Hoffman #3 Paul/Norwall vents

John S.

experimentation! I would love to get a look at this system.

I was at the Supply house today and they had 2 Hoffman #3s siting on the shelf. Owner wasn't around so I couldn't ask if he could still get them, but you're further along with that anyway. Any word from Hoffman?

I wonder if any of the Wallies have any documentation on the Paul System specifically how the exhauster worked or how it was made.

Please keep us posted with any further experimentation, Terry!

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ttekushan

Hoffman #3 Paul/Norwall rad vents

Hi everyone--

I am getting closer to putting my money where my mouth is and installing steam heating in a 1939 forced air house that by all rights should have been steam to begin with. I've got my boiler, and am missing radiators of the appropriate size for two bedrooms, but everything else I have. Due to the required care in retrofitting without utter demolition I have chosen a single pipe set-up. The house is 1800 square feet so this combination is a good fit.

Here's the catch: I want to use the Hoffman #3 radiator vents. Why? I want to be able to operate the system subatmospherically during start up in mild weather. I want the greater seasonal efficiency and comfort this would afford. I need to be able to experiment with different levels of initial induced vacuum based on outdoor temperature. I've done a portion of the electronic design, and it is quite simple, added complexity being of little use on such an otherwise simple heating system.

But I can't find any suppliers on line or locally who carry the #3 (which has the 1/4" outlet for connecting to a vacuum source). Hoffman technical support has not gotten back to me. The reason is that it might be nice to be able to offer an upgrade system that can easily be retro'd to existing one pipe systems. This thought of using a modified Norwall system was inspired years ago when looking through the 1906 Sweets architectural catalog where it is explained in some detail. Then after buying a copy of "The Lost Art..." I see Dan ponders this as well.

But if there is limited supply of this type of vacuum vent or any current production will soon cease, I won't go any further down this path.

Does anyone out there have a feel for the current and future supply situation for this type of vent or equivalents?

In curiosity,

Terry

John S.

Hi Terry,

I have recently become intrigued by the Paul-type system as well and had thought that Hoffman still made the vents.

My supplier here in Detroit has a shelf-full of old vents (NOS). I will check and see if he's got any and if so, how many. However, if Hoffman no longer makes them I doubt that will help much (what to do if some go bad?)

My main curiosity was what are you using for a exhauster? Is it homemade? Please give me some details if you could.

John

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ttekushan

exhauster

I have experimented in the past on a two-pipe gravity return heating system with different exhausters. I tried a vane type pump and a vacuum pump recovered from a lithium bromide refrigeration system. These pumps were overpowered by the huge volume of steam developed by the boiler, i.e., the system built up pressure anyway.

Out of desperation and a limited budget (it wasn't my building. Don't ask how I managed all this) I realized that for experimentation a good shop vac would tell me a lot. Well, I never really ran it in a true subatmosperic arrangement, only as a start-up "vacuum assist." But the shop vac proved that a good volume of vacuum is necessary.

The boiler would fire, and with it the vac would activate. The return vents were Hoffman 76's with back check valves. There was a vacuum breaker and the vac was hooked up to the line that the 76 sat on top of through a ball check. I placed an adustable thermo-switch on a convenient riser towards the end of the system that would activate a timer that would open the series power relay in the vac's power line after a specified period of time. I randomly chose 10 minutes. This whole thing would reset upon the cooling of the risers, the cycle being repeated at the next firing.

This system worked great. That steam would fly through the main, filling that 100' pipe in about a minute. All of the radiators began filling within a minute of each other. Temp differential in the building (coolest to hottest apartments) went from about 8 degrees to about 1 degree. The system could run a short time in mild temps on dead cold start with virtually perfect balance even though the radiators were only about 1/3 filled. Imagine 5 storefronts and 8 apartments all the same temp. It was really quite a thrill.

Really, on the Paul system with intermittent boilers, I don't think that the pump would have to run anywhere near all the time. I would be inclined to put the pump's shut of temp sensor at the end of the coldest radiator. Or better yet, the radiator nearest the T-stat so no one can shut that radiator off. There shouldn't be a "cold radiator" with this set up anyway.

So I am going to hit our local industrial surplus store to find something suitable, or buildable. The vac needs longevity, which a consumer vac won't deliver.

And something else. It must be quiet. The shop vac was noisy but it never mattered in that experimental system because it was in a boiler room sub-basement where NOBODY could hear it.

I'll update with my findings.

-Terry

Steamhead (in transit)

You didn't happen

to see how much vacuum the shop vac produced, did you?

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Bob W._3

The Hoffman website still lists the #3 Paul vent.

http://www.hoffmanspecialty.com/pdf/hs900/HS900-3474.pdf

Christian Egli_2

Speaking of things that suck

Vacuum cleaners, the types we use for dust, don't suck a high vacuum, around 2 PSI tops. For better results and deeper cleaning you need a multi stage impeller. Shop vacs typically have two stages.

But vacuum cleaners handle large volumes of air quickly.

By contrast, a displacment pump (pistons and such) can go total vacuum (14.7 PSI) but have no volume handling capacity.

It's just sad.

The best compromise is probably the water jet tube venturi action. Plenty vaccum pump brands available, but none affordable.

The pay back: super accelerated system heat up time and super uniform and you can use orifice schemes with no concern for slow natural venting, which means no traps no vents, just one concentrated pump problem.

A miracle, I'm holding my breath. See

http://forums.invision.net/Thread.cfm?CFApp=2&&Message_ID=158938&_#Message158938

Science is fun.

ttekushan

vacuum

The shop vac was able to communicate a bit less than minus 1 PSIG back to the compound gage marked in psi (it looked like about minus 1.2) at the boiler. At the point of boiling the pressure would temporarily rise to about 0 psig until a good amount of steam was condensing in the radiators. It would slowly drop again until the vac was told to shut off. In mild temps this was also about the time the T-stat was satisfied. If very cold, I figured its just as well to let it go at atmospheric as the extended run time suggested that I needed all that the system could deliver.

You had to see this place. About a mile from Lake Erie, northern exposure, badly leaking doors and windows. With cold snow blowing in the bitter winds, I would have a snow drift at the front door. INSIDE the front door! Yet it was cozy in there with those big window radiators cooking away. Under those conditions you can understand that after a certain amount of run time I was unconcerned about running the vac. The balance was already achieved, and mild temp conditions were quickly fading into the past, at least for the season...