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# Mystery Dimensions

#1
09-26-08, 05:32 PM
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Join Date: Jul 2008
Posts: 35
Mystery Dimensions

This is the piping diagram originally spec'd by rbeck in this forum and then modified to included an ESBE TV valve:

It's a great design but the A, B, and C dimensions shown in the diagram were never properly defined.

This does not include the distance between the closely spaced tees which is clearly shown to be 12" maximum.

Dimension "A" appears to refer to the distance between the "Second Secondary Tee" and the first circ pump. I don't know why this dimension is important or what it should be.

Dimension "B" appears to refer to the distance between the air scoop output and the "First Secondary Tee". I don't know why this dimension is important and no air scoop manufacturer's spec sheet I've found references this dimension.

Dimension "C" appears to refer to the minimum length of pipe before the air scoop inlet. The Taco air scoop spec sheet spec's 18" minimum. That make sense to allow the air in the water to come to the top of the pipe.

So what are dimensions "A" and "B" suppose to be??? Does anyone know?

#2
09-26-08, 05:51 PM
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Join Date: Oct 2006
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The 12" MAX between the CSTs (Closely Spaced Tees) would probably be better defined as 4D (4 x pipe Diameter), but, CLOSER IS BETTER. The goal is to have as small an amount of pressure difference between the two side ports as possible. A small amount of difference in those pressures won't make a significant difference in performance, but AS CLOSE AS POSSIBLE should be the prime directive.

I take dimension A to be enough distance to allow the hot boiler water that is being injected into the system loop to thoroughly mix with the system water that is flowing past the tees. Note that the flows split at the return tee, with a portion through the boiler, and a portion through the tee, and these flows re-combine at the next tee. If the first take-off is too close to the tees, it is possible that the laminar flow could 'rob' the downstream circulators of sufficient hot water.

Dimension B ? I'm not too sure the significance of that one, but I suspect that it's similar to dim A... In general, enough distance for the flow to be unified (no turbulence).

You are correct about dimension C as far as I can tell.

What _should_ the dimensions be ? Most accept the distance ahead of and after CSTs to be 6 x pipe Diameter ( 6D ).

#3
09-26-08, 06:05 PM
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Join Date: Nov 2005
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A: As short as practical.
B: 6D.

you can find similar stuff here:

http://burnham.com/PDF/IO/Alpine%20I&O%20manual.pdf

Note that the figure you're using was modified by NJ Trooper. The ESBE thermic bypass approach may be fine for normal boiler protection, but may not function properly in a full outdoor reset application. The regulars here have kicked this around with no definitive conclusion.

Last edited by xiphias; 09-26-08 at 07:05 PM.
#4
09-26-08, 07:31 PM
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Join Date: Jul 2008
Posts: 35
Originally Posted by xiphias
A: 12" max, or 4 pipe diameters, whichever is smaller.
B: As short as practical.

How do I know? I looked here:

http://burnham.com/PDF/IO/Alpine%20I&O%20manual.pdf
Ok but that conflicts with:
http://www.comfort-calc.net/Bypass_P...laination.html
which appears to say B should be a minimum of 8 X the pipe diameter. I don't know which is correct.

Originally Posted by xiphias
Note that the figure you're using was modified by NJ Trooper. The ESBE thermic bypass approach may be fine for normal boiler protection, but may not function properly in a full outdoor reset application. The regulars here have kicked this around to no definitive end.
I know. I believe I was the first to question it on this forum here:
http://forum.doityourself.com/showth...ght=lessismore

Reference post number 12 and 14.

I was distressed to read that this piping is now considered very iffy to do full ODR.

Too late for me because I ordered all the parts including the Tekmar 260 and the very expensive ESBE valve.

I was originally thinking of going with the 360 which will do full ODR with boiler protection but the piping diagram provided by Tekmar was daunting and confusing and they never answered my inquires about it. I doubt anyone ever uses it for residential applications anyway. Too costly and complex.

Looks like the 260 can at least do partial ODR if you set the BOILER MIN temp above 113 degrees (ESBE oil). I guess there is no inexpensive and simple way to have boiler protection and full ODR, at least none that I've seen.

What disappoints me is that almost everything I read about adapting conventional boilers for full ODR with boiler protection is far more theoretical then based on actual proven applications. If anyone out there is piping such a system that is actually proven to work then they sure aren't providing much input here or elsewhere. I can find no definitive answers.

For now at least I think someone is better off paying the big bucks for a manufacturer designed system such as the Energy Kinetics System 2000 rather then trying to adapt a conventional boiler to do both full ODR with boiler protection. Please corect me if I am wrong.

#5
09-26-08, 07:54 PM
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Join Date: Nov 2005
Location: USA
Posts: 2,338
tekmar has some good technical essays on mixing methods and boiler protection

http://tekmarcontrols.com/literature/acrobat/e021.pdf
http://tekmarcontrols.com/literature/acrobat/e022.pdf

Yes, the ESBE method is rather unproven, so far as the regulars here know. I know directly of only one system that has this setup doing full ODR. Haven't heard about it in a while, though.

The 260 is an excellent control for doing full ODR if you have a boiler or boiler protection scheme and other controls to do it. I have such a system, for instance. It happens to be a mostly off the shelf Burnham Revolution, which has built-in primary-secondary piping and an internal variable speed injection system (controlled by a tekmar-manufactured mixing control). So your point about a packaged, designed system is well-taken.

However, adapting conventional boilers for full ODR is (was, before widespread adoption of modcons) very common. Primary/secondary piping with injection mixing is the preferred approach. Lots and lots of low-temperature systems running this setup. You are correct the tekmar 360 (or 361) would be a good control for this application. Before some other issues with my old boiler came up, I was absolutely headed toward full repipe for p/s and ODR. And it wasn't going to be cheap.

You quoted some stuff I misstated based on looking too quickly at the Alpine manual. Info is corrected above. I think it's 6D. Maybe a bit more coming off an elbow.

If you've got all the stuff, and it's not returnable, then I'd consider piping it up and letting 'er rip.

#6
09-27-08, 12:55 PM
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Join Date: Jul 2008
Posts: 35
If you've got all the stuff, and it's not returnable, then I'd consider piping it up and letting 'er rip.
That's exactly what I intend to do. For better or worse it looks like I'm going to be the test case.

I think it'll work well for partial ODR. I'll have to tweak the 260 until it works optimally. If anyone can make it work it's me. I've been an electromechanical and software engineer working on far more complex systems for IBM test operations for over 30 years.

I'll report back what happens here so there will be an actual application to reference and everyone will know if it works or not.

If anyone has any last suggestions please let me know now, piping will begin sometime next week.

Wish me luck, I may need it.

#7
09-27-08, 01:25 PM
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Join Date: Oct 2006
Location: USA
Posts: 19,710
There surely IS a way to do full ODR with a conventional boiler, and it has been mentioned. Primary / Secondary piping, with two separate loops for the system and the boiler, connected by an 'injection bridge' and controlled by something like a Tek 360/361.

What is required to do full ODR is TOTAL hydraulic separation between the two loops so that you can run the boiler without condensing, and injecting heat across the bridge to the system loop so that it runs only hot enough to match the heat loss of the building.

Yes, any of the other 'schemes' that you've seen are experimental, and 'iffy'.