Crossover trap

JStar

Has anyone used a thermostatic trap as the only main vent, with the trap open to the atmosphere? If the outlet is piped to a safe location, is there any reason that this would not work?

DanHolohan

I've seen it

And it works

JStar

Thanks

Dan, for a writer, you sure make a lot of short posts...but it gets right to the point. Thanks!

Rod

Trap as a Main Vent

Hi- I think Dave in QCA was doing this. You might ask him how well it works.

- Rod

JStar

Trap

I'm very intrigued by this idea. I think the biggest factor is inital cost and future maintenance cost. If a system requires a lot of venting, this seems like a simple solution. Less moving parts. Less initial cost. Seems about as close to an open pipe capacity as you can get.

DanHolohan

Brevity

rocks.

gerry gill

certainly.

Done it myself, many times, with a 3/4'' monash trap that passes huge amounts of air. Today, we fixate on calling these radiator traps..but in the early days they were just known as thermostatically operated valves and were used for many purposes.

Dave in QCA

It works pretty much

Joe, I did it as an experiment because I was frustrated with my Gorton 2s and the fact that they vented great on a cold start up but once the system was warm, the mains didn't cool down enough to get them wide open and their performance on my system was not satisfactory.

I replaced one of my three stations, which was an antler with 2 G-2s on it with on single Dunham/Mepco 1--E trap with a straight through configuration.  It performed as well as the pair of G-2s on the cold start and it worked equally as well when the system was warm.   I was mainly wanting to observe the performance because my plan was to install crossover traps, which is now complete with  the new boiler installation.

The one downside was that during each cycle there would be a few drips of condensation fall out of the outlet of the trap, perhaps 2-5 dribbles, not more. If i had reconfigured the trap so that an collected condensate would not run out, but would gather in the outlet port and then run back through the trap when the steam was down, I don't think I would have lost a drop.  Of course most main vents have a float to close on water and this would not give you that.



It would be important to consider the venting capacity of the trap.  The new Hoffman 17-c is very slow.  Mepcos are fast and trouble free as always.  Armstrong has a nice little bellows trap that is very fast. 



As for brevity, it is a luxury for those who know what their talking about.  It takes me so many words because I'm thinking it out as I'm talking....   Sorry.  

ChrisJ

Comparison

How does a Monash  Model 48-AP compare to  a Gorton 2 as far as volume?

Dave in QCA

here is a link

Here is a link to a diagram of the Mepco trap I used.  http://www.mepcollc.com/content/products/1505J.pdf 

Main reason I used it was that I already had it.  It just occured to me that a simple angle trap could be install upside down and it probably wouldn't ever lose a drop.

gerry gill

the gorton 2 at 1 ounce

vents slightly more than 1 cfm....the monash 48 at 1 ounce vents slightly more than 2 cfm.

Hap_Hazzard

These look great!

Why don't they make main vents like this? They look kind of like an automotive thermostat in a special housing. Simple and reliable. I'd like to see a main vent guaranteed for 25 years!

JStar

Vent

Well, I've got a job with a 6" main that would require 20 Gorton 2 vents. It has an 1-1/2" tap for the current (single) vent. I remember Steamhead doing a job with a monster of a Nicholson trap that would be a pretty good fit here.



To avoid condensation loss, I figured on using the trap oulet as the air inlet, and turning straight up out of the trap inlet for a few inches before going somewhere safe, in case of failure and steam leaks.

JStar

Also

The other advantage I see is the ability to reduce the trap outlet, giving you the ability to balance each main very accurately.

Ban

Crossover traps

I think the idea of being able to enlarge or reduce the amount of air traveling through the crossover trap is brilliant! I am in the process of determining what brand to replace my crossover trap with. It was originally a Dunham, now it is a Hoffman 17a. I was told to use a Barnes and Jones. What do you think works the best? Mepco is the current company for Dunham right? Where can you purchase Mepco products, it seems all of the supply houses just carry Hoffman and Barns and Jones.

Noel

Vacuum vent

I've done it on a system with a vacuum pump and it works VERY well.

Dave in QCA

dunham/mepco availability

I always look on ebay first.  search [dunham trap] or [mepco trap].  Every now and then there is new old stock available.

If you dont' have time to wait, State Supply carries a full line at http://www.statesupply.com/steam-traps/mepco-dunham-bush/radiator-traps 

SWEI

mains and crossovers

Since these things appear to have more than one use, can someone help me understand their installation as main vents versus crossover traps on a two-pipe system?





thanks~

Jamie Hall

Perhaps think of it this way...

At the end of the steam main you want to have some way to let the air out, fast -- but keep steam in (and, should there be much, condensate, but let's not worry about that; it should go down a drip).  You can do that with a nice big main vent or two or three or whatever.  You can also do it with an ordinary thermostatic vent -- i.e. trap -- such as the various one described in this thread.



Now the difference is where does the air go?  If you are using an ordinary main vent, or you are using a thermostatic trap as a main vent, the air just goes out into the basement.  However, if you are using the thermostatic trap as a crossover trap (as they are installed in my Hoffmann system, and indeed most vapour systems) the air goes into a dry return and back to the boiler.  In which case, the air needs to have some way to get out of the dry return.



Now... what do you do with the air in the dry return?  Back in the old days, if the system was intended to operate at times in a vacuum (and a lot of them were), you had vents which opened on positive air and closed on steam or water, but also closed and held a vacuum.  Otherwise, you would just have had a good big main vent or vents there at the boiler -- or in some cases the air just vented up the chimney!

SWEI

thanks

So given that (on a non-vacuum system) a crossover trap still requires downstream venting, is there any reason to use one?



Studying up on two-pipe variants (including vapor) so I can begin to understand the de-knuckleheading options.  We have quite a few older plumbers here but steam knowledge is rare as hens' teeth.

Ban

Vac to ??psi

Since we're on the subject of crossover traps I was curious about vacuum. Some traps, i.e., Dunhan and Mepco specifically indicate they will work on vac systems of X"Hg to Xpsi. Is this the standard for steam traps? Will Hoffman or other brands work with vac?

DanHolohan

Yes.

The trap element responds to whatever pressure is outside of it, above or below atmospheric. It adjusts its temperature to discharge condensate about 10- to 15 degrees below the relative temperature of the steam. 

Jamie Hall

Sometimes...

There is a very good reason to use crossover traps rather than vents at the ends of the mains: a number of vapour systems have devices at the boiler which are more or less important for their operation, and which depend on the dry returns all returning to the boiler together -- above the water line -- and then whatever contraption or vent is required is there.



For instance: on a Hoffmann equipped system, there is a device known as a Hoffmann Differential Loop at the boiler.  It takes three pipes: a pipe directly from the header, a pipe which is the connection to all the dry returns, and a pipe down to the wet return and the boiler feed.  All the venting is on the pipe from the dry returns, as close as possible to the Loop.  What happens is this: if the steam pressure rises too high (over about six to seven ounces) the Differential Loop allows live steam from the boiler to pass into the dry return(s).  This closes the vent and pressurizes the dry return, which pushes the condensate back into the boiler -- and not incidentally, limits the pressure differential across the radiator traps to a very small value, thus saving wear and tear on the traps.  The Loop immediately closes off again, though, and as condensation continues in the radiators, the vents open and things get back to normal.  If you put venting at the ends of the steam mains instead, this action is defeated and you wind up with pressurized dry returns, which is not the idea.

SWEI

crossovers on vacuum

I understand (well, I'm starting to anyway.)



I'm curious if they have applications on conventional two pipe?

Hap_Hazzard

You might find this helpful.

http://completewatersystems.com/wp-content/uploads/2012/08/HS-203C.pdf

PMJ

Main Vents

With so much discussion about main venting I do wonder how it is that the Mouat system gets away with no main vent at all - only one on the dry return?

Jamie Hall

Take a look

At my comment a few steps above entitled "sometimes" -- a lot of vapour systems used crossover traps with the main vent (and sometimes other wizardy associated with the vapour system!) located where the dry returns join before they drop to the boiler.  I kind of explained it up there for a Hoffmann Equipped system, but Mouats do much the same sort of thing.

Charlie from wmass

Remember they were set for solid fuel firing

once the heating season started you were on simmer all winter.

Steamhead

Here's the link

http://www.heatinghelp.com/forum-thread/142217/The-King-Of-All-Crossover-Traps



We don't have any fuel-savings figures yet, but the building heats much more evenly now.

JStar

Trap

That's the one. There's a Nicholson supplier about an hour from me. They're closed on weekends. I have a feeling that the price is going to be frightening...?

SWEI

simmer all winter

Is do-able with a modulating gas burner.  I'm hoping to find a project where we can experiment with control strategies.

Steamhead

Make sure

you're sitting down.

PMJ

Still not really understanding the comments

I have a Mouat system and there is nothing special. The boiler was originally coal and now it is gas. The piping is all still per the original Mouat diagrams. Original radiator valves and traps - no vents on those either. At the farthest point away from the boiler in the loop the steam main and dry return both drop vertically down and join below the water line. No steam main vent, just one on the dry return - just like their literature shows.



And I don't follow the only works with coal comments. The thing with coal is only that you can't just turn the fire off - not that it would hurt anything if you could. So Mouat designed a special automatic damper setup to close and open the boiler flue dampers based on changes in single digit ounces of pressure. Quoting now from their original literature "The Mouat system has several distinct advantages over all other methods of heating. It is a two pipe gravity vapor or atmospheric steam heating system operating at from one-half to three ounces of pressure". And the design didn't change whether on just a house of multi-story buildings. So Mouat made it possible to keep a system at very low pressure with a coal fire that can't be turned on and off. But I know from first hand experience that the rest of the piping doesn't fail to work if you do supply steam on and off - it still works great.



Quoting again form the literature " the Mouat system can be operated in conjunction with any standard steam heating boiler equipped for burning coal, coke or gas. It can also be used with central station steam supply. No special radiators are needed, ordinary hot water or steam radiators may be used. Radiator heating plants already installed may be changed to Mouat Vapor Heat".



Incredibly low pressure, incredibly low maintenance because there are almost no moving parts. Amazingly simple compared to what I read about here.

MikeyB

Trap

JStar, if you need some more contact info for suppliers of steam traps send me an email and I can give you the suppliers I use, Im sure they could find you a Nicholson trap, maybe one guy might be cheaper than another, Like Steamhead has said these traps are not cheap.

Dave in QCA

I have a Spare Trap -- Nicholson?

Joe,  I ended up with a new, unused, spare trap.  It is a thermostatic trap and I am pretty sure that it's a Nicholson.  I will go over and check it out a little while later.  It is NOT the same on that Steamhead used, not quite that big.  But, it is pretty hefty and it passes air like an open 3/4" pipe.   Maybe I should put it on the swap section of this site?

JStar

Trap

I'd be interested in some smaller size, too. This estimate I'm working on would require 100 total vents. I'm trying to consolidate.

gerry gill

Most Mouat systems

of any appreciable size had a main vent (waffer style) at the end of the supply pipe, if the return wasn't vented into the chimney, but the smaller systems didn't have any at the steam mains end as the system was small and the systems generally didn't have intermittently fired boilers..ever read the instructions of an antique gas boiler? open several burner tubes in spring, as as it gets colder open more,..so they worked better at mimicking the coal boiler than do todays gas boiler..im not sure where your confusion lays..if the system is working great without main vents on the supply, thats wonderful and a testimonial to the designer and installer..but most need main vents.

SWEI

Mouat vent

Gerry Gill describes it here http://www.gwgillplumbingandheating.com/webapp/GetPage?pid=557

the patent make it seem like something that could (especially the inline version) be field fabricated today.  Other than the general coolness of re-making a piece of 1920 technology, is there any particular advantage of the Mouat vent for an existing two-pipe system?  I see no radiator traps, but then he shows each radiator dropping to the wet return.  No vacuum, either.

PMJ

Mouat/main vents

From your comment I gather that a system that doesn't need main vents was designed/installed better than ones that do need them. So I am just looking to understand better what those deficiencies are. Clearly an enormous amount of time is going into struggling with vents. The Mouat literature surely implies that they think most systems would run their way without them.

gerry gill

guys, we are kind of highjacking Joe's thread,

so i would humbly suggest this tangent get its own thread.

JStar

Gerry

It's okay. I got the answers I was looking for. Hijack on.