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    •  
      CommentAuthorBenpointer
    • CommentTimeJul 22nd 2011
     
    Hi we have a Vortice Prometeo 400 MVHR unit. It's been in about a year now and seems ok. We had the filter warning light come on and realised is was probably time to change the filters. Big shock - 2 x F5 filters =£70! (bet they cost less than a couple of quid each to make). So that's going to add £70 pa to my running costs.

    That got me thinking, why do I need filters? We are not hayfever sufferers, so not bothered about pollen (and in any case have the unit off and windows open during the summer). It's good to keep insects out but I could easily make some permanent mesh filters to achieve that? There'd be the added benefit of less air resistance in the system so less enregy running costs, i'd guess.

    Anyone think why this might be a bad idea?

    Thanks
    • CommentAuthorCWatters
    • CommentTimeJul 22nd 2011 edited
     
    I have a very simple MHRV system that just has filters made from a very porous foam about 50mm thick. They can be shaken out and washed which is a good job as they need to be done every 6 months.

    Edit: In my case the 6 month interval is based on experience with the filters blocking not a timer. After 8-10 months the input filter is covered in a layer of dust and dead bugs that pretty well blocks it. It's possible this is because we live in the countryside (so more bugs around than normal) but I doubt it's our filter because it's pretty coarse.
  1.  
    I have a Vent-Axia Sentinel Kinetic BH MVHR unit. I'm pretty sure that the "check filters" warning on it is driven by a count of operating hours rather than a direct measurement of filter performance. Other MVHR units may use the same approach. I just remove them, give them a gentle shake or very careful use of a vacuum cleaner and put them back. Haven't had to have the filters replaced yet, probably on an annual maintenance visit.

    The main job of the filters is to keep larger dust particles off of the fan blades and out of the ductwork. My guess is that not using approved filters might at the very least invalidate your warranty. There might be other considerations that might make it a bad idea.

    Most MVHR units have fairly basic specification filters. If you want to remove allergens such as pollen and mould spores or even small particulates you would probably require a separate filter on the input. I considered an option for a separate electrostatic filter (~ £600) on my system but have decided to try without one initially.
    • CommentAuthordocmartin
    • CommentTimeJul 23rd 2011 edited
     
    My unit came with G3 filters as standard. The specs state that these will remove 70 - 85% of 10uM particles and 15 - 35% of 3uM; the figures for F3 filters are over 98% & 70 -90%, repectively. Pollen is stated to range from 15 to 75uM in size.
    After nearly 2 years I can see a deposit of fine dust on the fan blades. Currently I am wondering whether to remove this manually with a fine brush as I cannot access with standard vacuum cleaner nozzles.
    When I installed the unit the installation guide advised the fitting of a pre-filter on the intake when a summer by-pass is fitted, although it has its own small filter. However the inlet filters are only trivially soiled compared with the exhaust side from the rooms. My machine came with a spare set of filters to change after 3 months to deal with the extra dust from the fitting and other re-furb works. Since then I have removed the filters to vacuum every 3 to 6 months swopping the intake and exhaust. After a year I discarded the blackest filter.
    • CommentAuthorGreenPaddy
    • CommentTimeJul 24th 2011
     
    Apart from keeping fans and ducts dust free, I assumed the main reason for the filters is to keep the heat exchanger clean. I suspect these would be quite sensitive to surface coverage, and so reduce the efficiency of heat recovery - the main point of having the MVHR unit.

    Vacuum off the surface debris (some filters even recommend gentle washing with warm water and a mild detergent). I supose they can withstand wetting, as they will see condensation in normal use. I guess that without re-checking the flow rates around the house, you won't know what the increase in differential pressure across the filters will be, so you won't know what the actual "blockage" level is. I have more experience with large industrial HEPA filters, and it is quite amazing how much the air flow can be restricted.

    Ignoring my comments above (as they don't actually answer the OP), you could do the vacuum cleaner thing, for a year or two, and see if you notice a deterioration in air quality around the house - ie. just begining to feel a bit stale in the morning (the air that is, not you personally):shamed:.

    Also, make sure you have an insect mesh on the fresh intake - and clean that out every few months.

    Hope something in that helps.

    GreenPaddy.
    •  
      CommentAuthornigel
    • CommentTimeNov 30th 2011
     
    I have a Prometeo HR400 and have just had to replace the filters.

    The filters they sell are a total rip off and they are only a bit of paper and as the OP says over £70 for a set.

    I have bought a roll of 25mm thick reticulated poly foam G4 filter and have cut this to size and fitted.
    This is washable and therefore resuable.

    Only downside is that I had to buy a large roll of the stuff so if there is anyone else out there that wants to do the same I would happy to provide some at cost - which would be less than £10 for enough to do two filters.
    • CommentAuthorCWatters
    • CommentTimeNov 30th 2011
     
    The filters in mine are quite coarse and easily cleaned by banging them on the wall as you would a rug. Now four years old.
  2.  
    Posted By: docmartinWhen I installed the unit the installation guide advised the fitting of a pre-filter on the intake when a summer by-pass is fitted, although it has its own small filter. However the inlet filters are only trivially soiled compared with the exhaust side from the rooms.


    Ha. You obviously live in the country....

    My extract filter has a layer of grey dust. The 'air from outside' filter is black with London filth after 3 months or so...
    •  
      CommentAuthordjh
    • CommentTimeJul 31st 2017
     
    Posted By: Simon Still
    Posted By: docmartinWhen I installed the unit the installation guide advised the fitting of a pre-filter on the intake when a summer by-pass is fitted, although it has its own small filter. However the inlet filters are only trivially soiled compared with the exhaust side from the rooms.


    Ha. You obviously live in the country....

    My extract filter has a layer of grey dust. The 'air from outside' filter is black with London filth after 3 months or so...

    No, it sounds like he lives in a pigsty inside a clean room! In the country, our 'air from outside' filter gets covered with brown stuff, presumably dust from ploughing, harvesting etc laced with fertiliser, insecticide, weedkiller. Oh and a good smattering of crane flies in season. Our 'air from inside' filter however remains fairly clean, as do the ducts.
    • CommentAuthorCerisy
    • CommentTimeAug 1st 2017
     
    With you djh - our filters need cleaning every month. Washed them many times, but had to buy new ones. Not too expensive from Titon, but I could have just bought the filter medium.

    I've also started cleaning the green mould off the cladding after four years since we started painting and fitting it. Bad on the north elevation, but pretty clean on the south?? We'll repaint it as the cladding and the house has settled and a few joints have opened up.

    This country living is wonderful for the peace and quiet - just hate the horse flies and the muck from the tractors, the fertiliser in the air and the cluster flies. Wouldn't change it though.
  3.  
    Posted By: CerisyWith you djh - our filters need cleaning every month. Washed them many times, but had to buy new ones. Not too expensive from Titon, but I could have just bought the filter medium.


    I washed out our heat exchanger yesterday (which is why i was came across this post). Instructions for the filters for my Vent-Axia said that the inlet/outlet filters could/should be vacuumed but *NOT WASHED* (in bold, explicit).
    •  
      CommentAuthordjh
    • CommentTimeAug 1st 2017
     
    My filters and presumably also Cerisy's are polyester fleece G3s and or foam G4s so quite safe to wash. I do have an F7 paper filter that I wouldn't dream of washing but we haven't used it apart from a quick test.

    Vacuuming gets the crane flies and some dirt off but washing gets far more dirt out.
  4.  
    I vacuumed my Vent Axia filters and they still seemed pretty dirty so I washed them which removed a lot more dirt.

    I hadn't read the manual, but it didn't appear to do them any harm. However, I don't know what I cannot see...
    • CommentAuthorsnyggapa
    • CommentTimeAug 1st 2017
     
    I wash my vent axia filters Sentinel Kinetic BH in hot soapy water quarterly then leave to dry in the sun or wind.

    My filters are some kind of fine plastic mesh on a wire frame, not paper. About 5 years in so far and still on the first set of filters. Probably due for a replacement if I could find somewhere sensible to buy them from!

    What I don't know is which way round to install them - they appear to be "keyed" as they have a metal hook on one end and a cloth tab on the other. It goes in either way round at my whim, no idea which is correct!
    •  
      CommentAuthordjh
    • CommentTimeAug 1st 2017
     
    I bought replacement filters and filter material from http://www.fairair.eu/en/
    •  
      CommentAuthordjh
    • CommentTimeAug 1st 2017
     
    Posted By: CerisyI've also started cleaning the green mould off the cladding after four years since we started painting and fitting it. Bad on the north elevation, but pretty clean on the south??

    We haven't been in that long and most of our house is rendered. We have a bit of cedar cladding which is well on the way to becoming grey but we haven't seen much in the way of green except in a couple of spots on a north-facing bit where some rain collects. We have a fence that runs north-south and is made from brown treated softwood and that has got a greenish tinge on the arris rails, which face east. But it's greenest underneath some trees, which I suspect may be connected.
  5.  
    Posted By: snyggapaWhat I don't know is which way round to install them - they appear to be "keyed" as they have a metal hook on one end and a cloth tab on the other. It goes in either way round at my whim, no idea which is correct!


    The Hook is just a spacer to stop them being pushed in too far/line them up with the opening on the heat exchanger. The tab goes at the front for you to pull them out with.

    I'm using FairAir filters - they don't have the hook so you just need to line them up at the front.
    • CommentAuthorborpin
    • CommentTimeAug 2nd 2017
     
    I have washed my filters before but have taken to pressure washing them - seems far more effective. No noticeable degradation. Bought some spares so I let them fully dry out. They do need cleaning more often than you expect.
  6.  
    Pressure washing? How?
    • CommentAuthorCerisy
    • CommentTimeAug 2nd 2017
     
    In reply to djh's comment, the east elevation of our house is 6 - 7m from a small road to our local farm. The other side of the lane is a reasonable sized maize field - so we have dust and fertiliser from the field and dust and all the other stuff from passing tractors. The contract guys in particular rush by, so I guess the mould comes from the "polluted" air. The north-east elevation gets lots of dust but not a lot of sunshine - best answer I can come up with!

    I'll repaint the worse parts with the Deluxe Weathershield with added poison to see if that helps. But, I always knew it was going to be an on-going task - low energy and low budget meant timber cladding was the only option and we don't like dull grey buildings!!
    •  
      CommentAuthordjh
    • CommentTimeAug 2nd 2017 edited
     
    Posted By: Cerisywe don't like dull grey buildings!!

    I was amazed we got away with it. Normally around here if it's part of a house then it must be painted white and if it's not part of a house then it must be painted black. It was partly as a reaction to that policy that we put untreated cedar in our application!

    To be fair, I don't think our building is dull. The walls are almost all a pale cream render (actually its very pale ochre (3%) but that doesn't convey the colour very well) and the roof is silver, so the bit of cedar cladding provides a bit of relief.
    • CommentAuthorborpin
    • CommentTimeAug 9th 2017
     
    Posted By: Simon StillPressure washing? How?
    Place on something clean (piece of plastic) outside, dirty side down (so forcing dirt out the way it came), place foot on corner and spray (not too close). Turn round so bit where foot is is at other end and repeat. Also used a rubber doormat with holes in it.

    Really does work a treat. Can't see how the filter itself could be damaged by this, but the are not the very fine ones.
  7.  
    If you have not got a foot to use can you use 0.3 of a metre?
    • CommentAuthorborpin
    • CommentTimeAug 10th 2017
     
    Posted By: Nick ParsonsIf you have not got a foot to use can you use 0.3 of a metre?
    :bigsmile::bigsmile::bigsmile:
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