So how often should I change my MHRV filters ?

fclauson

Been in house 5 plus months and did a filter replacement today

inbound fly filter (on duct just in from outside wall vent) was defiantly doing its job
supply filter was not too bad
extract filter manly blocked with "fluff" (see my other posting about temp differences when filters are blocked)

sas

This is interesting for me.

My extract is always the cleanest. It will have dust on it, no fluff as you mentioned.

However my supply is always the most concerning. I'm using the F7 filters and they always go in white and come out very dark grey. No visible dirt on it, just it's very much changed colour. This will happen in as short as 3 months. I'm still using them for 6 though because of the cost associated with them.

I do have a fly filter also and it too goes black, rather than the brownish colour of yours.

fclauson

sas wrote: »

This is interesting for me.

My extract is always the cleanest. It will have dust on it, no fluff as you mentioned.

we had curtains fitted plus there was probably a lot of "builders dust" around.
We tumble dry and although we do have a "fluff" filter on the extract from the utility I only installed this recently.

I cheated here - I have a "bounce" fabric sheep normally used in the tumble drier as a filter on this extract - and replace it ever month or two - it gets rid of the first set of fluff before it gets into the system. Its cheap and seems very effective. I only installed this recently so hope that we will have less trouble next time

However my supply is always the most concerning. I'm using the F7 filters and they always go in white and come out very dark grey. No visible dirt on it, just it's very much changed colour. This will happen in as short as 3 months. I'm still using them for 6 though because of the cost associated with them.

I am just building a monitoring device which will measure pressure drop across the filters - this will give an indication of filter "blockedness" -hope to have this up and running soon.

I do have a fly filter also and it too goes black, rather than the brownish colour of yours.

We live next to farm land - and its a very clay rich soil - in the dry weather this can be very dusty. Specifically during the harrowing/planting season.

fclauson

For all those living near farmers who are cutting corn - you might want to turn off you mhrv when they are immediately adjacent to save all the corn dust blocking your filters

runawaybishop

sas wrote: »

However my supply is always the most concerning. I'm using the F7 filters and they always go in white and come out very dark grey. No visible dirt on it, just it's very much changed colour. This will happen in as short as 3 months. I'm still using them for 6 though because of the cost associated with them.

Maybe you can buy a roll of synthetic filter in whatever grade you require and cut it to size, its significantly cheaper.

cuculainn

runawaybishop wrote: »

Maybe you can buy a roll of synthetic filter in whatever grade you require and cut it to size, its significantly cheaper.

before I go and google this, is it possible to get the filter in rolls?

runawaybishop

cuculainn wrote: »

before I go and google this, is it possible to get the filter in rolls?

Yup, i picked some up myself from ebay. You may, depending on your system, need to pick up some mesh to make a frame to support the filter. I used some of the mesh off 2 large disposable bbqs. I think i spent maybe 25 euro to replace both filters - 8 euro for mesh, 15 for filter roll and 2 euro for plasters after i ripped my hand on the mesh

cuculainn

runawaybishop wrote: »

Yup, i picked some up myself from ebay.

Would you have a link? what sort of HRV system have you? Thanks

runawaybishop

cuculainn wrote: »

Would you have a link? what sort of HRV system have you? Thanks

Vortice prometeo hr400, it uses 2 pleated f5 15x7 inch filters and I couldn't find anywhere that did 3rd party replacements. The filters from vortice would be about 70 euro each, with shipping i think.

edit: gonna remove the links as i think they infract the charter and pm you instead.

cuculainn

runawaybishop wrote: »

Vortice prometeo hr400, it uses 2 pleated f5 15x7 inch filters and I couldn't find anywhere that did 3rd party replacements. The filters from vortice would be about 70 euro each, with shipping i think.

edit: gonna remove the links as i think they infract the charter and pm you instead.

Do you know does the roll have a similar performance level as the pleated filters?

Seriously expensive price for paper filters.....

runawaybishop

cuculainn wrote: »

Do you know does the roll have a similar performance level as the pleated filters?

Seriously expensive price for paper filters.....

The filters will be to a certain standard grade. G is coarse and goes from 1-4, F is fine and goes from 5 to 9, with f7 stopping pollen (hepa is higher again). Just pick up the grade you require.

Filter classes here

Paper filters are supposed to be cheap, but that's not my experience. The pleated ones are able to hold more particles before you need to change/clean them. You cant wash pleated paper though, unlike synthetic sheets.

fclauson

As mentioned previously I was looking to build an electronic differential pressure monitor for my two HRVs - having spent €40 on bits an pieces I failed to get this to work - but then the penny dropped - use a manometer - http://en.wikipedia.org/wiki/Manometer

not to single out any company which makes these but there is good info https://www.dwyer-inst.com/Products/AirFilterIntroduction.cfm

specifically Series 250-AF Solid Plastic Gages

You can achieve the same with

• a length of plastic tube (aquarium or similar )
• two short pieces of copper brake pipe or similar drilled and the end closed off to for ma static vent (see http://www.dwyer-inst.com/Products/AirVelocityIntroduction.cfm about what a static vent in a duct needs be
• a fluid (I am going to use two stroke oil - its red, won't vaporise easily, and has a "good miscues")

More info on manometers here http://www.instrumentationtoday.com/manometer/2011/09/

What one is aiming to achieve is not an exact measurement - but a limit of degradation of the filter performance. e.g. if when new there is 1 inch of difference in the manometer and say after 6 months there is 2 inches.

A weekly/fortnightly check on this will give you warning on how things are doing

I will also use my temp difference as discussed in http://www.boards.ie/vbulletin/showthread.php?p=83836597

fclauson

So I have no built the manometer - very simple - but here are the results

I know we are only talking about 3mm of difference - but that's the results so far

The HRV was running on Boost for this test

I need to find some better oil to use with a low density and low viscosity


EDIT : added a PDF with the 3 pics next to each other

fclauson

re did my maths - I suppose the unit does only have a resistance of say 20pa which is 2mm of water - hard to measure

that's why my manometer hardly moves - but its and interesting exercise - we have to come up with something like this to detect when the filters need changing

fclauson

re-bumping this thread - as its very important one and no one has given any feedback on how this problem can be addressed

as we install more HRV units the issue of filter maintenance will become more important

runawaybishop

Buying a roll of synthetic filter material and making your own replacements seems viable to me.

fclauson

Thanks - these types of filters have less surface area and less filtering capability

It also does not get around the issue of when to change

runawaybishop

fclauson wrote: »

Thanks - these types of filters have less surface area and less filtering capability

It also does not get around the issue of when to change

That just means you need to change them more often and given that they will wash clean and cost a fraction of the price that's not such an issue really.

The frequency of changing depends on the conditions of the environment though. I had to clean/change mine every 2/3 months (there's a sensor to detect when the filters need changing) initially due to the dust from the build.

fclauson

Interested in the sensor - what unit do you have ?

runawaybishop

fclauson wrote: »

Interested in the sensor - what unit do you have ?

Vortice prometeo hr400

fclauson

Just read the manual for this - do you think the filter replacement has a detector or is it time based ?

runawaybishop

fclauson wrote: »

Just read the manual for this - do you think the filter replacement has a detector or is it time based ?

The manual that comes with it has more data in it than i can find online - if i remember correctly you will see one of 2 indicators, a "filters are completely saturated and must be changed" indicator and a "filters are getting dirty" indicator. If you do not change/clean them (i.e if you just turn the unit off and on again to trip the reset) the indicators will not go away.

fclauson

Wonder how the do - by diff pressure or by current draw on the fan

fclauson

fclauson wrote: »

we had curtains fitted plus there was probably a lot of "builders dust" around.
We tumble dry and although we do have a "fluff" filter on the extract from the utility I only installed this recently.

I cheated here - I have a "bounce" fabric sheep normally used in the tumble drier as a filter on this extract - and replace it ever month or two - it gets rid of the first set of fluff before it gets into the system. Its cheap and seems very effective. I only installed this recently so hope that we will have less trouble next time

I am just building a monitoring device which will measure pressure drop across the filters - this will give an indication of filter "blockedness" -hope to have this up and running soon.



We live next to farm land - and its a very clay rich soil - in the dry weather this can be very dusty. Specifically during the harrowing/planting season.

quick photo of the "bounce" filter after two months in situ

fclauson

So last year I reported a sudden drop in temp across the MHRV around this time of year

I have now identified the issue

with an F7 filter I think that smoke from candles (those nice smelly xmas ones) is enough the block the filter

the filter temp over the past week has just moved from a delta of about 1 to around 5

remove the filter and the temps recover

So - does that mean a house with HRV needs to be devoid of candles ?

mfceiling

fclauson wrote: »

So last year I reported a sudden drop in temp across the MHRV around this time of year

I have now identified the issue

with an F7 filter I think that smoke from candles (those nice smelly xmas ones) is enough the block the filter

the filter temp over the past week has just moved from a delta of about 1 to around 5

remove the filter and the temps recover

So - does that mean a house with HRV needs to be devoid of candles ?

Looks like we'll never see a passive church!!:D

gctest50

fclauson wrote: »

re did my maths - I suppose the unit does only have a resistance of say 20pa which is 2mm of water - hard to measure

that's why my manometer hardly moves - but its and interesting exercise - we have to come up with something like this to detect when the filters need changing

An inclined manometer works better for tiny diffs

AstraMonti

I just cleaned my 6month old filters today. They were disgusting, there must have been like a trillion dead bugs in there, the hoover could only do so little so I 've just ordered a new set of filters. I think I need to clean them every 2 months and change them every 6.

So a friendly reminder to all, remember to check your filters, it's vital for your well being.

fclauson

AstraMonti wrote: »

I just cleaned my 6month old filters today. They were disgusting, there must have been like a trillion dead bugs in there, the hoover could only do so little so I 've just ordered a new set of filters. I think I need to clean them every 2 months and change them every 6.

So a friendly reminder to all, remember to check your filters, it's vital for your well being.

Do you have an external filter as well as the ones in the unit. Well worth it - catches the big stuff and stop the duct getting too dirty between the outside and the unit

AstraMonti

Unfortunately I don't have an external filter, just the two in the unit, but it's a good idea, I ll ask the installer if it's possible to put one.

fclauson

Well worth doing - will post pictures - farmer currently harvesting next door and all that Chaff is ending up in the external filter not the internal one