G3 or G4 filter?

[cwr]

MVHR is another area that I'm starting on the steep learning curve of, and have been absorbing lots of great info from this forum and browsing MVHR and duct specs.

 

So, first newbie question, how important is the filter type supplied with MVHR units? Most I've seen are G3 or G4, some with F7 optional. From googling, G4 is a finer filter, but is likely to be more restrictive than G3.

 

But in practical terms which is better, or does it make little difference?

 

 

[Dreadnaught]

G4 is the standard dust filter. F7 is the upgrade option and a much finer filter, and so captures more fine particles such as pollen.

 

An MVHR has two built-in filters to prevent the heat exchanger becoming clogged with dust. One prior to the heat exchanger on the fresh-air intake side. And one prior to the heat exchanger on the stale-air extract side.

 

Personally, for my forthcoming build, my intention is use an F7 on the intake side and and G4 on the extract side.

 

But to protect the F7 (which are quite pricey to buy) I also intend to mount a filter box outside the MVHR within the intake ducting run from the outside. In this filter box I will place a second filter, a G3 or maybe G4 pre-filter to catch some of the particles before the clog-up the F7. (G3 might be best as it will resist the airflow less than will a G4).

 

 

[RandAbuild]

We just bought a new supply of filters for our Vent Axia. They were G4 rather than G3 ones. I found this during my searches:

 

[cwr]

So it's ok to replace the filters with a different type? In which case I'll not be concerned if a machine is supplied with G3's. Though presumably each machine and installation may be a bit different...

[PeterW]

I’m upgrading G3 to M5 as you can buy the media fairly cheaply as it’s used for spray booths so you can buy by the roll. It also doesn’t need to be framed the same way as F7 and can usually fit into standard hold down frames. 
 

@Jeremy Harris who did you use ..??

[Ed Davies]

Do the higher grades of filter cause significantly more resistance to the airflow?

[PeterW]

13 minutes ago, Ed Davies said:

Do the higher grades of filter cause significantly more resistance to the airflow?

Broadly the numbers for 20mm filter I’ve seen are a pressure drop of 40/80/120Pa for G3/M5/F7 respectively 

[Jeremy Harris]

3 hours ago, PeterW said:

I’m upgrading G3 to M5 as you can buy the media fairly cheaply as it’s used for spray booths so you can buy by the roll. It also doesn’t need to be framed the same way as F7 and can usually fit into standard hold down frames. 
 

@Jeremy Harris who did you use ..??

 

 

I've been getting custom made filters from Jasun Envirocare.  They make filters and frames to any size you like, and were a lot cheaper than buying from the UK Genvex supplier. 

[RandAbuild]

There was little difference between the G3 and G4 ones we bought - the G4 were slightly thicker and felt more substantial. Doen't seem to have impacted on the flow rate