Main vents?

[Deleted User]

I've discovered the main vents on the two main circuits of my steam system (see photo). They're difficult to get at and I had to remove some paneling to get a good look at them. I can't read much, but I see "Hoffman", and "No. 16", although the 1 could be a vertical scratch in front of the 6. On the other one I see "Vacuum Valve".



I can't tell if they function, but from the looks of them they need replacing. I don't want to try removing them until I have replacements. The system is rather unbalanced now, and I want to make sure I have good main vents before fiddling with radiator vents.



So what should I replace them with? And is the current install position OK, or is it really important to move them?



(sorry about the rotated pics, they are correct on my computer)

Paul S_3

how

long are the mains?, and what size pipe are they? main vents shouldnt be directly at the end of the main, water hammer can damage them. they should be 15"inches back from that elbow and 6-10 "inches up on a nipple. i usually use Gorton #2 vents when i vent mains, great vents but expensive. you can also use traps to vent main if you want. Paul S

[Deleted User]

Main line sizes

Thanks for the reply.



From where they leave the boiler to the main vents, the two mains are 63' and 62' long. But the last radiators are connected at 37' and 46'. Both mains start with 3" pipe and are reduced to 2.5" at some point. In more detail



Main 1: 3", 3 radiators connected before reduction to 2.5" at 32'. Last 2 rads at 36-37'. 63' to vent.

Main 2: 3", 4 rads connected before reduction to 2.5" at 35'. Last 2 rads at 46'. 62' to vent.



I wonder how important the position is, because this old pipe is not something I can handle, and I'm guessing it would be $350+ to get someone to set the pipes up for moving them. As far as water hammer, this system is really quiet. Maybe that's because the vents don't vent. And one does look like it had rusty water dripping out of the top at some point.

Jamie Hall

Not the ideal location

but they should be OK, particularly if you were to offset them -- go up, then go over (make sure you have a ptich back to the main!!!) then up to the vent.  Looks like you have the headroom to do it.

[Deleted User]

How

Do you make it slope back to the main when the fittings are at right angles?

Jamie Hall

Ah ha!

Don't just go up to a 90 -- go up, 90, then use a street 90 (or a very short nipple to another plain 90) laying horizontal -- but not quite horizontal, angled a tad up to get your pitch.

[Deleted User]

Ohhh

I think I get it. Clever. So is it OK if the final vertical part with the vent is slightly off vertical, or do I need to do the double-90 thing again to make it perfectly vertical? Thanks Jamie.

Hap_Hazzard

Vents

I'll bet those are Hoffman #76 vents.



Model 76 Part No. 401431

Vacuum Valve

• Float-type themostatic vent

• For medium and large one-pipe vacuum systems

• Single non-adjustable port

• 1⁄2" NPT female and 3⁄4" NPT male straight shank

• Install 6-10" (150-250mm) above horizontal return and 8" (450mm) above the boiler water line

• Maximum operating pressure 3 psig (0.2 bar)

• Maximum pressure 15 psig (1.0 bar)



Is this, in fact a one-pipe vacuum system you're working on?

[Deleted User]

I'm thinking Hoffman #16?

Thank you! The vents don't look quite like that. I found there was a Hoffman #16 that looks like these, and I believe they are not made anymore. Anyway, I'm pretty sure they are not working - I've never felt any air coming out of them through a whole boiler cycle (on to off). I ordered som Gorton #2s to replace them.



I am so ignorant I don't know a vacuum from a non-vacuum system. These are apparently vacuum-type vents, but the ones on the radiators are not, ordinary Hoffman #40s on most of them.



How do I tell which type of system it is? It is definitely a single-pipe system - only a single pipe connects each radiator to the mains.

Hap_Hazzard

Vacuum

I'm not that familiar with vacuum systems myself, but I know there are differences in the vents they use. I would think they'd use vacuum vents on the whole system, not just the radiators, but someone may have changed them either because they couldn't find the right replacements or they just didn't know any better. At any rate, the Gorton #2 is not a vacuum vent, so it's not a replacement for what you have.



If the #16 is discontinued, the #76 would appear to be an exact replacement. If there is a difference it might be that the #16 was a non-float vent and the #76 has a float. The shorter body would seem to suggest this. If that's the case, you can always replace a non-float with a float, but not the reverse. The floats are meant to protect the vents from water damage, so it's possible that they discontinued the #16 because they tended to end up like yours.



This is all speculation on my part. The pros who frequent this forum would be able to explain how vacuum systems work and may even know the history of these vents, but they might not respond to this thread because the subject doesn't mention vacuum and the number of replies makes it look like your questions have all been answered. You might want to start a new thread for help with venting a one-pipe vacuum system and see if you can get their attention. You could also try searching the forum for discussions about vacuum systems.

[Deleted User]

Need help fast!

Geez, if the Gorton #2 is inappropriate for my system, I need to figure that out right away so I can cancel the order to PexSupply before they ship it! Thanks for bringing this to my attention Hap. Actually, the proper replacement vent was my original question, so I hate to start a new thread with the same question.



So, any experts out there, how do I know if I have a "vacuum" system or not? And do I need a vacuum-type vent instead of the Gorton #2? If so, I would be grateful for recommendations. Thanks!

[Deleted User]

More confused than ever

Dave in QCA has a post on vacuum systems (that I don't really understand). http://www.heatinghelp.com/forum-thread/139813/Another-Look-at-Vapor-Vacuum

But he quotes the Hoffman vent guide as follows:

"Determine if the vent is to be installed in a vacuum system. The Model 76 Main Vent is for vacuum service.

It should be used on systems with a vacuum pump or a vapor system with a coal or wood fired boiler.

Systems converted from coal or wood fired to oil or gas should use non-vacuum vents such as the Model 75."



I don't think I have a vacuum pump, and my boiler. although originally coal, burns gas. So according to the quote I should use a non-vacuum vent.

That said, Dave was of the opinion that vapor/vacuum could be used in gas-fired boilers also. So I guess I'm still not sure. There's no reason to assume that just because vacuum vents were put in there who knows how many years ago, they were the right ones to use.

Jamie Hall

You can use

the Gorton #2 on a system which was formerly a vacuum or vacuum vapour system.  It just won't go into a vacuum as the boiler cools down, that's all.



Do you want it to go into a vacuum when the boiler turns off?  Well... that's one of those questions.  The old coal burning systems did that; as the coal fire died down, the temperature dropped and the system could continue producing useful heat, although at a lower temperature, because the vacuum created allowed the water to boil at a lower temperature.  Increased the overall efficiency of the system quite a bit, particularly on the systems which had devices on them to control the pressure by controlling the draught on the fire -- as many of the better ones did.



But that was then, and this is now.  When your gas or oil furnace shuts down, it's down, and the boiler itself is a lot smaller and lighter.  It cools below the boiling point of water at any reasonably achievable vacuum very quickly.  If you are a genuine fanatic, you can get slightly more heat out of your system by using vacuum vents, but the effect is small.



Bottom line?  Me I wouldn't bother (and haven't) -- the ability of a nice big Gorton #2 to exhaust the air quickly trumps the purist factor of the vacuum...

[Deleted User]

That makes sense

Thanks Jamie, that's good logic and I will stick with the Gorton #2s I ordered. Actually, I just realized we're kind of operating in a bit of vacuum here already. Here at 7703 feet elevation in Colorado, the boiling point is 198 F. So maybe we're already enjoying some of the benefits of a vacuum system ;-)

[Deleted User]

Ready to install

Here is one of my new Gorton #2s ready to install. The main steam pipe has a 1/4" female tap for it. This pipe is all 1/4" up to the reducer which goes to the 1/2" Gorton stem. The plan is to install the part below the union, then put the union with everything above on it.



My fear is that the old rusty vent pipes will break or screw up the threads when I take them out. then I am screwed since we are currently in heating season. Maybe I better get a plumber/pipefitter to put it on.

[Deleted User]

No steam reaching new vent

I installed one of the new Gorton #2's (the other was DOA, did not vent air and had mineral deposits inside the stem, so was apparently not even new).



The good news is I can detect some modest air flow from it when the boiler is going. The bad news is, heat/steam never reach the vent. The boiler shuts down before the vent closes.



Could this be because the other main line still has a plugged vent, so pressure builds and shuts down the boiler prematurely?

[Deleted User]

Update

After 4-5 cycles, steam is now getting to the end of the line. The valve is warming up and seems to be closing. Hints of warmth getting to radiators that almost never used to see it. After I get the other main vent replaced, it should be a simple (or not) matter of balancing the venting on the radiators. Yippee!