Indirect WH question


  #1  
Old 11-20-06, 04:46 PM
Z
Member
Thread Starter
Join Date: Sep 2006
Location: usa
Posts: 78
Upvotes: 0
Received 0 Upvotes on 0 Posts
Indirect WH question

OK folks,

I hooped up my indirect and everything is fine just one problem,
one of my return pipes getting some of hot water from indirect zone.
Here is my setup. boiler------>supply with circulator---->that 1 zone T's off into 2 loops::::::::::return to boiler.
You can see on this pic (before I hooked indirect zone). The return for indirect is the farthest one the manifold from my boiler (blue valve on the pic). Indirect circulator is the closest one on supply to the boiler.
My situation: One of the heating returns (closest to the indirect return) gets hot when another one stone cold. All 3 returns are about 6" apart on the return manifold. I know I should of piped indirect return to be the closest one to the boiler on the manifold. But it still doesn't make a ny sense, one would think water flow will choose the most straight way (to the boiler) rather going up into the heating zone. Circulator have check valves built into them. Indirect manual has nothing about installing check valve on return. Should I pipe it closest to the boiler or just install check valves on heating returns?

http://i3.photobucket.com/albums/y95/zaq_944/boiler/CIMG0061.jpg
http://i3.photobucket.com/albums/y95/zaq_944/boiler/CIMG0058.jpg
http://i3.photobucket.com/albums/y95/zaq_944/boiler/CIMG0057.jpg
 
  #2  
Old 11-20-06, 05:32 PM
X
Member
Join Date: Nov 2005
Location: USA
Posts: 2,338
Upvotes: 0
Received 0 Upvotes on 0 Posts
My offhand suggestion is to not worry about it. What you are probably sensing is heat migration, not actual water flow. Maybe a bit of turbulent mixing, but I'm thinking no biggie. Check valves further throttle system flow so if you've already sized to the right flow rate, I would not start adding check valves.

How far up the zone does the pipe feel warm?

What diameter is the return header?

Is this one circ serving 2 zone valves, and a dedicated circ for the indirect?
 
  #3  
Old 11-20-06, 06:29 PM
Join Date: Aug 2006
Location: usa
Posts: 839
Upvotes: 0
Received 0 Upvotes on 0 Posts
return

My indirect return is piped into a tee on the 1-1/4" return to the boiler, and I also notice that the return pipe is heated for a few feet above the tee when the DHW is being fired. I'm not sure if it is worth worrying about.

Pete
 
  #4  
Old 11-20-06, 08:04 PM
Z
Member
Thread Starter
Join Date: Sep 2006
Location: usa
Posts: 78
Upvotes: 0
Received 0 Upvotes on 0 Posts
So far I have only 1 heating zone (to be 2 next summer)
That circ you see in the pic has 1" pipe going into T with 3/4" pipe forming 2 loops . Kind of like this

--circ-----T
I
< _________3/4"return__CI base_
 
  #5  
Old 11-21-06, 05:00 AM
X
Member
Join Date: Nov 2005
Location: USA
Posts: 2,338
Upvotes: 0
Received 0 Upvotes on 0 Posts
I'm temporarily at something of a loss, but I'm also not sure I completely understand the heating circuits either.

I believe the applicable technical term here is "ghost flow."

You have two space heating loops served by one circ, correct? What is the piping above the circ? Do you bullhead T to go to the zones or something else? I see what looks like 1" coming out of the circ up to an elbow, then the pic is cut off.

For the moment, I'll guess (and this really is a guess) that perhaps the loop that does not get hot is the longer of the two space heating loops, and the one that does, is somewhat shorter. And the answer is?

Guessing at possible reasons:

1) if the shorter one is getting warm, then there's a pressure differential or something similar at work here, allowing migration/flow/mixing/whatever in the shorter loop rather than the long one. If the longer one is the one getting warm, forget this.

2) Having two loops basically uncontrolled except for the flowcheck in the circ might be a no-no. Not sure on this. Would be kind of a corollary to 1) above. Most everything I've seen and read would control the loops with zone valves in this application, but I am definitely not what you would call long on experience. Grady, what do you think?

Guessing at possible solutions:

a) swap the returns as you suggest, putting the indirect closest to the boiler. FWIW my return manifold is set up like this, and there's basically zero heat migration. That said, my indirect is last off the supply manifold, but no heat migration into the space heating zones (two zones using Taco 007 IFCs -- built in checks). The layout made much more sense that way, although tradition and the manual suggests indirect should be first. Proximity to the flowchecks (or lack thereof) is kind of what motivated my thinking about 1) and 2) above.

b) elevate the return manifold off the floor and pipe in heat traps for the space heating loops. Probably a heck of a lot more work than a).

c) put zone valves downstream of the circ. Probably a heck of a lot more work than a), esp. when it comes to the wiring, etc.

d) Put zone valves on the returns a bit above the return manifold. Probably more work than a), but less than c).

e) go ahead and finish the future zone addition now (I assume you'll extend the supply manifold and use another circ?). Probably a heck of a lot more work than a).

On the whole, I would not be in a rush to address this. Think some more, get other feedback.
 
  #6  
Old 11-21-06, 09:39 AM
Z
Member
Thread Starter
Join Date: Sep 2006
Location: usa
Posts: 78
Upvotes: 0
Received 0 Upvotes on 0 Posts
Here is my quick drawing of the setup.
http://i3.photobucket.com/albums/y95/zaq_944/boiler/untitled.jpg
Loops 1 and 2 are existing (old boiler setup), however the circ on old boiler was on return vs. on supply now.
In the future I plan to separate those 2 loops into 2 zones.
In the above pic I colored the return pipe that gets hot.
Actually, loop 1 has slightly larger volume than loop2.
 
  #7  
Old 11-21-06, 06:06 PM
X
Member
Join Date: Nov 2005
Location: USA
Posts: 2,338
Upvotes: 0
Received 0 Upvotes on 0 Posts
Sounds like a ghost flow problem and the a-e list above should help with that. Also flow checks as you suggested earlier down near the return manifold. But I'm flow-check paranoid so I'd avoid that. Personal preference. If you do go flow-check, then check your head and flow with them in there. A Taco swet-check goes 143 ft equivalent length. That's about half a typical space heating loop. With that 3-speed circ, you could always up the speed, but why waste the energy if you don't need to.

First thing I'd try is swapping the returns to put the indirect closest to the boiler. No big deal, right?

Something of an aside. What you've got going on the simple split to two heating loops is probably something covered in hydronic design school where I've never been. Maybe ok, maybe not. I'm sure if the loops are significantly different (equivalent) lengths then the shorter length is getting a higher flow rate. Whether it matters performance-wise is probably a "hey if it works, fine" kind of thing. Esp. if you plan to do real zoning at some point.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: