end of return venting

dabrakeman

I have a 150000btu one pipe system with two primary mains. I notice that neither main has venting at the end as I see written,but, there are two Vent-rite #75 vents on top of two high risers at the ends of the two return systems. Is this location for main venting fairly standard? Should it be as effective as at the ends of the mains?



Assuming this location of venting is OK I would then like to understand whether I have enough. What concerns me is that I have a few radiator vents that seem to work hard with noticeable hissing (although no water or steam release). I can feel with my finger air rushing out of them at some times. When this is occurring I have checked in the basement to see if noticeable air is escaping the main vents and I do not sense that any is. These main vents were installed when a new boiler was installed early in the winter. Could they be plugged or insufficient in size? Or, are they just not located properly. Just a note, when the old boiler was in place I used to see air releasing from these main vents.

BobC

The location is ok

but they might be to  small; they are slow vents and only good for short steam mains. How long are your steam mains?



If you suspect the vents might be closed, unscrew them and try blowing through them while holding the vent upright.



Bob

Fred

Better to change those vents

You will be much better off if you change those vents on the returns to either Gorton #2 or Hoffman #75 vents. They are very reliable and fast venting and that should help a lot

dabrakeman

main lengths

South main is about 35 feet of 3". Has one long 20 foot runner amongst 5 others. North main is a little more complicated. it is about 8 feet of 3 inch pipe off of which the upstairs 3 radiators and one downstairs radiator is fed. it then reduces to 2 1/2" inch and feeds 3 more radiators. hard to define were the end of this main is. the house is fairly big and two storied. Worth noting perhaps is that two of the upstairs radiators are shutoff as is 2 of the downstairs ones. So 4 radiators of 7 off the north main are shutoff (one of the bigger ones is only temporarily shutoff, another semi-big one is in the thermostat room thus remains off and the two upstairs would just heat the bedrooms too much)



I will try removing the main vents and check them for blockage.

BobC

Much bigger

The first main contains about 1.7 cu ft of air and the ventrite you now have will take almost 20 minutes to vent all that air. I would replace that vent with at least 1 Gorton #2 vent, you may need two there but I would start with one and see how it goes.



Depending on the relative length of the second main it sounds like it needs less venting, perhaps 2ea Gorton #1's (one Gorton #2 equals about 3 Gorton #1's). The ventrites have about 1/10 the venting rate of a Gorton #2.



You want to balance the venting so the mains will vent all the air at about the same time so it may take some adjustments to get it right.



Bob

dabrakeman

north main

I would estimate that the north main system probably has at least as much pre-radiator pipe volume as the South (south being the one with the 30ft long straight main). I timed the radiator heatups from a cold start and the radiators fed from the south main all reached 100% or near 100% after 34 minutes. The big dining room radiator off the north main was only at 50% (and it was just starting to heat when the others were at 50%). This radiator has a Hoffman 1A at highest setting. So, heatup is not even between mains (north slow). If you notice my earlier post 4 of the 7 radiators on the north line are shutoff. I don't know if this matters or not. Intuitively I would think if anything this would reduce total air volume compared to if they were open.



I assumed a Ventrite 75 would be roughly equivalent to a Hoffman 75 but maybe not. I believe Hoffman 4A's were in there before the boiler replacement. These Ventrites were put in during the new boiler installation.



Is there a chart online with the ventrite venting capacities?



Also, just to confirm, you think changing or adding vents at the location they are presently in should be OK?

BobC

Vent Rates

At one ounce of pressure -

 Ventrite 75 is 0.116 CFM

 Hoffman 75 is 0.50 cfm

 Gorton #1 is 0.33 cfm

 Gorton #2 is 1.10 cfm



Note the Gorton #2 has a 1/2" thread all the others are usually used with 3/4" and the #2 is a large vent 7-8 inches so make sure you have room. I would start with a single #2 at each location but you may well need 2ea.



If you need more than one it's easy to use a 90 and the T off the horizontal to add more vents, just make sure that horizontal pipe has a bit of slope so water can find it's way back to the boiler.



The current location should be fine. If not available locally the vents can be bought from pesxsupply.com



Bob

dabrakeman

thank you

It appears I have less than a quarter of the venting that I originally had which already was probably too little. Probably why it seems the radiators take longer to heat up with this new boiler and my radiator vents have become noisier...

dabrakeman

Hoffman 4A

Do you know the comparative vent rate for the Hoffman 4A? That is what was in there before on both return ends. Right or wrong, just want to understand whether my installer put equivalents in or not.

BobC

Much like the Ventrite 35

the Hoffman 4a is 0.133cfm. They may have changed the pitch on some of your piping while doing the work. I would go over all the horizontal pipe i could reach and make sure there is pitch so water can find it's way back to the boiler - and make sure there aren't any dips that might let water pool in the pipes.



Bob

dabrakeman

thanks

It seems what was put in was fairly close to what I had even though it appears they are both well undersized. Probably can't really fault the contractor since he was just matching. Guess I will cough up whatever it takes to install more venting. I don't think there is enough overhead in current location due to a beam to simply screw in Gorton #2's, so, will probably try to antler out between joists accommodations for either same or a couple Hoffman 75's.

dabrakeman

gorton #2's

Out of curiosity what should I see when I look inside the fitting of new Gorton #2's? Got two in today from Pexsupply and there is a white scale buildup inside.. Someone who deals with alot of these new perhaps could tell me if this is normal from testing or something, or, was i not shipped new parts? Threads not 100% clean either.

BobC

Call them

They have been used somewhere before, the question to ask is why were they returned?



Bob