Main line air vent spitting water in steam system

Unknown

If the two pipe steam system is a true two pipe the mistake in the piping is having the main return drop to the floor.

The main return unless the condensate receiver is below grade is trapping the condensate in the return line.

Air vented from the system needs to flow above the condensate water. If not the air will stay in the piping system until the steam pressure overcomes the lift pressure of the water trapped in the condensate piping.

To end this problem run a 3/4" copper tubing line from the highest discharge point of the end of the line F&T traps to the highest opening of the condensate receiver.

That modification will allow air to leave the system unimpeded by trapped water.


Jacob Myron

Robert Kushner

Main line air vent spitting water

We have a 2 pipe steam system in a church. The radiators thermstatic traps. We have 2 mains that end with a F&T trap. The returns drop to the floor and go back to the boiler room. Thet go back to a make up water tank with a pump. We replaced the boiler, at the customer's request. They never gave me any indications of problems. After we installed the new boiler, we could not heat the radiation and would lose the boiler water. The returns going to the floor is causing a trap, so we cannot bleed out the air in the mains. Can I install main line air vents in the alternate outlet tapping in the F&T to vent the air before the condensate drops to the return. Any help would be appreciated. 8/29/08 We tried the air vents and the system seems to work. We are getting some spitting of water put the air vent. We used a Hoffman #75H air vent, rated for 10 psi. The system is set to work with a 1-1/2 psi pressure. We have 2 mains that are vented like this, only 1 is giving us a problem.

Unknown

I've tried that too.

Mine spit pretty hard (3,000,000 BTUH) on start-up.

I increased and elbowed up from the F&T with a 1" long nipple, then I reduced to 1/4" to make a chamber, then I increased back to 1" with another long nipple. I reduced above that and installed the vent.

It gurgled, but didn't spit.

Since then, I've reconsidered. I'd now try coming out of the return below the F&T trap with a mini header that was dripped back into the return (near the union that must be there somewhere). I'd put the vent up above the tee in the mini header. I'd probably try 3/4" nips to see how it worked out.

Noel

Unknown

I have to agree with that.

On my job, I wasn't going to raise 100' of 3" pipe to have the air that was released do so by passing through the tank first.

Also, the only reason I used an air vent on it (instead of an open pipe), was in case the steam traps weren't maintained and there would perhaps be steam in the returns at some point in the future.

This had been a Dunham Vari-Vac system, with lift fittings at the vacuum/condensate tank, but it was converted to atmospheric with TRVs on it before I got there.

Noel

Unknown

Rais 3\" pipe?

If you read 3" pipe I made a type O

The air bypass is 3/4".

Vent valve in that application can and will eventually cause a problem.

The 3/4" copper tubing will always vent air and if the system ever gets flooded water will drain down the tubing to the condensate recever.

Jake