Math on more venting for steam main

Mhollis

I have a 2 pipe steam system, steam main is a single 110 foot loop in the basement to existing main vent.  There is only one main vent, also a vent on the return though.  I came-up with about 10 minutes for steam to circle the loop and reach the main vent, so I wanted to add more venting capacity. 

The main is 2.5" id pipe, so searching this website I came-up with .33 CFM for 10 feet, so that would be 3.63 cfm for the total main, so add 3 Gorton 2's.  Is my math right here, just seemed like a lot to add, so looking for some confirmation. 

BobC

Your math is correct

What kind of vent do you have now, and is the steam main insulated? I know the Gorton 2"s are expensive but they will pay you back with reduced fuel usage.



If you don't want to spend that much right now just build an antler and add Gorton #2's as your able. let us know what the differences are in the time it takes to get steam to the main vent with each step.



Bob

Mhollis

Insulation

Thanks for the quick reply.  Yes, the main is insulated.  Not sure what the main vent is, its old and tough to see - I will take a picture when I get it out.  Its jammed up inside a notched out support beam for house, can't imagine why they did that, but it was done.  I will also let you know how much the speed improves with the Gortons. 

nicholas bonham-carter

Main vent jammed up in ceiling

Maybe you have a counter-flow system where the main slopes upwards from the boiler, and therefore the end of the main is as high as possible. If this is the case, then you have no choice but to put the main vent on the end.

Most of us have parallel-flow systems which rise up to the ceiling after exiting the boiler, and then gradually slope downwards on their way back to the wet return, and in that case, the vent should go close to the drop down to wet return.

You can never have too much main venting. You can either do the math (including the volume of the steam chest of the boiler), or you can tell from a good low-pressure gauge when the resistance to the escape of the air is close to zero. Looking at such a gauge, if you see the pressure remaing below 2 ounces, you know you have enough venting capacity.--NBC

BobC

They are large vents

You need at least 7" of headroom to fit a #2, can you angle off the vent port and get into a joist bay? Just keep a slope on the pipe so water will find it's way back to the boiler. If you don't have room for the #2's 3ea Gorton #1's almost equal a #2 (0.33 vs 1.10CFM) and are a lot shorter.



Bob

Mhollis

resullts

Just wanted to post results on this and get input on one more problem. I now have 4 gorton 2s on main supply and equiv of 2 on return. Had to drill and tap 3/4 for the antler which took some work but is fine now. Also insulated all near boiler piping. Main will fill in about 2-3 mins and almost all radiators have steam in 3-4 mins on all floors house is 3 stories plus a basement 19 radiators in the whole house. Now my last problem is I still have 2 radiators that are slow to heat, they must be on same leg, one on 2nd and one on 3rd they take about 15 mins to finally get steam. Even when i crack union at radiator it won't move it any faster. Odd part is takeoff is right in the middle of the 100 foot loop main. All steam traps were replaced at start of season. Any advice on troubleshooting would be appreciated. Last just want to say this website and books I bought are the best, never would have done all this on my own without getting the confidence from what others have done.

Hap_Hazzard

Troubleshooting

If the valves on those radiators are good, try removing the vents and see if they get steam in a reasonable amount of time, but be ready to shut the valve when the steam gets there. You don't want to be trying to screw a vent back into a tapping with live steam coming out of it.



If you still don't get any steam there, check the supply piping for any places where water might be collecting and blocking the flow of steam. If you don't see anything, try shutting down some of the other radiators to see if you can force the steam to these radiators and see if you hear any gurgling or banging.