Empire State Bldg. steam pressure

Joe_Dunham

There is a lot of talk about the steam pressure in the Empire State Building being 2PSI. While this is true, it is important to understand that the building has, and always has had, a Vacuum Heating Pump. (In fact the original Nash unit is still there as a back-up!!!) I know because I (GS Dunham LLC) was involved in the sale and installation of the new unit. A vacuum pump is just a huge mechanical air vent that pumps the air out of the piping and creates a vacuum (depending on how tight the pipe is) in order to "stretch" the steam and help it move quicly and quietly through the system. Steam distribution is as much a function of Vacuum (air removal) as it is pressure in such large buildings. A vacuum also lowers the temperture of steam. So it is not truly accurate to say the building heats at 2PSI because without the Vacuum Pump the pressure would need to be higher to overcome the HUGE amount of pipe. Also remember that you either have a Vauum Pump OR air vents, not both. The vast majority of NYC Hi-risers have Vacuum Pumps.

george_42

Thanks for the interesting info, I never do steam work but I always like to know more. George

Steamhead

@Joe_Dunham , are you by any chance descended from Charles A. Dunham, who started the Dunham steam-heating company over a century ago?

Joe_Dunham

No my last name is Stropoli. I am a partner at GS Dunham. We are in fact the manufacturers Rep from that very same CA Dunham, which became Dunham Bush, then Mepco which fractured into Mepco and Vent-rite to complete the steam specialties line of Vacuum, boiler feed, condensate pumps, radiator traps, F&T's orifice radiator valves, and last but not least a control system called Vari-Vac

Pumpguy

Interesting information Joe.
Do you have any information as to what vacuum is maintained on the return lines of this system? And what is the CFM air removal capacity of the vacuum pumps being used?

Joe_Dunham

It was back in 2014. I believe the CFM was 150@10"Hg. Two 10HP Liquid ring pumps. The old Nash unit only handled the air, not the condensate. This 750 gallon unit does both. We did Tightness testing with tracing odorant but you can imagine what a daunting task this was. I dont think we got it over 4"hg, but that's not terrible considering. It got the job done. In fact the whole building is over heated.

Pumpguy

150 CFM, 10 HP is really quite efficient; 15 CFM/HP. I'm really surprised such small vacuum pumps are used for a building that size.

I've seen vacuum pumps with twice that capacity used on much smaller buildings, but then it all depends on system air leaks, the temperature of the returning condensate, and the desired operating vacuum.

Do you know what vacuum they are able to achieve on this system?

Steamhead

OK- we finally have confirmation on who the go-to person is for Vari-Vac!

@Joe_Dunham , are you aware of the small "DH" system Dunham marketed in the 1920s for residential use? Any chance of putting a modern version of this together? I know a lot of Vapor systems that could benefit................ go here:

https://heatinghelp.com/heating-museum/dunham-differential-system/

Joe_Dunham

That's very cool. The oldest handbook I have is 1953. I have to say 100% of my exposure to Vari-Vac is with Hi-rises. But as they say, size doesn't matter!! I don't see why it cant be done, it WAS done I guess. The thing is is it cost effective nowadays? The pump you showed me works on the jet pump (venturi) principal. That's what the tank is for -"hurling" water. I don't think anyone sells vacuum heating pumps that small but I do think you can rework a small condensate pump with a jet pump (check mcmaster Carr) and a fast acting motorized ball valve (check Indelac) and turn it into a combo boiler feed vacuum pump. You would have to put a pump control on the boiler. You would have to connect the wet return(s) to a float trap and probably jump up into the new tank but I think that would work, vacuum would help lift the water in. I wouldn't bother with a control valve but at the boiler supply put an orifice plate between two companion flanges or better yet a hot water type flow balancing valve that's adjustable. You would need to super restrict steam flow. And of course every radiator would need a trap or vent which goes to the new pump and connect down stream of the float trap. The obstacle would be if its one pipe, the radiator returns would have to dump into a main that pitches toward the wet return, not the supply. It would have to be a big house to make it worth it but I'll bet distribution would be spot on.
there is a Russian engineer in Massachusetts that invited us to his house to see his vacuum return conversion, he used a refrigeration type vacuum pump. He ran pex to and from every radiator (abandoned the one pipe main) He really just reinvented the Paul system or similar. It worked, but the fact is, he went through so much trouble he could've converted to hot water. But if its a big old house with two pipe, it may be worth it.

Steamhead

Joe_Dunham said:

there is a Russian engineer in Massachusetts that invited us to his house to see his vacuum return conversion, he used a refrigeration type vacuum pump. He ran pex to and from every radiator (abandoned the one pipe main) He really just reinvented the Paul system or similar. It worked, but the fact is, he went through so much trouble he could've converted to hot water. But if its a big old house with two pipe, it may be worth it.

That's @Igor . I've seen his system too, and like it. But as a contractor, I want to see this refined to a point where I can simply spec certain standard, easily-serviced components. Igor's effort never got that far.

And, the whole point is to NOT convert away from steam. There are a whole bunch of pitfalls to going that way which we have discussed on here many times. I really think we'll see more and more vacuum being used to make steam more efficient, if suitable standardized equipment is available.

Pumpguy

We've done very small vacuum condensate return pump sets for residential applications.

Vacuum conversions of straight condensate return pump sets too.

PM me with system requirements and I'll reply with comments and recommendations.

dopey27177

I Have worked on many low vacuum systems (2 pipe steam). Many of these systems had Skidmore vacuum pumps. These systems never produced more than 4" Hg. The reason for this is the steam piping and zone valves were quite larger than the piping in a Dunham Vari Vac system.

4" Hg is equivalent to a 4 PSI differential.

That being said the steam would flow quite rapidly thru the system.

AS the steam in volume moved thru the system the condensate temperatures would rise as high as 150 degrees (provided the steam traps were not defective}. At that point the vacuum in the system would be maintained near 4" Hg.

When the boiler or zone valve was satisfied and the condensate cooled the pumps would be able to produce vacuum at the design vac for proper operation. All vacuum pumps need a hurling tank so the water in the accumulator can be pumped thru the venturi and back to the accumulating tank) to produce the needed vacuum.

These buildings had drips on on all the risers, A dry return from the radiators and a wet return from the the riser drips. All the return lines were uninsulated. This kept the returning water from becoming super hot.

These systems had a full open or closed zone valve equipt with a micro switch or a control in the heat panel to start the vacuum pump when heat was needed.

Nash systems were designed for the building either from original installations or retrofit.

There are no short cuts or fancy retrofits. Nash has available thru the internet all the different Nash heating installations.

Because of the length of this post I am entering a post under a new discussion.

Referbishing an old hybrid vacuum system.


Jake

ChrisJ

dopey27177 said:

I Have worked on many low vacuum systems (2 pipe steam). Many of these systems had Skidmore vacuum pumps. These systems never produced more than 4" Hg. The reason for this is the steam piping and zone valves were quite larger than the piping in a Dunham Vari Vac system.

4" Hg is equivalent to a 4 PSI differential.

That being said the steam would flow quite rapidly thru the system.

AS the steam in volume moved thru the system the condensate temperatures would rise as high as 150 degrees (provided the steam traps were not defective}. At that point the vacuum in the system would be maintained near 4" Hg.

When the boiler or zone valve was satisfied and the condensate cooled the pumps would be able to produce vacuum at the design vac for proper operation. All vacuum pumps need a hurling tank so the water in the accumulator can be pumped thru the venturi and back to the accumulating tank) to produce the needed vacuum.

These buildings had drips on on all the risers, A dry return from the radiators and a wet return from the the riser drips. All the return lines were uninsulated. This kept the returning water from becoming super hot.

These systems had a full open or closed zone valve equipt with a micro switch or a control in the heat panel to start the vacuum pump when heat was needed.

Nash systems were designed for the building either from original installations or retrofit.

There are no short cuts or fancy retrofits. Nash has available thru the internet all the different Nash heating installations.

Because of the length of this post I am entering a post under a new discussion.

Referbishing an old hybrid vacuum system.


Jake

4" HG is 1.97 psi.

HVACNUT

> @ChrisJ said:
> (Quote)
> 4" HG is 1.97 psi.

He didn't say he was @doc27177.

jumper

We can get deeper vacuum with less power with dry pumps. Complication is handling moisture.

Dave in QCA

You are the person to ask! All of the old Dunham publications mention the Dunham Regulator Plates. Information on the orifice sizes of these plates would be immensely helpful. Maybe you would want to produce them?
By the way, I have collected a number of Dunham publications.
I have May 1911 book entitled Dunham Vacuo-Vapor System of Heating, in which our building in Davenport, IA is shown.
Also, Dunham Specialties, 1915, which contains a series of small pamphlets on systems and devices.
The Dunham Handbook #114, published 1920
The Dunham Handbook #314, published 1925
The Dunham Handbook #414, published 1929
The Dunham Handbook #514, published 1935

See attachments for the 2 oldest items.

Joe_Dunham

They no longer make regulating plates (orifice plates) That stopped long ago. Available are SWRFB and SWRFC adjustable orifice valves. There's no easy way to say how they are adjusted. A valve adjusting schedule is produced at time of building construction, However, they are adjustable so they can be tweeked and a little common sense as far as distance from steam source, exposure, room size, etc. can be used. You can get the SWRFB with a TRV head as well. From what I've seen If you can find orifice plates the holes are 7/64ths thru 7/32nds in 64th inch increments. They are very cheesy, made of copper and will wire-draw. A SWRFB valve is adjustable from 1/8 turn to 4.5 turns in 1/8 turn increments

JUGHNE

Tunstall Corp. makes valve inlet union orifices..copper cup type.
1/2 thru 1 1/4" (probably larger).

I got them pre-drilled to 1/8" and size them in the field as needed, 60-80% of EDR. Remove trap guts and no problems.
Pressure must be controlled.

Joe_Dunham

Problem is even a 1/8" hole (and that's the starting size) , with no radiator trap, unless there is a lot of heat loss and condensing going on which will create a water seal at the empty trap body, is going to pass live steam into the return. You won't see any problem in the apartment, but the pumping equipment, especially a Vacuum pump, is going to take a beating. So abandoning the trap is a bad idea. That's NOT to say there is not A LOT of this going on. but I know some horror stories. The directions say remove the trap guts. 90% of the time, an assumption is made that the guts are bad (passing) anyway, so why bother to remove them?. So they are left in place. Therefore, there can be no true scientific study as to how good it is to remove guts. Orifices are meant for a fixed load, and comfort heating is the OPPOSITE of a fixed load.

Dave in QCA

JUGHNE said:

Tunstall Corp. makes valve inlet union orifices..copper cup type.
1/2 thru 1 1/4" (probably larger).

Yes, I have the system fully orificed with Tunstall cup orifice plates and/or cups. I also repaired all of the radiator traps. My thinking is that the Dunham plates had much larger holes, as their purpose was only to improve steam distribution. They still depended on the trap to keep steam out of the returns. When they developed the Differential Vacuum system, it was dependent upon vapor reaching the traps, causing them to close.

I have been thinking about reconstructing a Differential Vacuum system, and I foresee issues with the Tunstall orifice plates. This is because the way they are sized and the way they operate, the orifice place is the point of separation between the boiler/mains, and the return piping. That is, a differential is produced by the orifice plate and this is in conflict with the proper operation of the Differential Vacuum system in which the differential is established on either side of the trap.

Dave in QCA

Joe_Dunham said:

Problem is even a 1/8" hole (and that's the starting size) , with no radiator trap, unless there is a lot of heat loss and condensing going on which will create a water seal at the empty trap body, is going to pass live steam into the return. You won't see any problem in the apartment, but the pumping equipment, especially a Vacuum pump, is going to take a beating. So abandoning the trap is a bad idea. That's NOT to say there is not A LOT of this going on. but I know some horror stories. The directions say remove the trap guts. 90% of the time, an assumption is made that the guts are bad (passing) anyway, so why bother to remove them?. So they are left in place. Therefore, there can be no true scientific study as to how good it is to remove guts. Orifices are meant for a fixed load, and comfort heating is the OPPOSITE of a fixed load.

Joe Dunham, actually, Tunstall does make orifice plates that are sized at 8oz or 16oz. They have a margin built in. If you put in the an orifice rated for the proper EDR and control the steam pressure to not exceed the sizing parameter of the orifice, the radiator will condense 100% of the steam so that none will be passed into the return pipes. Their smallest size is way smaller than 1/8". If my memory serves me right, 1/8" orifice sized for 8oz is rated for around 12 EDR. They produce orifices for EDR down to 4.5 at 8 oz.

Joe_Dunham

I may have the original adjustment schedule. We obtained all of them years ago. With a Differential system (Vari-Vac), that has a Dunham RTMS Zone valve, under many mild weather conditions, steam never actually reaches the trap because of the orifice and other factors. In fact Partial filling (half hot radiator) of the convector is normal and desired under mild weather. BUT when it gets real cold out, steam will reach the traps and they need to be there ready to do their jobs. Mild weather=high vacuum=cool steam. cold weather=low or no vacuum=hot steam. So you are right-the Dunham valve opening allows more steam in the event of cold weather. To use an orifice plate alone, you must err on the small side or you run the risk of live steam in the returns. I think an adjustable valve is better than a plate. Plates evolved into adjustable valves. I think Tunstall really wants to sell TRVs so they couple it with orifice plates and the pitch is--"look, you did away with that thermostatic trap!! " The irony is, you now have a thermostatic valve instead. Thermostatic devices go bad, trap or valve. Its just a trade off. Most important thing--get the system tight so you get good vacuum

jumper

>> you now have a thermostatic valve instead. Thermostatic devices go bad, trap or valve.<<

What is expected life for steam TRV? And is it the valve or the control that wears out?

JUGHNE

In the cases I have worked on there was no vacuum involved.
All systems had been hacked over the years. All were over sized radiators for the present building. Usually oversized boilers.

Because of the restriction, IMO, of the orifice limitation of passing air, I added air vents to the end of the steam mains.
Air vents installed ahead of the F&T's.