Recommend inline filter box with drop in easily replicable HEPA / charcoal filters?

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timmmay

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#304146 8-Apr-2023 20:42

I have a positive pressure ventilation system with this type of filter (HRV box filter). It's a pain to have to fit as to get it airtight it has to be taped in, then next year cut out to get the next one in, which is annoying when you're sitting up in a the ceiling space.

I'd quite like to replace this with something like an inline filter box with drop in filters. I found this one online but don't know anything about them. All I really want is a filter box that can take HEPA and charcoal filters that are effective and easy to replace. There has to be a way to have the filters reasonably easy to fit / remove without tape, and still have the air go through the filters rather than around them. I've tried emailing a couple of places about them but no-one seems interested in selling them, I've never gotten a reply.

Can anyone provide any advice here?

NB: this is a bit of an old thread now. 2025 conversations start here.

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#3060391 8-Apr-2023 21:03

Could you get one 3D printed at the local library ?

Thingiverse has a whole lot of STL models, search it with "hepa filter box"

Hope that helps

timmmay

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#3060393 8-Apr-2023 21:19

Reanalyse:

Could you get one 3D printed at the local library ?

Thingiverse has a whole lot of STL models, search it with "hepa filter box"

Hope that helps

Thanks, I'd rather buy a commercial one with commercially available refills. Seems a lot easier.

itxtme

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#3060398 8-Apr-2023 22:38

Not sure if these are suitable but I have bought off them multiple times

https://www.smooth-air.co.nz/product/catalog/1.DuctFittings*12.Filters*/?cat=7.7&sku=SOCK350

scuwp

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#3060411 9-Apr-2023 07:53

We have a Smartvent system. The filter is in itself part of the 'box', the sides are held on by 4 springs/hooks. Pretty simple to replace. Filters are about $100 off the shelf from Bunnings.

https://www.smartvent.co.nz/shop/filters/125mm-chrome-bezel-extract-a-lite/

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timmmay

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#3060433 9-Apr-2023 10:49

itxtme:

Not sure if these are suitable but I have bought off them multiple times

https://www.smooth-air.co.nz/product/catalog/1.DuctFittings*12.Filters*/?cat=7.7&sku=SOCK350

Smooth Air are good, they're the distributer for Airtouch. One of those box filters might do the job, but I'm not sure which one. I could call them up and ask, but I was hoping someone here might have some advice.

timmmay

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#3060434 9-Apr-2023 10:50

scuwp:

We have a Smartvent system. The filter is in itself part of the 'box', the sides are held on by 4 springs/hooks. Pretty simple to replace. Filters are about $100 off the shelf from Bunnings.

https://www.smartvent.co.nz/shop/filters/125mm-chrome-bezel-extract-a-lite/

That's what I have, and that's the problem. The springs aren't sufficient to keep the air in, at least on mine, so I have to tape it up then cut the tape off later. I also want multiple filters, HEPA and charcoal. That's why I want a box filter.

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tweake

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#3060449 9-Apr-2023 11:48

keep in mind that box filters simply seal by the air pushing it against the rear face of the box and the filter is the easier path. better ones will have foam so it seals better.

i'm not sure whats currently out there. i don't recommend the one i have because the filters are slightly different sized and are hard to get.

mattenz

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#3060798 10-Apr-2023 07:34

You might need to uprate your fan and increase the size of the filters, ventilation filters are generally just to protect the equipment.

tweake

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#3060810 10-Apr-2023 09:11

mattenz:

You might need to uprate your fan and increase the size of the filters, ventilation filters are generally just to protect the equipment.

no need to change the fan, i would increase the filter size if going to hepa filters or multiple filters.

positive air pressure filters are there to clean the air, most do come with a filter far finer than what is used to protect the equipment. however with balanced systems the core is protected by some fairly low spec filters and you really need to add a filter/box to clean the air.

timmmay

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#3060814 10-Apr-2023 09:34

I already have HEPA and charcoal filters inline, just done in a sub optional way. The fan / motor is set to 50% as we only have two outlets, throughput is fine.

I'm after a recommendation for a filter box and suitable filters, something commerical, ideally standard sizes that multiple vendors produce.

scuwp

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#3060824 10-Apr-2023 10:37

timmmay:

scuwp:

We have a Smartvent system. The filter is in itself part of the 'box', the sides are held on by 4 springs/hooks. Pretty simple to replace. Filters are about $100 off the shelf from Bunnings.

https://www.smartvent.co.nz/shop/filters/125mm-chrome-bezel-extract-a-lite/

That's what I have, and that's the problem. The springs aren't sufficient to keep the air in, at least on mine, so I have to tape it up then cut the tape off later. I also want multiple filters, HEPA and charcoal. That's why I want a box filter.

Can't say I have ever noticed a problem. Sure it's not hermetically sealed, but the sides fit snuggly enough and the springs create enough tension that is stays together. Depends on your expectations I guess.

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timmmay

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#3060829 10-Apr-2023 11:11

scuwp:

Can't say I have ever noticed a problem. Sure it's not hermetically sealed, but the sides fit snuggly enough and the springs create enough tension that is stays together. Depends on your expectations I guess.

My house is about 80 years old. The air quality in the ceiling space is pretty bad - old insulation, old wood, multiple old poison's (borer, rat, etc). When it gets hot it smells pretty bad. It's pretty obvious when there's a small split in the ducting particularly on a warm day. That's why I want a pretty decent seal - the air I push into the house is fresh air from outside, rather than from the roof cavity. A good seal means we get fresh air through good filters, rather than rat / borer poison.

mattenz

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#3061014 10-Apr-2023 15:14

Could also be an idea to relocate the fan, so that as much of it is under positive pressure as possible, maybe locate the fine filter downstream.

I got the 600x600x10 filters for my heart pump from RS Online, and the housing fabricated as part of the plenum by Jensen.

timmmay

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#3061103 10-Apr-2023 16:44

mattenz:

Could also be an idea to relocate the fan, so that as much of it is under positive pressure as possible, maybe locate the fine filter downstream.

I got the 600x600x10 filters for my heart pump from RS Online, and the housing fabricated as part of the plenum by Jensen.

That probably makes sense, but I'm very unlikely to relocate anything. Right now the fan is about half way along the ducting, just before it splits to go out to the rooms. There's no fine filter, there's just the one set of filters. Ducting, then filters, then ducting, then fan, then splitter, then diffusers pushing air into the room. It's very simple.

Interesting that RS have filters. If I can find a standard size and a box that fits them they might be a decent option. Hence this thread... looking for a filter box.

mattenz

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#3061118 10-Apr-2023 18:14

I think that HRV filters are a standard size: 300x300x100 (nominal). There are heaps of filter boxes out there with a similar form to the HRV one, though a slide-in filter is easier to work with. You could probably modify one to be pretty airtight with adhesive foam seals.

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