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I would like to install a UV Air cleaner, but most of them seem to be listed as return air models.

Due to the .. odd nature of my furnace setup, I would really like to install this in the plenum that connects the furnace to the main supply trunk. Is there some reason I cannot or should not do that?

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  • I can't think how this type could work ahead of the main plenum. It would restrict the flow too much. Dec 15, 2021 at 22:29
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    @JimStewart Am I misunderstanding something? It seems like they are just some long tube style light bulbs. Does that really restrict airflow? I am asking if I could install them in the main supply plenum in case that wasn't clear.
    – negacao
    Dec 15, 2021 at 22:33
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    You would probably get better information by calling the customer service/ technical support people listed in the instructions.
    – JACK
    Dec 16, 2021 at 0:25
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    The UV Air Cleaner you mention is meant to be installed on the return air side. Installing it on the supply side would probably reduce/negate it's effectiveness. They do have a UV Surface Cleaner meant to be installed on the supply side but as JACK suggests you'd best contact the manufacturer.
    – HoneyDo
    Dec 16, 2021 at 5:03
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    <SWAG> It's got something to do with the rate of air flow. My return duct is 18" or 24", but my supply lines are 8" round and 6x9" rectangular (I dunno, never measured, that's a reasonable guess). The speed at which the air moves through the 2 different sections of duct work for the same volume of air moving is going to be noticeably different. The UV bulbs probably require that the air be in front of them for a certain amount of time for them to be effective, and on the supply side the air is just moving too quickly. </SWAG>
    – FreeMan
    Dec 16, 2021 at 16:11

2 Answers 2

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In general, UV purifiers can be installed on either side.

The size of the unit in question makes it impractical for the supply side.

For a supply side install, the unit would have to be small enough to fit within or just downstream the AC's A-coil assembly, where it sterilizes the AC coils which are prone to fungal and mold growth.

"Return Side Install" here is a limitation, not an advantage, and probably the result of developing a product for easy DIY installation.

I would think that it is fine for a supply side install if it's in the plenum, as long as you have the space (which you do).

enter image description here

When installing on the return side, be sure not to install it close to the filter as the UV will rapidly degrade the filter material.

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Images:

https://www.hvachowto.com/how-to-install-uv-light-in-an-hvac-system/

http://www.iaqsource.com/uv_duct_lamps.php

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<SWAG> Alert

It's probably got something to do with the rate of air flow.

My return duct is 18" or 24", but my supply lines are 8" round and 6x9" rectangular (I dunno, never measured, that's a reasonable guess). The speed at which the air moves through the 2 different sections of duct work for the same volume of air moving is going to be noticeably different.

The UV bulbs probably require that the air be in front of them for a certain amount of time for them to be effective, and on the supply side the air is just moving too quickly.

</SWAG>

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  • Thank you, today I learned all about SWAG
    – P2000
    Dec 16, 2021 at 17:48
  • You're welcome, @P2000!
    – FreeMan
    Dec 16, 2021 at 17:51

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