Dunham Vapor Heating

Dave in QCA

I was just looking back at the information on the Dunham Vapor Heating system.  A few of things are noteworthy. 

1.  The regulating plates that it mentions as being part of this system are orifices.

2.  While it mentions that this "can" be used on a coal boiler, it specifically shows an automatic boiler, which fires on/off.

3.  It claims that a self induced vacuum of 10-20" can be established.  10" vacuum would be about 190 degree steam and 20" would be about 160 degree steam.  WOW!  Modulating steam temperature.... sounds like the advantages a hot water system??

4.  The return trap is shown apparently because the description says that the system can go above 8 oz. if needed and therefore the dimension B might not be adequate.

5.  There is an equalizer connection between the supply and return piping with a check valve to allow flow in the direction of the steam main only, so that steam side vacuum will not exceed return side vacuum, which would cause an impediment to condensate flow back to the boiler.



Could it be that the deadmen found an advantage in self-induced vacuum systems for ON/OFF fired boilers? 

It appears that the advantage is indicated to be during times of partial steaming cycles, and in my system, that's pretty much all I have unless I am 10 below 0 outside.



The image is rather poor, so I am including another.  It is not for the exact same vaport heating system, but does clearly show the equalizer line and check valve.

Rod

Vapor Heating

Hi Dave- Thanks for the info. As I'm constantly thinking of ways to increase the efficiency of my system, I find articles like this very interesting though I have a feeling that in my case it is questionable if my ancient system will actually hold a decent vacuum. I think a lot can be done in this area though I'm waiting till gas becomes available to our town (hopefully this year) so I can install a modulated burner.

- Rod

Dave in QCA

Burner types

Rod,

I think you have told me in the past, but I do not recall now.  What type of boiler are you running, and what type of mod burner are you thinking getting.  Seems to me that you are runinng a one pipe system?

Sometimes I wish I had a one pipe, it sure would be easier to get balanced!  However, I have concluded that the only way my system will ever be balanced is with orifices, perhaps they were there in the beginning, who knows?  



 I know that I do have a 1/2" in steam line coming off the header, heading to the direction of where all of the return piping converges.  The steam line stops short, has an old stop cock valve still in it.   It is remarkably like the pictures I posted.  But, I have no air eliminator or return trap. Anyway, I sure looks like it might have been set up as a vapor / vacuum system.  Might have even been a vacuum pump, but if so, it is long gone!

Rod

Vacuum

Hi Dave-  I'm one pipe oil so have been thinking along the lines of a modified Paul system. Lack of modulation in residential oil burners has me rather frustrated at the moment so that's why I'm considering natural gas if and when it is available here. My feeling is that vacuum has rather limited benefits unless you have a modulated or at least a two stage burner.

- Rod

moneypitfeeder

Similarities

Hi Dave, this system looks almost identical to my system, except for the air chamber below the return trap. The piping check valves equalizer etc are all the same (I have the Marsh Vapor System, diagrams in the library) So I'm interested to see if you figure all the intricacies out. How is it holding a vacuum? and how do you measure it? All very interesting, I hope you post any other info you dig up!

Dave in QCA

Marsh System

Hi Moneypit,

I just looked up the Marsh information in the Heating Help Library.  You're right!  The two systems are very similar!  The only difference I can see is that Dunham used a crossover trap to vent the mains and Marsh used a vent with a vacuum check, then, as you noticed, Dunham used that air chamber on the outlet piping of the return trap, probably to eliminate any chance of water hammer when the trap cycled.



It will be a slow project before I get the my system set up for vacuum.  The first thing will be to get orifices installed.  The dunham / Mepco traps are very fast.  That combined with very large supply piping to each radiator creates a situation similar to overventing on a onepipe system.  The steam will just not go where you want it to on a partial steam cycle.  When I finally get the system balanced with orifices I will be able to remove the various radiator vents that I have had to install in a feeble attempt to balance the system.



Then, I would like to get the condensate pump removed, since it is really not needed. When I do that, I will need to vent the return line and will install a check valve.  Will also have to modify the 3 main vents with check valves, or change the vents to crossover traps - not sure which way I will go with that.



I will post my progress on the system on the previous running thread on the

"Best Heating System".   http://www.heatinghelp.com/forum-thread/131216/The-Best-Heating-System

 

Ban

Pulley

I just found strange pulleys on my ceiling in the boiler room. It seems to fit this diagram for the modulator. I will post photos soon. This diagram worries me, I am missing some of these components.