Dunham Vapor Heating System

scottrice31

I am trying to get a 1923 Dunham Vapor Heating System to function the way it was intended. My understanding is that this system will work best at ultra low pressure. The boiler is now a 2003 Dunkirk 247D-400S with a Honeywell 4079A PressureTrol and a PA404A Pressuretrol safety controller. The system has a Dunham 220B air eliminator. Most of the traps are CA Dunham 1 series, some with cartridges that look like they have been around forever. There is at least one end of line Hoffman 17C cartridge between the steam side and the dry condensate. Additionally, a number of the radiators on the 3rd floor that have vents. I believe that I need to do the following:

1) Replace the 4079A Pressuretrol with a Vaporstat
2) Replace the pressure gauge which is measuring 0-30 pounds, with something in ounces
3) Replace all the trap cartridges.
4) Remove and plug radiator air vents
5) Do something about the Air Eliminator. It looks like a combination of a F&T Trap plus air vent.
a) Is there a company that does rebuilds of these things?
b) If not, do I replace with an F&T Trap with an air vent on the outlet side?
6) Some illustrations (diagram below) showed a boiler return trap with an air outlet to the dry condensate. Is this needed?
7) Some illustrations also showed a swing check valve on the wet condensate in the first horizontal run below the air eliminator wet outlet. Is this needed?

Is this the right plan? Am I missing anything?

Thank you for your help!

Scott

Jamie Hall

Some thoughts... first, the Dunham was a very good vapour system. Perhaps more complicated than it needed to be, but very good. It's worth getting it to work again, though not necessarily as a full Dunham system. So...

1. Vapourstat. Yes indeed. Start with it set at 8 ounces cutout, 4 ounce subtractive differential.
2. Do not replace that 30 psi gauge, though it doesn't seem helpful. The insurance companies and building inspectors want it (they want one which reads to twice the pressure relief valve setting). Instead, get a 0 to 3 psi gauge and mount it on a T arrangement on the same pigtail as the vapourstat.
3. Replace all trap cartridges? Maybe not. It won't hurt, of course, but if they're not broke... why fix them? All the traps must be working, of course!
4. Yes.
5. and 6. and 7.
Let's consider this. All the steam mains need a crossover trap (you mention one, that Hoffman 17C -- all the mains need one. If some of the mains don't have one -- find out where they were and replace them. Now. What happens is that the air from the steam mains and the air from the radiators all winds up in the dry returns -- and has to go somewhere. In the Dunham system, it was exhausted through the air eliminator. The return trap (here's the patent -- clear as mud, as most of them are: https://heatinghelp.com/assets/documents/425.pdf) was rather ingenious, and was arranged to collect the condensate and allow it to get back to the boiler. Part of the problem back in the day was inaccurate -- or wholly non-existent -- control of boiler pressure, and so such gadgetry was needed to make sure the condensate could get back if the boiler pressure went too high. So...

Do we really need it all? No. So, if the boiler return trap is missing -- which wouldn't surprise me a bit -- you don't really need it, provide -- big proviso -- your system is arranged so that the boiler pressure can never get high enough to back water into the dry returns. 8 ounces of pressure will raise water about 13 inches, so if your vapourstat is set to cut out at 8 ounces, and the lowest dry return is at least 18 inches above the boiler water line, the thing will work as advertised, with a bit of a margin (always nice to have).

Now if the air eliminator isn't working properly, you can try to have it repaired, but again there's a work around: it's main purpose is to let the air out, after all, so you can add two or three good main vents, such as Gorton #2s, at the ends of the dry returns where they join before they drop to the boiler, and make sure that there is a way for the condensate which gets into the dry returns to drop to the boiler. At which point the air eliminator becomes decorative...

The check valves in the wet returns are not needed (and might better not be there) -- if the pressure stays low. If there is still the pipe from the header to the … once it went to the return trap … and on to the air eliminator, that does need the check valve; otherwise steam will get into the dry returns where you don't want it.

dopey27177

Show us a picture of what you have in the building. Nearly all that Jamie Hall wrote is correct. As to installing air vents on the dry returns that wont work out well as air will enter the system when the boiler shuts down and you lose all the vacuum in the system. To get a return on your investment you want the system to hold vacuum as long as possible even after the boiler is shut down.

Jake

Jamie Hall

If you want the system to hold vacuum as @dopey27177 suggests -- which will help the efficiency of the system, although with a somewhat doubtful return on investment -- use Hoffman 76s as your main vents instead of Gorton #2s. Problem solved. Of course, 76s don't come cheap...

Joe_Dunham

Below is some literature. It comes from a book dated 1963. the pic you attached is really the one shown as page 20 (vapor system with a return trap) Is that what you have? You may want to open the return trap up this summer and see if its in good shape. I dont think you can get one. The air eliminator I THINK is just a float trap vented to atmosphere. You can buy an F&T, remove and plug the internal thermostat, then add a 76s at the unused upper tapping (or any vent but use a 1/2" swing check in line with the vent so as the vacuum is not broken). Radiator traps do not last long, you will want to get rebuild kits FOR sure. (Mepco, Barnes and Jones, etc) it seems as though many people do not like condensate pumps but if you look at page 21 its another option (given you have space) though you will sacrifice the vacuum which is a disadvantage if you feel you want that. if you go with a pump a boiler feed is always best because it is smart to boiler water level, condensate pumps are not. If this literature were current it would show a boiler feed. Question is if you resurrect what you have, can you maintain fractional pressure? Vapor came about in the days of coal. With coal that's easy.

scottrice31

@Joe_Dunham Thanks for the literature. No, my system doesn't have a return trap. I spoke to a gentlemen this morning who was referred to me by the engineer at Mepco. He has worked on several Air eliminators. He said the Air Eliminators are fairly durable. The only problem is a sometimes corrosion with the attachment points on the float valve, but most are fairly easily cleaned out and maintained.

Joe_Dunham

Look at the pricing on some of this stuff. 1939.. I thought TRVs were European.

scottrice31

@dopey27177 @Jamie Hall @Joe_Dunham Pictures of the system. Let me know if I missed any angles that would be helpful. In case it isn't obvious from the pictures, there are 3 main steam runs coming out from the T.

Joe_Dunham

The 222 air check is still available and made by Ventrite. It was commonly called a penny valve because there's a brass disc in it the size of a penny. Its just a check valve to atmosphere. The 220B is not available but I don't think you need it. You can open it up and see how it looks inside. If it looks good leave it. If not You can remove it and install a 1/2" swing check horizontally, and a couple of large vents in parallell (same for any other basement vents) Like Hoffman #75 or even one of those mepco "Big mouths" . The check valve will prevent the air from getting back in. Install them at the top of the upper reducing tee. As you know, the vacuum, it is produced by the collapsing action of steam which occurs as it condenses in the radiators and the piping system. Steam occupy s 1600 times the volume of water when it changes state. There can be no air vents on the radiators and the valve packing must be good or you'll have no vacuum. The cast iron radiators will collapse the steam quickly. but once again, the pressure must be fractional. The picture you originally posted showed a return trap which it says is more forgiving if you encounter higher pressure, but that's not what you have, so the pressure will be important. Use two gauges, the existing 0-30 because it may be code, and a 30"Hg-15Psi compound so you can see if you're actually getting Vacuum. 10" - 5 psi would be great, but don't think they are made.

scottrice31

I put together a diagram of the system with corresponding pictures. Thank you everyone for your assistance. - Scott

Joe_Dunham

Sorry for this LONG comment, but;
Its hard to tell from a 2D diagram, but is this what you have? The supply mains should be pitched towards the ends. It looks like you have 4 ends (whats the yellow and green that end abruptly at the black line in the center? Just capped?) At each end, they should connect to the wet return, which is normally at ground level. The wet return will pick up the condensate from the Ends of supply mains, and it will terminate at the Hartford loop (a jump up) going back into the boiler. There should be a connection (for air removal) connecting the end of Supply main to the Dry return (the Dry return should pitch back to boiler) Some might say you need a "crossover trap" at that location (a thermostatic radiator trap) to vent air into the Dry return. However, the original design was to do all of the atmospheric venting though the air eliminator, which is NOT thermostatic, it was float actuated. Under fractional pressure, non condensable gases accumulated in the air eliminator. The float is away from the seat and the air goes out. When condensate level rises, the float shuts the inlet to the 222 air check. If you find that the 220B air eliminator is no good, worn, whatever, and you convert it to a thermostatic air vent, what may happen is this; as soon as steam reaches the newly installed air vents where the old air eliminator was, the vents will close. So if one main heats quickly, or a radiator trap is passing, the vents will close, and the "crossover traps" even radiator traps will have no place to discharge air. This is sort of like double trapping (two traps in series) This can slow distribution even cut off some areas. Proper practice is to vent at the end of mains. So if you REALLY want to keep the vapor system, I'm afraid the air eliminator is important because it is the point at which ALL of the air is vented to atmosphere. Otherwise, you can do traditional atmospherics venting. Each end will need a vent and so will each radiator. You can remove the guts from the radiator traps. That pipe will only serve to drain condensate. Make sure the Wet return is not blocked, flush it.

scottrice31

@Joe_Dunham The black lines are walls and the runs do not end at the walls. The entire system is properly pitched. Both of the mains that run toward the east, join to a condensate pipe at ceiling level that then dumps to the wet return. The pictures previously posted show the setup of the boiler piping. I am in the process of getting replacement trap cartridges ordered. I have three radiators that I need to remove the vents and plug. What material should the plug be?

Dave in QCA

Here are some comments on the Dunham Systems of this era. In 1929, Bulletin 414 describes in detail, The Dunham Return system. It utilized both a return trap and an air eliminator. It was intended to operate at pressures as high as 1-2 Psi. The Dunham Home Heating system had an air eliminator, but NOT a return trap. It was designed to operate lower than 1 Psi. It was set up with a vaporstat, which was to be set at 10 oz. In earlier publications in 1915, the Home Heating system was called the Dunham Vapor system. That publication made a point of clarifying that it was NOT the Vacuo-Vapor system, which had apparently been a failure.

In regard to your system, I seriously doubt if there is anything wrong with your air eliminator. Most of the time it just sets there and does nothing but let the air pass through it. If however, your system pressure rose high enough that condensate could not fall by gravity to the boiler, and therefor began to pile up in the returns, the float in the air eliminator would rise and cause the exhaust port to close, preventing the loss of water from the system.

I am not able to see all of the various parts of your system, but I suspect that one area where two steam mains are connected to a pipe that then drops to become a wet return, was the result of an alteration. One would expect each of the steam mains to drop to be come a wet return and that each of the end of steam mains would have a crossover trap venting to the dry return.

I generally agree with the rest of the comments that have been offered and there is no point of me running through those again.

I am attaching a few files. One, is from a VERY early publication in 1915 describing the Dunham Vapor System, later known as the Dunham Home Heating system. The others are from Bulletin 414, published in 1929. The show details of your air eliminator and of your air check. My apologies for 2 of them being turned sideways. Your PDF viewer will let you rotate them.

Dave in QCA

Joe_Dunham said:

The 222 air check is still available and made by Ventrite. It was commonly called a penny valve because there's a brass disc in it the size of a penny. .

Joe, do you have more information on the Ventrite Check? I am not able to find it online.

scottrice31

@Dave in QCA I beleive that the reason that it may not have dropped down at that point is due to the fact that there is a door at that end of the basement near the NE corner that leads to an elevator equipment room / pit. so there is not a path directly on the wall. The original Otis elevator is a story for a different chat board. The only way to pipe would be to go in and out of that room with the wet return. They may have avoided that because the elevator shaft is not well climate controlled.

scottrice31

I received a referral to a gentleman who has knowledge of this particular type of system from the head engineer at MEPCO. He suggested to potentially install a Barnes and Jones Condensator 2.0 (which is still made). He believes that there was a return trap on the system and that the Condensator will create the correct balance in the system. There is a metal insert in the floor very close to the Air Eliminator that may have been used to support the weight of the return trap. Who knows?? His idea assumes that I first deal with the PressureStat, radiator vent removal, and traps first.

As it relates to the PressureStat, I found a Honeywell L408J Pressurestat 0-16 ounces. I had a hard time finding a pressure gauge that registers in ounces. I have attached one that I found at Grainger. Are there other options or sources I should look at for pressurestats and gauges? There is currently a Honeywell PressureTrol of the system.

Dave in QCA

I was not aware that Barnes and Jones was making a return trap! That is good to know.

However, its important to remember just exactly what a return trap (condensator) does. Like the air eliminator, than does nothing except allow air to pass unless high pressure (over 1 psi) causes condensate to back up into the returns, a return trap does nothing in normal conditions. Returning condensate, by gravity flow, will freely flow through the return trap, just as if it we a simple piece of pipe, on its way to the boiler where, by its own weight, will freely flow into the boiler. When the boiler and steam main conditions rise above 1 Psi, this gravity return flow is impeded. Then, and ONLY then, the return trap will begin to function, to allow condensate to return to the boiler. There is nothing magic about it and it will have no effect on other balance or steam distribution issues that may exist in your system. If you choose to control your system with a Vaporstat, say to 10 oz., then, as long as your vaporstat is working, the return trap will NEVER operate. If you didn't have a vaporstat, and such a device was no longer available, and there was no way for you to control you boiler to less than 1 Psi, THEN, I would strongly suggest a return trap. But, on a Vapour System (friendly nod to Jamie's spelling) you need a Vaporstat, or a return trap, but not both.

Hope this is helpful. I mean no disrespect to the engineers at Mepco, CA Dunham, et al.

dopey27177

The boiler header should have been one size larger. The connection to the steam main was reduced. The boiler equalizer should have been the last connection into the boiler. There is a counter flow condition at the equalizer. As to the air vent check, take it apart, clean the seat and penny with a fine steel wool.
That should allow the vent check to hold vacuum in the system.
See simplified boiler piping install. As to the operating pressure
Maxis normally less than a pound pressure. If all the condensate does not return to the boiler you may have to jack the pressure up a bit.

After the vaporstat is installed use a 4" differential between the burner shut down and restart.


Jake