I find that the innards have been removed. Makes no difference. Any insights?

EBEBRATT-Ed

If the drip from the main goes through the trap directly into a wet return by it self then no trap is needed. If the outlet from that trap is teed into other trapped returns above the water line then you need that trap

Harry_6

Thanks, and agreed, but these all go directly from the trap into the wet return individually. I opened one and found that someone had removed the innards, perhaps wondering why it was there also.

Steamhead

Is there a Return Trap at the boiler?

neilc

how are rads venting if they all drip to wet returns?
shouldn't they be trapped to dry returns ?
was an original boiler lower, and what are wet returns now, dry then ?

Harry_6

To answer the last first, there is a dry return that the radiators are trapped into. The mains are dripped into the wet return and are vented at their ends.

Steamhead: I am interested to see where you are going with this. Yes, there is an original Trane Return Trap.

EBEBRATT-Ed

Even with a return trap I see no need for traps at the end of the mains as long as they are dripped individually below the water line.

Harry_6

And you can see why I ask the question. I've seen this more than once - and always with a Trane system. Mains vented at the end (sometimes with a crossover) and dripped with a radiator trap into the wet return. It's a puzzlement. . . in one case I think the trap was even below the original (and current) waterline.

EBEBRATT-Ed

@Harry_6

On the other hand they probably do no harm