Anyone know which brands can take a MERV 18 filter?

[CalvinHobbes]

After talking to family members (chemists) I would love to use a decent filter on the ventilation for our new house. Any recommendations?

[Temp]

How do people stop fine filters getting blocked quickly? We live in a rural area but half a mile from a busy dual carriage way. Our MVHR system has a very coarse filter that really only stops insects - but even that gets blocked in 2-3 months. By coarse I mean something like this..

 

[markocosic]

Use a separate filter box on the inlet then pick your own filters 

 

https://www.ductstore.co.uk/acatalog/Panel-Filters.html

[Simplysimon]

i have been meaning to ask about external filters. the outer casing is one of these and the holes seem quite large, would fixing some stainless insect mesh inside be useful to cut down the amount of larger debris which could be taken in?

[JohnMo]

I have one these, you would dramatically decrease the open area of the intake grill, the resistance at the intake could jump up.  To compensate your fan speed would have to increase - more noise etc.

 

The ductstore ones in the link have a much larger surface area, so get around this to some extent, but not completely.

[Simplysimon]

23 minutes ago, JohnMo said:

I have one these,

so is there a course mesh filter inside or is it just straight in to unit?

[JohnMo]

No it's just the punched holes in the casing that you see on the link earlier.  Think the holes are 4 or 5mm across

[markocosic]

For what it's worth, my as yet unimplemented plan for this involves a fish box as the filter housing:

 

https://www.jbpackaging.co.uk/polystyrene-boxes.html

https://www.thermocateringbox.com/171-thermobox-epp

 

To suit a common (24x12", 24x18", or 24x24") panel filter:

https://www.airclean.co.uk/panel-filters/pleated-panel-filters/

https://www.airclean.co.uk/panel-filters/minicell-high-performance-panel-filters/

 

Though perhaps a bag filter would be better:

https://www.airclean.co.uk/bag-filters/general-purpose-bag-filters/

https://www.airclean.co.uk/bag-filters/high-performance-bag-filters/

 

The EPP boxes are essentially the same thing as many MVHR units are made from. Cut by knife. Glue in inlet / exit ducts. Done.

 

 

I'm also toying with adding an automotive radiator or two as a duct heater / cooler. They're of similar size to the filters:

https://www.ebay.co.uk/itm/152455361709

 

 

It's also possible to make a house dust remover using a few of those panel filters, sticky tape, and a couple of small aubergines:

https://www.energyvanguard.com/blog/diy-box-fan-air-cleaner-update/

[markocosic]

Filter grilles also an option:

 

https://www.energyvanguard.com/blog/the-advantages-of-filter-grilles-for-your-hvac-system/

 

Any idea where to buy these in the UK?

[SteamyTea]

You could use baffles, instead of filters, for the incoming air.

Not hard to make and can be self cleaning.

Basically just a box with sticks in them to increase the path distance the air takes.

[MikeSharp01]

On 02/06/2022 at 08:09, SteamyTea said:

Not hard to make and can be self cleaning.

How can they self clean, the muck will pass on into the rest of the system won't it - have I missed something?

[SteamyTea]

Just now, MikeSharp01 said:

How can they self clean, the muck will pass on into the rest of the system won't it - have I missed something

You missed something.

 

Basically there are rods that deflect and accelerates the air, but the particles, which have more momentum, keep on going straight and hit the rods and become stationary, then gravity pulls them downwards into an entrapment area (a bucket).  As the rods can move slightly, there is a shaking effect that can enhance the removal of particles.

The ,number, diameter and density of the rods is what governs the size of the particles removed for any given airflow.

 

Been 25 years since I worked in the air filtration business, but apart from cyclone filters, which we did not make, the principles are the same, Actually cyclone filters are the same principle.  You either make a hole so small that particles cannot physically get through, or you use the different densities, acceleration and gravity (remember the true definition of acceleration, and change in speed AND/OR a change in direction, why the moon is accelerating around the Earth, and the Earth-Moon system around the Sun).

There are oil bath/other solvent filters that, once the particles are in the working fluid, can then be filtered out traditionally.

And electro-static filters that, depending on the surface charge of the particles, can be quite good, but not as good as some manufactures claim as they can repel some undesirable particles and increase the overall level of that particle in a room.

 

All filtration system need regular maintenance i.e. cleaning.

[MikeSharp01]

1 hour ago, SteamyTea said:

Basically there are rods that deflect and accelerates the air, but the particles, which have more momentum, keep on going straight and hit the rods and become stationary, then gravity pulls them downwards into an entrapment area (a bucket).  As the rods can move slightly, there is a shaking effect that can enhance the removal of particles.

The ,number, diameter and density of the rods is what governs the size of the particles removed for any given airflow.

Clever - every day is a school day. What shape are the rods, surely not just round, and what is the density (or method for working it out)?

[SteamyTea]

10 minutes ago, MikeSharp01 said:

Clever - every day is a school day. What shape are the rods, surely not just round, and what is the density (or method for working it out)?

Usually round.

Not sure of the formula used, I was the production engineer, the 'lads in the design office' used Q, A, PL a lot.

Think it was basic aerodynamics. All I remember is they used to use my company car to get to Silverstone where the Dyno was, and use all my fuel. And break my favourite tapes.

 

[MikeSharp01]

37 minutes ago, SteamyTea said:

Think it was basic aerodynamics.

So the air round the rods has to be going slow enough not to pick up the particles / accelerate them so much that they miss the bucket and still get the total air flow needed through.

[SteamyTea]

4 minutes ago, MikeSharp01 said:

So the air round the rods has to be going slow enough not to pick up the particles / accelerate them so much that they miss the bucket and still get the total air flow needed through.

Kind off.

Imagine a wall facing the wind on a rainy day. The rain is the particles you wish to remove.

Wind and rain hit the wall, rain sticks and drops down in, the air, finds a path out the top and sides.

 

[Temp]

My input filter actually points downwards. Moths and flys get sucked up and stuck to the underside blocking it.