E-Classic 2400- Question regarding double-walled flue pipe outside temperature

[garret]

Hi Folks,

New to the forum, but not to wood heating.  Just installed a new CB-2400 in a 12'x16' shed with metal roof to get out of weather and stash a little wood.  Where pipe penetrates the metal roof at rear, I spaced combustible roof members several inches from the double-walled flue pipe and installed heat shielding just in case.  Now the actual question:  I fitted a pipe flashing  (10.5" cutout-type) atop the roof penetration having a high-temperature silicone rubber boot made by Aztec Master Flashing, but not specifically designed for this purpose.  However, the specification on the silicone is a sustained temperature of 450F and a peak of 500F.  Would anyone anticipate the pipe to exceed these parameters at about 48" above the furnace during normal operation?

[beenthere]

Probably safe at "normal" operation, but it is the abnormal time when you have a chimney fire that you might want to consider.
How about a pic or two so we can be certain what you are doing and learn some more from it. Sounds like a good build.

[garret]

My first attempt at posting pictures anywhere.  I designed everything based on things I learned at this forum over last 2 months:

Woodshed I built for my new E-2400
 

Flue pipe roof penetration and homemade heat shielding
 

metal roof high temp silicone flashing
  
rear panel plumbing and electrical.  Mounted on 1 1/4" bung and as low as possible (120' run of 1" thermopex).
  
Primary-secondary loop inside plumbing. First pair of closely spaced tees will heat house and second garage (when finished).  At least that's the plan. Went with 1 1/4" manifold and thermostatic valve to reduce head loss
  

[beenthere]

Can't imagine you would have a thing to worry about.
Keep an eye on the wood adjacent to the pipe, and any heat damage will show up. Or hang a candle or two near the wood and watch for any melting, or more than expected.
Good on the pics, and thanks.

[garret]

Candles a great idea!  Thank You Mr. beenthere.

[albirk]

I agree with Beenthere should not be a problem but the one thing I don't understand is the manifold in the last picture it looks to me that the water will go around the loop and back to the stove and very little to your coil {please explain}

[Holmes]

Great job garret. 8)  albirk the system you see basically puts the boiler inside the house.  All the btu's travel thru that loop and go back to the boiler, the closely spaced tees allow you to take the heat from the loop and deliver it where you want it.
Excellent installation. 8)
I agree with beenthere about the flashing, keep a 2nd one around so you will never need it.

[garret]

Holmes is correct.  Perhaps a little explanation.  I had previously installed a home-built OWB that was horribly inefficient and smoked like a locomotive.  The pair of red O2 barrier PEX tubing you see coming out of the first close spaced tees in the above photo was connected directly to the OWB and hot water was circulated through a home made DHW side arm tube Hex and finally, a 50 brazed-plate Hex.  This in turn exchanged heat with my pressurized, oil furnace/hot water baseboard system via a wrap-around loop that is pumped independently (a commonly encounter and widely accepted system).

The old system worked, just barely.  We had one of the coldest winters here in PA as did many others.  The old OWB consumed a measured 13 (seasoned) cords between Thanksgiving and March 1st.  Required regular feedings EVERY 4 hours.  I was miserable but determined.  If the new system even makes it through the night after what I went through I will be ecstatic. 

Anyway, I believe I had made a mistake installing the 1" thermopex  at 120 ft from the house (that's 240 ft round trip).  Combine that with the 100 additional feet inside the house going to and from the Hex.  If anyone would care to do the calculations as I did, indeed it was a mistake.  You simply cannot move enough BTUs and therefore, cannot realize the full potential rated output from an E-2400 (based on my design heat loss calculations and during periods of high-demand).  UNLESS, you can further reduce the water temperature below the normal design limits (typically, delta 20 F).  That way the same volume of water can deliver more heat.

The manifold and close spaced tees offers a solution to this dilemma.  First, it knocks off the additional 100 ft of pex going to the Hex (about 8 ft of head loss at 8 gpm), as this is pumped separately.  Also, the second close spaced tees will service my garage (1200 sq ft) where I installed a slab-on-grade radiant system.  Since the radiant system only requires ~115 F water, and is downstream in the manifold, it can utilize the lower temperature water that was returned from the first pair of close space tees.  Hope you are following me so far. 

At least from an engineering and theoretical perspective, I should achieve the desired lowering of water temperature and extract the needed BTUs.  Of course, it is totally untested and in the R&D stage.

My only other options would be to:
A. move the wood furnace closer to the house
B. install another 1" thermopex
C. install 1 1/4" thermopex (should have done in the first place)
D. Purchase another ridiculously expensive OWB for the garage.
E. Shut up and pay the oil bill   

[albirk]

garret first I hope you don't think I was bashing your install very nice workmanship I think it is topnotch! I am just asking [I installed CB stoves for 5 year] and the water will take the path of least obstructions so the water comes in goes around your manifold with very little water going to your side arm or your plate Hex or is there a pump to push the water to them. I just like to learn

thanks Alan

[garret]

Albirk, I wasn't thinking along those lines at all.  I gave what I thought was a very well thought out (and lengthy) explanation of why my system is configured as it was, but perhaps not very much about how the manifold works.  You are right that the manifold is simply looping back to the OWB and very little if any hot water would circulate through the loops originating at the tees.  The closely spaced tees provide what is referred to as hydraulic separation.  You are also right that the secondary loops thus created must have their own pump.  The magic is that the pumps effectively do not see each other because in the very short section of straight pipe between the tees there is essentially no resistance to flow (spacing between centers of the tees should not exceed 4 pipe diameters according to most texts).  In fact, you can actually have backward flow if the rate of flow in the secondary loop is greater than the primary.  So, effectively as Holmes so eloquently described, it would be the equivalent of moving the furnace indoors (to the location of the manifold). Theoretically, there is no limit to the number of primary-secondary loops.  You can place closely spaced tees in the secondary loop, creating a tertiary loop (I've done this and it works great).  For further info Google primary-secondary loop hydronic heating.