F/T Trap vs Thermostatic Trap

BAB

Have read many times the need for F/T tarps on the end of mains.  I understand the principals.  However, the F/T traps on our steam vapor pressure (less than 1 oz/sq in) system do not appear to do too much during the heating cycles.  The longest main (we have 5 zoned mains) is about 200 feet long with a drip leg at the mid point.  The 2-1/2 " pipe is reduced to 2" for the last 50-75 feet.  The end of main drip leg (not the mid point), when left wide open, produces only 2 gallons of condensate per hour or less than 20#/hour.  The charts for the smallest 3/4" F/T Trap give flow rates of 200-300 #/hr.



We  pulled the F/T Trap & installed a Thermostatic Trap with a piped wide open air vent after the trap.  It seems to work fine if not better that the F/T trap.  The flash steam on the down side of the trap appears cooler. 



Is a F/T <span style="text-decoration:underline;">always</span> needed?



The pics are <span style="text-decoration:underline;">not</span> before & after, ... rather they are different end of mains.

Note:  pics did not stick yet ??? ......  will try again

Jamie Hall

The short answer

is no.  Many vapour systems use a standard radiator type thermostatic trap at the ends of the steam mains, set on a T up and 90 over to the inlet of the trap, then straight down to a dry return.  The purpose of these traps is the same as a main vent -- they allow the air to go out of the steam main and into the dry return, from which it goes back to (in the original systems) a set of main vents or other air release contraptions where the dry returns go down to the wet return and to the boiler.  If both the dry return and the steam main pitch back to the boiler, there need not be a drip at this location; if the steam main pitches away from the boiler, there will need to be a drip to a wet return at the end, of course.



The setup you describe should indeed work just fine.

BAB

traps

here are the pics attempt again

gerry gill

many risers and mains

are dripped via a thermostatic trap instead of an f&t..the important thing is the ability to have a cooling leg or condensate 'storage' area in front of the trap..which you did..the f&t can just handle more condensate without the need to cool it..one of my mains in my mini tube steam system is dripped with a thermostatic trap, while two others are with an f&t..which ever works best for your situation would be your best choice.

gerry gill

many risers and mains

are dripped via a thermostatic trap instead of an f&t..the important thing is the ability to have a cooling leg or condensate 'storage' area in front of the trap..which you did..the f&t can just handle more condensate without the need to cool it..one of my mains in my mini tube steam system is dripped with a thermostatic trap, while two others are with an f&t..which ever works best for your situation would be your best choice.

BAB

FnT Traps

Thanks for the quick & informative answers.  Your advice coincides with our field observations and puts to rest our previous trap confusion.