Vent Location Followup

greengiant

Hi Everybody,

I took Steamhead's advice from a couple of weeks ago but changed it a little. I was wondering if my modification is OK.



Please see the diagram in conjunction with the following.



I wanted to improve venting on the two mains of my system. Steamhead suggested adding a Gorton D just after the riser to the radiator labeled "slow" on the main. He also suggested adding a Gorton D to the end of the other main at point C on the diagram.



Here is what I did. I added two D's at point C. The line vents quickly and the rads at the end heat up fast. This next part is where I deviated a little. Instead of adding two D's on the main just after the last radiator riser (labeled slow on the diagram), I added the D's up at the end of that last riser just before it enters the radiator. I thought that putting the vent as close to the end-of-the-line target as possible the better. There was an improvement but not as much as I had hoped. Previously it took 12 minutes to get steam to that last radiator. Now it takes 8 minutes. There should be enough venting with the two Gorton D's to vent the volume of air in the pipe in one minute. The following are my calculations for volume of the pipe to be vented in the slow main.



31’ of 2” pipe = .713 Cubic Feet

8’ of 1 1/4 “ pipe = .112 Cubic Feet.

Total CF/Ft. = .825 Cubic Feet



Venting capactiy of two Gorton D's together = .88 Cubic Feet



The line is only partially insulated and I will be fixing that soon however I still think it should vent faster than 8 minutes.



Any ideas?

Hap_Hazzard

Try removing one of the Ds from point C.

The rate of venting depends on the pressure acting on the volume of air, and the more venting you add, the lower the pressure. If one main is venting a lot faster than the other, you can either increase the venting of the slow main or decrease the venting of the fast one. In this case I think a single D at point C should be adequate. If it's possible to rotate one of those two vents 180 degrees without removing it, you can test it without having to actually remove anything because the vent closes when it's upside-down.



This will, of course, make the venting of that main slower, but there's no way I know of to make one faster without making the other slower, short of increasing the firing rate of the boiler (which you probably shouldn't do if it's sized correctly), because you only have so much steam pressure to work with. You just need to balance the venting so both mains fill with steam at the same rate.



If this improves the situation, I wouldn't do any more fine-tuning until I got those pipes insulated. Unlike balancing, preventing condensation will increase the sum total of steam available in both mains.

greengiant

I tried

what you suggested, taking one of the D's away from point C and the timing was exactly the same. That main didn't vent any slower and the main with 2 D's didn't vent any faster. I'm wondering if I'm not getting the full venting power of the vents because of how I have them attached to the system. I've got a pair of vents connected to a T atop an 1/8" nipple. Maybe the diameter of the nipple is restricting air flow so in effect I'm only getting the venting power of one of the D's at each location. Does that sound plausible? I believe the diameter of the vent port is .19".

Hap_Hazzard

Pipe diameter

The ID of 1/8" nominal pipe (schedule 40) is .269, so the cross-sectional area is about .057". The combined cross-sectional area of two .19" ports would be pretty close to that, so I'd think a 1/8" nipple would be enough for two Ds, but just barely. But by shutting off one of those vents, you're reducing the venting capacity by half, so you should have seen a significant change.



I could be wrong but I think this means you need a lot more main venting, because currently you're venting more through some of your radiators than you are through your main vents. If you have some radiators that seem to heat up quickly, try flipping their vents and see how long it takes to fill the mains. Then see what size those vents are and you'll know what you're up against.

Hap_Hazzard

oops!

duplicate post (deleted)

greengiant

Is 1 minute venting really possible.

Hi

I've been fooling around with venting on my system. It used to take 12 minutes for steam to get to the end of one of my lines. I've now got it down to 5 minutes. I added 3 Gorton D's to the end of the main and turned down the Vent Rite 1's on all of the radiators. I can't get the steam to move quicker than five minutes. I even took out a fitting, opening a 1 inch hole near the end of the line. It still took the steam five minutes to get there despite the gaping hole. Is venting a main in 1 minute really possible? I had been thinking of ordering some Gorton 2's to install because I know they have huge orifices but if a 1" hole makes no difference why would adding Gorton's?

Abracadabra

1 minute main venting?

Uhm, where did you get 1 minute for venting the mains?  The fastest you will ever be able to vent your insulated mains will be when the pipes are hot and you have an open 1" pipe where your vents go.  Unless you are using a vacuum, you aren't going to get the steam there any faster than that.