Can there ever be too much Main Venting?

Jeff_44

My one pipe system is working pretty well but am trying to fine tune the balance.

I have attached a 'map' that gives all the stats.



The main issue I'm having is that on the main venting, I have one side that has two Hoffman 75's and on the other I have two Gorton #2's. When the boiler comes up to steam, steam always gets to the end of the main with the two Hoffman's. The other main with the two Gorton's doesn't ever get enough steam for both Gorton's to close.



Should I remove one of the Gorton's and see if less venting will allow steam to fill this main as fast as the other? OR is it possible that I have a Rad (or two) that may be 'stealing' steam before it ever gets to the end of the main?

nicholas bonham-carter

too much?

i would have said that each of your circuits should have 2 gorton #2's, as you can not have too much main venting. are the gortons clear?

what is your pressure? it should be as low as possible.

check and see if there is a sag in the slow leg, whch may hold water, and slow down the exit of air.--nbc

BobC

great diagram

Add the vent types to each radiator so we can see how they all share the steam. As NBC said check the mains and runouts to be sure the slope is constant - use a level don't trust your eyes.



Bob

Jeff_44

Well...

I have a 3 lbs gauge that never gets off zero when the boiler is running. Recently, I tried an experiment and closed all the RADS, fired up the boiler and watched the gauge. After the main vents closed, the pressure built up just fine, and I shut things down around 1.5 lbs. The Gorton's are clear and in good working order.



I just can't figure with both Gortons, why there's never enough steam at the end to get them hot so the both shut down.??? How do I check for a sag in the slow leg?

crash2009

Jeff, you could just use some twine

  Run a line along the entire length of the 2.5" main, tighten it up like you are going to snap a chaulk line.  The low spots should be evident if you have any.  Then just jack up the low spots and and hang them to the floor joists. 

Gee, I made that sound easy.

Hap_Hazzard

I can make it sound even easier. ;-)

I didn't bother with jacking up my mains. I just cut the redi-rod long enough to connect the plates to the hangers, then I cranked on the nut until the pipe got up to the right height.



I also used a magnetic laser level instead of twine, but twine will work too.

Hap_Hazzard

Is there really no header on this boiler?

If you're really feeding the two mains with two separate risers, I'd expect that to present some problems, especially since the difference in the connected loads is so different. How do the risers connect to the equalizer? Can you post some pictures of your boiler and piping?



Removing a vent--assuming you're going to plug the hole--will make that main vent slower, not faster, but assuming the vents are all working as designed, you should have a little more than twice as much venting capacity on the longer main than the shorter one. That should be more than enough: the ratio of the volumes is only 5:6. Either there is something wrong with your Gortons, you are venting significant amounts of air from one or more radiator vents, or you have a leak somewhere.



If any radiator is getting hot before steam reaches then end of the main it's on, that radiator is venting too much air. Try shutting down any such radiators by turning the vent upside-down, then see where it goes next.



To give you some idea of what should be happening, the vents you currently have on these mains should be capable of venting them as follows:



main 1: 46 sec. @ 3 oz.

main 2: 24 sec. @ 3 oz.



If steam isn't hitting the ends of your mains in under a second, there's either something wrong with your vents or you pushing too much air through the radiators before the mains are filled.

Jeff_44

Here's a photo

of the near the boiler piping. It was done in 2006 and of course, is now covered in insulation. They used only one side but per what I've learned here, I had them use a dropped header. The only thing I notice is that the instructions called for 2 1/2" pipe on the header but they reduced it to 2" before going to the mains.



Per your other question, I do have a couple of rads getting hot before steam gets to the end of the main. I need to dial them back. Also, when I was checking for any low spots in the main, I did notice a place where there was a lot of cold air from the rim joists pouring in on the main in question just after it leaves the boiler.

Jeff_44

/

Jeff_44

Can the Drip Returns ...

effect the performance of the main vents? After fixing the cold air issue on main #2, I fired up the boiler and there was a difference with the performance between the side with the Hoffman's and the Gorton's. The Gorton's were still about five minutes the Hoffman's.



I also noticed that the drip returns at the end of each main was very hot with steam.

The way these were piped, they put the main vents fittings, directly below the main vents as shown in the attached diagram. Would this have an effect on the performance on the main vents? Am I losing steam back down the drip risers?

Hap_Hazzard

Cold air

Gets drawn in while the boiler is running. That's another good reason for insulating those mains. All the hot basement air goes out the flue when the damper opens.



I'm glad to see you've got a header; looks like a good one too. When I looked at the picture I imagined that you were drawing the risers coming directly from the boiler. I know it's just a sketch, but I had to ask. Imagine how complicated it would make things if the boiler risers went directly to the mains.



I think you're on the right track just throttling back the radiators that are heating like gangbusters. Trust me on this--you can put the smallest vent you can find on those hot mamas and they'll still get hotter than a June bride in a feather bed. Only difference is the rest of them will get a crack at heating up too.

Hap_Hazzard

I'm afraid I can't see the PDF.

Can you repost that without the "#" in the file name? Apparently this BBS only encodes spaces in URIs, so the browser sees a # and thinks it's just a fragment identifier and doesn't send it to the server.



Anyway, drips will get hot. Condensate is still very hot water, and some amount of steam in the return is normal. You can't lose it through the returns because it can't go through the water, and it would only return to the boiler if it could. I think you're losing steam through your radiators. The ones closest to the thermostat are heating up first and telling the boiler its job is done. You need to slow them down and let the steam find its way to the end of the main. Try turning them off like you did before and then see how fast the steam travels to those vents.

crash2009

Dunkirk PVSB-4D

I don't know how we missed this in the past.  This new picture tells the whole story.  I looked at the manual for the Dunkirk PVSB-4D.  Page 7 clearly suggests that using "one boiler tapping" is acceptable.  However, many of the pro's here suggest that using one side is just not going to work with that type of boiler.  



Your EDR calculations would suggest that this boiler is a perfect match for your system, however you are plagued with random rads that don't heat.  This would suggest to me that maybe the pro's here know something about this boiler that the manufacturer doesn't.



Maybe this boiler doesn't put out it's full potential when piped using only one side.

      

 http://www.dunkirk.com/uploads/product/literature/6adaea8eec50b8d618e77f2037dd3751.pdf



Here are a few photo's of how I have seen this type piped. 

Hap_Hazzard

I agree, but...

I'm not sure how much that will improve things unless he makes the header bigger. It looks like the riser is already bigger than the header. It should be the other way around. You want the steam to slow down in the header so the water can fall out, but here, that section from the reducing coupler to the first supply riser is a choke point. If anything is limiting the steam velocity it would be that section. That said, if I were going to repipe it I'd add another riser.

crash2009

Looks like

 the Gortons are on the first riser.  At times, I'll bet they are sucking air rather than expelling it.  Did I say "bet" again?  I never win betting against steam.



Probably sucking air could be tested with an insense.

Jeff_44

Thanks for all the great discussion

AND Expertise. So are you saying the riser is too LONG and the header is too SHORT? OR is the size of the pipe of each of these components the wrong size? The instructions in the manual call for 2 1/2" pipe as it leave the boiler and it says that the header should also be 2 1/2". If I were to change the header pipe size would this change anything? OR should I add the other riser, make the header 2 1/2" or both?



I guess the other thing that factors in is that as of now, I have three different kinds of vents on the rads. There is a combination of Maid o Mist, Vent Rite, and Hoffman. It seems like what I should do first is get all the same type of vents on the rads and then see what effect that may have.

BobC

make a list

Of all the radiators with their EDR, the vent make and model, and what floor the radiator is on. It may become obvious that a little vent switching, or adjusting if they are adjustable, will start to balance things out.



The goal is to get everything heating up at about the same time; venting the mains fast and the radiators slow is usually a good start.



Bob

Jeff_44

Wet Return

Here's the chart of the way the end of the mains join the wet returns.

I'll take a look at the venting on the rads and post what I have.



Thanks for all the great comments here!

crash2009

The returns

 look normal to me.  Assuming that the drop below the Hoffmans's actually connects to the wet return.  Here is your other diagram. 

crash2009

What I'm saying Hap

 is that it's not piped right.  There are posts here explaining why it is critical to get it right with this type of boiler.  Smaller steam chest than normal, you have to build the steam chest on site by using both tappings and 2.5" all the way through to the system takeoff.  All of a sudden the bargain boiler ain't a bargain no more.  Anyway that's just what I read, and everybody knows, you can't beleive everything you read, (or can you?)



Here is a pic of whats under the skin.  This is the 0-30

Jeff_44

No Bull Head T

There's no bull headed off the header, but on main #1 (with the two hoffman's) the take off is fitted on to a T and there is one Rad on the left side of the main, and three rads on the right. BUT...the end of this main is capped so if it would help the system, I could easily tie into the end of main #1 and then put a plug in the T where the take off connects to the main.



The issue is, this main does well and steam gets to the two hoffman's before it gets to the other main with the two Gorton's. If I did redo this piping and left it with one riser but put say, 3" pipe on the header would that help?

Hap_Hazzard

You can't have too much riser.

You need at least a 24" vertical rise above the maximum water level to prevent carryover. More is always better.



The header should have at least twice the cross-sectional area as the risers so the total area doesn't decrease. You want the velocity to be low in the header to allow any remaining water to fall out of the stream and drain into the equalizer.



I think you could leave that riser right where it is, add another one just like it on the other side, then, where you now have that nipple connected to a reducing coupler, you could have a 3 1/2 x 3 1/2 x 2 1/2 tee. On the other side you'd have a 2 1/2 x 3 1/2 elbow, and a 3 1/2" nipple connecting the elbow to the tee. Then you'd need a 3 1/2" close nipple, then a 3 1/2" elbow and a nipple to extend back to a tee for your first supply riser, then another nipple and a tee for the second supply riser, then an elbow into the equalizer.



Don't buy vents until we see what you have. You do not want to get all of the same type. The radiators with the longest supply piping need to vent the most air, so they need to be your fastest vents. You need less venting on shorter supplies and especially those radiators nearest the thermostat. The objective is to get all the vents to close at the same time. That won't happen with identical vents unless you have identical radiators with identical piping. Also, several people have commented that the bimetal actuated vents, like the Maid-o-Mist and Gortons, are quieter than the bullet-shaped vents, making them better for use in bedrooms.

Bill_110

If venting increases already high velocity ?

In The Lost Art Of Steam Heating , the chapter on Near Boiler Piping (where problems are born) gives a formula for determining your steams velocity, based on your pipe size(s), pressure, and boiler capacity.  If you plug your numbers into this formula I think you will find that your velocity is probably really high.  Fifteen feet per second is the ideal,  with only one 2" pipe your exit velocity might be twice that.

I would argue that there can only not be too much main venting when your near boiler piping allows your steam to exit at a reasonable velocity. If your velocity is already way too high the heavy venting on the mains which would otherwise be a good thing is actually just aggravating the problem by increasing the velocity even more. I think Dan Holohan wyrly observes that increasing the pressure actually seems to relieve this problem because it helps slow down the steam, but of course it also raises the waters  boiling point and thus wastes fuel.

I have a similar boiler with two  2" boiler risers (they are supposed to be 2 1/2") .  By my calculation the velocity is still too high, and together with undersized header, equalizer, and bullheaded main this gives me wet steam and uneven heat between the two mains.

Note: I don't know that much about steam, but I'm trying to apply what I've read logically.  If I have this right I think it is simply a matter of mathematics. The velocity formula gives you three variables, your boiler capacity (not readily changeable), your pressure (variable but the formula assumes 2), and the size of your pipes.  Based on this formula your only good option, if some trouble , is to add the correct piping to lower your velocity.  You don't want to lower it with greater steam pressure, and I don't think venting can resolve it either.

Jeff_44

Thanks Bill

I just got back from a local supply shop to price out what it would take to get the extra black pipe to make this all work. I must confess, I was shocked at the price of a 2 1/2" El (about $24). I also spent a bunch of time making drawings and thinking through how to add the extra riser and corresponding header. It was suggested that I use a 3 1/2" header but when I checked with the supply house, they sold 3" and 4" pipe. They can thread every thing for me except the 3" pipe. Will have to find some help here locally. I'm in Western NY and have not been able to find any local contractors who specialize in steam so most of what I've done I learned from this site. Thanks to all of you for your help.

crash2009

I like the way Bill explained that

  I am going to re-read that chapter and just out of curiosity figure out my own.

Enreynolds

Where in Western NY

If you are in the Rochester or Buffalo area, Commercial Pipe is a good supplier.  They were able to make me a couple of custom 4" nipples for my header on my Burnham Megasteam, at a reasonable price.  You can also check out PexSupply and SimplyPlumbing for online ordering of parts.

Eric

JStar

Big pipe

We thread everything up to 2" pipe. Larger than that, we use pre-cut nipples and very careful planning. We also have about 3 times as many nipples as will be required, so we have a lot more options available than just trying to measure once and buy once. Maybe if you get some measurments, we can draw a diagram for you with pipe sizes and lengths. I see an "easy" way of at least adding one more riser.

crash2009

I figured out the velocity

 of the steam in my own header.  I get 8.25 feet per second.



Then I figured your existing, and this would be if you had 2" all the way through to the system risers. I get 19.14 feet per second.  If you had 2 boiler risers you could divide the 19.14 by 2, which would reduce your velocity to 9.57 feet per second.



Then I figured if you went with two 2.5' boiler risers to a 2.5" header.  If my numbers are correct, the manufacturer is trying to get you down to 6.70 feet per second.



Bill, this really explains the "why" part well.  Thanks! 

Jeff_44

Thanks Crash

The system has 2 1/2" pipe from the rise through the bottom of the dropped header and then is reduced to 2" at the point where the take offs go into the system.



I talked to a plumber friend of mine and he is coming over next week to help me measure and plan this out. If I use a 3" header with 2 1/2" pipe until the take offs, would that get the velocity down to a more reasonable rate?



I can't thank you enough for all your help!

Bill_110

Main venting dry steam wet steam

The implications in the near boiler piping chapter seem pretty clear.  If my understanding of the It's All In The Venting chapter is correct, fast venting in the mains  means you are going to get heat at your radiators faster which is a good thing.  I'm making the assumption from what I remember reading that the high velocity and quick venting in the mains is predicated on the steam being dry.  It seems to me that if wet steam is coming out of the system mains at a high velocity already(because of inadequate near boiler piping) than a very large venting capacity on the mains will just increase the water hammer problem and the danger of maybe damaging the main vents by throwing slugs of water toward them at high velocity? So I'm thinking in this case (wet steam at higher velocity) that venting capacity on the mains could be too large in the sense that it could aggravate aspects of the wet steam problem? But I'm not really sure.

Jeff_44

I don't know...

But I can tell you that the system runs silent. No water hammer at all. The only sound is some ticking in the risers as they move from the basement through the walls to the second floor. I don't think the risers are insulated. I did open up the 2nd story floor once where a riser comes up and fill the space with insulation. It helped keep the heat in the pipe so that the steam reached the radiator.

crash2009

I couldn't tell from here

  2.5" gives you 13.4 up to the reducer, then the velocity would change.



Two 2.5's, 13.4 divided by 2, would be 6.7 feet per second.  Three inch header would reduce it some more.  Not sure if you want to go nuts with this but there is a few other header tricks that can help even more. 

Asymetrical drops into the header.

Spacing between drops and system risers.

Spacing between system risers.

Full size T's to a short nipple and a reducer to the system

King Valves.

The pro's here got this stuff down to a science.  Lot's a little details.

crash2009

Counterflow Main?

Sounds like you are committed to eliminating the problems.  I just wanted to add another suggestion for you to review.  If it is the way it looks, the radiator named 17.5 appears to be part of a counterflow main.  If that is correct, what it means is that the steam is going to the radiator, and the condensate from the radiator is draining into the header. 

Condensate should be drained to the wet return, not to the header. 



Maybe someone has some ideas on how to overcome that one?

Jeff_44

Yes, this has bothered me

You can see this if you look at the pic of my boiler. There may be simple way to fix this as at the supply side is capped about four feet passed where the T is and I could tie in there and then cap that T so all the condensate travels as it should. The only thing is, this T is on the main with the two Hoffman's and it's working very well.



This morning, I removed one of the Hoffmann's and then on the other main (with the two Gorton's) I reduced the venting on three rads that are the closest to the boiler on this main, and things were MUCH more even.



STILL, I want to get this right and am ready to repipe next week.

crash2009

I don't know

 exactly what to suggest for a drip.  All I know is that the rad named 17.5 should not drain into the header.  You wouldn't need much of a drain, there is only 17.5 EDR.  I seem to remember a special fitting that I saw Steamhead use.  I'll see if I can find a pic.



Unable to find a pic, wonder if a right-angle reducing tee would work.  Then drop the 1" into the wet return. 



http://www.mcmaster.com/#catalog/118/53/=k2xenx

Jeff_44

Bull headed T on Main

Here is a photo of the bull headed T on the main. The photo also shows that the very end of the main could be tied in to and then Then I could cap the T. What will change if I repipe this?



The strange thing is that even though there is a bull headed T on this main, it is not the one that is having trouble with balance. But I do see Crash's point that the condensate's quickest path back to the boiler is NOT through the wet return but through the Bull headed T.



What will the effect of making this

crash2009

Here is one idea

  Not sure if it's the best or not. Leave the bullhead alone and just drip the supply.



Found the elbow I was thinking about, here is the pic.

Jeff_44

One way or the other

I'm going to have to add pipe to remedy the bull headed T on the main. Crash, I really appreciate your thoughts on this and am trying to weigh the two options of adding a drip to the T or to plug it off and tie in to end of the main.



If I tie into the main the steam will have to travel 180 degrees in the opposite direction in a very short distance and I'm not sure if this is good or bad?