Adjusting orifices on a vapor system.

tmw

Some day in the near future I will write about the experiences I've had rebuilding my beautiful old Arco Model K vapor orifice system. Please note that the orifice valves in this system have all been rebuilt as new.



Anyway, for now, I need some advice on how to  properly tune the orifices. For a picture and description of the valve please refer to the Lost Art...



The orifices adjust by turning a threaded rod within the valve body to increasingly block the passage of steam into the radiator. This is done so that steam is always kept out of the returns, as there are no traps on this two-pipe system. I believe that in theory, the radiator should heat up to no more than 80% of its EDR  thereby allowing no steam to get to the return, just hot air and condensate.



So right now, I've got all of the main valves opened all the way and have all the orifices throttled down so that the returns are warm, and not steam temp like up at the valve. This keeps the system nice and quiet and heats the house up nicely at 2 oz. Obviously I can always close down the main valves for less steam.



I know that this is a rather unscientific technique. Would measuring temps up at the valve body and then at the return be useful in adjusting the orifices?  Also, how does one go about balancing this type of system? Would Gerry Gill's book be useful here?

Steamhead

That's how I'd do it

if I was there. But if the system overheats on a mild day, I'd use 3 or 4 ounces instead of 2. That would slow them down a bit, but not too much. 

Rod

IR Thermometer ?

It seems to me that this would be an idea application of an IR thermometer. I have a Ryobi Tek 4 Model 4030 which are available from Home Depot. I've found it very accurate and handy for checking traps. It should be easy to determine when steam reaches the outlet and then just back it down a bit.  Put one on the list in your letter to Santa Claus. That's who brought me mine last year!

- Rod

jpf321

Mr. Gifford's article may prove useful...

I refer you to the table on page 5 of this PDF: http://is.gd/gB3nK



No, Mr. Gill's article is simply for balancing by way of vents.

tmw

I don't understand...

Hi Steamhead,

The settings on the vaporstat haven't been touched since you and Gordon adjusted them in the Spring.  2 oz. is actually the highest reading I've seen since  replacing all the valves w/ the newly rebuilt ones. And the system doesn't overheat on mild days anymore.  When you guys were here you may remember that one of the overhead dry returns in the laundry room was extremely (too hot to touch) hot, probably from one of the unorificed radiators dumping steam into the return. System climbed to 4oz. at that time.  That return is now barely warm since the new valves went in. Would keeping steam out of the returns cause the system to run at less (i.e. 2oz) than before?



So when you say you would "use 3 or 4 ounces instead of 2" what are you referring to?



p.s. A warm greeting to you and Gordon from all of us here at Knockbawn!

tmw

Bump...

anyone?  and how does one go about trying to balance this system after it's been adjusted so that steam never gets to the return when main valves are fully open?



And can I assume that returns can still be plenty hot but still not have steam in them? Like maybe they only need to be 5-10 degrees cooler than the valves to see the steam condense? So maybe I am underheating my radiators by adjusting the orifices so the returns are warm, maybe they can be 25-30 degrees hotter and still condense steam. I guess the IR thermometer could help with this one...

tmw

please look at my posts from 11/2 and 11/4

thanks..

Steamhead

What it means is

If you choke down the orifices a bit so it takes 4 ounces to fill the rads to 80% or so, and reset the Vaporstat for 4 ounces, it will take a bit longer to fill the rads. This can help prevent overheating of the house on mild days, by keeping the rads from getting too hot too quickly.



But if it's working properly and doesn't overheat on mild days, don't change a thing.



Someday I hope to have a place like Knockbawn.

Rod

Exit Temperatures

Hi-  With the caveat that I know practically nothing about orifice systems, it would seem to me that your exit temperatures are a bit on the cold side.  I base this on my IR gun readings of traps on a regular two pipe system.   The temps on the exit side of the trap are in about the 185F to 190+ F region.  If the trap is open (non functional)  and steam is going through the trap, the temp is much higher, usually at least 200 +.  Use the radiator inlet piping temperature as the reading indicating steam and decide how much you want to deduct for the target outlet temperature. You just have experiment a bit I would think.  One of the things I learned with an IR thermometer is to take your reading up close. The farther away, the larger the area that is sampled which can give you a false reading.

- Rod

tmw

thank you Steamhead and Rod...

this is EXACTLY what I needed to know. I am definitely throttled down too much, but at least I have a starting point now to experiment with outlet temps.

jpf321

did you....

look over the gifford orifice article that I posted above? was there nothing useful there? 

Dave in QCA

I find it very useful, and interesting!

JPF,  I find the article very interesting, but I'm not sure how much it will help the person with the question on this thread.  Henry Gifford's chart is for 2 PSI and our writer here is running 4 oz.

If I had found this great article before repairing / replacing some 20 traps on my system, I would have definitely used orifices instead.  It would have made getting the system balanced easier too.

jpf321

in theory ...

once he figures out the opening for a single rad at his lower pressure, he can recalibrate the chart.



so at a higher pressure, according to Gill paper, a hole will vent MORE .. thereby at a lower pressure a hole will vent LESS .. so if he went by the Gifford chart, his holes would be too SMALL.



hope this is clear.

Dave in QCA

Chart for lower pressures is needed

Yes, perfectly clear.  You restated the point I was trying to make. 

tmw

Thanks...

and yes, I actually found that very interesting article last year. I just don't find it helpful for my particular question .



Actually, I could as you suggest figure out the orifice area in one of my valves and then extrapolate (or attempt to) between my 2 oz system and Gill's 2 psi system. But then I would need to figure out how many turns of the  threaded orifice rod would give me an X increase or decrease of orifice area, which seems to be a pain in the butt when one can simply use an IR thermometer and adjust the orifice rods to a certain temperature in the returns. That temperature should be the highest possible where steam will still condense at the return  with the main body valves wide open. In this way I can still achieve individual room control while never having to worry about dumping steam into the returns.



The REAL challenge will be in balancing this system.

Rod

Exit temps.

It's an interesting puzzle.as there are a lot of variables: radiator capacity, different pressures and the different steam demands of radiators at hot and cold temperatures.

I guess since I have a new toy, I'm IR oriented. I haven't tried this but I think the IR thermometer might also be useful in determining the progression of steam (steam volume) in the radiator and it might be helpful to experiment a bit and see if there is a correlation of exit temperature to  % of steam volume in the radiator. That might give you a better idea of  target temp for the exit temperature. 

Just a wild thought with no experience to back it up.

- Rod

jpf321

i was under...

the impression that you could see into one of the orifices, if that's the case, i was thinking you could use drill bits of various sizes and turn until you caught the width of the bit. you could also test with 1 orifice that you can see through and count the turns for various sized bits (then you don't have to take apart all your rads) .. well good luck, we are all interested to see how it goes.