home HRV ducting question

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  #1  
Old 02-28-08, 07:48 AM
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Post home HRV ducting question

Hi

I have a home with a lifebreath dcs 300 unit installed in the basement, by the builder in a most simple method. This is the unit:



When I look at the install documents it shows me this setup for the ductwork for this hrv.

The actual ducting is the reverse of this diagram. The air is beeing heated then dumped outside by the hrv , the return air is pumped into the intake plenum on the furnace




My question is --- IS this right ? the builder said this setup is more efficent-- really?

I ask you guys
 
  #2  
Old 02-28-08, 02:00 PM
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Builder is wrong! your fans are working aginst each other.
 
  #3  
Old 02-29-08, 04:52 AM
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A breath of fresh air

There is a reason engineers draw up installation instructions I guess the builder is right in one sense, you are more efficient because your not bringing in outside air so the money spent on the HRV is wasted. I hope that maybe there is some misunderstanding.
 
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Old 02-29-08, 12:25 PM
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Wink

Id take the duct that goes to the trunk line just off the plenum . Called fresh air to inside and run it right into the cold air drop there. If I have the lay out right
 
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Old 02-29-08, 01:19 PM
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ok sry

what I mean is the hook up is right so far as which line goes to the fans and all in the hrv but the hrv is cross connected to the furnace

what seems wrong are were the hrv ducts for stale air pickup and return to the furnace are odd. as in cross conected.

The stale air intake duct for the hrv is now from the hot air plenum just above the furnace side
meaning freshly heated air is beeing dumped outside....

and the fresh air duct from the hrv is dumping fresh air into the cold air Return duct in the furnace


this is opposite the manufacturers diagram and is said to waste fresh air as well as heating resources.. thanks

so I should reverse this connection as per manufacturers spec and the system should be a waste heat recovery system as it was intended.
 
  #6  
Old 02-29-08, 06:32 PM
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You lost me! All I know is the diagram is wrong!!! Supply air from the AHU should be going to stale air from inside. Return should be coming rom HRV fresh air to inside.
 
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Old 03-03-08, 08:36 AM
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Hi thanks I'm going to change the exisitng ductwork to what is shown in the diagrams

there are 2 diagrams in my orginal post ,
top-- hrv inards
bottom -- hrv hook up as per manual

I'm more interested in the ducting for the second diagram -- which seems in my install to be cross connected to the furnace as comapred to the diagram
 
  #8  
Old 03-03-08, 07:09 PM
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HRV hook up is wrong!
 
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Old 03-04-08, 10:17 AM
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Mmm ok I have three options below

This is what I have now for the hookup,
fresh cold air comes in the hrv side to the furnace intake
then some
fresh newly heated air is being dumped into the hrv and out side,


Present #1



according to the pdf manual that wastes fresh air -- but the builder says it is more efficent ? if so why does the manual not state this ??




http://www.lifebreath.com/Manuals/en.../TI-84R-NE.pdf


or is this a better way?

Possible #2]



AS per manual #3]
 

Last edited by geoimpala; 03-04-08 at 10:37 AM.
  #10  
Old 03-04-08, 11:37 AM
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Wink

USE that # 2 But run that blue duct down and in to the cold air drop right as it goes into the furnace near the floor.
 
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Old 03-04-08, 05:17 PM
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I'm for #1! #2 will be 2nd #3 will not work!
 
  #12  
Old 05-02-09, 06:45 PM
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I was just reading around about HRV and came to this post.

I was in favor of #2 (with same comments as Ed)

Now why would you favor design #1, wouldn't you be wasting heated furnace air in winter (heating) time more

(Keep in mind you are talking to a novice and pls. answer like a novice, so I can understand)
 
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Old 05-02-09, 07:22 PM
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Originally Posted by airman.1994 View Post
I'm for #1! #2 will be 2nd #3 will not work!
Why would #3 not work?

Also wouldn't you be sending the fresh incoming air out again after heating it in #1
 
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Old 05-06-09, 03:07 PM
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OK. I don't know where some of this info comes from, but several of you are wrong. As you have drawn it, your #3 is correct. Your #2 will also work. #1 is dead wrong and will not work and will be a waste of your heating and cooling dollars. Either 2 or 3 is acceptable, but with 2 you MUST have your furnace blower running all the time that the HRV is running or your air will just go in a circle. Even with 3, its a good idea to run the furnace blower as it will help push the air through and keep things moving along. 1 will not work because you are taking conditioned air and sending it to the HRV stale air input, from there it is exhausted. Following this? There is a reason its called STALE AIR. That is referring to air that is return to the unit, BEFORE its again conditioned and sent out as supply air. I am surprised that your manual doesn't show both 2 and 3 as acceptable installations. Neither of these are the preferred installs, but both will work and are the easy ways to do it, and less costly.
 
  #15  
Old 05-06-09, 05:47 PM
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#3 would be the hardest on the blowers in the HRV
#2 would be hard on one blower
#1 I still think would be the best.
You said it would use more electricity. I say it will be a wash because you will be pre heating or cooling the fresh air more this way. 6 one way half a dozen the other. #2 and 3 will work you just will not be running the HRV at 100%. If it is over sized then it will not matter.
 
  #16  
Old 05-07-09, 11:02 AM
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I favor #3

I am not planning to run the furnace blower all time, so I'll go with 3.

Originally Posted by Sparky88 View Post
Neither of these are the preferred installs, but both will work and are the easy ways to do it, and less costly.
Then what's the preferred one?
 
  #17  
Old 05-07-09, 04:39 PM
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Originally Posted by airman.1994 View Post
You said it would use more electricity. I say it will be a wash because you will be pre heating or cooling the fresh air more this way. 6 one way half a dozen the other. #2 and 3 will work you just will not be running the HRV at 100%. If it is over sized then it will not matter.
Look, the HRV is designed to extract the remaining heat from STALE air and transfer it to the incoming fresh air, and vice versa. When hooked up, as in #2, it will operate as designed and at 100% of its design eff. Its actual eff is probably around 80%, at least mine is. Its designed to extract residual heat only, not heat from air that has just been heated. Surely you can obtain a manual on line, if you don't have one. I don't know what brand you have, but I would think it expains all this. Working the blowers hard or not is somewhat irrelevant, as the unit is working as designed.

In answer to your question about the best installation, it should be ducted to the living space itself with its own ducting. In this way, you get the best bang for your buck. I don't have time now to expain it all though, I have to get going somewhere.

Thanks. I check back.
 
  #18  
Old 06-03-09, 08:05 PM
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I agree with Airman. Although it would work a whole lot better if you would draw the stale air directly from the living space then put fresh air into the return.
 
 

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