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Ventilation: MVHR Without Need For Condensate Drain??? Vents 100 P Mini

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61 to 88 of 88

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    • CommentAuthorEd Davies
    • CommentTimeDec 20th 2015
     
    Bungee was what I was thinking. But I'd back them up with some slack wire or chain, for a decade hence when I've forgotten to look at the bungees to see if they're rotting for 3 or 4 years.

    Or push the threaded rod up through the timber (decent clearance hole) and put the top on a block of rubber (with a big washer). Then if the rubber rots the worst that'll happen is that the rod and washer subsides onto the timber.
    • CommentAuthorborpin
    • CommentTimeDec 20th 2015
     
    I used some silicon pipe like the type sold for aquariums. Got it off ebay IIRC. It has a slightly tortuous route so did it in the flexible pipe until the run became sensible then into the small 'overflow' pipe (siliconed up). This drops through a tundish then into a waste pipe with a std u bend in it.

    Coincidently, I was changing the filers yesterday (about a 4 monthly job) and noticed a buildup of water in the bottom of my Helios unit. Pulling the silicon pipe out, water flowed out of the unit so I simply blew through the silicon pipe and it all works fine now. I've noticed the amount of condensation is highly variable (no surprise) but I suspect it may sometimes stagnate which might be what blocked the pipe.

    I also found this which may be of use when fitting. http://www.mcalpineplumbing.com/wc-overflow-kit-with-tun-dish.html
    •  
      CommentAuthordjh
    • CommentTimeDec 21st 2015
     
    My MVHR instructions show to use a dip pipe into a deep trap rather than a tundish, presumably to keep the condensate drain isolated from interior air, which I suppose is to do with airtightness rather than hygiene. But since I used a dry trap instead, who knows ...
    • CommentAuthoratomicbisf
    • CommentTimeDec 22nd 2015
     
    Thanks for all the suggestions. Should I be concerned that it hasn't discharged any condensate yet or is that to be expected with the mild weather? So far I've just used a flexible aquarium hose to a container so can see that nothing has come out yet.

    Ed
    •  
      CommentAuthordjh
    • CommentTimeDec 22nd 2015
     
    Posted By: atomicbisfShould I be concerned that it hasn't discharged any condensate yet

    That's why I used a dry trap - I don't expect it to collect enough condensate all the time to keep a normal wet trap full.
    • CommentAuthorborpin
    • CommentTimeDec 24th 2015
     
    Posted By: djhMy MVHR instructions show to use a dip pipe into a deep trap rather than a tundish, presumably to keep the condensate drain isolated from interior air, which I suppose is to do with airtightness rather than hygiene. But since I used a dry trap instead, who knows ...
    Dry Trap? Never heard of such a thing.

    Interesting thoughts on air tightness; MVHR aren't (by design) :bigsmile:
    • CommentAuthorEd Davies
    • CommentTimeDec 24th 2015
     
    Posted By: borpinDry Trap? Never heard of such a thing.
    HepVO thing, as discussed on this thread.
  8.  
    The recent high winds and heavy rain have proved my exhaust vent bodging wasn't really good enough (should have looked at it from the outside too and it would have been obvious!), so can anyone think of a better solution?

    I'd attached it to what used to be a soil vent pipe that had been cut off in the loft when the part below was removed for bathroom renovation. Unfortunately I didn't notice that the whole process of insulating and boarding the loft and attaching the duct to it has raised it up so that rain can get under the flashing.

    I could get up there, lift it out, cut it down a bit, take off the wire cage from the top and replace it with a mushroom type cap and then refit, but seems like too much effort for what would be another bodge. The pipe is asbestos so ideally I don't want to cut it, but could with a mask, with some water etc, also it's too small (about 95 mm internal diameter).

    There's room through that flashing plate for a larger pipe, but as the whole thing is non-traditional I'm not even sure what you'd call it to look for a replacement.

    Ed
      SAM_1971.jpg
    •  
      CommentAuthordjh
    • CommentTimeJan 5th 2016
     
    googling for mvhr external roof terminal showed me this:

    http://www.polypipe.com/ventilation/products/domus-rigid-duct-systems/-125mm/external-roof-duct-terminals

    I'm sure there are other similar products.
    • CommentAuthoratomicbisf
    • CommentTimeJan 5th 2016 edited
     
    Posted By: djhgoogling for mvhr external roof terminal showed me this:

    http://www.polypipe.com/ventilation/products/domus-rigid-duct-systems/-125mm/external-roof-duct-terminals" rel="nofollow" >http://www.polypipe.com/ventilation/products/domus-rigid-duct-systems/-125mm/external-roof-duct-terminals

    I'm sure there are other similar products.


    Thanks, I'm not sure the flat plate will work well with the existing weather apron (think that's the technical term) - it's the galvanised corrugated thing that the pipe pokes through (at a slightly jaunty angle at the moment!)

    Does it have to be specially for heat recovery or would one of the mushroom type be suitable? I was thinking one like this - http://www.amazon.co.uk/Pack-125mm-Plastic-Vent-Brown/dp/B00BJLFKFE" > http://www.amazon.co.uk/Pack-125mm-Plastic-Vent-Brown/dp/B00BJLFKFE - might work if I lifted the old asbestos pipe out, inserted a new 125mm pipe and capped it with the mushroom cowl, if the cowl was fitted low enough to prevent rain getting into the weather apron.

    Ed
    •  
      CommentAuthordjh
    • CommentTimeJan 5th 2016
     
    I don't think there's anything special about MVHR terminals as long as it keeps the rain out. I suppose you don't want anything that is going to grow stuff, it's not like a chimney that might burn off or poison any growth. But I think most metal or plastic cowls should be OK.
  12.  
    It seems what I'm looking for isn't (easily) available - a cheap and simple 125mm mushroom type cap. There is this thing that may work, but the "hat" part may be too high to keep rain out of the weather apron opening if the wind is blowing: http://www.amazon.co.uk/diameter-chinamans-chimney-galvanised-ducting/dp/B00BSWRY7Q/ref=cm_cr_pr_product_top?ie=UTF8

    Not keen to spend too much as I'm planning on reroofing and probably it will be better to move the vents off the roof surface to avoid any penetrations.
    •  
      CommentAuthordjh
    • CommentTimeJan 8th 2016
     
    Posted By: atomicbisfthe "hat" part may be too high to keep rain out

    If you bent each of the 'straps' inwards, that would reduce the height of the opening and shouldn't weaken the cowl or obstruct the flow too much, neither would it look too naff?
    • CommentAuthoratomicbisf
    • CommentTimeJan 8th 2016 edited
     
    <blockquote><cite>Posted By: djh</cite><blockquote><cite>Posted By: atomicbisf</cite>the "hat" part may be too high to keep rain out</blockquote>
    If you bent each of the 'straps' inwards, that would reduce the height of the opening and shouldn't weaken the cowl or obstruct the flow too much, neither would it look too naff?</blockquote>

    Thanks, that's a pretty good idea as the 125mm "mushroom" caps only seem to be available in Australia!
  15.  
    Actually I don't think it will be necessary to modify that cowl, as I can simply mount it lower and partly inside the existing weather apron. The weather apron has an exit about 150mm in diameter so if I mount the cowl partly inside it, the hat bit should keep the rain out.

    The unit is producing a fair amount of condensate now, about two litres per week. One thing I found is that the seals of the base of the unit are not watertight, so if it is not sufficiently level it will leak.

    Ed
  16.  
    If you remember I guessed that would be the case on mine so I piped a thick bead of silicone around perimeter of the area I guessed condensate would fall and then laid cling film over the the whole base then closed it. Wait 20 mins and open and check all OK, when fully cured, peel of cling film - this gives you a little more flex with level but also prevents water going anywhere that might cause a problem in the long run.
    • CommentAuthoratomicbisf
    • CommentTimeJan 10th 2016 edited
     
    Posted By: GotanewlifeIf you remember I guessed that would be the case on mine so I piped a thick bead of silicone around perimeter of the area I guessed condensate would fall and then laid cling film over the the whole base then closed it. Wait 20 mins and open and check all OK, when fully cured, peel of cling film - this gives you a little more flex with level but also prevents water going anywhere that might cause a problem in the long run.


    Sorry, I don't think I took in that bit before as the way the unit opens at the bottom isn't really intuitive until you see it. Mine also has two removable metal covers to access the filters which leak if it isn't level, I'm not sure if yours has those.

    Ed
    • CommentAuthoratomicbisf
    • CommentTimeMar 19th 2016
     
    Hmm well the cowl I ordered online never arrived so I'm thinking of a different tack as originally I thought it would be a cheap and easy semi-temporary solution. But as it seems quite a palaver and expense a for partial solution (doesn't give a proper inlet, just an exhaust), it'll be better to do it properly with a pair of soffit vents.

    I've been reading though on here that the intake and exhaust should not be on the same level, but soffits are usually horizontal (they are here), so how does that work?

    A little update: I've been setting the unit to high while showering and for a short time after (in the evening), then setting it to low overnight and off during the day if the heating is off. I've also been using a dessicant dehumidifier while and immediately after showering and when drying laundry indoors when it's too wet to hang outdoors. So far none of the mould I cleaned off the windows and surrounds just before the unit went in has reappeared.

    Ed
  19.  
    Posted By: atomicbisfSo far none of the mould I cleaned off the windows and surrounds just before the unit went in has reappeared.
    Modern magic isn't it! I would leave it on low during the day if I were you (this is unquestionably std practice) - when it is on (is 24/7!) but in any event should be unrelated to when the heating is on.

    Ref external vent and intake - all that is needed is to have 2m between them - I suppose you could argue that the vent shouldn't be below the intake but apart from that it doesn't matter. Also I, and a couple of others on here, have had to fit them a little under 2m apart, to no ill effect.
    • CommentAuthoratomicbisf
    • CommentTimeMar 20th 2016
     
    Thanks! At first I had it on 24/7 (high while and after showering, low the rest of the time) but then I thought that probably wasn't necessary and haven't noticed any difference. I thought during the day while we're out there will be very little evaporation inside (no showering, cooking, breathing). If I'm at home I'll normally be going in and out with doors or the loft hatch open anyway.

    That's good about the soffit vents because there's up to 7m horizontal distance available between them but none vertical.
    • CommentAuthorEd Davies
    • CommentTimeMar 20th 2016
     
    Posted By: atomicbisfI thought during the day while we're out there will be very little evaporation inside (no showering, cooking, breathing).
    Still, all the time the house is at low RH you're drying out any hygroscopic materials available (e.g., walls if they're not sealed with vapour-closed “paper”) leaving extra water buffering capacity for later.
    •  
      CommentAuthordjh
    • CommentTimeMar 20th 2016
     
    Posted By: atomicbisfThat's good about the soffit vents because there's up to 7m horizontal distance available between them but none vertical.

    You don't want them too widely separated either, because then they might experience different external pressures as the wind blows and make life hard for the unit. So I'd aim for the 2 m and space them a bit more if there's some obstruction that makes the exact separation difficult.

    It might be interesting to get a cheap humidity meter if you haven't got one, and see if it measures any difference between leaving the unit on low 24x7 versus turning it off when you're not there.
    • CommentAuthoratomicbisf
    • CommentTimeMar 20th 2016 edited
     
    Posted By: djh
    Posted By: atomicbisfThat's good about the soffit vents because there's up to 7m horizontal distance available between them but none vertical.

    You don't want them too widely separated either, because then they might experience different external pressures as the wind blows and make life hard for the unit. So I'd aim for the 2 m and space them a bit more if there's some obstruction that makes the exact separation difficult.

    It might be interesting to get a cheap humidity meter if you haven't got one, and see if it measures any difference between leaving the unit on low 24x7 versus turning it off when you're not there.


    Hi I don't have a humidity meter as such, but the dehumidifier has one built in. It doesn't indicate when it is actually dehumidifying or when the fan is just running, but you can feel the air coming out is warm and I assume only then is it dehumidifying. It will seldom if ever do this during the day if there's no washing, cooking etc going on.

    Ed
  24.  
    So long as they face the same way differential pressures are v unlikely.

    So many factors affect what a humidity meter will say that data from this alone will not allow any useful analysis, you'll need internal RH, Internal Temp, External RH, External temp, MVHR on and off for lots of comparable data days and some decent analysis before you can be sure you were not being led up the garden path.
    • CommentAuthoratomicbisf
    • CommentTimeMar 20th 2016
     
    The way I see it, I don't need to use the MVHR very 'scientifically' as one might in a very well sealed home. There's a lot of air leakage here which I'm gradually working through, which is enough to keep the humidity and general air quality OK unless showering, cooking etc (also condensation on bedroom window which I guess is from breathing), so it seems to work fine leaving it on low overnight and then switching it off during the day.
    • CommentAuthoratomicbisf
    • CommentTimeMar 20th 2016
     
    Do I need to avoid placing a soffit vent above an upstairs window? The soffit is about 200 mm above the tops of the windows.

    Ed
    •  
      CommentAuthordjh
    • CommentTimeMar 21st 2016
     
    Posted By: atomicbisfDo I need to avoid placing a soffit vent above an upstairs window? The soffit is about 200 mm above the tops of the windows.

    Ideally, yes, especially if the window is likely to be opened. You don't want to suck in 'fresh' from inside the house, or equally to blow out stale air only to have it blow in through a window.

    If you followed the spacings for siting a boiler flue, that would be more than sufficient.
    •  
      CommentAuthordjh
    • CommentTimeMar 21st 2016
     
    Posted By: GotanewlifeSo long as they face the same way differential pressures are v unlikely.

    Pressures can vary quite a lot near corners, so what you say may well be true for vents in the middle of a wall.

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