Hoffman 2 Vents?

ChrisJ

reggi said:

ChrisJ said:

@PMJ

I think the issue is 25% is substantial.
If there would be a 25% savings on my system where is that 25% currently going?

It's right on page 23 , now thats with coal..very popular when the article was written


Correct me if I'm mistaken but that works simply by making a fire that's not hot enough, or barely hot enough, to produce steam, produce steam and therefore continue to heat the house?

So it doesn't apply to an ON/OFF burner setup.

Jamie Hall

Seems to me that a lot of the problem and debates revolves around two factors: first, perception of warmth vs. actually maintaining certain temperature levels. Perception will win, every time, in most cases. Second, some real problems with managing the concept of total system thermodynamics of a temperature conditioned structure. But it really isn't worth arguing about. If one is convinced that one's perception and position is the one and only correct position, well, so be it.

Mark N

This is from the Hoffman Specialty Catalog for the Number 2 Vent.

"In systems using oil or gas burners, the number of operations of the burner per day is reduced about 25 per cent through the use of No. 2 Hoffman Vacuum Valves on the radiators and No. 6 or No. 16 valves on the pipe lines. In coal burning systems reduction in fuel consumption of 33 1/3 per cent is common."

They mention the number of burner operations is reduced about 25% per day. There is no mention as to what the reduction of total burn time is reduced per day.

109A_5

Hello @Mark N,
I intend to, since I like the idea of a vacuum enhanced system. Since my old vents seem to work just fine and I see no point in destroying them for an experiment and then having to replace them with the modern junk. I wanted a way to supplement the vent with a vacuum check valve or totally block off the vent non-destructively.

So I came up with the idea illustrated above in this thread. I've used the silicone tubing as an interface to a Dwyer flow gauge on the vents and it seemed to work well.

However since this system works well (as is) the motivation is low and life gets in the way of some projects.

I am surprised that @ethicalpaul has not gone down the vacuum road, he loves to experiment on his system.

To me with a two pipe system there is an alternate vacuum equalization path through the returns, which may mask the ill effects of a small vacuum leak. My system is a one pipe system, so the only vacuum equalization is during the time when the boiler is not running and each radiator is its own vacuum reservoir or accumulator. I don't know how tight my system is.

Jamie Hall

There are, indeed, some rather interesting considerations and possibilities present in considering steam -- or, to be more general about it, water vapour -- heating systems which can operate at sub-atmospheric pressures. However, first one needs to be very clear indeed as to whether they are sealed, or nearly sealed systems or if they are vacuum assisted systems of one kind or another.

Sealed systems, in particular, have very real and demonstrable advantages when used with solid fuel fired boilers (or, indeed, potentially other low temperature energy sources), and lesser, but still significant, advantages when used with very high mass boilers. They could also be of use with modulating burners, or in large systems with multiple staged boilers.

I would encourage casual experimentation, but at the same time suggest that a thorough understanding of thermodynamics and fluid flow would be useful, if only to help reduce unproductive lines of research, but more in understanding what it really going on.

As to more general applications, it is my overall impression that for modern systems with relatively low bass boilers and easily pulse modulated burners the benefits do not outweigh the costs, however.

ChrisJ

That clip @reggi shared specifically says you can produce steam in 15 minutes, not an hour. Suggesting an hour was normal.

My system will get steam to the radiators in roughly 20 minutes from an ice cold start. That's with 60 degree water and piping.

Normal starts, like during the heating season I get steam to my radiators in 2-3 minutes tops. A chilly night and I can do it in under 90 seconds and before I downsized the boiler I could do it in under a minute.
That 90 seconds includes the time it takes for the flue pipe damper to open and burners to light which I never timed but I'm going to guess takes 10-15 seconds.

I don't know.....

Jamie Hall

Sounds pretty normal to me, @ChrisJ . Cedric takes a little longer -- but he's bigger and so is the house (longest main plus riser is about 100 feet...)

ethicalpaul

In coal burning systems reduction in fuel consumption of 33 1/3 per cent is common.

Color me skeptical to say the least!

I did attempt to make a vacuum/check valve on top of my MoM vents with my lathe. I couldn't make an attachment that would hold the vacuum and also allow venting at the low pressure I like to run (2" -5" of water column).

Jamie Hall

Actually, @ethicalpaul , as I have explained privately to another member of the Wall, I can see a significant reduction in fuel use with really sealed systems -- capable of holding a vacuum down to 5 psia -- for at least four hours. BUT. ONLY for solid fuel systems. Liquid or gas fuel systems, no. But solid fuel (coal or wood), it's at least plausible.

reggi

ChrisJ said:

ChrisJ said:

@PMJ

I think the issue is 25% is substantial.
If there would be a 25% savings on my system where is that 25% currently going?

It's right on page 23 , now thats with coal..very popular when the article was written

Correct me if I'm mistaken but that works simply by making a fire that's not hot enough, or barely hot enough, to produce steam, produce steam and therefore continue to heat the house? So it doesn't apply to an ON/OFF burner setup.

Well I never saw a Historical Reenactment of the Exact process but later he was offering a 50%  savings (more heat, from your fuel )though you had to write for information !
Now I imagine that was only for customers that didn't already have the 33% savings as cutting another 50% usage would be very difficult.. but I'm not sure (pretty sure though)

delcrossv

I'll throw in a couple of cents:

It seems reasonable that steam flow into a partial vacuum would be more rapid than having to expel air, so there's that.

What I don't see is when the burner is off on a modern , low thermal mass, system how much extension of steaming time would occur as , say, 30 gallons of water cools from 212 to say 150 or so. That should be calculatable. At a guess, it'd be a declining exponential function. If the slope is fairly shallow, it might make some gains.

On a fully modulated system I could see an increase in comfort as that slope could be tuned with the burner level, but BTU's would still need to be input, just less for longer. It's not clear to me whether that would add up to actual savings. It would seem also that an oversized , but downfired system would see better results, just because of the added thermal mass of the water.

109A_5

SteamCoffee said:

The Silent Steam Team video of the Hoffman #2 salesman demonstration device video is quite instructive.ymmv

Hoffman #2 Vacuum Steam Vent 1920s Demonstrator
https://youtu.be/4ple0cVv6ow

ethicalpaul

50% he said it. I retract my previous statement— he was a con man. Regardless of kind of fuel 

but he did say they were only guaranteed to work for 5 years, that seems reasonable 

Mark N

@ethicalpaul the advertisement posted by @reggi states this,

"50% more heat from your fuel"

Let's say that you used 1000 lbs. of coal in a one-pipe system equipped with regular vents. Then let's say you then converted it to a vacuum system with the Hoffman #2 vacuum vents and the #6 main vacuum vents. Their literature states a saving of 33 1/3% in fuel. So, the vacuum system will use only 667 lbs. of coal compared to the non-vacuum system. The difference being 333 lbs. of coal which is 50% of 667 lbs. of coal. So, if both systems used the same 1000 lbs. of coal the system equipped with the vacuum vents would theoretically provide 50% more heat from the same amount of coal.

ethicalpaul

Yeah, sure it would

The savings they tout are from the buildup of the morning's fire getting to the radiators faster. OK I'll give it to them.

And also from the burning-out period during the night. OK I'll give them that too.

The rest of the time the family is keeping the coal fire burning all day, that's probably 16-18 hours.

Now Mr. Hoffman is telling me that during those two times above, the ramp-up and the ramp-down, can save 33% or 50% (however he is stating the math) of your coal vs the other 14-16 hours of an actual fully stoked boiler? Con man.

Jamie Hall

Cheer up, @ethicalpaul . The same con men -- or their lineal descendants -- are still out there. Now it's a 96% boiler which will save you 50% on the fuel. Same tune, different verse.

ethicalpaul

With an imaginary ROI to go along with it despite dramatically increased maintenance costs and 1/2 the service life, right?

You'll be happy to know I am in full agreement with you on this one, Brother Hall!

Mark N

@ethicalpaul, theoretically wouldn't the vacuum equipped system, once it dropped into vacuum use less coal all day long too? Not as much coal would need to added to maintain steam production because steam would be produced at a lower temperature. If this 33 1/3% less I have no idea.

ethicalpaul

Well if your need for heat was below that provided by the smallest fire that could produce steam at 212F, then conceivably yes. You could start a small fire that could maintain the boiler at let's say 180F and have it steam I guess.

I've never lived with a coal boiler so I don't know how often that occurred, or how easy or desirable it would have been to maintain a fire like that.

Would that save 1/3 of your total coal that year? Or is old George just saying those savings are only during those particular times?

Mark N

Most steam system have more radiation then is needed to heat the structure at design temps. Theoretically this excess radiation could be used to heat the structure with the lower temperature steam. According to the TLAOSH, for systems designed for naturally induced vacuum the radiators were sized to take into account the lower temperature of the steam.

ChrisJ

Mark N said:

Most steam system have more radiation then is needed to heat the structure at design temps. Theoretically this excess radiation could be used to heat the structure with the lower temperature steam. According to the TLAOSH, for systems designed for naturally induced vacuum the radiators were sized to take into account the lower temperature of the steam.

Correct
And assuming I did my math right, if you pull the entire system down to 16"HG, 200" WC, 7PSIA you can gain 2% on an atmospheric boiler according to WM's published specs for a hot water EG series.

Mark N

@ChrisJ was the latent heat from the lower temp steam taken into account in your calculations? Not sure if it matters.

ChrisJ

Mark N said:

@ChrisJ was the latent heat from the lower temp steam taken into account in your calculations? Not sure if it matters.

I'm sorry Mark but I don't understand what you're asking?

Mark N

Chris, I was looking at the specs for Burnham Baseray. For a 3.40 sqft EDR section you get an output of 860 btu/hr with 215 degree steam. The output is 720 btu/hr with 220 degree water. I guess the output is 20% higher because of the latent heat in the steam. Thats where my question comes from.

ChrisJ

Mark N said:

Chris, I was looking at the specs for Burnham Baseray. For a 3.40 sqft EDR section you get an output of 860 btu/hr with 215 degree steam. The output is 720 btu/hr with 220 degree water. I guess the output is 20% higher because of the latent heat in the steam. Thats where my question comes from.

They actually give a spec for 220F water? That's surprising.

Latent heat isn't lost and is 100% recovered when the steam condenses back into water, so vacuum won't effect that.

Mark N

ChrisJ said:

Mark N said:

Most steam system have more radiation then is needed to heat the structure at design temps. Theoretically this excess radiation could be used to heat the structure with the lower temperature steam. According to the TLAOSH, for systems designed for naturally induced vacuum the radiators were sized to take into account the lower temperature of the steam.

Correct
And assuming I did my math right, if you pull the entire system down to 16"HG, 200" WC, 7PSIA you can gain 2% on an atmospheric boiler according to WM's published specs for a hot water EG series.

Chris I think I may have misunderstood your post. Were you comparing a steam boiler operating in vacuum to a hot water EG boiler.

ChrisJ

Mark N said:

ChrisJ said:

Mark N said:

Most steam system have more radiation then is needed to heat the structure at design temps. Theoretically this excess radiation could be used to heat the structure with the lower temperature steam. According to the TLAOSH, for systems designed for naturally induced vacuum the radiators were sized to take into account the lower temperature of the steam.

Correct
And assuming I did my math right, if you pull the entire system down to 16"HG, 200" WC, 7PSIA you can gain 2% on an atmospheric boiler according to WM's published specs for a hot water EG series.

Chris I think I may have misunderstood your post. Were you comparing a steam boiler operating in vacuum to a hot water EG boiler.

The EG series comes as both a hot water boiler, and a steam boiler.
It has published specs of it's efficiency for steam and for hot water. That's what I used in my example. That specific boiler gains 2% running at 180F vs steam.

Mark N

Ok understood

ChrisJ

Actually the EG series would also have quite a bit more water in it as well when used for hot water.
So, 16"HG may not gain that full 2% if used for steam at 180F.

I don't know.
But I don't think cast iron steam systems with valves and packing nuts are going to hold 16"HG anyway.

Dan_NJ

I used to pull 10" Hg with my one pipe system for several minutes, until a rad vent opened. It was a vent not so far from the boiler so I would actually hear it open from the boiler room and watch the vacuum dissipate on the gauge while it wooshed away one floor above me. If a vacuum vent existed I would have tried it.

ChrisJ

Dan_NJ said:

I used to pull 10" Hg with my one pipe system for several minutes, until a rad vent opened. It was a vent not so far from the boiler so I would actually hear it open and from the boiler room and watch the vacuum dissipate on the gauge while it wooshed away one floor above me. If a vacuum vent existed I would have tried it.

That's 10" hg and not water column?

If that's true I'm curious now.

Dan_NJ

WIKA wouldn't lie ...


Honestly I was sure it was 10" Hg but after reviewing the picture and seeing 11" on the gauge I just could not resist
https://youtu.be/4xgx4k83zzc?si=wn8NehfqwW3mCxAB

SteamCoffee

Wow, I leave town and…..boom! Ok, I’m converting to coal! So there! 🤪

ChrisJ

SteamCoffee said:

Wow, I leave town and…..boom! Ok, I’m converting to coal! So there! 🤪

If that'll work for you, go for it.

SteamCoffee

Kidding! But gotta pursue the hunches!