O where o where can the air go !

heatguy

Hello all,I am involved on a job site with 2 pipe steam system with a f & t trap installed before condesate return tank .The trap is below the tapping for return tank and is basically piped up to the tapping forming another trap.The only way I see to get air out is vent on condesate return tank which is useless with trapped piping.This is a commercial site and of course it worked perfect before new boiler went in.System is apox.85 years old with no connections between supply and return at steam main ends so where o where can the air go.

heatguy

<img src="https://us.v-cdn.net/5021738/uploads/FileUpload/51/1217fa546cbe84c589bd0f09297622.jpeg" />

Pumpguy

I think what you have is called "master trapping" which for a conventional 2 pipe system is knuckleheading and a no-no.

We sometimes see this where steam is leaking past traps in the system, and so rather than fix those that are leaking, the knucklehead just installs a Master Trap right at the condensate pump's inlet, and thinks he fixed things because now there's no steam venting out the condensate pump's vent pipe.

Problem with this is, when that trap is closed, the entire system, supply and return, goes to the same pressure, and where there is no pressure differential, there is no flow, and with no flow, no steam in the radiators.

Remember, as quoted in Dan's books, ALL FLUIDS FLOW FROM HIGH PRESSURE TO LOW PRESSURE, ALWAYS!

Now, if there's something special or unique about your system that actually requires this trap, well that's a whole other matter, and I'm sure others will chime in with their expertise.

heatguy

Thanks pumpguy that is kinda what I was thinking.I need to explore system a little more as there are multi-able mains heading down unbearable long crouch crawl places with no insulation on a system bouncing between 3 and 5 lbs on presuretrol at all times, which makes things a little warm. God I love my job.I know I know I have been a fan and student (By student I mean I have had to replace his books because I wore them out )of Dan s for more years then I care to think about.There are glaring system issues and other issues and you know once you open that can of worms...

JUGHNE

I have a similiar system with even more issues. Two dry returns teed together going thru a check valve into the discharge of the condenste pump. No vents anywhere, where did that air go??
The only way i think it worked at all was that the 4 to 6 PSI operating pressure pushed all the air to the end of the dry return. Or is it possible to push the air thru the Hloop into the boiler
The check valve is sticking sometimes open-closed-and in between.

So when the 3" zone valve opens and both the main and dry return are full of water, (there is about 130' of main alone) the water hammer is enough to see the 2" end of main shudder.

I am adding air vents before and after the F&T and will replace the check valve ASAP.

Dave in QCA

Yep, sure looks like master trapping. It's one way to make a problem worse.

Condensate return lines on a 2-pipe system must be pitched and vented to atmosphere. They must be able to carry both water and air and the water must not block free flow of air.

If however, these lines are actually the drips or dry returns of a steam main, yes, they must be trapped to keep the flow of steam out of the tank. But, they should be piped in a manner so that the F&T trap can vent air, meaning there cannot be any water seals, intentional or unintentional.

Nagato1

First of all, get rid of the master trap. Secondly, and maybe I am looking at the picture wrong, but how is the condensate suppose to return to the return pump with a vertical rise just after the trap and before the return inlet? The return should be via gravity... With that said, I would look into changing the pitch of the return pipe and make sure its coming in at an slight downword angle into the return inlet.

Thoughts? Or am I missing something?

- Nagato