Trying to rebalance my steam system

Sethamin

I have a 4-story townhouse with a 1 pipe steam heating system, and it's never quite heated the house evenly, so I'm now trying to rebalance the system. I bought the "Balancing Steam Systems Using a Vent Capacity Chart" e-book, and I've put together what I think makes sense for what my vent sizes should be. Since I've never done this before, can someone take a look and tell me if what I have here makes sense?

Specifically, I have several risers that have multiple radiators hanging off them, but no vent at the top of the riser. How should I treat these? I included the whole riser for the "Total Air" of the topmost radiator, but I wasn't sure if that was correct.

I also have one radiator where the air vent on it is at the very top of the radiator, which is the wrong location for steam. As a result, the vent closes early (before the radiator is hot top to bottom). It seems fine since it's oversized for that location, but how should I size the vent for it? It will clearly not push out all the air before closing so I should probably reduce the vent size, but I'm not sure by how much.

My diagram is attached, and my spreadsheet that catalogues all my radiators is here:
https://docs.google.com/spreadsheets/d/1Ae5IRmkorrb3v3ELV2ihsF1R0xp8wFL6CkZysA0Sraw/edit?usp=sharing

Thanks!

nicholas bonham-carter

First of all, make sure your main venting is generous to the point of overkill, and the radiator vents are slower.
Then as you measure the different temperature differences, add bigger vents to any top flor rads, which are lagging behind the others. Identical pats of butter should all melt at the same time on the rads. You will still have to use a toaster to use up the butter!
When your system was first installed, the radiators were sized perfectly for the rooms in which they were installed, and the piping was also appropriately sized, and installed. The job now is to return the system to its previous early state of perfection-silence, evenness of temperature, and economy.--NBC

Abracadabra

I looked at your spreadsheet. I wouldn't use C vents on any radiator unless absolutely necessary. I tend to stick to #4 and #5 vents. Maybe a #6 on a larger radiator.

Sethamin

nicholas bonham-carter said:

First of all, make sure your main venting is generous to the point of overkill, and the radiator vents are slower.

My main venting is a bit undersized right now, and I am planning on increasing that. I have 48' of 2" pipe on one main, and 28' of 2" pipe on the other - each is currently vented by a single Gorton's #1. That vents the shorter main in about 2 minutes, and the longer one in a little over 3 minutes. I'm going to purchase a Gorton's #2 for the longer main, and move that #1 to the shorter main. That should get both my mains vented in about a minute.

Abracadabra said:

I wouldn't use C vents on any radiator unless absolutely necessary.

I have large radiators sitting on top of 36' of 1.5" and 2" riser pipes. I don't see how I could possibly vent them in time without something larger than a 6. What's the rationale behind not using larger vents?

nicholas bonham-carter

You need 2 Gorton #2's on the longer, and 1 on the shorter, in addition to what you have now.
What we are trying to balance here are the resistances of the air escaping from each main. This will get the mains filled with steam even before the risers begin to fill. Slower (hoffman 40's help with this).
Once balanced in this way, you can identify any slower rads (on top floors), and increase those vents to get all the rads receiving steam at the same time.--NBC

Sethamin

nicholas bonham-carter said:

You need 2 Gorton #2's on the longer, and 1 on the shorter, in addition to what you have now.

So you're saying two Gorton's #2 AND a Gorton's #1 on the long main? That would vent 2.53 CFM (at 1 oz of pressure). The longer main has 1.104 CF in it, so that would clear it in 26 seconds. Doing similar math, I get 26 seconds for the shorter main with a Gorton's #2 and a Gorton's #1. Is 30 seconds of faster venting worth the $150 in cost for two additional Gorton's #2?

nicholas bonham-carter

How much gas will your boiler burn in 30 seconds times 30 times a day, 7 days a week, 4 weeks per month--etc?
Remember the aim is for all radiators to get steam at the same time, and that time should be as short as possible.--NBC

Mark N

"I believe every minute the boiler operates without steam in the radiators is totally wasted fuel"

That is not exactly true. You have to burn fuel to heat the water in the boiler to make steam, to bring the mains and all piping up to steam temp and vent the air in the piping. What is wasted fuel is this taking longer then it should because of inadequate venting. Also, the length of time all of this takes varies with how hot the boiler and piping is when the heating cycles begins.

Mark N

Sure is because without it my rads would never get hot. Also my rads put out heat long after the boiler has turned off.

Sethamin

Wouldn't the extra burn time while the mains are venting still increase the pressure, which would cause the risers to vent faster? The only "lost" heat should be radiated from the pipes in the basement waiting for the mains to clear, which shouldn't be terribly large if you have well-insulated pipes.

Or to put it another way, the heat was to go *somewhere*. It doesn't just disappear. The first law of thermodynamics tells us that.

Mark N

Actually the only loss is the heat that went up the chimney. All the others btus are lost inside the house. Therefore technically not a loss. It would cost an astronomical amount of fuel to keep it all at steam temp all the time. They did that back when the burned coal.

ww

i looked at your spread sheet and understand it...i may be missing something but where is the calculation of cubic feet in the main and the branches to the radiators added into the formula?

i may have missed it so let me know where it is please anyway.

also i agree with abracadabra...Balancing steam systems states you should vent slow. there are alot of factors..trial and error..condensing of steam to consider too.

will have to look into this total riser figure..i have to look and see that one..those risers have to be incorporated into each radiators calculation to vent out the air as well.

in column L i presume you are dividing by 3 to use 3 minutes as an acceptable figure to vent out the radiators?

could you get back to me on this one please?..thanks.

Mark N

Hatterasguy, don't forget much of the energy put into the boiler and pipes is available to you on subsequent heating cycles. if well insulated much of the heat is retained.

Sethamin

ww said:

i looked at your spread sheet and understand it...i may be missing something but where is the calculation of cubic feet in the main and the branches to the radiators added into the formula?

The mains are being vented separately, though I assume you're referring to the risers here. I had implicitly added their CF into the "Total ft³ air" column, but I just now went ahead and broke it out into its own column ("ft³ air in Riser"). That was actually good to do, since I spotted a few errors in doing that.

ww said:

also i agree with abracadabra...Balancing steam systems states you should vent slow. there are alot of factors..trial and error..condensing of steam to consider too.

So I guess you're saying that I should not go and change all my vents based on these calculations, but should instead just tweak my existing vents depending on whether the room is too hot or cold?

ww said:

will have to look into this total riser figure..i have to look and see that one..those risers have to be incorporated into each radiators calculation to vent out the air as well.

Yeah, I suspected that would be the case. On the other hand, I also worried that if I added too much venting on a lower floor radiator, then it might steal all the steam and never let the top radiators get hot. However, this is just conjecture on my part.

ww said:

in column L i presume you are dividing by 3 to use 3 minutes as an acceptable figure to vent out the radiators?

Correct.

ww

ok..i'm going to look at the sheet..whatever pipe from the main you have going to the radiator has to be measured and counted in as air to be vented in addition to the amount in the radiators.

this has to be done using a formula using pi r squared x length...and make sure it's converted from inches into cubic feet as well..

once this is done you can see where you stand on the vent sizes..we'll see what happens..and you should have accurate figures to base your decisions on..

it may not be conjecture...you have to look at the steam hogs that are referred too..and make adjustments.

ww

at first check it doesn't look like enough air in risers to vent out...although i don't see the length of risers per radiator either...just looks low in most cases to me..i could be wrong.

maybe since it's pretty easy for you and you understand this you should break it down in a column with the pipe size, riser length and the other columns on how you arrived at that figure...

when you want to look at the sheet to figure out how much insulation you need it will be a handy guide to do so at a glance.

Sethamin

I think I've done that - look at the column entitled "ft³ air in Riser" in the spreadsheet. I used the figures in the "Balancing Steam Systems Using a Vent Capacity Chart" eBook that gives the "cubic foot of air per foot" for each pipe size (though I did double check those calculations, and they seem to be rounded up a bit on everything). I then used that derive the ft³ air in each riser - it's all labeled on the diagram attached to the original post. There's is one label missing from a section of pipe between radiator I and J, but all the other lengths should be there.

ww

ok..i didn't seem to see the diagram..i'll look on the spreadsheet..i guess it's just my preference...sometimes when i make spreadsheets i go overboard..because when i look at them a couple of months down the road i see it all right there and don't have to go back to think what i did.

Sethamin

The diagram is attached at the bottom of the first post. It's called "Venting Diagram.jpg" and in a little gray box.

Captain Who

@Sethamin‌
It seems to me that where a riser (or portion thereof) is shared by 2 or more radiators, the full cross sectional area up to the junction point is not effectively available to the steam molecules that are destined for each radiator. Therefore you should have to calculate the effective cross sectional area that is available to that radiator up to each diverging junction point. For example, for radiators A and B, the 10ft section of 1-1/4" riser is not fully available to both and it should be necessary to take the ratios of the volumes for each radiator and associated pipe above that junction and use that to determine the effective volume in that section of pipe up to the junction point for each radiator A and B.

Also, regardless of that you made a mistake for radiator A. The volume should be 0.1 + 0.036 + 0.10125 = 0.23725 (not 0.13725). But as I said, I think this will undersize the vents needed due to what I said above.

This is very interesting to me because I think I downloaded the same ebook years ago. I think I'll have to try to find it now.

Captain Who

Oops, I meant to say "this will oversize the vents needed". The vents on each radiator A and B both combine their efforts to vent that 10 ft section up to the junction point.

Sethamin

@Captain Who‌
Here was my thought process: I figured that the proportion on venting on one radiator versus the other shouldn't make much difference either way. After 3 minutes, the entire riser and all the attached radiators should be vented one way or the other.

The only exception I could think to this is if one radiator is fully vented much more quickly than the other, in which case it might have an opportunity to condense some of the steam, open its vent, and suck some more air back in before the vent on the other radiator has closed. In that case, the total air increases, and that radiator will steal some steam from the other radiator. Hence, my reasoning was that the largest vent should go on the farthest radiator to minimize the chance of this happening.

Captain Who

I was just referring to the fact that vents on other radiators that share a vertical riser throw off the calculation (in your ebook) for any one radiator vent size due to the fact that they help to fill that shared vertical riser with steam. I doubt that the charts in the ebook take this into account so you may have to, if you want the caclculation of vent size needed for a 3 minute radiator fill to be reasonably accurate.

That's aside from the issue of needing all the radiators to get steam around the same exact time, but hopefully that will take care of itself if the charts are correct.

ww

ok..i see it now...how are you looking here as far as actual happenings and the heating of the radiators and air from the mains.?..

i gather you must figure out what is about right before buying the vents,etc. the maid o mist vents you have listed have the ability to unscrew the air vent orifice so you don't have to take off the vents from the radiators.

i make a note of what vent was in and what i replaced it with..to observe what happens. i did that yesterday and found the radiators heated up more evenly.

Fred

Maid-O-Mist makes a radiator vent that comes with 5 different orifices and Hoffman makes the 1A which has 5 or 6 different settings using a cap on the top. I use the Hoffmans and have great success with them. That allows you to buy all the same vents and adjust them as you wish. Makes "Trial and Trial" a lot easier and much less expensive.