On the chance of committing steam blasphemy, I am going to question the supreme status of the Gorton #2 air vent.
Dave takes a deep breath, "Here Goes!"
Observations: On a cold start-up, or during a steaming cycle which occurs after a LONG off time, the Gorton vent seems to work just great.
However, with my cycles set for 1/hr, close observations reveal that the Gortons are venting at a rate far below their rated cfm. My system is controlled by a Tekmar 279. At the start of a cycle, that occurs one hour after steam was established in the previous cycle, my end of main temperatures are around 135-140F. When the boiler starts to produce steam and I am registering 1-2 oz of pressure at the boiler, I can hear venting on the line that is vented with 2 Hoffman 75 vents. I hear nothing and can detect nothing on the Gortons. As the pressure starts to climb to 3-4 oz. ( I should mention this is a 2 pipe system with orifices set to operate at 8-10oz) I can hear very minor sputtering at the Gortons. They are hot, but not steam hot. I would say they are the temperature of the air in the 135-140F main. As the steam works its way through the steam main, (venting of course is occurring through the radiators) my condensate sensor, which is located on the steam main, just after the last radiator riser takeoff, comes up to temperature quickly when steam arrives at that point. Pressure continues to rise and as it gets to 8 oz., the sputtering sound on the Gortons gets louder. If I bump the Gorton, I can hear the inner workings rattle, but can tell that they are not as loose as when cold. After about 5 more minutes, the sputtering will stop and I can feel that the Gortons are now steam hot. When bumped, they do not rattle. It has taken 5 minutes for the last section (30') of 2" pipe to vent under 4-8 oz of pressure. The Hoffman vents completely vented the line they are one many minutes ago and snapped shut.
This leads me to believe that the Gortons are not venting at the rate they would be expected to, on my system with well insulated mains. GW Gill has a video that shows the inner workings of the Gorton vent, and his comments indicate that the vent "starts" to close at 110F and may be fully closed at 130F. <a href="http://www.youtube.com/watch?v=Wl8vQ2MYhMs ">http://www.youtube.com/watch?v=Wl8vQ2MYhMs </a>
Do most systems cool down to a temperature around 110F between cycles? If not, it would appear to me that in real applications the Gorton vent is probably venting far less than it amazing capacity as is stated in the charts.
I am getting very good distribution as a result of the orifices that I installed about a month ago. But, I am wondering now, what the closing temperature is a Dunham 1E trap. I am seriously considering removing my vents and installing crossover traps as would have originally been installed on my Dunham system.
One of the drawings for a Dunham system that I have shows a simple swing check valve on the system vent coming from the air eliminator and return trap. Since I can control the system pressure at 1 psi or lower, neither the return trap or air eliminator are necessary. Dunham indicated that its vapor system was appropriate and effective for ON/OFF systems and they even show the setup in conjunction with a gas fired boiler.
It would seem to me, that if I connected the system the way it was originally, that venting would be as good or better than they way it is functioning with the warm Gortons. Further, if I can get the system tight enough to hold a vacuum, that venting would be even faster because their is little or no air to expel.
Also, on of the comments that I have heard from some of the most experienced pros is that vacuum can cause the condensate to get "held up" and slow return. It appears that Dunham had a provision to correct this phenomenon as they included a line between the steam header and the return piping with a swing check to allow flow in the direction of the return line to the steam line. Thus, when the boiler shut down and a strongest vacuum is pulled in the cooling steam mains and radiators, this vacuum would open the check valve until the return piping was at an equal vacuum, thus eliminating backward flow in the condensate lines and letting gravity do its work.
I would really like to hear everyone's thoughts and comments. Tell my why I am wrong.
Dave in Quad Cities, America
Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.http://grandviewdavenport.com