Basement Vents Flooded Condensate Spilling Out

Mike11

I have a mid sized apartment building in the northeast that is heated with a one-pipe downfeed system. The vents (Gorton 2's) are located in the basement at the end (bottom) of each riser above the "A" dimension (28"). The system has worked fine up until the beginning of January when periodically, the condensate level will rise above the vents and spill out of them onto the floor. The boiler water level is constant and operates at a steam pressure between 0.5 lbs and 1.5 lbs. The condensate return piping was all replaced over the summer and flushed out prior to putting in service. I'm not sure why the condensate level periodically rises well above the "A" dimension. This seems to have been occurring since the weather got colder.

BobC

Are you really sure about the pressure? Did something change with the new return piping?

Bob

Mike11

The return piping did not change. It is all 2" steel that runs just above the floor, well below the boiler water level (wet returns).

The pressuretrol is set so the pressure is operating between 0.5 and 1.5 psig. This is also apparent on a new pressure gauge that was installed.

As a side note, if the pressure in the boiler was set higher wouldn't the pressure at the end of the system be higher as well? Also, since steam is more dense at higher pressure, wouldn't the pressure drop across the system be less and therefore the head pressure required by the height of condensate at the end of the system be less?

Mike11

The return was all replaced in kind, but the route remained the same. There were no vents on the piping so the system was slow to heat and the super was raising the pressure to 5 lbs. We installed the vents this summer and have been operating the system between 0.5 and 1.5 since.

I do not have photos now but can access tomorrow and submit.

Abracadabra

Was the boiler properly skimmed?

New piping introduces oils to boiler water.

Oils on boiler water surface + automatic feeder = wet steam + boiler flooding

pecmsg

Mike11 said:

The return was all replaced in kind, but the route remained the same. There were no vents on the piping so the system was slow to heat and the super was raising the pressure to 5 lbs. We installed the vents this summer and have been operating the system between 0.5 and 1.5 since.

I do not have photos now but can access tomorrow and submit.

There were "No Vents" but you had them installed? Were talking about the condensate return not the main supplies!

Jamie Hall

These vents giving trouble: are they on the lower ends of the steam mains, which then drop further down and connect with the wet returns?

In such a scenario, one has to remember that the pressure at the end of a steam main is lower than the pressure in the boiler. How much lower will depend very much on the size of all the piping and the demand of the radiation. There is a pressure drop through the piping; steam is moving along in there at a pretty good clip. If the radiation is fully vented, and is condensing strongly, that will also reduce the pressure.

The reason for the commentary above is that there are only two ways that condensate will rise in the risers from the wet returns: one is that there is a partial blockage in the returns, but as has been said this should show up as a drop in the water level in the boiler -- which may not be all that much of a drop, since the volume in the riser pipes isn't that great. The other is for the pressure in those pipes to be enough lower than the pressure in the boiler to cause the water level to rise. That will also show up as a drop in the water level in the boiler -- in fact, when you think about it, it will be the same drop either way! The biggest difference between the two scenarios is what happens when the boiler shuts down. In the case of a blockage, the water level will recover slowly, probably very slowly. In the case of a pressure difference, the water level will recover within a minute or two, sometimes even more quickly.

Observe closely what happens when the boiler shuts down.

Mike11

Jamie, yes i think you may be onto it. The system is a John Mills downfeed one-pipe steam system. So the last radiators to get steam are on the first floor. The vents were installed in the vertical riser directly below the first floor in the basement near the ceiling. They are 28-inches above the boiler water level. It appears the water level in the condensate piping is rising even higher than that. It does not happen all of the time. I'll have to log when it is occurring (beginning, mid, or end-cycle). The boiler water level appears to be constant.

The boiler was skimmed by the contractor and the condensate lines were flushed out.

The main steam riser goes up 8 stories before dropping down branch risers, so i do not believe this is a carryover issue.

I am wondering if the radiators are being closed by tenants and then opened when they want heat. The in rush of condensate from the radiators may be too much for the piping to handle and could be filling the pipe before it has a chance to push back into the boiler. (Just a theory, not sure).

Are there any vents out there that would not allow the condensate to spill out?

Mike11

Jamie to answer your question directly:

These vents giving trouble: are they on the lower ends of the steam mains, which then drop further down and connect with the wet returns?

Yes

Jamie Hall

The Hoffman 75 vent -- non-vacuum -- has a float as well as a thermostatic element. Doesn't have the capacity of, say, a Gorton #2, but for all that it's a nice big vent. State Supply SKU is HK1060. It might well do the trick.

Abracadabra

How much is the water line bouncing when boiler is steaming?

Mike11

Thanks Jamie,

Abracadabra: Not sure, i will make not of it during operation and let you know.

JUGHNE

Was the insulation removed for the horizontal main in the attic? Problem started when cold weather set in. Maybe more condensation from the main is running down. This could have always happened and not noticed until the vents were added?

Mike11

The steam mains are insulated. The wet returns are not.
I attached a photo. The riser drops down in the wall. We broke the wall out a bit to add new fittings.

I agree with you JUGHNE that this could have been going on before the vents were installed but we did not notice it.

nicholas bonham-carter

If you can get a 10 foot length of clear plastic tubing, and the fittings needed to attach it to the drain of the boiler, then you can see by its water level in the tube, the height of the wet return water level. If you see the level up at the same height as the main vents, then you know what is happening.
This level will rise 1.75 inches per ounce of pressure, during steaming, and that is why we like low pressure!
If my math is correct, the previous pressure of 5 psi equals 11.6 feet of rise, which would be enough to submerge most main vents.--NBC

Mike11

We are currently running between 0.5 and 1.5 psig. If we are getting a 1.25 psig drop across the system at high load, that would put us at 35" above the waterline. That would be enough to cover the vents. We have a vaporstat connected to the boiler. We are going to try running the boiler up to 1 psig in lieu of 1.5 and see how things settle out. I'll keep you posted.