Author Topic: Simplified HRV installation with T-shaped return - how do I do it?  (Read 2449 times)

Offline alex99

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Hello:

I want to install HRV in existing house with finished basement, and I have very little space to work with. Simplified installation with return-return connection seems to be the only option for me. I'm reading the manuals, how fresh air port should be at least 10' away from furnace, and stale air duct should be 3' ahead of it. That's all clear. However, my furnace return duct is T-shaped (furnace is installed in the middle of the house). Right part of the T collects return air from master bedroom and living room, and the left part takes it from large family room upstairs.

so my questions is: can I attach fresh air supply to one side of the T, and stale air duct to another? Basically, furnace will be in between them?

And another question is - how bad would it be if I install fresh air supply only 4' away from furnace fan? Am I getting marginally worse performance, or that would completely unacceptable? The manual explicitly calls for 10' minimum :(

I'm thinking of getting VenEE 65H HRV btw - for 2000 sqft 10 years old townhouse in South Ontario. Any red flags?

Thank you.

Offline Admin

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Re: Simplified HRV installation with T-shaped return - how do I do it?
« Reply #1 on: December 18, 2018, 09:20:01 AM »
The Vanee 65H is a good product.

All the return air goes back to the furnace so it shouldn't matter which side you install the stale air from building. 

I think the concern is being too close to the furnace fan which could cause higher static pressure and balancing problems or early wear on the HRV motor.  Usually the return air drop is about 7' high so the the fresh air to building connection could be relatively close to the furnace.

Offline alex99

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Re: Simplified HRV installation with T-shaped return - how do I do it?
« Reply #2 on: December 18, 2018, 12:13:53 PM »
Thank you, I appreciate your prompt reply. However, I'm still not quite clear. Please see the picture below of my installation. Essentially I'm trying to understand if I can connect fresh air port into point A, and stale air return into point B - they are on different sides of vertical pipe (that's what you called a drop, I assume?). Both about 2-3 ft apart from the drop (which is about 7' tall). In this case, both point are about 10' from the furnace. And then, if I understand you correctly, I cannot connect to point C at all - right?



sorry if these are lame questions.. but I'm learning! :)

Offline walker

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Re: Simplified HRV installation with T-shaped return - how do I do it?
« Reply #3 on: December 18, 2018, 02:18:00 PM »
Thank you, I appreciate your prompt reply. However, I'm still not quite clear. Please see the picture below of my installation. Essentially I'm trying to understand if I can connect fresh air port into point A, and stale air return into point B - they are on different sides of vertical pipe (that's what you called a drop, I assume?). Both about 2-3 ft apart from the drop (which is about 7' tall). In this case, both point are about 10' from the furnace. And then, if I understand you correctly, I cannot connect to point C at all - right?

sorry if these are lame questions.. but I'm learning! :)

that would be the drop

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Re: Simplified HRV installation with T-shaped return - how do I do it?
« Reply #4 on: December 18, 2018, 02:22:01 PM »
Yes, the return air drop is the piece I labeled as A = 7' high in my first attachment.  From the top of the return air measure over 3' on the trunk line and you would install the fresh air to building duct where my red circle is.  (A + B = 10')  You measure the duct distance not the actual distance to the furnace.  Even though the fresh air duct is within 10' of the furnace and directly above it, we've satisfied the 10' rule.

3' away from that install the stale air from building duct where my green circle is.  Or you could install the fresh air to building on the return air drop, just follow the instructions below and install a tee.

The Vanee 65H manual says,

Quote
If the pressure exceeds 0.25 in. w.g., or if the fresh air distribution duct cannot be connect at least 10 feet away from the furnace, perform the following step.

If you can't install the fresh air to building duct at least 10' away, follow the instructions on my second attachment.  Essentially install a tee and leave it open, unless your gas appliances aren't sealed or direct vent then they want a duct from an outside room connected to the tee.

Offline alex99

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Re: Simplified HRV installation with T-shaped return - how do I do it?
« Reply #5 on: December 18, 2018, 07:50:11 PM »
sorry to be the pain - but the question still remains - can I install fresh air port into point A, and stale air return into point B - on different sides of furnace? The reason I'm asking is because I only got 10' clearance either way - meaning I can't do stale duct to be 3ft ahead of fresh air port. Or fresh air port should go into the drop - probably 6ft from furnace fan then. Please let me know what are your thoughts on this. Thank you.

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Re: Simplified HRV installation with T-shaped return - how do I do it?
« Reply #6 on: December 18, 2018, 08:58:52 PM »
Yes, your A and B locations should work, but I would install the stale air from building duct on which ever side serves more of the house.

The important thing is to interlock the HRV with the furnace fan.  That will make sure things even out.

Offline alex99

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Re: Simplified HRV installation with T-shaped return - how do I do it?
« Reply #7 on: December 19, 2018, 06:52:22 AM »
got it - thank you! Regarding interlocking - essentially running a wire from one controller to another, right? I'm sure i can figure this out.

What about balancing the unit? Is that still something I should do right away, or modern devices can figure this out automatically now?

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Re: Simplified HRV installation with T-shaped return - how do I do it?
« Reply #8 on: December 19, 2018, 07:04:52 AM »
Follow the instructions and use the 3 wire method to connect the HRV to the furnace control board, so that anytime the HRV starts so does the furnace fan.

You need a manometer to balance the Vanee 65H HRV.