Expected efficiency gains from main vents vs. insulation

draft_dodger

Hi,
It's my first winter in this home. I'm having an issue with the furthest radiator not getting steam if the system doesn't run for long enough.
That doesn't bother me as much as my desire to save on fuel.
Here's the thing: It seems that the main vents are not working (a Hoffman 75 or so and another one that looks like a bigger version of the Hoffman but unidentifiable). They were painted over. Not sure if that's what did it.
I would also like to insulate the mains in the boiler room (but not the rest of the basement, which I am using as living space)
I'm wondering which of the 2 improvements (vents vs. insulation) would get me a bigger return.
Thanks.

ethicalpaul

The main venting will, IMO, provide a much better heating experience. The $$ savings are questionable.

The insulation will help you put heat where you want it better which may result in a little savings (but the payback time will be loooooong).

Do the vents first, they require very little $ and time and can make your system way better.

Jamie Hall

The insulation question... it must be kept in mind that insulating the pipes has two functions, not one, and the most important one is usually ignored. The obvious function is that the pipes lose less heat. Now in your situation, you say you want them to lose heat as they are heating the basement.

Fair enough, but the joker is the other, more important function of the insulation: allowing steam to get to the end of the pipe and not just sit there and condense. In most situations the steam will, eventually, get the pipe hot enough to make it to the far end and whatever radiators are out there. Eventually. In rare situations, it may never make it at all. No amount of venting will speed this up.

Which leads me to enquire: is your problem child which heats slowly on the far end of an uninsulated main, by any chance? Because if so, you can't vent your way to heat -- you'll either have to insulate the main or live with a slow cold radiator.

ethicalpaul

I only have experience with my system, but I never saw anything close to a main being able to condense fast enough to deny a radiator to get steam. It was completely uninsulated for many years.

We know that a pipe has very little EDR. A main, even at the end where it is supplying the last radiator, I just can't imagine that it could suck up all the steam that is heading to that radiator unless the system is very undersized to the point where there is exactly enough steam to supply the radiation, with zero extra (zero pickup, or even negative pickup would be required to see this occur I think).

ChrisJ

I suspect if you submerged the main in water, like in a lake it may be able to condense enough steam to keep up with the boiler attached to it.

ethicalpaul

I'll let you know when I upload that video!

ChrisJ

ethicalpaul said:

I'll let you know when I upload that video!

You flooding your house for science Paul?

Chris_L

I only have experience with my system, but I never saw anything close to a main being able to condense fast enough to deny a radiator to get steam. It was completely uninsulated for many years.
The point is not that the uninsulated main prevents all the steam from reaching the farthest radiator, but rather that it takes much longer to get there.

As the OP stated:
I'm having an issue with the furthest radiator not getting steam if the system doesn't run for long enough.
Steam doesn't travel down a cold main. It condenses. Insulating the main lets it heat up much faster, and it keeps it warmer between cycles--so the steam can move faster to where it needs to go.

I'd say insulating the main is more important than increasing the venting in most cases. But there is an
easy way to check. Measure the time it takes the steam to reach the cold radiator after the boiler has been off for a few hours. Then repeat when it has been off after only a few minutes. The latter time will be much shorter.

You can reduce the long delay by insulating the pipes and reduce the short delay by adding venting.

ethicalpaul

Yes he said that, you're right. Now it's my turn though You said "increasing the venting" but he said his venting was not operational/painted over.

so I'll stand by my opinion that fixing inoperable main venting is going to help him more than insulating his mains.

Additionally, since his main venting is not working at all, that may be the reason his far radiator takes a long time to heat so that problem will likely be solved with the main vents anyway.

KC_Jones

50' of 2"steel pipe weighs ~180 pounds, specific heat of steel is .122, if the basement is at 50° (pipes included) and we say the pipes need to be raised to 212° that's a 162° temperature rise.

180*.122*162=3,557 BTU to heat 50' of 2" pipe

my 125k boiler outputs 106,000btu/H or 1766 BTU/Minute. That would mean it takes my boiler about 2 minutes to fully heat that amount of pipe up, if the venting on the main is such to allow it to travel that fast, in my house it is.

After that the EDR of that pipe is .62 per foot, for a total of 31, which gives an output of 7440 BTU/H which is only about 7% of the total boiler output. Given that a exactly sized boiler would have at least 33% to heat that 7%, it amounts to nothing.

I can tell you for certain that in my house, the insulation didn't make a measurable difference in the speed to heat the main. Did it change? Sure, but not to the extent being presented in this thread.

The venting is the primary issues, not heating the pipe.

With inadequate main venting the radiators will start allowing steam in prior to the mains fully heating, this is why the main venting is so important. So if the steam is going to a radiator, it's not going down the main, or may never make it to end of main on a normal call for heat.

Put the money into main vents first.

If you post how long and what size the mains are, we could recommend the proper amount of main venting for your system. I'd say that 75, even if working, isn't adequate unless your system is really tiny.

To be clear, I am not saying insulation isn't important, but the original question is where to start. With the above in mind to me it's obvious.

clammy

Insulating mains increases the amount of steam that ends in the radiators instead of heating your basement and having condensing forming in your mains till they get up to temp and stop condensation ,just insulate it s the right thing to do if not good luck . Steam systems where designed and installed w insulated piping as part of there design . Having your mains and run outs not insulated increase the condensate in your mains over time this extra condensate will etch a groove in the bottom of your mains and you will get leaks either in the sag points of your piping or at the joints where your piping is the thinnest due to the pipe being threaded . If your expecting large savings after insulating I would say maybe a little ,the upside is dryer steam at the ends of the mains less condensate in your mains and better more even heat to your rads . Get rid of the Hoffmann and get a gorton no 1 and if your radiator vents have not been changed in 5 years toss them and install new they have done there time . If you choose to hold on to old vents cause u think they work stop fooling yourself penny wise dollar foolish I say . On a side note check all radiator valves for signes of leakage and either tighten packing and tail piece nuts if they don’t stop leaking replace ,make sure all rads are properly pitched towards hand valve . For myself when asked about steam system balancing and I see the mains are not insulated I suggest insulating before playing musical air vents that is not the way to balance a system . Also exposed steam mains are not heat emitters for basements but it’s yours so do what you wise but remember those pipe purpose was not to heat your basement it’s to supply steam to your rads . Peace and good luck clammy

delcrossv

The missing point here is it's not just the uninsulated main that's condensing steam, it's also all the radiators along the line that are also condensing steam. Add also that the cycle is intermittent. In the old days with coal firing, even with the dampers closed there was still a heat source putting energy into the system. No so with oil or gas. When the boiler is off, it's OFF.

So if there isn't sufficient input over a long enough length of time to both heat the main over losses AND feed the radiators in the line, then yes, you'll have a situation where even with essentially open pipe venting, you'll get poor heating at the end of the main.

See: https://forum.heatinghelp.com/discussion/185113/fast-return-slow-return

Finally had to put almost all MOM#4's in the first apt on the line to get steam to the end of the run. That'll keep for this winter. Next spring's project is replacing all the old insulation.

cross_skier

I would do both as they are great winter projects.  I see strong arguments by experienced colleagues that both are important.

delcrossv

cross_skier said:

I would do both as they are great winter projects.  I see strong arguments by experienced colleagues that both are important.

Replacing main vents is a half hour job. Insulating mains can take all day. If you don't have working main vents do that first.

Pure efficiency? No sense heating the basement, insulation will get the steam to the living spaces.

ethicalpaul

Yeah I think people lost track of the original question:

I'm wondering which of the 2 improvements (vents vs. insulation) would get me a bigger return.

No one is saying insulation isn't good. What I'm saying at least is that in the face of no working main venting, how can anyone really say that should be left alone and instead install insulation?

cross_skier

They're both quick fixes, not terribly expensive, and pretty important.  I say that's an amazing opportunity, it would be a shame not to do both.

ChrisJ

cross_skier said:

They're both quick fixes, not terribly expensive, and pretty important.  I say that's an amazing opportunity, it would be a shame not to do both.

I'd argue that the cost to insulate all of the piping is actually a bit pricey.


Id also argue that most of the heat lost in a basement isn't actually lost. I'm sure some of it is but I'd bet 70-80% makes it to into the living space.



Yes I insulated all of my piping and even some stuff that most wouldn't. My returns are also insulated. I just don't think it's as big of a deal as others. Also I don't believe the earlier systems had insulation originally, I think that became "a thing" in the 1920s-30s when they were pushing asbestos sales.

draft_dodger

Thanks for all your replies.
I'm cash tight right now so not doing anything for time being, but will probably get a pro soon to replace the main vents first. (I'm not that handy).
I know some mentioned that I should insulate in the basement to get steam to the living spaces, however I'm my case, most of the basement is living space for me. Is it recommend to add some radiators there? Wall mounted I guess?

ethicalpaul

if the basement heat that you get from your system as it currently exists is welcome, honestly I would not spend money to add insulation that will force you to spend even more money to add some kind of radiation (either hot water or steam) to that same space.

But definitely get the main vents taken care of. Get a quote that explains what they are going to do and what vent(s) they plan to add and we can tell you if it sounds correct. But leave the dollar amounts out, you can't share those here.

cross_skier

My college basement apartment had uninsulated mains as a hear source.  I remember it worked better for me than some friends in other apartments.  Good luck!

EBEBRATT-Ed

and in @KC_Jones example 3557 btus is 3.557 lbs of steam=3.557 lbs of water just under 1/2 a gallon of extra condensate which may impede the flow of steam somewhat.

But fixing the vents is the first thing to do.

ChrisJ

EBEBRATT-Ed said:

and in @KC_Jones example 3557 btus is 3.557 lbs of steam=3.557 lbs of water just under 1/2 a gallon of extra condensate which may impede the flow of steam somewhat. But fixing the vents is the first thing to do.

So the main can handle all of the condensate from the radiators but not 4k btuh from the main?

I didn't do the math but that doesn't seem realistic.  Especially since that'll be long gone before the radiators start condensing