Air vent valve on boiler

acl10

My newest addition. I installed a t and put a Hoffman75 on the boiler. It lets out air for a minute and closes. Now the steam gets right to the main and the air in boiler on startup gets out right away. any comments pro or con

nicholas bonham-carter

That vent belongs after the last radiator before the drop to the wet return. Having it close to the boiler will close it early, before all the air in the pipes has escaped. A big mouth vent will have 5 times the capacity, and cost 2/3’s of the price.—NBC

KC_Jones

To be blunt, that serves absolutely no useful purpose other than costing you money in parts.

If you like spending money for nothing keep going, but this makes zero sense.

JUGHNE

Yes, that vent should be at the end of the steam main.
If you have no port there than even close to the end of the main will help you out. It needs to be installed on the top of the steam main and not down on the wet return.
It is really a good vent but does not have a lot of speed to remove air.
As NBC mentioned the Big Mouth is a better investment.
Although from your previous posts you have had issues with perhaps condensate build up in your returns then perhaps the Gorton #2 would be better as it has a float as does your 75, this would close if water got to it. IIRC the Big Mouth does not have the float closing ability to prevent water spitting?

Also your pop off relief valve should be installed in the vertical position with the male threads down, then piped with a 90 to almost the floor.

ChrisJ

No sir, I don't like it.

newagedawn

trying to reinvent ( no pun intended) the wheel after 100 yrs is going to take more than spending money on parts, those who dont know might find it a great thing, but to those who know say it must go,lol, i always knew i was a poet, good luck with that

acl10

Thats beside the main vents I have at the end of the return and on the main. I just figured letting the air out of the boiler on startup would be an extra benefit besides the other mains. It does let out some air for a minute so I think its a win win situation.

acl10

Also your pop off relief valve should be installed in the vertical position with the male threads down, then piped with a 90 to almost the floor.
Can you please explain why?

nicholas bonham-carter

It certainly does not hurt anything, but is wasted in that location.—NBC

Neild5

> @acl10 said:
> Also your pop off relief valve should be installed in the vertical position with the male threads down, then piped with a 90 to almost the floor.
> Can you please explain why?

So the relief valve does not have sludge build up in it. And code requires a pipe extend to approximately 6 inches from the floor with no threads on the lower end.

acl10

i had an extra Hoffman valve that was to big for my pipes so I decided to experiment. I think it does add to the system by getting the air out of the boiler even if its a little bit.

nicholas bonham-carter

It would be more effective on the dry return drop, where it will speed up air removal from the boiler, and the pipes, as well.—NBC

JUGHNE

What pipe size is available on your steam mains or DRY returns for your air vents?

acl10

I already have ones on the dry returns and mains. The Hoffman is to tall so I have Gortons and Ventrite

JUGHNE

How large is the fitting they are screwed into?

PMJ

@acl10,

Everyone is so focused on getting air out. The more important thing to focus on about vents is that they let air in. You end up turning your system into an accordion - not anything like the original plan of operation. With this vent you provide yet another way for air to get back in - and right at your boiler the very second it shuts off! I wouldn't recommend that at all. You will simply fill your main with air even faster than before on each shutdown because you now fill it from both ends. This air will need to be pushed out at the far end of the main and not through this new vent because it closes too fast on startup. For this reason I think it is a net-negative.

PhilDavid

Kudos for trying. That’s definitely thinking outside the box. But it does belong on the end of the dry return 15 inches back before the drop. Can’t see the benefit of having it there.

ChrisJ

Main vents will perform better at the end of the main rather than the dry return due to less friction.

Though I've considered moving mine to the dry return so I can see them. Most of mine are stuck in a crawl space.

PhilDavid

@ChrisJ Crawlspaces are awful. You gotta love swinging 24” wrenches in them. There are two systems I service with one in a crawl space and they have vents on both the end of the mains and dry returns. This is probably ideal for getting the air out fast and they do heat up quickly. But most others I service just have em on the dry returns. If you can get to yours I’d leave them and add them to the dry returns.

nicholas bonham-carter

Before I saw the light, and installed decent main venting on my one-pipe, the Hoffman radiator vents would whistle like canaries overcome by gas in a (clean) coal mine, when the burner shut down.
Practically, I think you can only have a vacuum in a two-pipe system, and therefore have to put up with air reentering the pipes at shut down.—NBC

PMJ

NBC,

This site has had quite a few happy one pipe vacuum operators going back 10 years simply looking to replace their old Hoffman vent valves which are no longer made. The common response they get here is that Hoffman stopped making them because they really didn't work. Of course these operators know that isn't true - some even listed the reasons they want to keep on with the vacuum. The reasons they cite (more even heat, rads stay hot much longer after shutdown, more efficient, much more quiet) are the same reasons I do it in 2 pipe. These posters usually don't return - having been told what they see working with their own eyes doesn't work. I will also point out that I was told here it wouldn't work in 2 pipe either.

Yes, it is easier and less expensive in 2 pipe. But it is a major loss for steam heating overall for vacuum to have slipped from use - and on bad information. It is not for coal only, or only 2 pipe - of that I am quite sure.

Dan_NJ

PMJ said:

NBC,



This site has had quite a few happy one pipe vacuum operators going back 10 years simply looking to replace their old Hoffman vent valves which are no longer made.
...

I had glossed over the Hoffman vacuum valves in the vent capacities chart probably since they're marked obsolete. I would almost be willing to try these if I could get my hands on some, or something comparable. I can hear 5-10 minutes of boil continuing after my burner shuts off due to vacuum. Seems like things would be a little more efficient if the vacuum broke later.

PMJ

Dan_NJ said:

I can hear 5-10 minutes of boil continuing after my burner shuts off due to vacuum. Seems like things would be a little more efficient if the vacuum broke later.

@Dan_NJ,

I assure you that once in vacuum you will never want out of it at any point in the cycle. Yes, boiling continues after shutdown but equally important it begins almost instantly on each fire if the system is still in vacuum. I will still show 30+ inches H2O vacuum even 3 hours after the last fire ended in my 92 year old piping. I virtually never start atmospheric anymore. I am not above atmospheric pressure even 10% of the time the burner is actually firing. Totally different experience than vented - and all free natural vacuum.

ChrisJ

30+ inches of vacuum? That's a neat trick, how do you do it?

Canucker

I'll give you 3 inches of vac after 3 hours @PMJ There's no way your 92 year old piping is holding 30 inches. Pics or it didn't happen. Haha

PMJ

> @Canucker said:
> I'll give you 3 inches of vac after 3 hours @PMJ There's no way your 92 year old piping is holding 30 inches. Pics or it didn't happen. Haha

You guys did see I said 30 inches water right?

Canucker

> @PMJ said:
> > @Canucker said:
> > I'll give you 3 inches of vac after 3 hours @PMJ There's no way your 92 year old piping is holding 30 inches. Pics or it didn't happen. Haha
>
> You guys did see I said 30 inches water right?

No, not at that late hour. Haha

PMJ

Here it is. Took pics this morning. PLC shows last burn ended 207 minutes ago. Vacuum 20 something inches still. Last pic shows typical vacuum between burns during a call.

Before you argue the gage is damaged it does go to zero after 6 hours or so. I have tried several. Beyond that I don't care the actual value. Guys this is 3psi. On the pressure side you would say too much. On the vacuum side by the same logic is it enough to do plenty.

I really don't know why there is so much resistance to this. I have been doing it 15 years now. In pressure the steam goes by vents and valves which don't change with sun and wind. In vacuum steam goes to the rads condensing the fastest ( those in colder areas). The result is much more even heat. I spend over 90% of the total time in vacuum - 75% of the burner on time too! The result is dramatically different and self adjusting.

Dan_NJ

Seems like it could be possible to design something that would work like the diaphragm in the old Hoffman #2 vacuum vent for one pipe system to hold the vacuum, that could be made to connect to the radiator directly and provide a port for the conventional vent of your choosing, and that would give some of the vacuum benefits and allow to retrofit single pipe systems without any additional piping.

Gsmith

there was a post on this board a little while ago with details of how someone made one using, of all things I believe, a bullet casing and a plastic disc. It would operate like a check valve. But I can't seem to find it right now. If I do, I'll post the link.

BobC

A Maid O Mist vent outlet has an OD of 0.430", the knurled orifice that screws into that outlet has a OD of 0.455".

A 45 cal ACP brass has an OD 0.476" and a wall thickness of 0.010" so the ID if the case should be 0.456 +/-. It should be a pretty good fit with maybe a few wraps of tefton tape to insure a seal.

A plastic disk or a 1/4" ball could be used as a check element, if yiou use the ball it might be prudent to countersink the face of the orifice. Note the MOM orifice plugs have the size stamped on the face so a thin rubber washer might be needed to insure an airtight seal.

All of this is conjecture, I have not put one together so there may be other things to consider.

Bob

Dave in QCA

I'm glad to see someone is working on 1-pipe vacuum. I have been running our 2-pipe dunham system on self-induced vacuum for 6 years with good results. I'd like to install a pump someday and try to replicate the Dunham differential vacuum setup and the benefits of 150F steam (vapor). All things in time, I guess.

PMJ

Dave in QCA said:

I'm glad to see someone is working on 1-pipe vacuum. I have been running our 2-pipe dunham system on self-induced vacuum for 6 years with good results. I'd like to install a pump someday and try to replicate the Dunham differential vacuum setup and the benefits of 150F steam (vapor). All things in time, I guess.

I wish more would work on it Dave. I hope to report soon on the best vacuum based control I have run yet - one that is so simple it does not need a PLC. I have run with it since mid January. It self adjusts the cycles with the weather with components that don't total $200. Best heat control and efficiency I have had.