Vapor system

gerry gill

its contained in four word documents, so they will be attachments, dont delete it thinking its spam..you may or may not have this info, if not, you do now.

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Ken_8

Steam system parts?

This grand old home is undergoing complete restoration. The architect heard about us and we are restoring the system to orginal condition, except for the coal...

The obvious problem was a P404 pressuretrol instead of a vaporstat and the fact that all the traps are original, and probably blown so we'll simply replace them all. The Hoffman Differential Loop is fine and we'll just clean it out and replace the main vent. Like Steamhead, we like Gorton vents. However, I'm under the impression the # 1 and 2 are not capable of vacuum retention - and that is critical to proper operation of this system, which goes well into a vacuum under normal operation, or at least should be.

Should we simply put a check between the Gorton # 1 or 2 and diferential loop? Hoffman does not make a vacuum type air vent any longer.





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clammy

still in vacume

ken my assumption was that unless your burning coal the system isn't or should only pull a vacume after the burner is off on temp?I agree with you on installing a vaporstat but i would just opt for a gorton # 1 or 2 depending how much your venting and i'de probalby raise them up on a nipple or two to keep them from getting to hot .Is this just a tne up or are you doing a complete boiler replacement to ?Would love to see more pics of the boiler and near boiler piping and maybe some rads if they aren't run of the mill .Keep up the good work peace clammy

Ken_8

Clammy,

Yupper. The only time we'll pull a vacuum is when the gas burner goes off. I just like the gentle latent heat "drifting" that occurs when you allow some vacuum to take place.

The boiler is an old A/S c.i. job with millivolt control. Since the incease in efficiency of a new steam boiler would probably only raise efficiency by 10% tops, the boiler stays as is, especially since it is piped beautifully.

There's no insulation of the mains so that's going to be done too. We need to add one entirely new rad for the top floor but other than that, just a major tune up and a few riser extensions from new tile floors is in the mix.

I still like the idea of a check instead of no vacuum feature with a Gorton # 2 but that ain't in no book (:-o)

Here's a rad and near boiler piping.

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gerry gill

here is one,

http://www.hoffmanspecialty.com/pdf/hs900/HS900-76.pdf : but i'd personally opt for no vacuum since its not coal..and i'd opt for faster venting provided by the gorton 2..

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Ken_8

Thanks Ger,

I just got off the phone with Wallace Eannace, the local Hoffman reps and they said there is no vacuum vent mae anymore. I'm pretty sure they forgot about the 76, I just bought a few last year, but then...

I am puzzled why everyone (Noel, the "other" steam wizard, also suggested dumping the vacuum without coal as the fuel) is opposed to the "soft" landing a vacuum would induce in regard to latent heat release at the end of the cycle. As long as the system goes into vacuum the latenet heat of steam collapsing will take minutes instead of a few seconds. Is not that slow action a good thing?



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gerry gill

well, when ive accidently

allowed a gas fired system to drop into vacuum, it dropped so deep that the water actually got sucked out of the gauge glass and i broke the needle gage..the dropping into vacuum of the coal boiler wasn't so intense as the coal was still ''on'' so to speak..but with gas it drops into such a severe vacuum, well, do you remember the picture of the railroad tank car that collapsed..thats my fear..

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Ken_8

Yeah,

I had similar visions as well. I suspected that I'll have to see what happens. But then, the system has functioned for roughly 25 years with the components that are already in place, and probably undergone a vacuum a few thousand times before I came into the picture. There is a compund pressure gage. I'll let you know what I find when I find it...

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Joe Grosso

Ken, the problem with running vacuum on this system

is that with automatic firing, you can get vacuum long before all the air is out of the system. This can lead to problems with steam distribution as the air expands under the vacuum. It can actually block steam distribution.

The original vent on this system was probably a #11 vacuum vent. It vented a lot faster than that wimpy little #6 vent. So you really need high capacity- and here the Gorton #2 rules. I'm sure you didn't forget, that's (usually) the only vent in the whole system.

Hoffman also made the #10 vent, which was the same as the #11 except it didn't have the vacuum checks. This was also made for use with the Differential Loop, but you didn't see it as often.

I wouldn't put a modern check valve under a Gorton #2. Not only would it take more than the few ounces this system requires to open the check, but steam above the closed check would condense into water. This would add more weight to the check, and also cause banging if steam reached the trapped water.

Your best bet is one or more Gorton #2 vents.

Ken_8

Frank,

Thanks for the input. Now it all makes sense.

One Gorton # 2 coming up.

"What check valve"?

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patrick linhardt

to vacuum or not, that is the question

> I had similar visions as well. I suspected that

> I'll have to see what happens. But then, the

> system has functioned for roughly 25 years with

> the components that are already in place, and

> probably undergone a vacuum a few thousand times

> before I came into the picture. There is a

> compund pressure gage. I'll let you know what I

> find when I find it...

>

> _A

> HREF="http://www.heatinghelp.com/getListed.cfm?id=

> 68&Step=30"_To Learn More About This

> Professional, Click Here to Visit Their Ad in

> "Find A Professional"_/A_

patrick linhardt

to vacuum or not, that is the question

Hi Ken,

I'm going to weigh in on the side of historical precedence. That system, and many others throughout this great land, have been subjected to a vacuum at one time or a thousand others, and most survived.

I know a retired service manager that would only use a #76, rarely a #75. Swore by them, could never convince him with the arguement about automatic fire.

My advice would be to try it both ways. Steam systems react to different components in different ways. See which vent works best, and use it.

Are you going to use new innards for the traps? They look like the old #8 Hoffman return line valve. Very nice trap body, I hope they stay. The new brass would look out of place.

Best regards, Pat

patrick linhardt

quote from the Hoffman book

Hi steamhead,

I love old Hoffman stuff because we have some great archived literature here. I dug out a wonderful 38 page sales book from 1918 that does a wonderful job of explaining the loop.

To quote : "To obtain a proper service from a vapor heating job equipped with the Hoffman Equalizing Loop, it is necessary to use in conjunction therewith, a thermostatic return line valve on the return end of each radiator or heating unit, the thermostatic member of which is the steam chamber of the valve and subject to the conditions in the radiator, and also to use a highly sensitive air relief valve on the discharge end of the return line, a valve that will instantly distinguish between steam and air, stopping the passage of steam, but freely permitting the outward passage of air from the sytem. For such service we recommend the Hoffman No. 10 Vapor Valve, as this valve has a full 3/4-inch port, being large enough to pass all air coming to it, without back pressure."

That's quite a run-on sentence. How about that "full 3/4-inch port"? That is huge! The Hoffman #75 now is less than 1/4". What is the size of the #2? I say mo venting - mo better. They were very concerned with air vent rates at that time, "freely permitting the outward passage of air from the system". I call it Air Out, as in ... Steam Up - Air Out - Water Back. Do you have one of those t-shirts? If not, let me know.

No mention of vacuum with the 1918 equalizing loop. I will look deeper to find something regarding the era of the loop in question.

Best regards, Pat

Ken_8

Which vent

would you choose as the combination air elimination & vacuum creating unit? The check and Gorton # 2, or the Hoffman ???

Thanks for the help.

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Steamhead (in transit)

Those were two different Loops

The Equalizing Loop was the predecessor to the Differential Loop. The change occurred some time in the early 1920s. The Differential Loop itself was redesigned sometime around 1930.

Here's a pic from an old USRC catalog.

The Gorton #2 is not quite 1/2-inch at its port. Still it's the biggest one made today.

No, I don't have one of your shirts......

patrick linhardt

timeline

Hi steamhead,

I found the differential loop in a 1929 book, but a different configuration then Ken's picture. The dry return connects at the top, with a #15 vacuum vent at the high point of the dry return. The steam supply connected to the loop below the cast iron body. The overflow connection came off the side of the body to connect to the wet return. And yes, the #15 had a 3/4" vent port, the huge kind. And yes, it had the vacuum feature. So sometime between 1918 and 1929 the equalizing loop with a non-vacuum vent changed to a differential loop with a vaccum vent.

In 1934 the Hoffman Data Book was recommending using two #15 vents with the differential loop for systems between 7500 to 15000 square feet. Again, they wanted to get the air out. The boiler return trap was in there, being recommended for oil or gas fired equipment, quote: "where pressure builds up quickly".

In 1948, no mention of the differential loop, but the return trap is still there. Same in 1950.

In 1957, no mention of the boiler return trap.

E-mail me your shipping address off the wall. I want to send you something. customersupport@steamupairoutwaterback.com

Best regards, Pat

patrick linhardt

which vent

Hi Ken,

How large is the system? It might take a bunch of #76 vents to equal the original venting rate.

I'm thinking about how to work in that check valve. I'm concerned with the weight of the check and the pressure required to open it. The old literature always mentions the "light" check to produce the vacuum. And it is always located at the discharge side of the vent. Does a #2 Gorton have any type connection or tapping on its discharge?

Best regards, Pat

Ken_8

Pat

Under 300 S.F. of EDR

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Steamhead (in transit)

That was the later version

in your 1929 book. Both versions of the Differential Loop are shown in chapter 15 of Lost Art. I went back and looked up the Hoffman data in my US Radiator Corp catalogs- the older Equalizing Loop appeared in 1920 and 1921, and the earlier version of the Differential Loop appeared in 1922. The earlier Differential Loop still appeared in the 1926 ASHVE Guide. I don't have anything for 1927 thru 1929 though- at least not yet.

Steamhead (in transit)

The Gorton #2

has no provision for a check on the outlet.

I believe this vent was designed for Gorton's "One-Pipe Vapor System" which was marketed in the 1920s. My friend Gordon "El Gordo" Schweizer found several houses in Baltimore that have this system.

patrick linhardt

vent selection

Hi Ken,

If the steam main is 1-1/2", around 100' in length and vented to the dry return through a radiator style trap, then I would say that one #76 would be the vacuum style vent for the end of the dry return, in this case, on top of the differential loop. If non-vacuum, then go with steamhead and the Gorton #2 since what I've read about the Hoffman vapor/vacuum systems indicates that they really wanted a large vent port. Mo venting, mo better.

Let me know how it works out, I'd love to know.

Best regards, Pat

Ken_8

Actually,

It has two 2" mains and each is ~30'long.

But "close enough" (:-o)

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patrick linhardt

diff loop connections

Ken,

I just looked at the big photo of the differential loop. Is it connected to the wet return anywhere? From the picture, I see a capped drop from that cross to the left of the diff loop.

When I was reading up on them yesterday in old Hoffman literature, they were always connected to the wet return. I just looked it up in the Lost Art so everyone can have a common reference. Page 232, fig #7 shows your model with the connection on the left to the wet return. Is that out of the camera lens, or was it capped off?

Inquiring minds want to know. If you are restoring to original condition and operating characteristics, then the wet return connection needs to be there.

Best regards, Pat

Ken_8

Ya know...

I'm not sure.

I assumed the capped drop was a drip/trap. It looks to be original, not a capped former connection.

They verbally gave us the job last night and I should scope that out before getting too obsesed with true vacuum restoration.

As Frank said, the Gorton # 2 is "cake." Everything else is somewhat loaded with "what-ifs."

I'll let you know wassup, when we get into it.

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patrick linhardt

let me know

Hi Ken,

Glad you got the job. Keep me posted if you can, you've peaked my curiousity.

Best regards, Ken

patrick linhardt

my bad

Hi Ken,

My guess didn't hit the mark. A lot of systems have a split main, going to the front of the house and to the back, or side to side.

Best regards, Pat

Christian Egli

Bang bang, Hoffman differential loop shoot out of the Old West

I have an explanation for the dopey analogy Dan H. found in some old book. He relates it in the Lost Art; the one that says the differential loop is like a six shooter, always ready for action. We should just put our tools down and back out of the room...

This one's got me thinking.

The differential loop is nothing other than an automatic double trap device. After all, each radiator has a thermostatic trap and as long as no steam leaks into the condensate returns, the extra trap or vent on top of the differential loop will never close. So far, just like in any problem free two pipe system.

But, when it's time for action, the differential loop will release some steam from its cage (that's the boiler) and the lion will go roaring upstream in the condensate returns. Get your gun out, lions bite. At this point, the extra trap or vent on the differential loop will close. Now the system is double trapped. And you have condensate and live steam together in the returns which are being pressurized.

Of course, as we all know, if the conditions are lined up, this could cause a major shoot out - bang bang - from all the water hammer going on in the returns. I suspect the mysterious curves inside the Hoffman differential loop act like the silencer at the end of a barrel; they restrain the rush of steam.

The six shooter analogy, with all this banging thus seems appropriate.

With this in mind, I don't thing differential loops are as innocent as they look, plus, they do rely on the check valve in the return. If the check valve does not properly prevent boiler water from sneaking back into the return, the differential loop will shoot every time something moves. Not just a six shooter anymore, this is an automatic pistol!

The best bet is to make sure the boiler pressure never calls for the "cage release", just the thought of this should keep the vaporstat quaking in its boots. Keeping the pressure below 10oz (or whatever the Hoffman loop model calls for) is all it takes. This sheriff has an easy job: keep the pressure real low, this is the most important point here.

Next, since this is an automatic double trap (but a double trap set-up nonetheless) there is a great risk whenever a radiator trap fails: you'll be besieged by all sorts of problems that don't seem obvious. Especially considering the basement will not ordinarily fill up with steam since there is the double trap. There will be no tell-tale sign at first that a trap is broken.

So, trap maintenance is super critical.

There's more good stuff.

A great benefit that comes with the Hoffman differential loop is the safety it provides from a vacuum forming in the boiler which would mess up the return flow of condensate. It provides all the safety that has to be specially installed around systems that use vacuum and vacuum pumps.

Vacuum is good because it means there is no air to bug the steam in its rush towards the radiators. Sadly, vacuum also prevents natural downflow of condensate, it even promotes backflow of condensate! but you can fix this with the required special piping or with a Hoffman differential loop.

Thus, a differential loop system is pre-equipped to handle vacuum. Since getting rid of air is the sore spot of steam heating and since vacuum helps greatly in remaining air free, I would recommend using a vacuum vent for the extra trap or vent on the loop. A check valve would be just as good, providing it is one with a vertically hinged poppet that causes nearly no back pressure.

But of course, a non vacuum vent will work just fine too, just without the bonus and with less parts to fail...

The port hole on this master - double - vent should be as big as possible, the way the old brochures want it. That's been brought up before like the Hoffman no. 10.

So here is my idea of a solution to the original vent question.

Since today's vents only come in small sizes, why not install an ordinary radiator thermostatic trap instead? A large one. Choose one with the biggest hole (as per the e-booklet by Gerry Gill and Steve Pajek I find the Monash 48 3/4, Mepco 2E 3/4, B&J 134A 3/4, even the B&J 122 1/2, all bigger than Gorton 2), and install it so that the thermostatic element is included on the inside of the system. Its outlet will most typically be pointing horizontally, onto which you can easily screw the low back pressure check valve.

That should de just fine, don't you think? and it would provide a much much bigger port than a Hoffman 75 or 76.

To further improve the flow of steam and the speed of start-up, add however many Gortons (or 76's to follow on with the vacuum theme) on the steam mains only. This will provide accelerated steam arrival at the radiators. It will not however prevent the Hoffman differential loop action. For that, the returns must remain quickly pressurize-able. The returns should only open to the atmosphere at the Hoffman loop itself, the only place where the hole can close itself real quick when the lion is released.

OK, it's now time for me to put down the keyboard and slowly back out...

Best regards, thanks for reading. Can you tell there were no good westerns on TV tonight?

gerry gill

okay, but lets not forget

the differential loop is not a boiler return trap..it doesn't really return the water to the boiler..per say..it maintains a differential..between the supply side and the return side..even when its being used..say it takes 10 ounces for the steam to blow thru the loop, okay, so on the 11th ounce on the supply side, one ounce blows thru the loop to the return, this keeps the B dimension water from ever climbing high enough to go horizontal and fill up the dry returns..so its doing more than a boiler return trap, in that it maintains a difference in pressure and it instead of ''stuffing'' the water in the boiler like a boiler return trap, it keeps the boilers own pressure from pushing so hard that the B dimension goes horizontal..this is a difficult device to verbally explain its operation so i hope i did okay..

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Ken_8

U

dun just fine!

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