Main vents

vinceM

Is this right??

KC_Jones

Is that the right spot for the vent? It's not optimal, but a lot of us have them like that. Is that the right amount of venting? Without seeing your system hard to say, but if I was a gambling man I would say it probably isn't enough.

vinceM

Thank you KC.
I recall reading that ideal location of the vent is minimum of 8 inches from the end of the main pipe. I believe the vent is a Hoffman. I don't know the exact size of the aperture but it looks like its about 1.5-2mm in diameter. The pipe size is 2 1/2 " outside diameter. As for the system I believe the boiler is around 300K BTU(40 years old). A home energy audit last summer returned an 83% efficiency on the boiler(Surprising!) The house is 2/1/2 floors, around 3000sq.ft., balloon frame Tudor. No insulation.
I know you need more precise numbers, which I can get, What would you need to know?
I know the Gortons are commonly used. If I add more vents , how /where?

Fred

We really can't see the vent that's on there. All we see is the coupling, and it looks like a good size to add all the venting you might need. Typically you want the equalivent of one Gorton #2 for every 20 feetm of 2" main. If your mains are 2.5" outside, it is most likely 2" pipe so measure the length of each main and decide how many Gorton #2's you need on each main. A gorton #2 is 7" tall so if you don't have that much headroom, you can use about 4 Gorton #1's or 2 Hoffman #75's on an antler to equal each Gorton #2. As KC said, that location is ideal but many, if not most of us have them there and they work fine at that location.

vinceM

Thank you Fred.
I have attached a closer look at the vent. I have enough headroom for the Gortons. I understand and have seen the antler setup. Is it a matter of taking off the vent that is there, adding a few connections to extend the line horizontally then adding the extra vents?

vinceM

This same setup is on the other main in the adjacent room. I'm assuming I should make the same change for that main as well.?
Also, in the first image, can you confirm that the vertical pipe dropping at the elbow below the main vent is the return? It's copper btw.
Thanks

Fred

Yes, it is as simple as removing that vent and adding what you need. Just make sure when you add your antler that you tilt the antler a little so that any consensate/water can run back down that pipe. Do the same on the other main as well but if it is shorter, it doesn't need as many vents. if it's about the same length, then add the same amount of venting. Also, yes that vertical pipe is the return and it drops to a horizontal wet return.

JUGHNE

IIWM, I would remove the coupling, even the reducing coupling if it cooperates with your pipe wrench, insure the remaining nipple is fully open and then put a 90 ell pointing back towards the steam main. Add enough pipe to get your antler in the full joist space before the return drop pipe.

This adds some length & fittings before your vents to protect them from surge/water hammer that could happen at that tee. (that was what the 8 to 16" spacing was supposed to do). Also gives you more working room in a full joist space. What size is the old first nipple out of the tee?

Steamhead

How long is each steam main, and what pipe size? This will determine what vents you need.

vinceM

Thank you to all that responded. I will make it this weekend's project. I hope to report on Monday how things vent...I mean went.

vaporvac

d

Steamhead said:

How long is each steam main, and what pipe size? This will determine what vents you need.

So what vents are you installing?

vinceM

There are 2 mains. One is about 30ft the other is 28ft. I think I will go with #2 Gortons and use the formula to figure how many I need.
In addition to what I've been inquiring about the main vents..... the branches that T off the mains and continue to there respective radiators are all smaller than the main (2 1/2 in). They are 1 3/4 inch outside diameter. I'm guessing that they continue up through the walls the same size. I know I can't do anything outside of tearing open the walls to run new lines, (which I won't be doing), my question is, is that size pipe running to the radiators sufficient?

BobC

Radiator piping is determined by the EDR of the radiator, your 1-3/4 OD pipe is probably 1-/4" pipe which should be good for a radiator with an EDR of 55.

Bob

vinceM

Thanks BobC. I have Tube type radiators of varying sizes. So the EDR of each is different but close. I did the calcs on all the rads and they all fall at or below 55 EDR.
Also, I've been trying to figure out why the rads in my kid's rooms, which are on the front(East facing) side of the house, on the 2nd floor, heat up but don't stay uniformly or consistently hot. The same for the one on the 3rd floor. That rad is on the North facing side. I've put new Varivalve vents on all of them, made sure the inlets are fully open, and made sure they all have adequate, even pitch.
I will add that the house is a 1929 balloon frame, stucco Tudor with NO insulation. But , I've air sealed where I found any leaks.
Any thoughts?

KC_Jones

vinceM said:

Also, I've been trying to figure out why the rads in my kid's rooms, which are on the front(East facing) side of the house, on the 2nd floor, heat up but don't stay uniformly or consistently hot. The same for the one on the 3rd floor. That rad is on the North facing side. I've put new Varivalve vents on all of them, made sure the inlets are fully open, and made sure they all have adequate, even pitch.

Could you clarify what you are talking about here? The radiator will heat as much as the call for heat and the venting allows. They won't necessarily stay hot all day long only as is needed by the thermostats call for heat. If the heat call is short and your venting isn't "up to snuff" then the rad might not heat at all or very little. If the call for heat is longer it might heat more. The main venting is the main contributor to these types of issues. Need to get that main filled with steam as fast as you can so it can go where needed. Have you upgraded the main vents yet?

BobC

Varivents are very aggressive, in general you want to vent the main very fast and the radiators slowly. That should allow everything to heat up at the same time.

If a radiator vent is too fast the steam tends to shoot across the base of that radiator and shut of the vent before the hole radiator is hot.

Tell us how long the steam main(s) are and what the diameter of the main is. As KC said we can then tell you what size main vent(s) you should have.

Bob

ChrisJ

Ugh Varivalves.

vinceM

Ok. Two mains, both around 30 ft., pipe OD is 2 1/2 ".
To clarify, The kids rooms are very cold when its cold out. Again, NO insulation in walls.
Three bedrooms on the second floor. The master faces West, opposite the other two . The master gets warm and stays warm. The rad gets hot and responds appropriately to the ambient temp keeping the room consistently comfortable all night. As this is occurring, the rads in the other rooms get hot initially, then once they heat from end to end they begin to cool, then get cold. This all happens over 20 minutes. Then stay cold for the rest of the night. All three rads have Varivales on them. I'll admit that they are all fully open( I read BobC's comment). I'm still perplexed as to why the master works properly but the other two don't.
BTW, the rads on the first floor all work very well. They range from 9-14 sections. No Varivales on them, Maid-O-Mist/Jacobus vents ranging from #5 to C (I'm using the "go by the size of the rad, not the distance from the boiler, theory). The thermostat is on the first floor, in the dining room, on the wall opposite the rad. Someone, not on the WALL, suggested that the two upstairs rads don't work properly because the therm. gets satisfied since its on the first floor so it shuts the boiler down before rads can heat up sufficiently. So why does the rad in the master work just fine?
I was supposed to have put new Gorton valves on antlers on the mains this weekend but didn't get to it.

KC_Jones

I am going to go with more main venting as a start. I will also suggest your radiators are over vented which is wreaking havoc with you trying to get them to work correctly. The main venting needs to be correct or it's impossible to balance the system. Gerry has an anecdote in his balancing steam about rads "robbing" steam from other rads to the point that he removed the none heating radiator and no steam came out. Aggressive radiator venting can cause problems. For 30' of 2" main (actually 2 3/8" OD) you should start with 1 Gorton #2 vent, but I would guess you could add a #1 or even 2 #1 vents to that. I can't for sure make out what main vent you have now, but I am guessing either a Dole or Hoffman (4A?). If that's the case the Gorton #2 vents 16 times the amount of the Dole and roughly 9 times the Hoffman. No matter what your main is MASSIVELY under vented and you need to start there or the rest is an exercise in futility. I will suggest once you get the main venting right you start with #4 vents on the first floor and #5 vents on the second. That is usually a decent baseline to start. Another option is adjustable vents, I think Maid o mist has a kit that comes with different orifices that can be changed out. There is also the adjustable Hoffman, it's all a matter of personal preference. I don't have much experience with brands other than Gorton and a little with Hoffman.

vinceM

I should add, that one radiator was removed from the first floor when we did some remodeling. So the rad system got smaller. Also, there is a second thermostat controlling a water baseboard on the first floor that runs about 25 feet. In a straight line, the two therms are about 35 ft apart.
To add some more to the mix, the 2nd floor bathroom has a
5 1/2 ft. cast, fin-tube rad baseboard, that has one pipe coming in from below on the right side and another going out and up on the left side. It gets warm, but could probably do better. Since there is no inlet valve and no air vent, I'm not sure if it's connected to the steam or to the water zone.

Fred

If those two rads initially get hot, are they hot just across the top and the lower part of the rads stay cool/cold? This may well be a case where the vents are too large and allow the steam to initially race across the top (or bottom) of the rads, close the vent before all the air is expelled and then no more steam can get into those radiators. You must start by getting the Mains properly vented. Eliminate one problem at a time until you narrow the possibilities down.

vinceM

Thank you KC. The mains are definitely under vented. The pic I posted at the beginning of my conversation shows a single Danfoss main vent. The aperture is small, probably 2mm in diameter.
The other main, not pictured, has a Gorton. I can't see the size but it looks old(that may or may not mean anything). Regardless, I will be putting new, correctly sized main vents on both mains.

vinceM

Why is a #2 Gorton 3x the price of a #1!!!

Abracadabra

Don't put C vents on radiators, except as a last resort. Use 4 or 5. The varivents need to go.

KC_Jones

vinceM said:

Why is a #2 Gorton 3x the price of a #1!!!

Because it vents over 3x what a #1 does.

vinceM

Fred, you are concurring with BobC. I think you are both correct. I didn't check the bottom of the rads. I will.
So far it appears that Varivalves are not too popular on the WALL.
KC, point taken.
I see that the connection on the #1 and #2 are different. The #1 has a smaller diameter, 1/2". The #2 has 3/4 ".
Why?

vinceM

Abracadabra, please elaborate on your comment about the C vents.
Thank you.

KC_Jones

A "C" vent is a large vent just a little smaller than a "D" which is essentially the same as a #1 main vent so it's huge. In a typical 2 story house there is probably almost never a need for venting that big. I think if you look the #2 vent has 1/2" connection and the #1 has either 1/2" FPT or 3/4" MPT threads. Why it's like this I don't know.

vinceM

KC,
Yes, the C vent does have a large opening. Putting a C vent on a rad that's 10 or so sections isn't necessary. It would not help but probably hurt the situation???
So, if using Jacobus vents on ANY size rad in the house don't go higher than a #6?

KC_Jones

Here is my best take on your situation and many peoples situations and why there can be confusion. Your rad vents are currently trying to vent the entire system. They are only supposed to vent the radiator and it's piping. That is why you have such massive vents on the rads and are getting some amount of heat out. If you vent the mains correctly you will reduce the radiator vents significantly and get heat faster and more evenly in your house. The rad vents just aren't capable of venting fast enough to vent the system effectively. The main vents are. The other problem is with those huge vents the first rad on the main will try and suck up as much steam as it can handle before the next rad will even see the steam. So you end up uneven. In the end you may end up with a similar amount of total venting in your system, but it will be in the proper locations. I would say yes a #6 would most likely be the max you will need on any radiator, but you need to get the main venting right first then see what happens. I have a large 12 section 60 EDR in my house and I have a #6 on it and it works great. As I said a decent starting point would be #4 on first floor and #5 on second, some others might have opinions on this as well.

vaporvac

Start with the main venting and THEN address the rads. You'll never get it balanced until you do that!

Abracadabra

vinceM said:

KC,
Yes, the C vent does have a large opening. Putting a C vent on a rad that's 10 or so sections isn't necessary. It would not help but probably hurt the situation???
So, if using Jacobus vents on ANY size rad in the house don't go higher than a #6?

Correct, and even a 6 is pretty aggressive imho. In large apartment buildings I've rarely had to use a 6. Don't use the pamphlet MOM or Gorton provides to decide what vent to use on which radiator. Most radiators with proper main venting will work fine with a 4 or 5.

ChrisJ

Abracadabra said:

vinceM said:

KC,
Yes, the C vent does have a large opening. Putting a C vent on a rad that's 10 or so sections isn't necessary. It would not help but probably hurt the situation???
So, if using Jacobus vents on ANY size rad in the house don't go higher than a #6?

Correct, and even a 6 is pretty aggressive imho. In large apartment buildings I've rarely had to use a 6. Don't use the pamphlet MOM or Gorton provides to decide what vent to use on which radiator. Most radiators with proper main venting will work fine with a 4 or 5.

What typical pressure were those apartment buildings running? Startup, as well as near shut down?

neilc

maybe I missed it in the start of the thread,
but what system pressure are we running ?
on those rads that are heating once , then cooling off,
is system pressure closing the vents and not letting them reopen?

and, vent the mains first.
but you know that.

vinceM

neilc,
The Honeywell Pressuretrol is set at 0 .5psi cut in. I believe it's a model PA 404B.

vinceM

In an earlier post I mentioned the, "The distance from boiler vs the size of the radiator theory" of rad venting. I have read on the WALL , that some favor one theory over the other without actually explaining either(or maybe I overlooked it). Can someone explain the two theories and is there a definitive formula or practice that is optimal...
Thank you.

nicholas bonham-carter

The perfectly balanced, and vented system will have very low resistance (back-pressure) on the mains because of generous main vents. The radiators will have each vents whose back-pressure is higher.
As steam is made the main supply pipes fill up before any riser, because of the back-pressure difference. When the mains are full, then all risers begin to fill, and finally the radiators, (all simultaneously).
Many people talk about the time of steam arrival, but it is the resistance to the escaping air which is being balanced here. A long time elapsing between firing, and steam arrival indicates a venting problem, but it is what you see on a low-pressure gauge during the venting which tells the story. 1ounce is best.--NBC

vr608

vinceM said:

In an earlier post I mentioned the, "The distance from boiler vs the size of the radiator theory" of rad venting. I have read on the WALL , that some favor one theory over the other without actually explaining either(or maybe I overlooked it). Can someone explain the two theories and is there a definitive formula or practice that is optimal...
Thank you.

I've often wondered about this as well, but I eventually joined the camp that favors the distance to the boiler. Logically, it makes more sense to me since the steam has to travel different distances to each radiator based on a typical layout of radiators in a 2-story home. Moreover, one also has to consider the radiators in close proximity to the thermostat; you typically need to use much slower vents on those regardless of radiator size in order to ensure all radiators have enough time to heat.

BobC

As i understand it the venting on a radiator should be proportional to the amount of air in the piping from the steam main to the radiator and the air in the radiator itself.

As an example my dining room radiator is a 38" high three column with six sections (EDR 30), I figure it contains about 283 cubic inches of air (educated guess). That radiator has 10 ft of 1-1/4" pipe feeding it and that pipe contains about 176 cubic inches of air. The air vent on that radiator has to vent 459 cubic inches of air.

I have the same radiator in an upstairs bedroom and that is fed by 20 ft of 1-1/4" pipe that has about 352 cu in of air in it and the radiator has the same 283 cu in of air in it. The vent on that radiator has to handle 635 cu in of air.

If you want them both to heat up at the same time the radiator with the longer run out will need a vent that can handle 635/459 = 1.4 times the air as the shorter run out.

All of this is just my take on the matter, others may have a different take on it.

Bob

vr608

I think Bob nailed it, his explanation offers the most logical argument, ie the radiator and its attached runout is the total CFM that need to be vented at any given time.

Abracadabra

ChrisJ said:

Abracadabra said:

vinceM said:

KC,
Yes, the C vent does have a large opening. Putting a C vent on a rad that's 10 or so sections isn't necessary. It would not help but probably hurt the situation???
So, if using Jacobus vents on ANY size rad in the house don't go higher than a #6?

Correct, and even a 6 is pretty aggressive imho. In large apartment buildings I've rarely had to use a 6. Don't use the pamphlet MOM or Gorton provides to decide what vent to use on which radiator. Most radiators with proper main venting will work fine with a 4 or 5.

What typical pressure were those apartment buildings running? Startup, as well as near shut down?

2-3oz until mains shut, then cycle between about 7-14 oz.