Over venting

SteamingatMohawk

There is lots of talk about no limit to venting. Take some time and read the Update to the article, "Balancing Steam Systems" by Gerry Gill and Steve Pajek. This article is amazingly helpful for two reasons, first it provide a table of venting capabilities of many, many vent valves, and you can see how they relate to each other for your situations. Second, there is an eye opening update, "Can you vent too fast?" I had Varivalves installed throughout my system with many fully open. I also added up to two Gorton #4s at different locations in the condensate return. I couldn't come close to balancing the system until I removed the #4s and swapped out the Varivalves (fully open is like a #1, shut is like a #5) for Maid O' Mists with individual orifices. I even had to get some Vent Rite #1s so I could further reduce the vent rate in overheating apartments, below a #4.

Bottom line, I am now a true believer that a system can be overvented.

Take the time and at least read the update, https://heatinghelp.com/systems-help-center/balancing-steam-systems-using-a-vent-capacity-chart

Its slightly more than a page long.

KC_Jones

The comment that you can’t vent too quickly is in reference to main vents only. For radiators we have always advocated for slower is better.

On mains you want to go as fast as possible, and too much essentially isn’t possible. There is a point of diminishing returns, that more vents gets you little or no advantage for the money spent.

mikeg2015

I have first hand experience that venting radiators too fast is a problem. The steam rushes across the radiator and it heats unevenly and ultimately consumes less steam making the venting effectively lower. The purpose of venting is to consume steam without raising system pressure.

nicholas bonham-carter

I don’t know about the consumption of steam, but there is a required balance of venting radiators with venting mains which must be followed.
Fill the mains first by allowing the air in them, and the boiler to escape at very low resistance. Vent the radiators with smaller vents, such as th Hoffman 40, and then all the rads will receive steam at the same time.—NBC

SteamingatMohawk

I have two runs, one to the back and one to the front. They each have Gorton #1s. I installed #4s in those locations and it didn't help at all. I also installed a service saddle and put different combinations at it and that did not help. I only made real progress when I removed my Varivalves, most of which were just about fully open and installed MoMs, using different orifices for different locations. I was amazed when I turned on the boiler and the pipe to the radiator in the room with the thermostat heated up much quicker. I have since had to go to Vent Rites to slow down the radiators below the #4 orifice capability. They can only pass up to a #5, but can shut completely off. Read the report I mentioned earlier, it's an eye opener.

KC_Jones

I’d say your mains aren’t vented fast enough if I’m reading your description correctly. A #1 vent is fine if your main is less than 10’ long. A #4 on the main is even smaller. You weren’t over venting the mains by a long shot.

I’d keep the rad vents how you have them and speed up those mains, a lot. How long and what size are the mains?

EBEBRATT-Ed

Of course you can over vent it's just common sense. If you over vent you will have no pressure to balance with.

But water changing to steam increases in volume 1700 times so I think over venting would be difficult to achieve in actual practice.

nicholas bonham-carter

If your main vents never closed, then there would be no pressure to send up to to the rads, however, as they do close when steam hits them, then there is pressure.—NBC

gfrbrookline

What vents do you have on your mains, Gorton #1's or #4's? Gorton 1's and 2's are main vents, 4-D are radiator vents and should not be put on mains. You are likely mixing up main venting and radiator venting. Remember the golden rule "vent your mains fast and your radiators slowly."

SteamingatMohawk

I used Gorton #1s and #2s on the mains. I messed up. I didn't pay attention well enough when I previewed my post. Thanks.

Today there is a #1 on each of the two condensate return lines just before where they connect to the boiler return.

The pipe from the boiler to the back of the house is about 20 feet long before it u-turns uninsulated to return the condensate.

The pipe from the boiler to the front of the house is about 27 feet long before it u-turns uninsulated to return the condensate. Near the beginning of this return, I installed a service saddle and tried a couple of combinations of #1s and #2s.

After I swapped the Varivalves for MoMs, I havent gone back and put anything on the service saddle. I'm trying to decide if I should try it, just to see what happens.

gfrbrookline

You want a minimum of 1 G2 for every 20' of 2" main, those G1's aren't enough to vent your mains and you are forcing the radiators to vent the whole system. I would put a G2 on the 20' and a G2 and a G1 on the 27'. You want to get the air out or the mains quickly and so the steam can be evenly divided as it goes up to the radiators which should be vented very slowly. You should not hear the radiator vents hissing when they are filling.

SteamingatMohawk

With G1s installed before I removed the Varivalves, it would take about 5 minutes for the rear main to fully vent and at least more than another 5 minutes for the front main to vent. With the MoMs on the radiators and G1s at the end of the condensate returns, I get the front main to vent a short time after the back one. I don't have the exact times with me at my home, but it is less than a couple of minutes.

The two G1s are about a foot apart feeding down through a common tee, one G1 on the run and the other on the branch and another tee. Initially when I put the G2s there, it seemed like the back main was venting through the front G2, presumably because the two are so close. Its hard to visualize and I need to figure out how to attach photos. I have .jpg files, but the browse function for adding a photo transferred a link and drag and drop didn't work.

The saddle is about 30 feet from the beginning of the supply main. I could put the G2s at the end of the line and a G1 on the saddle. I also have the fittings to put two valves on the saddle.


What do you think about it?

gfrbrookline

What orifices are you using on your MoM's?

Draw a picture of your mains and returns showing how they come out of the boiler, the condensate returns to the boiler and where your vents are located.

SteamingatMohawk

I have some sketches and photos that I can email separately, if I am unable to upload them here.

SteamingatMohawk

I apologize for not sending sketches. I've been tweaking the vents almost every day. I got the coldest room to be at the right temperature and now need to continue to tweak the rooms that are still a bit too warm. Lately, with the coldest room at 70ish, the others can get as warm as 74 after the boiler turns off.

I am considering installing a Gorton #1 at the beginning of the condensate return for the front supply line, but am concerned with what it will do. Early on in this escapade I think I was overventing the entire system with open Varivalves. Now, the only Varivalve I have is on the radiator in the coldest room and putting the #1 on the condensate return for that end of the house may reduce how long the heat is on by venting that supply quicker and getting steam to the coldest room quicker.

nicholas bonham-carter

Does that means the radiator vents are doing the whole job of letting the air escape? What is the time needed for steam to arrive at the last radiator? Probably you could shorten the cycle time considerably with Big Mouth vents on each return.--NBC

Fred

@SteamingatMohawk , you may have to go back and readjust the radiator vents again, after you put the main/return vent(s) on. There will be a lot less air for those Radiator vents to vent, once the main venting is optimized.

SteamingatMohawk

There are two supply lines, one to the front (30 ft) and a shorter one to the back (25 ft). Each has a Gorton #1vent on the condensate returns (same length, but smaller diameter) just before they meet to feed back to the boiler.

I tried to upload a picture using the "attach image" thingy above this text, but all I get is an unusable URL pasted into this box. If someone can educate me, I will upload the pic...help, help..

gfrbrookline said "You want a minimum of 1 G2 for every 20' of 2" main" in the December 16 comment threads above. That makes sense, but I don't know the background for sizing the mains.

If I neglect the smaller diameter of the return lines, the total length is 2 x (25 + 30) = 110 ft of 2 inch pipe.

If the return is 1-1/2 inch that has about half the cross-sectional area so it would be 25 + 30 +12.5 + 15 = 82.5 ft.

Result is either 4 or 5 G2s. According to Gorton specs a G2 is worth 40 #4 vent valves at 3 oz. pressure according to the table in the Balancing Steam Systems report.

Fred

The URL will paste in the box but it should actually convert to the actual picture after you click "Post Comment"

As to the main venting, you are overthinking that. A Gorton #2 is good for about 20ft. of 2" pipe. The Mains need to be vented, the returns don't so put a Gorton #2 on each of those mains and be done with it. If your vent location is on the return, put them there but you don't have to worry about the air in those returns. You just want to push the air past the last radiator run-out.

SteamingatMohawk

Guilty as charged. I usually do, especially when I am not familiar with the subject matter.

JUGHNE

The shorter main/return piping will get steam to its vent first and then with that first vent closed the steam will travel thru the return fittings right over to the next vent and close it.
This leaves the longer/slower piping without any main venting at all.

Each of those returns need to drop individually down below the water line of the wet return. Enough water loop will isolate the steam of one from the other.

SteamingatMohawk

Wow, science triumphs again. Here you can see the two G1s. The two pipes with black insulation are the returns. When I bought the house in 1989, there were G1s on the tees. These are at the end of the return line.

I was going to try some calculations, but wasn't sure how to approach it.

When I started trying to balance the radiators, the rear supply would heat up in about 5 minutes and the front one would take as much at 10 minutes longer to heat up. I installed a G2 on each return and it made the situation worse. I put the G1s back in. At the time I was using Varivalves and when I swapped them for MoMs, the difference between the rear and front became much less.

Also, before swapping out the Varivalves in between trying different combinations of G1 and G2, I installed a service saddle at the beginning of the return for the front supply. I tried several combinations of G1 and G2 on the saddle with no improvement.

Today, I have a G1 on each return (see the photo) and the saddle has nothing being used.

I changed the lone thermostat to a wireless one and put it in the coldest room to get it to the right temperature. The tenant has been in that apartment for 4 years and never complained the temperature never got to 70. With the thermostat in her apartment, her temperature is fine, but the others are a bit too warm and I am carefully reducing the venting in those apartments.

I am considering making a change in the main vents to reduce the needed venting at the radiators. I can put a G1 or G2 on the saddle, swap the existing return G1s for G2s, or some other combination. With the return vents so close together, do you think having 2 G2s that close (as shown in the photo) will favor the rear line over the front one? I was thinking of trying a G1 vent on the saddle first.

These threads have been very useful in trying to get everyone warm without anyone being too hot or too cool.

Of course, the future performance depends on what the winter turns out to be, but at least if I can get pretty close to balancing, any deep cold periods should be easier to deal with.

SteamingatMohawk

Here's the service saddle with 2 G2s installed. As I said, today, nothing is being used, but it's easy to install a vent.

JUGHNE

Is the slower front supply main the longer of the two?

You might be spinning your wheels with balancing and venting until the returns are separated. IMO

SteamingatMohawk

JUGHNE, that's what I thought. I have no clue as to why it was that way when I bought the house, other than the fact I had to replace the boiler once and there was a separate condensate return tank that was removed when the new boiler was installed. I don't have any "before" photos to see how the two return lines were connected when the tank was part of the system.

Rerouting to connect below the water line could be annoying. It might be a lot easier to just build the equivalent of a U shaped trap, like in a sink that is deep enough to not get blown dry if a large enough pressure difference gets created. Although if you look at the photo of Hartford Loop, it wouldn't be difficult to bring the right hand return down below the water line.

SteamingatMohawk

I think this thread has given me some good opportunities to get the system performing really well.

Thanks guys.

Fred

All you have to do is cut that pipe that is tee'd into the return that drops to the floor, install a new Tee anywhere on that return that drops to the floor, anywhere below the boiler water line and tie the second return back into that Tee. Bothe vertical returns don't have to be separate, they just need to tie together below the boiler water line.

Gsmith

You might try, as an experiment, taking the vent off the longer line (the one with the service saddle) where the two vents on the returns are and replace with a plug or cap. That may balance the venting enough. Doesn't have be perfectly balanced just close. Or add a service saddle to the other main just after the last radiator roundup, and move the vents from the returns near the boiler to the new service saddle, and plug the holes near the boiler where the two vents were. Might be easier than sweating new piping in.

gfrbrookline

Once you have the returns corrected I would use Big Mouth main vents for your mains, that vent at 3 times the capacity or a G2 and cost the same. Very robust vent both in venting and quality. If I knew your mains were that long I would have suggested them in the beginning.

KC_Jones

Correcting the return piping to tie together below the waterline is simple, especially since you are copper. I see 1 hour of work and a few fittings max. The faster venting causing problems proves the short main is impacting the longer mains venting

IMHO you will never get this working correctly until you resolve that return piping.

gfrbrookline

Once you have the returns corrected as described I would put a nipple where the turn down, as tall as you can go for clearance, add a 90 with a 6" nipple running parallel to the return and add the a Big mouth on a 90. This will protect the vent and let it drain. Also plug the saddle.

SteamingatMohawk

All ideas make sense to me. Thanks for the inputs. I have already tried with the G2s at the existing return vent locations and know they can fit. I had to use a union on one because I could not turn the second one with the first one in place. No big deal, since I already invested in the parts.

I will let all this soak in until after Christmas.

SteamingatMohawk

The picture with the 2 G2s on the saddle is not what is there today. I have a ball valve and 1 G2, which is currently not being used. I could experiment to see what happens if I put it on line, just for the heck of it.

JUGHNE

Also while correcting the return drops, I would put a tee at the floor on each end of the lowest horizontal piping. A valve/plug on each end will let you flush out sludge that will gather there.

That horizontal pipe is the lowest point for junk collection, the cleanouts let you remove it before it passes thru into the boiler.

gfrbrookline

That is probably the best advice any of us have given you for the long term maintenance of your system. My mains drag a huge amount of gunk down that needs to be flushed out of the returns annually with the normal service.

My previous contractor did not flush the returns, even though they installed the ball valves to make it easy to do so. They became slow to drain condensate back to the boiler which made the LWCO add too much water. Ryan at New England Steam Works fixed that this year.

SteamingatMohawk

grfbrookline: Your comment about the drain is right on target. I already have the parts to install the drain. I have been focused on balancing first, since I have had the house for 30 years (this boiler for 20) and never had occasion to drain the entire system, other than when the boiler was replaced.

I used to like to sweat fittings, when I could use lead solder. With lead free solder, I use MAPP gas nowadays and in tight spots, it's more difficult because of the heat, even with using small heat shield "blankets". At least any work on the return piping won't be cramped.

Some time ago, I came across an article, "An Improvement to the Hartford Loop" that was in Heating/Piping/Air Conditioning, November 1999. I am curious if anyone has experience with doing what is suggested in the article. I haven't reread it in any kind of detail, but the idea is to raise the close nipple to raise the level in the loop to above the boiler water line, which the summary at the end of the article says it provides "drier steam, elimination of boiler flooding, elimination of pumps in many cases, and reduced risk of hammer when Dimension 'A' is right".

JUGHNE

As KC and I both have the opinion of fixing the dry return drops before attempting to balance your system, I believe you are spinning your wheels and will have to cover the same territory after fixing the piping drops....this would involve the drain/flushing fittings also.

You have to only drain the wet return and maybe a little of the boiler...a few gallons max. FWIW, I have found lead free much easier than old 50/50 solder.

SteamingatMohawk

I fully agree I probably got the cart before the horse in not dealing with the main vents being so close to each other. My instinct in recognizing that issue when I first started dealing with the project was good, I just failed to listen to my instinct. Having someone in on the discussions validate my thought is tremendously valuable, which is why I have three discussions going on. I think what may have diverted my attention is when I swapped out the Varivalves for MoMs and there was a large improvement in the venting times and I probably made the rash assumption that whoever installed the piping knew what they were doing.

That being said, I am pretty close to having the system balanced in that the coldest room in the house is now controlling by having the thermostat in it. I have been reducing the venting in the other rooms and now they are only a couple of degrees warmer. But as I reduce the others, I may be affecting what will happen when the weather here gets well below zero (minus teens). Time will tell.

In any event, I am going to reroute the rear return as suggested and install the drain, since I have the parts. I am still somewhat intrigued with the Hartford Loop improvement (it's name is Clifford Loop) and whether anyone has any experience with the concept. If it is the right thing to do, now is the time.

I have to wait to do the work until after this weekend...holiday/family stuff comes first.

Does anyone have any technical data sheet on the Big Mouths? The Barnes and Jones web site doesn't even have them listed in their list of products.

nicholas bonham-carter

I think that the fact that they are twice as capacious as a Gorton #2 for the same price would be enough technical information for anyone to see their benefit.
When you have installed the larger main venting, you will certainly need to redo the radiator venting strategy, in order to have good balance where all the rads get steam at the same time.—NBC

Fred

@SteamingatMohawk , I think you mean "Gifford Loop". A lot of the Pros here use it and I think it is incorporated in the Near Boiler packaged Piping kit from Burnham. See this link for more details:
https://heatinghelp.com/assets/Uploads/HPACGiffordLoop.pdf

Also, I think if you look at the Amazon website for the Big Mouth, it has some details/specs on the B&J BM.

ethicalpaul

Today I learned: accidentally or purposely, 25 years ago some dudes who didn’t know crap about piping a header installed a Gifford Loop on my system!