Can I use a Varivalve as a main vent? and where to put it?

Shalom

Two related questions.

First of all. The consensus here seems to be the Gorton #2 is the main vent of choice, because it vents faster than anything else. However, this seems to imply that the Varivalve is as fast as a Gorton 2 when wide open. It's ⅓ of the price and ⅛ of the height; why don't you see people using those as main vents?

(I know it doesn't have a float, so it spits water if there is any in the pipe. Is this a reason not to use it for a main, and if so, would putting it at the top of a long nipple prevent this?)

Second question. I was wondering about the setup in my parents' house. They've got two mains (see my previous thread); one has a Dole 1933 as a main vent, which is slower than the vents on every radiator convector in the house; the other may not have any vent at all, although it does have a crossover trap (which winds up in a dry return that may not have any vent at all either).

I can put a Gorton 2 on where that undersized main vent is, although I'll need a couple elbows to get vertical clearance because it's under a beam. (Side question: Is there any reason not to use two 45° elbows instead of 90° ones, so the branch comes out diagonally instead of straight to the side and then up? seems doing this would obviate the possibility of water pooling in the horizontal leg.) But if I want to vent that second main, where I have no idea where the end is -- there may or may not be a vent on it, and it may or may not be clogged if it exists -- it would seem the best place to put the vent would be in that dry return.

Problem is, I'm no plumber, I'm not capable of cutting and threading pipes. Best I could do is drill into the side of the pipe, thread the hole, and screw in a radiator-style vent, like the aforementioned Varivalve. Best would be to get a straight shank vent and put it on top, so water couldn't get in, but I can't do it there, because it's right against the wall, so I won't have clearance to use a drill on the top, and I don't have an angle drill. (yeah, I could use my grandfather's old hand crank drill if I wanted to spend all day at it, but even then I wouldn't have clearance to swing the tap wrench either.)

So then the question becomes, where do you put the hole so as not to get condensate in the vent? On the side of the horizontal pipe, or the side of the vertical pipe, and in either case, how far back/down from the elbow? Or drill the elbow itself? Or is this just a bad idea to start with? Will I destroy the pipe or the elbow if I start drilling holes in them?

Fred

First off, we need to understand what type system they have. if it truely has a Crossover trap, they act like a king size vent. Post some pictures and tell us more about the system before you do anything to the Mains. Vents may be appropriate at the end of the Dry returns but we need to see what is going on with the boiler and the piping.

Captain Who

Shalom said:

Two related questions.

First of all. The consensus here seems to be the Gorton #2 is the main vent of choice, because it vents faster than anything else. However, this seems to imply that the Varivalve is as fast as a Gorton 2 when wide open. It's ⅓ of the price and ⅛ of the height; why don't you see people using those as main vents?

(I know it doesn't have a float, so it spits water if there is any in the pipe. Is this a reason not to use it for a main, and if so, would putting it at the top of a long nipple prevent this?)

According to Gerry Gill, the Gorton #2 will start to close at 110 F and at 130 F it may be closed. I know from my testing and from talking to the mfg, that varivalves start to close around 155 F and at 165 F they are usually closed. So there is a significant difference there. The other issue is reliability. I just don't feel that the varivalves are extremely reliable or durable. I am using them on most of my radiators for the past 10 years and I seem to have to replace them an awful lot. Now, I don't have sufficient main venting so the large vent capacity varivalves on my radiators are spewing a lot more air and whatever abrasive particles may be in there, as well as acidic condensate with carbonic acid, etc.. So take that for whatever it is worth. The other issue that you already are aware of, which is the float is not inconsequential either in my mind. I already had one incident where someone accidentally left my manual feed ball valve open a crack and flooded the system. It would have made a lot more of a mess if water were spewing out of the vents in the basement.

STEAM DOCTOR

Using two 45's is always a good option. Never put a main vent on the side of a pipe. It can fill with water.
Vari vents have a ridiculously short lifespan and are prone to spitting

Dave in QCA

You present a number of questions and they are difficult to answer completely without more information and/or photographs, as has been already stated.
First, the flow rate data furnished by Heat Timer is inconsistent within the two tables. They show a measurable difference in the flow rate for a vari valve when shown in the radiator vent comparison and the main vent comparison. The testing pressures were reported as the same, so the difference does not make sense. That aside, the comparisons are also inconsistent with the Gill and Pajek testing. Those tests were done at 1, 2, and 3 ounces per sq in. While the pressures were slightly higher, the comparisons should be the same and they are not on the Heat Timer table. According to Gill and Pajek, a (cold) Gorton #2 will vent 1.1 cfm at 1 oz. and a Varivalve straight pattern will vent 0.66 cfm, the angle pattern will vent slightly less. So, a Gorton #2 will vent about twice that of the Vari valve according to Gill and Pajek, and I completely trust there accuracy and methodology.

That being said, I have used a couple of straight pattern Vari valves for main vents with good results. In helping a friend whose one-pipe system was terribly out of balance, I used Varivalves in place of the original Hoffman #41 valves, which were terribly slow. This, in combination with turning all of the #1A Hoffmans down to a level to match a #40, achieved excellent results. That being said, I am just as dubious of the varivalve reliability as other posters. However, even thought they may spit a drop or two now and then, in unfinished basement space, this is probably not an issue.

You indicated that you have one crossover trap. This would indicated that you have a 2 pipe system. Is this correct? If so, the dry (condensate) return line MUST be vented somehow. Many systems to not have a typical 1-pipe style main vent on the return, but rather a air eliminator type of device, or in some cases, an open pipe. Many 2-pipe systems never have steam in the return lines unless there is a bad trap. However, an example to the contrary is the Hoffman system with a Differential Loop device. This device, under climbing boiler pressures will indeed pass steam into the return piping and Hoffman always put a Float type vent on the returns on these systems. They main being vented by a crossover trap is a very good setup.

As to the popularity of the Gorton Main vents, the closing temperatures throw red flags all over the field. I installed Gortons in my system several years ago and discovered that they were ONLY open on a cold start. My mains are insulated, basement temperature is about 65F, and boiler cycles once per hour. I find that even on a short steam cycle, where the off time could be 55 minutes, that the temperature of the mains, and thus the air inside, only drops to 160F. It is the temperature of the air inside the main that prevents the Gorton from reopening, not the room temperature around it. And thus, Gorton #2 vents on my system proved useless because they remained closed, or nearly closed at all times except a cold start. So, with risk of having eggs thrown at me, I will say that in many conditions, a Gorton #2 may not work very well at all. I think their effectiveness should be retested using real conditions where the mains are insulated and cycles are at the recommended 1 per hour.

BobC

I think it depends on individual circumstances. I have 2ea MOM #! (equiv to Gorton #1) that are on a 18" long 3/4" pipe that runs parallel to the steam main and about 6" above it. All the main piping in the cellar is insulated EXCEPT for that 18" pipe and the vents. My cellar sits at about 50 degrees in the winter.

My system tends to come one once an hour when it's cold and the vents are probably in the 60's when the boiler starts. You might want to take the insulation off the pipe that feeds the vents and see if that changes things.

Bob

Captain Who

It seems like it might be a nice idea to have a thermowell at each main vent location, to have a temperature sensor monitoring what is going on, to see if the vents are operating in a way consistent with letting the air out when air is present. Also would be useful to keep track over time of any change in the operation of a main vent, especially since they are so critical.

jch1

So if Gorton 2s dont work for your system due to overheating, what's the alternative? Multiple Hoffman 75s?

Fred

I use Hoffman 75's but it takes about 2 of those for 1 Gorton #2. I think so many systems use the Gorton #2's that I would be surprised if you have any problem with them. (That's not to say it can't happen but it is not the norm).

Shalom

I'm going out there tomorrow, so I can take more pictures etc. It would probably be best to shoot a short video following the pipes to their ends, or I'd need too many pictures to show what's what. There are already some pictures on the other thread.

Meantime, some comments on your answers.

@Fred: The thing I'm calling a crossover trap is here:


The bigger pipe is the shorter main; it comes from the right and disappears into the wall; other end of it is who knows where. The smaller pipe comes from the wall and goes off to the right; it eventually drops into a wet return which seems to not have a vent on it anywhere. Nobody knows what's behind that wall, though.

@Dave: Definitely a one-pipe system; I got down and looked under the convectors, and there's only one pipe. Why this trap is installed here, I've never figured out.

@SteamDoctor: I can't drill into the top. If I put a hole on the side, then connect an elbow and a nipple going straight up, and put the vent at the top of that, would that prevent the water getting into the vent?

More details tomorrow when I get out there

STEAM DOCTOR

In regards to putting vent at side of main. You can always try it and see what happens. The lower part of the main will have water in the middle or end of cycle. This water can block the elbow leading to the main vent. In addition, you could have water spraying out of vent. Try to drill as high as possible on the side of the main.

STEAM DOCTOR

Does anyone have a list of closing and opening temps for various main vents?

STEAM DOCTOR

Case study. I have a customer with one pipe steam. Two mains, roughly same length(don't remember specifics offhand). Installed one Gorton#2 at the end of each main. The tapping for the main vent was at the very end of the main. I used a nipple, an elbow. a12" nipple, a elbow and the gorton#2. The point of the 12" nipple was to pull the main vent away from the end of the main in order to protect from water hammer. The mains heated up evenly and quickly and the house also heated up evenly. I few weeks later, I was in that same basement for something else. I took another look and decided that I was not happy with the pitch of one of the 12" nipples. I removed the nipple and replaced with a much shorter nipple pointed in a different direction(couldn't use a 12" nipple due to obstructions). The next day, the customer calls me up and says that half the house is much colder them the other half. Turns out,it was the side of the house with the main vent on the shorter nipple. Put everything back to the way it was originally and house went back to heating evenly.
What I took away from this incident is as follows. Gorton #2's are sensitive to temperature. If residual temp is too high, the #2 will not reopen. Offsetting the #2 will create somewhat of a heat trap,allowing the #2 to cool down in time for the next cycle.

BobC

This is why I specifically left my horizontal runner (runs back along the main about 16"), nipple and vent bare. I want that vent to not close quickly so I'm sure the steam has really filled the main. All the other piping in the cellar has 1" of fiberglass pipe insulation on it.

Bob

Shalom

Well none of the mains in this house have any insulation on them, probably because they had asbestos that was removed before we got the house.

I didn't get a chance to get out there today, but I did build this thing:


That represents about eight bucks worth of fittings from Home Depot, two bushings from a real plumbing supply (where I shoulda gone in the first place), and a pair of Gorton D's that I had lying around the house. I blew lustily through it, and it moves a phenomenal amount of air, at least until you blow hard enough to lift the floats and it closes on pressure. If a D is the same as a 1, then that assemblage ought to vent about half as much as a 2, which should be good enough until I can lay my hands on a real 2.

I'm going to screw that in where the Dole is, and see how it works.

Question: Can you use anti-seize compound on these pipes like they do for spark plugs, so as to make it easier to disassemble the thing later if you need to?

Another question: Has anyone ever tested to see just how much air you can vent through a Maid-O-Mist vent with the aperture unscrewed?

BobC

I just use teflon tape on things like that, it will come apart easily in the years to come.

i suspect the masimum flow through a MOM is the same as the D but I've never tested that theory. I'm surprised Gorton never adopted the interchangeable orifice model, it sure simplifies stocking. Probably the not invented here syndrome.

Bob

Shalom

Well I figured out what's making the banging, anyway.

I went back there today, installed my vent thing (had to stop off at a plumbing supply and get a longer nipple for the diagonal, because the one I had was just long enough to collide with a pipe) and fired up the boiler to check for leaks. Right when steam started coming up, the pipe behind my head begins the anvil chorus. This is a pipe that comes off the main, makes a 90 degree elbow, goes through a wall and hits that weird wall-mount radiator at the bottom of the side stairs. I put a level on it, and it's pitched down toward the elbow from both ends. Why? Maybe the building sagged, maybe we shouldn't have been hanging wet laundry on it for the last 20 years, who knows. I'm not sure what to do about that, as there's really no way to jack it higher given that the gas lines to the kitchen stoves cross directly over it; perhaps there's a way to run a drip from the elbow to the wet return, which is on the floor right under it, but I'm not a steamfitter and would rather leave that to the professionals. In any case it's not my house, and my parents may just decide to live with the noise for now.

As far as that dry return, I checked and there is in fact enough clearance to drill into the top for a vent. I think I'll wait until after the heating season for that, or at least until after this current cold snap is done.

I video'd the pipes; will post it tomorrow.

Shalom

http://www.youtube.com/embed/aLpRrkkSvB8

Vid's up.