Direct return trap

JMLLC

So I am working on a 2 pipe steam system and it has an old trane direct return trap built into one of the steam returns coming from 2 radiators that are not operating. Is there something else that can be used or does this have to be replaced. I have been doing HVAC for 30 plus years and this is the first time I am seeing this. But I would love to learn something new. If you take the trap out of the picture the radiators get hot. I took trap apart and it does not look like there is much to it. Should I just lube parts up and clean and re-install. No one in any supply houses seem to know about this. I was referred to you through Wallace/Ennis.

JStar

The return trap has no practical function in a modern fuel-fired system, but we here think they're worth restoring for historical integrity. It sounds like you have issues venting air. How's the main venting situation there?

JMLLC

So all radiators are getting hot in system except for the two that are attatched to this return with the trap. When we installed an end of the line trap on that return it worked and radiators got hot but water was coming out of vents.

JMLLC

Some one said to put a hoffman 76 in.

JStar

Water was coming out of which vents? Do you have pictures of the new F&T trap and piping?

JMLLC

Was not and f&t trap just a gorton #1 air eliminator

JMLLC

This is the Trane Direct Return Trap installed as is

JMLLC

So where the line comes out of the tee and into the trap we put that vent in. That is a return that is coming back from the two radiators that i mentioned previously. So when that vent is in the tee the radiators get hot. But then water will start to come out of vent.

JStar

Do you have the original check valves under the return trap? If so, you can take them out, especially if the water issue happens towards the end of a cycle. They may be holding water in the return and not letting condensate return to the boiler.

JMLLC

I was told there is no check valve under the trap. The check valve is located on the inlet of the boiler. But I do agree with you that water is somehow backing up. The thing is the vent is about 3' over the water line and out of all the vents in the system this is the only line that we are not getting the radiators to work.

JStar

There shouldn't be a check valve at the boiler unless you have a feed pump.

What pressure are you running at?

JMLLC

Went ther and installed a Hoffman 76 and new pressure troll boiler is cutting out at about 2.5 Lbs. and now system is running perfect. Had to be pressure at. Have pressure troll set for .5 with 1 differential and boiler is cycling now perfect water return is perfect and I can hear the 76 breaking the vacuum on the off cycle.

dopey27177

pressure at 2.5 will push boiler water about 5 feet above the boiler water line.

When you lowered the operating pressure to .5 the pressure in boiler could only push the water up about 1 foot above the boiler water line, there fore no water exiting the vents.
The Trane system is supposed to operate at max 3/4 psi.

The check valve is what should keep the water from backing into the return side of the system.

Jake

JStar

Glad to hear it's working better!

The equalizer at the header will keep the return from backing out. A check valve on these systems will slam shut at any slight pressure above the weight of the A Dimension, which isn't much on a dry two-pipe return. I've noticed that they cause lots of water issues on vapor systems with direct return traps.

JMLLC

It’s been about 2 weeks now and no news is good news. There is always something to learn in this trade that is one thing I know for sure.