Need help understanding Dunham system

gerry gill

your talking crossover traps right?

1/2'' you cand beat the barnes and jones...monash 38 is nice too..

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Long Beach Ed

Dunham DH Spec Sheets

Here are some spec sheet for the DUNHAM DH Home Vacuum Heating System. Excuse the big file size, but there's much detail here.

This is from the 1929 Sweet's Directory.

Check out how that pump works!

Long Beach Ed

Steamhead (in transit)

Nice find, Ed

I've never heard of Sweet's Directory- what is/was it?

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Long Beach Ed

Sweets...

...was and still is a multi-volume set of manufacturers' catalogues and data sheets. Most suppliers printed and inserted entire sections into the books. Dunham's contribution was about 40 pages, probably right out of the Handbook, perhaps with a little added sales fluff.

I believe Sweet's is now about a 50 huge volume set. Some big libaries have them and certainly they are now on CD.

They are published for the architectural/engineering gang to help them select and specify everything from windows to tile. Back in the 1930's they had a whole volume related to heating.

A little "social engineering" will get you a new set if you have the place to put it and care about asphalt floot tile designs.

Long Beach Ed

Long Beach Ed

Pump

I am surprised that the vacuum pump ran whenever the boiler fired.

Fisher

The pump

Ed,
Thanks for the good scan of the sheets on the pump. I could blow them up to read all of the details. Apparently the pump itself is a water pump, and it creates a vacuum with a venturi?
What maintains the water level in the tank?

I still have not found the differential controller. Do you have a suggestion for what I can use? What vacuum levels are we looking for?

Fisher

Long Beach Ed

Here's what I see...

Fisher,

Yes, the pump did nothing but circulate water from its tank around and around through a venturi. This nozzle, called an exhauster, shot water through a venturi, just like the one in an auto carborator, creating a suction that sucked air from the top of the steam system's "#220B air eliminator".

The air eliminator is nothing more than a float trap. It probably has a steam vent stuck in it now where the 1/2" or 3/4 line to the pump hooked up.

The pump tank was filled wither with a funnel or with a 1/4" pipe and globe valve to a cold water line. You added water when the sight glass ran low. The other tap on the pump was an overflow that ran to a drain.

I don't have the data sheet on the Controller, but should be getting one in a few days. From what I read, it appears that the system worked electrically this way:

The pump turned on with the boiler when the thermostat called for heat. It ran until the thermostat was satisfied, which on a mild day, would cause 133 degree steam vapor to be made at down to 25 inches of vacuum. I doubt it ever went that low. They told the operator to "lower the gas flame" on mild days. What an opportunity for a two-stage burner!!

On a cold day, pressure would build up to eight ounces, overcoming the vacuum and increasing the temperature of the steam.

Upon pressure building, the pressure in the return (which is right at the pump's suction) would be overcome by the pressure in the end of the longest main, operating the differential switch and turning off the pump.

If I'm correct on this (someone add their opinion, please) you could just connect the pump to a vaporstat set to turn off the pump on some pressure less than the burner shut-off. I'd be tempted to put that vaporstat on the end of the main (?). WHile it woun't actually be measuring the differential between the return and the main, it should give you some control until you find some better way.

Not a very sophisticated contol, but Dunham claimed it saved 30% to 50% when using gas as a fuel.

Go get 'em!! Or send me that beast pump!!

Long Beach Ed

Fisher

Plans

Ed-Thanks for the explanation of the pump operation. The old differential switch with the surge arrestors was connected between the end of one steam main and the end of the dry return, so it would shut off the pump based on reaching a setpoint of pressure difference between the steam supply and the mains. I don't see how it would know the difference between a mild day and a cold day.

BTW - I am expecting the Barnes and Jones cage units soon. We will repair the known problem radiator traps and evaluate the system at that time. We reduced the pressure to 8oz cutin and 12 oz cutout based on Patrick's recommendation over the phone. Eleanor is reporting that the room temp is 65 upstairs and 70 downstairs at the thermostat(which is set at 70). The radiator in the room with the thermostat has a leaking trap so I hope that fixing that trap will help with balance.

Steamhead - I have a hunch that you are correct in suggesting that the piping was sized for vacuum and will be too small to work well as a vapor system. There is so much piping that I have not been able to allocate time to measure pipe sizes (and spend all that time with friable asbestos). During a normal daytime cycle, the steam mains are venting in about 2-3 minutes and getting hot, but the end of the return doesn't get hot. I don't want to pass judgement until we fix the radiator nearest the thermostat, but I've got a feeling that the system will need the vacuum to perform. I suggested to Eleanor that we fix the radiator traps now and plan on a pump restoration project sometime between now and next winter.

Fisher

Eleanor's complement to Dan

Dan - I gave a copy of "We got Steam Heat!" to Eleanor and she borrowed my copy of "The lost Art". She is a PHD and retired English Professor. She reported to me: "I like the way that man writes".

Long Beach Ed

You may be surprised...

I know a selling point of most vacuum systems was the reduced pipe sizes (and costs) necessary when using a vacuum.

Most of the Dunham literature raves that their system can be added to any regular two-pipe system. While I have much of their material, they didn't appear to advocate the usual reduced vacuum piping sizes.

Maybe you'll be lucky and the thing will work fairly well without the pump and its noise.

But what fun would that be?

Long Beach Ed

Steamhead (in transit)

The dry return lines

are not supposed to get hot- warm, but not steam-hot. The traps keep steam from leaving the radiators and going into the returns.

You mentioned that the system was "upgraded" when your uncle bought the place- wonder if he added the DH and vacuum-capable traps to an existing Vapor system?

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FredR

Fisher, I have not used photos but will work on it.
The system I service is relatively new, about 1950-53?
Recently I aquired a D/B catalog circa 1971. It has the info for the Vari-Vac systems. Possibly Dan would like it copied for the library.
I do not recall if I mentioned that the boiler,condensate tank
and controls were replaced about 8 years ago. However the original differental controller (not used) is still in place. It is piped as you desribed earlier. Actually there are two diff/controllers one for each zone. The two movs are original with original Honeywell actuators.

FredR

Long Beach Ed

The Differential Controller

I just received information about that Dunham Differential Controller.

It's interesting to note that both the small vacuum heating pump and controller appear to have been introduced by Dunham in 1929 but were gone from their catalogiue # 514 by 1935. A short lived system indeed.

The controller was piped between the end on the longest steam main and the return. A greater pressure on the steam side than on the return side is needed to keep the differential conteoller "in balance". The controller is adjusted to turn the pump off when the pressure in the main exceeds the pressure in the return by 1" of mercury, or about one-half pound.

Remember that this system operated at about eight ounces of pressure.

If the differance in pressure between the two pipes is less than a pound, the vacuum pump turns on. The controller can be adjusted to a higher differential if that is needed "to prevent slugglish circulation at the ends of steam mains".

Where more than one zone was used, with motorized valves, additional controllers could be used for each zone. They would be wired in parallel so either one would turn on the pump.

I hope this is helpful in your understanding and restoring this fantastic Dunham system.

Long Beach Ed

Fisher

Remember Uncle Morton's system???

Last winter we serviced the radiator traps, crossover traps and added a vaporstat. Now it is time for the real fun!

I have the DH pump in my shop. To my astonishment, the motor runs!. It was full of dirt, and the brushes sparked like crazy, but it is alive. A local motor/pump shop owner is going to go over it for me. (he is old enough to have experience with an AC motor with brushes). Any suggestions for restoration of the pump are welcome - we havn't really gotten into it yet. I am optimistic that it can be put back into service without any big heroics.

Unfortunately I have not found the original differential vacuum controller. Therefore I am looking for info/suggestions.

What differential pressure does it operate at?

Does anyone have any leads for me to find a suitable controller? I have recently emailed MEPCO.

Fisher

Steamhead (in transit)

Try Heat-Timer

see Noel's post above.

Pics! We need Pics!

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Al_19

This is an incredible thread. I don't know how I missed it last winter, but thanks for bringing it back.

Fisher

some photos

Steamhead - here are some shots of the pump.

Soon (maybe tonight) I will post some photos from my other steam challenge - Cousin Margaret's system. It is a Webster.

Steamhead (in transit)

Looks better already!

I reread some of the earlier stuff in this thread- you should be able to fit the sight glass on the reservoir with a McDonnell & Miller #67 low-water cutoff. This can be wired to an automatic feeder valve (preferably a newer version using a brass valve body) so you don't have to fill the reservoir manually, and can stop the pump (via a relay if needed) if the level gets too low despite the feed valve. I wonder if the pump died because of low reservoir water?

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Fisher

I think that the pump was OK...

Steamhead - I have done a lot of speculating on this. I think that the pressure switch failed - not the pump. "Ollie" was the last "dead man" at our company to look after this system. Unfortunately he joined the rest of the dead men about 5 years ago, so I cannot ask him what happened.

Eleanor does not have any recollections at all about the vacuum pump.

Like I posted earlier - the pump motor runs. I could get proven wrong, but I don't think that there is anything seriously wrong with the pump. Since the differential switch is missing, I believe that the pressure switch failed, and Ollie diconnected the pump and installed an air vent in it's place.

I really like your suggestion to add a McDonnell & Miller to the pump reservoir to maintain the water level.

fireside

dunham system

if there is excessive steam coming out of the overflow of the vari vac what causes that is it a bad trap or vaporstat or anything else

fireside

dunham system

if there is excessive steam coming out of the overflow of the vari vac what causes that is it a bad trap or vaporstat or anything else

Dave in QCA

Bump

Posting a nul reply to bring this very interesting thread back to the top. 



I am also hoping that doing so will reactivate the images and attached files that are no longer visible.



Dave

SteamCoffee

Hate to dredge this oldie up.....

but wondering if any Dunham Differential info has surfaced since this thread?? Anyone know if the poster, "Fischer" every got this all sorted out? Thanks...

Dave in QCA

picture of controller

Boiler Wrestler was out on a job and found this controller, took a picture, and sent it to me. Don't think the vacuum is in use.



Also, I now have a copy of Dunham Handbook No. 514 from 1935. It pictures a much more modern type of controller, but the discussion is very complete in justifying the benefits of using vacuum steam from an efficiency and control standpoint.