Two Pipe Steam Wet Return Line Possibly Causing Main Vents to Sprout Water?

JimLew

I have a 1920 two pipe converted coal to natural gas steam system that may have a slow wet return line. Looking for trouble shooting advice to narrow the list of solutions/repairs. The system is in a three story 6000+ sq ft house with 31 radiators. Old abandoned pneumatic thermostat system that now runs wild and controlled by a single thermostat. Surprisingly it works fairly well. Great house, great heating overall. One of the three main vents will often sprout water after the system heats up, about 8-10 oz per cycle after I changed the steam trap at the end of the main to a 122a Barnes&Jones and added two Gorton#1’s. Before I changed the steam trap heat was sluggish in that bank of radiators and the return line never became hot. This main vent is at the furthest location away from the boiler. The old main vent did not work and Gorton’s now have an audible whistle. It is piped directly into the wet return. Oddly, the return line off that steam trap is warm at first, cools and then becomes hot again during the cycle which last 1.5-2 hours with a 3 degree differential main thermostat. The second main vent was spewing water and I opened the Armstrong inverted BT, cleaned it out, increased the pitch and it is quiet for now. However, there is standing water in the main during the firing; I’ve pulled off 2-3 gallons of hot condensate from the valve before the BTwhile the boiler is on. One hour after the boiler shuts down the inverted BT clears the condensate and I have 2-4 oz in the line. This line also drains directly into the wet return running across the basement floor. I cracked the union between the inverted BT and the line going into the wet return during a firing and it flowed freely onto the floor. The line was warm/hot. Unknown if the condensate is flowing all the time and the BT is just not clearing the water. It is an Armstrong 811. I am suspicious the condensate is stacking up in the wet return and not permitting additional water in the line. I just had the boiler serviced with a cleaning of the low water cut off valve; he flushed the water in the boiler and cleaned out the lines for the vaporstat which is running at 1.5. Service guy was good and though the Armstrong needed replacement even after I cleaned it and repitched the pipes. The sight glass on the boiler shows a high level before a cycle and a 4-5 inch drop during the firing. The level moves slightly and does not change wildly. The boiler has never shut down due to a low water level. I’ve replaced several steam traps and all the radiators are working well.
I’m sure I missed details to narrow this down. Could this be a sluggish wet return? I suspect the system was converted in the 1940’s. It has a 3 inch wet return that is over 60 feet long. Adding pictures for reference:
The goal is to prevent water from spouting from the mains and clearing the BT during a cycle.

EBEBRATT-Ed

Maybe you have tried this but if you open the ball valve in front of the bucket trap are you getting steam or a lot of water?

JimLew

Yes, I’ve opened the ball valve before the trap and that’s where I drained off 2-3 gallons during a cycle.

EBEBRATT-Ed

You have a union on the outlet to the trap. I would disconnect the union and pipe the trap discharge into a bucket or barrel. Cap the return to the system.

Run the system and see if the trap is working

JimLew

I did a short version of opening the union for a minute and it did flow. I’ll try an extended time for the entire cycle and see how the trap handles it. Good idea. If the trap is working that will narrow the possible problems to work on for both traps. Thanks.

JimLew

Disconnected the union and the Armstrong inverted bucket trap is draining condensate with no back up in the main when I open the valve before the trap. No steam came from the open union, only condensate. Steam did come out of the valve upstream from the bucket trap so it is preventing steam from entering the return. The BT was active and I could hear the movement from the open union. A full heating cycle produced 3 gallons, the same amount that I pulled off the valve before the trap when the union was connected. Related to this is the second main vent spewed 8-10 oz of water during the test of the Armstrong. Water level in the sight glass was high at the start of the cycle and dropped 4-5 inches during the firing. I have an automatic water feed so no low water shut off occurred. Looking for other possible causes for the main's not draining properly. Could the wet return be sluggish? Venting? ?????.

JimLew

Update: After re-tightening the union the Armstrong inverted BT did not pass any condensate as the main heated up four hours later. The main was hot and the trap body ice cold. I opened the union again and heard the air rushing either in or out. Condensate flowed immediately and the trap body became hot in 20 seconds.
I'm stumped. Don't want to start replacing parts if the failing parts are the symptoms and not the cause of the water back up.

Jamie Hall

Probably rushing out. I have a suspicion that you need a vent upstream of that trap -- and possibly a vent downstream. Bucket traps won't pass any air -- and won't pass any liquid if the liquid can't get in there in the first place.

JimLew

I’m thinking the Gorton #1 at the end of the main two feet upstream from the bucket is failing. I’ll replace it tomorrow and check the condensate flow. Agree that a down stream vent may be the solution for sluggish wet returns. Water won’t flow with a pressure gradient down the line. Thanks for the advice.