Vacuum Start?

Big-Al_2

As I was on my evening walk, I began to muse about how to get more efficiency out of a single pipe steam system.  Here's an idea I came up with:



1) Eliminate all of the air vents and create a sealed system.



2) Attach small vacuum lines to the top of each radiator, about where a hot water vent would go, and run them to a small vacuum pump.



3) At the start of each cycle, first run the vacuum pump.  It would need to draw a vacuum deep enough to boil the water in the boiler at whatever temperature it was at.  The pump would run long enough to vent any residual air and fill the system with vapor . . . it might take a few minutes.



4) At that point the vacuum pump would turn off and the boiler would fire up.  It would start steaming right away, raising efficiency.  When the burner kicks off, the boiler would continue to steam as it cooled down.



The idea is too simple to never have been done.  I'm sure somebody will be able to tell me about some dead man who invented this fifty years before I was born.

Steamhead

Andrew Paul

brought such a system to market, after buying rights to the patents of a man named Skiffington. We don't know much about Mr. Skiffington, but the "Paul system" proved quite popular, both in new systems and as a retrofit to older ones. When retrofitted, fuel savings were something like 35%. 

Big-Al_2

50 Years

Yep, I just looked him up.  The patents were issued from 1900 to 1908 . . . fifty years before I was born. I have a lot of good ideas.  Apparently I was just born a century too late for them to be of any use.



So . . . how did the Paul vacuum pump know when to stop running? Strictly a timer?  Or did it run all the time and return any condensate to the boiler?  There obviously weren't electronic controls or reliable vapor sensors a hundred years ago.



Does anybody offer a modern version of the Paul system today?  If not, why not?

The Steam Whisperer (Formerly Boilerpro)

Check out Hofmann

They still have all the parts.  I am considerinng converting a one pipe system myself to see how well they work.   A vacumn pump is probably not even necessary...just a vacumn cleaner or shop vac.



Boilerpro

Big-Al_2

PIAB

Thanks!  I looked at the Hoffman web site, and the Dunham-Bush site too, and their vacuum systems seem to be geared to larger systems.  I'd like to squeeze a little more efficiency out of my residential system.



I was toying with the idea of using a small venturi-type vacuum pump, run by compressed air, something like the ones made by PIAB.  I have used them for work

holding in my day job, for robotic machine tending..  They are capable of about 26" of mercury . . . quite a deep vacuum.  They have no moving parts and I'm sure they could withstand steam temperatures.  I'd need to design up some kind of condensate separation chamber so water didn't go through to the pump, and come up with a timer.  I'm thinking that on the start of each boiler cycle, the vacuum pump would run for a set time, maybe 5 minutes, whatever it took to evacuate the system worst-case, and then shut off with a solenoid valve to seal off the evacuated system. 



The rest of the boiler controls wouldn't even have to change.  The boiler would fire until the stat or Pressuretrol was satisfied.  It wouldn't need to operate under vacuum all the time.  The economy would arise from the boiler starting steaming at a lower temperature.  This could lower the stack temperatures to the point where they start condensing though . . . and that could have some bad consequences.  I doubt I'll actually do it this year.  Too many other projects in the works . . .



 . . . Just the musings of an old shop rat . . . turned engineer . . . gone over to the dark side, I guess . . .

Big-Al_2

PDF of Idea

Attached is a drawing of the way I think I could add vacuum to my single pipe system.  It seems incredibly simple.  Any reason it wouldn't work?



Thanks!



Al

Unknown

Vacuum is an Interesting Subject.

LOL at  "going over to the Darkside"!     Al - I know what you mean . It is a rather intriguing subject made especially so by Steamhead's comment on fuel economy. If one could get a large saving in fuel, say 25 % +, this puts things into a whole different ball park. i wonder if there is a way to approximately calculate this?



There are 2 areas where I can see vacuum helps: One - in not having to

vent air results in the quicker distribution of steam,saving fuel and

two - since in water boils (produces steam) at a lower temperature in a

vacuum, there is a saving of fuel not having to heat the water to 212

degrees F.



I don't really have a good handle on how vacuum really works during the system's operation and what is the relationship of naturally produced vacuum (condensing steam) to artificial vacuum from the vacuum source (pump). How one would design a modern vacuum system. What items: piping, vacuum pump,water trap, burner, and control wise etc ,etc.are necessary to put together such a  system? Does one need to use a modulated burner or would  the bursts of the on and off "blowtorch" burner we now use work?



As I've never seen a vacuum system in operation  I don't have a feeling for just how much vacuum a modern system could produce.  I've attached a vacuum / boiling point chart to this post and you can see if one could operate the system under high vacuum, the boiling point is quite low and would result in a large fuel saving or is there something here that I've overlooked?   This post  has got me really interested again in vacuum  and I'm going to have to re-read my copy of  "The Lost Art..." on vacuum systems. If you come across other sources of knowledge on vacuum systems  please share them with us.



May the (steam)  Force be with you!

- Rod

Unknown

Vacuum Line

I really need  read my "The Lost Art.." first and brush up on vacuum more before commenting but was wondering why with modern equipment, seals, etc.is it necessary to use an evacuation tube on each radiator?  I can see where it would be beneficial (especially with old leaky radiators) though wouldn't an single vacuum attachment on each main  work as well?  Just a thought as it would really help in a retro fit not having to run a tube to each radiator.  Al- Nice drawing! What program did you use to draw it?

Big-Al_2

Need to vent

Very useful chart!  Thanks, Rod!



I'd bet that no steam system would be totally tight, so there would be air getting in, if not from leaks, then certainly from the dissolved gasses in the feed water.  Additionally, if the vacuum pump started up with the boiler still warm, then the boiler might start making steam before the pump could produce a deep enough vacuum to eliminate most of the air.  I think the vacuum pump would need to be hooked up to every radiator, and probably the end of the main, and run for a decent amount of time at each start . . . to be able to vent the whole system much like atmospheric vents would.



I made the drawing with AutoCAD, and "printed" it into a PDF file using the open source PDF Creator from SourceForge.

LarryC

34 feet of water = 1 atmosphere

If you ran a pipe from below the boiler waterline up to the attic and back down to the vacuum pump, you could draw as much vacuum as you wanted without drawing water into the vacuum pump.  Plus you could use the water height as the mechanism to determine when you drew a deep enough vacuum to turn off the vacuum pump.

A remote reading TRV on the boiler piping would tell you when to release the column of water once the boiler has cooled down past the point of producing useful steam.

Larry C.  (a fellow dark sider)

nicholas bonham-carter

vacuum + burner modulation

i would think your vacuum steam system  would benefit greatly from modulation. that would mimic the declining heat from the coal fire, at 5:00 AM.

the early vapor systems did not always have a vacuum pump, just check valves, so maybe that would be the place to start. put check valves in front of all the vents, and steam at full burner until the air is out, then modulate down to 50%? 

steam can be used to create deep vacuums in the food processing industry, so why not at home?--nbc

ttekushan_3

Webster system of Steam Heating.

Don't forget the Webster System of Steam heating which is a two pipe set up but really cool. I've been tending to one of these systems and its going to get a NEW Nash Jennings vacuum pump. Also have to reintroduce the radiator inlet restrictors. The pressure differentials throughout the system are way out of control without them.



Look it up in the Library section. They even had an outdoor sensor to modulate the vacuum levels based on demand. Many of the ideas can cross over to single pipe steam.



-Terry