PMJ plc system

ethicalpaul

Not to muck up the thread ethicalpaul but the pressure drop in single pipe steam in the main is greater than two pipe steam because of the extra condensate load. You have a teeny boiler at 56MBH steam. Peerless recommends a super generous A dimension of 14 in. in single pipe steam for less than 100MBH. You are neglecting the stack up required for the condensate to get back to the boiler for overcoming the friction effects in the wet return piping as well.

I asked some time ago if you wanted me to make a dedicated thread to discuss the existence of Dimension A and you declined by clicking "disagree", but then you bring it up in other people's threads (shrug).

I'm not neglecting any stack up. I have a sight glass just above my boiler's water line on the far end of my main (as you must know), and there is no such thing as "stack up". There is no friction effect in the wet return piping, or any other force that causes that water level to rise any higher than the water line of the boiler (as measurable by reasonable means in anyone's basement).

Have you ever seen a water level work? That's what a wet return is, and there's no force in anyone's one-pipe system that will make the water level at the far end rise in any noticeable way, certainly nothing near 14" or 28"

I have shown it on video, I have explained it in writing, it's all there. Believe whatever you like but that doesn't make it real.

Captain Who

@ ethicalpaul start your own thread by all means. It might be helpful to clear the air.

I will politely tell you that there is no steady state flow condition in a water level, and yes I understand the physics of a water level. I have used it to check my piping to great accuracy and advantage since I have some marginal sections where it is pretty darn level, making things more critical.

You need to hit the books a bit on flow dynamics (respectfully). There is no observable friction effect without flow and it is proportional to flow rate. Also, I saw the water level in your end of main drip sight glass in the video where you restricted the takeoff on your very very small boiler. It rose up above the glass in the sight glass. Or did I just dream or imagine that?

Now, I don't want this thread to get off track any further because it is too good for that.

https://forum.heatinghelp.com/discussion/comment/1889512#Comment_1889512

ethicalpaul

You need to hit the books a bit on flow dynamics (respectfully). There is no friction effect without flow. Also, I saw the water level in your end of main drip sight glass in the video where you restricted the takeoff on your very very small boiler. It rose up above the glass in the sight glass. Or did I just dream or imagine that?

Now, I don't want this thread to get off track any further because it is too good for that.

But you keep bringing up new points to argue here (shrug).

The reason the level rose at the far end of my main is because I had constricted the steam flow going out of my boiler down to 5/8".

If you have a 5/8" steam supply out of your boiler, then you definitely have a Dimension A. But no one does.

PMJ

@ethicalpaul , The issue here is only about the magnitude of the pressure drop isn't it? Where there is flow through a pipe there is friction and there is pressure drop. I think what you are trying to point out is only that it is way smaller than is being suggested in standard diagrams. I agree that is true and the diagrams are indeed misleading. But you appear to be trying to argue that it is absolute zero which can't be true.

PMJ

https://forum.heatinghelp.com/discussion/comment/1889502#Comment_1889502

I use this one.

https://www.factorymation.com/SG2-20HR-12D

Captain Who

And the manufacturers have to be responsible and include large factors of safety in their recommendations. I sure would not want to be a daredevil, at the risk of being told it is a bad analogy, to fly in a commercial airplane without large factors of safety built in for when things do not go according to plan.

But denying the physics helps nobody really, especially when you have seen it in your own video with your extremely low output boiler. There are people out there who have bad water and piping in very very large boilers, so we need to be careful what we advise, just like the manufacturers, and condensate load is a huge factor at startup or near startup.

ethicalpaul

It's too small to worry about or consider. Someone who is probably dead apparently made some mistakes when consulting the fluid dynamics charts that keep getting mentioned here, and decided to tell everyone to worry about this dimension that they said should be 14"-28". Books were written about it, people designed systems based on it, diagrams were drawn showing it, and they named it Dimension A so that it could be discussed, planned around, and thought about.

That concern is unnecessary, that dimension causes zero problems, and so based on that I call "Dimension A" a myth.

Yes there is a pressure drop. It is a rounding error that is smaller than a lot of people's slope of their basement slab. And yet people keep bringing it up in threads where people are asking for help. That is wrong.

Edit: We posted at the same time, I was responding to @PMJ so I'll add this:

condensate load is a huge factor at startup or near startup.

Why do you think that condensate load is greater at startup? The exact same amount of steam is being created, therefore the exact same amount of condensate generated. Actually a little less at startup until the boiler is fully hot.

Jamie Hall

A brief observation on the balancing — and here I have a VERY limited knowledge, since I've never actually lived with any system other than the one Cedric powers — which is hardly "normal". In a nutshell, though — large system. House with extreme exposure to northwest wind but good solar exposure to the southwest. Some rooms go through from the east side to the west side, some do not. Result — heating load both overall and room by room in still air with no sun is radically different from a cold winter night with a 40 mph wind, which is equally different from a moderate winter afternoon with bright sun.

The whole show is controlled with a single T87 thermostat in a central location and a vapourstat (which rarely has to do anything)

Result? To an astonishing extent the radiators self balance. Not perfect, not by any means — but it's rare for the room with the worst wind exposure to be more than 5 degrees colder than the warmest room under those conditions, and equally it's rare for the room with the fiercest sun load to be more than a degree or two warmer than the rest.

And it's rather fascinating to feel it all working!

PMJ

Too small to worry about works fine. A lot better than doesn't exist.