Understanding working steam pressure

jpf321

good illustrations Rod..

Rod .. please make sure that you backup all your "old wall" files b/c everyone you post is extremely pertinent and useful.



I really enjoyed the illustrative view of everything we've been discussing here or otherwise trying to wrap our heads around. Since this is specifically designed to discuss p/u factor or firing characteristics, it still doesn't really help to answer my question of how to determine best pressure settings .. however, I think with a bit more inspection of the graphs, it will help me further formulate my approach towards perfect pressure. 

FJL

What Pressure Setting?

I was rereading this post, and I still have a question about whether my v-stat is set correctly.  I live in a four-story, four unit apt building.  My v-stat is set to cut-out at 12 oz. and cut in at 4 oz.  My vents do hiss to varying degrees during a heating cycle.  Some more, some less.  The boiler will cycle off due to pressure when recovering from a night time set back.  When it does, the vents will suck in air.  So my question is do I need to change these settings to reducing hissing and eliminate air sucking during cycling off due to pressure.

Jamie Hall

Doesn't sound

as though you need to change anything.  Recovery from a setback is tough, and the deeper the setback, the tougher.  One would expect the vents to bring in some air when the boiler is off -- we don't do vacuum systems any more -- and one would expect some hissing (though not much).  Raising the pressure limits won't accomplish much of anything, as once the pressure starts to rise (when all the radiation is as filled as it can be at the moment) it rises remarkably quickly.

jpf321

FJL .. any reason

FJL -- Is there any reason why you have 12oz as your upper limit? How bout 5oz or 8oz? does it take 12oz to completely fill your system? Or are all of your rads hot/vents closed at 5oz? I think these days my v-stat is set at 5oz/2oz-diff. Just curious really how you arrived at 12oz/8oz-diff

FJL

Current Settings

Last heating season, I reported having a signficant amount of whistling from my radiator vents.  At the time, the  v-stat was set at a cut out of 16 ozs and a cut in of 8 ozs.  nbc responded to my post and suggested lowering the pressure to 12oz/4oz and to see how it responded. 





I still get hissing from a vent on a large radiator in my master bedroom, which is fed by a riser that is farthest from the boiler, which is located at the opposite end of the building (under the living room).  The hissing seems to occur when the pressure at the rad exceeds about 1 ounce or so.  A radiator in my master bath (maybe 15 feet closer to the boiler) had hissed constantly before I lowered the pressure to the current setting and is now hisses very little and seems to stay closed, hissing only occasionally as the pressure rises. 





I don't have direct access to all of the radiators in the apt building when the heat is running.  I do seem to recall, however, that boiler would cycle off due to pressure some times when the large rad in the bedroom had not filled all the way with steam if that is possible.  Maybe it just doesn't get as hot as the other smaller radiators, which seem to fill quicker with steam.

jpf321

remember ...

remember to vent your rads based on SIZE not location .. a big rad should have a big vent capacity .. it's quite possible that the big rad in your bedroom has a small vent that is doing it's best to get the air out, but a bigger vent is actually in order.



the first thing you need to do is properly vent the mains .. then you need to properly vent the rads .. big rads = big vents. do you know the EDR of each of your rads? if not, there is a great book that Dan sells here in this shop... E.D.R .. once you know the EDR of each rad, you can get the book also for sale here call Balancing Steam Heating by Gerry Gill and Steve Pajek .. once you have the EDR and the Balancing book, you can have a stab at using my worksheet (linked below) to figure out venting needs.



steam *should* arrive at each rad inlet at approximately the same time and each rad should heat across to vent end in approximately the same time .. this is all based on the venting you have in place at each appropriate vent location (main, risers, rads)



if your bedroom rad is not heating at 12oz .. get a bigger vent on there and see if that helps .. then see about lowering the pressure at the boiler.



FYI .. after trying different setbacks and t-stat temps recently and adjusting for Heating Degree Days, I found that the best bet was to maintain a single set temp and not to drop it at night. if you have fuel consumption data, you can test this yourself as well.

FJL

Venting the Rad

I hear everything you are saying.  I am at work right now, so I don't have my facts and figures at hand.  I'm fairly confident that my mains are adequately vented.  I also have vents on the risers in the building to speed the arrival of steam to each radiator and to allow the radiator vent to vent just the radiator and not the riser. 



My heating system is hampered to some degree, I believe, by the layout of the boiler in the building.  The boiler is located in the front of the building underneath the living room.  The two risers for that room are fed directly from the header and they receive steam almost immediately after the boiler produces steam. 



The rest of the radiators for the top three floors are fed by risers connected to the main, which is approximately 55 feet long, and they don't get steam until the main is vented.  I don't have my notes in front of me, but I believe that the steam hits my second floor living room about 7 or 8 minutes after a cold start and it takes another 5-6 minutes for steam to hit the riser in the master bedroom. 



The t-stat is located in a common hallway, but we installed a sensor in the top floor apartment, in the living room.  On days when the temp is between 34-40 degrees, the t-stat will call for heat but often get satisfied before steam can travel to the risers that feed the master bedroom at the back of the building.  I have installed a Gorton D on that larger radiator in the bedroom.  I suppose I could go larger, but I'd have to go with another brand, such as varivent, which are quicker but there are a lot of posts about how these vents are of poor quality and break down too much. 

Jamie Hall

We sometimes...

get carried away, I think, in our enthusiasm for low pressure, and we need to be sure that we really have it right.  Conventional two pipe steam systems -- and one pipe systems -- were designed, it would appear, with a sort of 'rule of thumb' allowing for 8 ounces loss due to friction in the piping.  Therefore, I have never recommended running a conventional two pipe or a one pipe system at less than 12 ounce cutout (but equally, never suggested over a pound, either, unless I was in a situation handicapped by a pressurestat).  On the other hand, most vapour systems were designed, it would appear, to operate at a maximum of around 8 ounces -- so there we can run the lower pressures without worrying about it.



It isn't all that surprising that a really big, perhaps distant, radiator will not fill before the vaporstat cuts out.  Which is a very good reason for not setting it lower... not only is it big, but there may be enough frictional resistance to simply keep it from getting enough steam until the pressure differential to it is high enough.



Which is not to say that you should turn the thing up, either!!!

jpf321

if you want more

if you want more venting on the rad .. you can always add another vent .. either at a second vent tap on the rad or by building a mini 1/8" tree for 2 vents (a short nipple, a T and 2 street Ells).. 1/8" pipes are usually only available at plumbing supply house.



a D may be appropriate though .. it really depends on the actual rad size and system balance overall... i was afraid you may have had a much smaller vent on there. 

FJL

Vent

I had a Gorton 6 on that bedroom rad and then moved up to a C and this year to a D.  It has helped.



Two years ago, when the new boiler was installed, the contractor installed new vents on all of the rads.  But the size of the vent was based on the floor of the apartment, not closeness to the boiler or the size of the rad.  The top floor got all Gorton D's, the third floor got all Gorton C's, and my second floor apt got all Gorton 6's. 



I have asked the top floor resident to put Gorton 6's on the living room rads to see if that will give more time for the steam to travel to the rear of the building , and I'll Gorton D's on all of the rads connected to that rear riser to get those rads vented as fast as possible.  Maybe that will give me a more balanced system.



Now I just have to get that resident to actually switch the vents . . .

FJL

Bedroom Radiator

My bedroom rad is a 12 section, thin tube radiator.  Boiler cycled off due to pressure after running for at least 45 minutes, and the bottom of the last three tubes were warm in that I could put my hand on them and keep them there.  Does that mean that those parts were not filled all the way with steam?  Or filled with steam, but just not as hot as the other sections that had been filled with steam for longer?

jpf321

nevermind the bottom...

nevermind the bottom, what about at the vent site? could you touch it there? if you can touch it, the steam is not there yet. 

HenryT

tree?

JPF321: you mentioned to add another vent to a big radiator via a tee/nipple/els.

Are you saying to take out the current vent, add a 1/8th nipple and connect that to a tee and add 2 vents on either side of this device?

I didnt know this way works? I am not good at using tap and dye sets and dont know how to drill, but i have do have a huge radiator that requires more venting.

i have a gorton D on it, and was looking for ways to vent it more short of drilling into it..

will a tee/antler work the same way as tapping into the rad with no ill effects?

Thanks!

FJL

Vent Side

I was referring to the bottom of the last three tubes, those closest to the vent side of the radiator, as opposed to the side closest to the inlet valve.  I don't recall exactly, but I think the upper part of those last three tubes, those closest to the vent, were hot to the touch, but certainly not as hot as the first several tubes, which were too hot to touch.  My general impression is that the tubes closest to the vent were not as hot as the tubes closest to the inlet valve, and that the bottom of the last three were warm to the touch. 



I don't understand how that could be true after steam had hit that riser about 30 minutes earlier.  The vent is making a hissing sound as it vents the air.  I suppose I could travel to the visit the local plumbing supply store and purchase a 1/8 nipple and a tee (as described above, assuming that would work) and hook up a second vent and see if it vents faster and get hot quicker.  I don't recall the EDR of that radiator, but I expect that it should be fully vented after 30 minutes with a Gorton D.  I could be wrong, though.

jpf321

yes ...

Yes HenryT and FJL .. the radiator vents are threaded 1/8th inch .. so if you get 1/8th inch nipple and such as described above, you can add more vents on the rad .. this is not saying that you should .. but you can and the rad will vent faster .



BTW, in the last visit to both Home D and Lows ... i saw that they were selling a 3-way-radiator tool .. I believe it had a 1/8th tap, an 1/8th extractor and an 1/8th dye .. it looked pretty non-quality, mainly because the tap was pretty crappy, but for the $5 it may be useful for radiator tinkerers to have in their toolbox.

jpf321

yes MarkS

Yes MarkS .. I run wth a v-stat ar 5oz with a 3diff (2oz cut in) .. i think I once asked about a delay device back in late november/early december 2009 .. maybe you can find it .. 

FJL

Why Not Vent Faster?

What would be a reason not to vent faster?  Create too much condensate at one time coming back from a setback?  Would adding another vent reduce hissing?  The trapped air would now have an oppty to escape.

Mark N

How Come

How come if your rads are filled the tstat hasn't turned off your boiler? If your rads are completely heated your house should be plenty warm. If the the rad vents have closed your pressure should quickly rise and the pressuretrol will cycle your boiler off.

HenryT

JPF321

you mentioned that we shouldnt, but is there any drawbacks if we tee the existing hole instead of tapping a new hole?

thanks

jpf321

i didn't say shouldn't

but it could have been interpretted that way .. my point is that the entire system should be balanced, rather than concentrating on a single rad .. you can if you like start the balance process using 2 vents on that rad and then balance everything else to that limit.



yes there may be some drawbacks to venting too fast... as rod just mentioned in another thread, increased condensate production, not getting steam to other rads, i've heard of (maybe Mr. Gill) where the rad actually stole the steam from a nearby rad.



there is a great article off-wall called "it's all in the venting" http://www.heatinghelp.com/article/163/Older-Steam-Heating-Systems/1315/Its-all-in-the-VENTING

FJL

Understood . . .

I get your point about balancing.  Just trying to figure out the best way to vent the rads farthest from the boiler in my bldg.

tmw

equilibrium and burner settings..

This is a very interesting thread.  I just vented the 2 mains on my Arco vapor system using Steamhead's recommendation for one Gorton #2 on each 40 ft.main (2 mains, 2inches in size).



System reaches a pressure of about 3oz within 10 minutes and stays at that pressure for about another 15 minutes. At this point all the radiators are hot. But the pressure keeps building until cut off at 12oz. In fact pressure will continue to rise up to 2 lbs. if I allow it.. But instead I have it cut off at 12 oz and cut in at 5oz. It cycles off for 1 minute, then on for 3-4 minutes until T-stat is satisfied.



Question:  Since the radiators get hot at 3oz but the pressure keeps climbing, can I assume that my burner is overfiring?



Should I have a combustion test done?

Steamhead

That sounds about right

if it cycled while the system was still warming up, that would either mean the venting wasn't fast enough or the boiler was oversized, or both. You don't need as much steam once everything is warm- this is why low-high-low firing works so well on steam. Now if we could get boiler and burner makers to get together on this, we could save a lot of fuel.



If you haven't been able to get a combustion test done by the time I return, I'll do it then.

Unknown

Is Fast Venting on Radiators Beneficial?

Hi- Just a couple of comments. On pipe taps for radiator vents -I'd be a very leery of using a "cheapie" tap and I'm sure any one who has broken a tap will agree with me.

An ordinary carbon steel 1/8-27 NPT tap is about $5.00 and a HS (High Speed) about $17.00 It is well worth the $12.00 difference to get a HS tap!  I'd be scared to think about the quality of a setup which includes the tap that you can buy for $5.00! 



Venting- I think we get too hungup on rapid venting of radiators as I tend to suspect that by over venting a radiator you could be "shooting yourself in the foot" so to speak. You have to remember that radiator vents can vent air both ways - both in and out and that there are other things going on besides steam forcing out the air thorough the vent. We must keep in mind that a cubic foot of steam collapses to about a cubic inch of water. This creates a huge vacuum which steam and possibly a lot of air (especially from a large vent) rush in to fill the void.  This might not be as much of a problem with an over sized boiler or one with a generous pickup factor but with a boiler more evenly matched to the EDR (small pickup factor) it may cause a problem. The situation could be further aggravated if you rapid vent all the radiators on the system causing an overall shortage of steam available.  I sometimes run a test setup on my radiators which has a 0-3 PSI gauge.  I've noted in some circumstances that the needle remains hard pegged against the stop until the radiator is completely filled with steam. I've often wished I had a vacuum/pressure combination gauge to see what is really happening.



What I'm wondering is that in some circumstances, would a slower vent cause the radiator to heat totally more quickly than a fast vent?  The more I consider the venting situation of a one pipe steam system, the more the concept of the Paul system intrigues me. I'm now waiting for my copy of Greening Steam. Does Dan mention the Paul System at all in his new book?

- Rod