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Thread: Aircon : Whats wrong with this project ?

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    Gold Member daveob's Avatar
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    Aircon : Whats wrong with this project ?

    I need to bounce this idea off a few brains.

    We live close to the coast (900 meters) and typical Durban area, very humid.

    In fact, it's so humid that we need to keep buying de-humidity bags for the cupboards - and we're losing the battle. Mould ( and mildrew on the fabrics ) is a problem, and it even grows on the ceilings - and we have the windows open all day long with good air flow. Not to mention the associated health risks, the typical coastal 'miff' smell that lingers is not good.

    So having done a bit of research, I discover that the mould likes cooler areas, with relative humidity (RH) above 50%. This makes sense to me, and can verify this with the cooler winter months being the worst. Our average RH over the last few months is almost always well above 60%.

    So logic tells me that the solution is to de-humidify the air, or raise the air temperature ( which will lower the RH ).

    So I'm presented with a few options :

    option 1. continue with the de-humidity bags for the cupboards ( costing about R275 per month ), but this doesn't solve the problem with the ceilings, walls, health, etc.

    option 2. install air-cons in the house and keep the windows closed, and circulate the air from the room through the cupboards. Very costly solution, and this would mean running the aircon just to cool the room, purely to make the air-con de-humidify the air - not a great idea in winter. Also very high initial cost for multiple air-con units, and running costs.

    option 3. this is a DIY project and I would be interested to hear any pro's or con's you can think of :

    I want to install a de-humidifer / cooling / heating (DCH) unit in the garage. The floor of the garage is level with the top of the house walls, so piping over the 2 meter distance to the house should be simple.

    The DCH will be connected to 2 pipes - inlet and outlet. The pipes to/from the house will be the same diameter as the round gutter down pipes, so assembly in the ceiling should be easy - PVC weld and all standard fittings.

    The inlet & outlet from the DCH will go via the piping to each room in the house. At the end of each branch that leads to each room, will be a butterfly valve in the pipe.

    A valve will also be in the return pipe from the room to the DCH inlet. My logic on this, is using a microcontroller (MC) ( which I already have ) connected to a humidity and temperature sensor in each room. The MC will then detect the temp & RH in each room, and open the in/out valves for that specific room as required. The MC can also be programmed to automatically turn on / off the DCH unit, so it only runs when required. Also, the MC knows when the rooms windows are open ( via magnetic window contacts for the alarm system ) and would bypass that room if they are opened.

    In addition, the MC also registers temperature for each room. So with this info, I can set a 'preferred temperature' (PT) for each room. If the temp is below the PT, then the DCH unit will re-direct the cooled and de-humidified air, past the warm cooling fins of the DCH unit, which will then send warmer dry air back to the room. If the temp is above the PT, then the DCH cools and de-humidifies, and returns the cooler dry air to the room.

    A blower fan will be connected to the inlet and outlet pipes to push / suck air in-out the inlet / outlet pipes.

    Does anyone see any potential problems with this design ?
    Watching the ships passing by.

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    Sounds like a lot of work... My advice is to sketch it, have a visual representation of your house and the system. Work closely with an engineer and/or an architect to see where the system can go wrong and how you can further simplify the process. If this thing works well for your house and if you can find a way to make it simple and cost effective then you are looking at a golden egg. I say try the DIY solution (working closely with a seasoned pro of course, unless you are one yourself) it seems that it will be a great project. That's if you have money to play with.

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    Diamond Member AndyD's Avatar
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    I agree it's a bold plan and could get quite complex. Maybe start smaller with a similar unit and arrangement just for the kitchen cupboards. Once you have it up and running you could scale it up and make one for the rest of the house.

    A few immediate thoughts;
    If mould is you main motivation maybe look at other ways of skinning that particular cat. Possibly look at some kind of chemical treatment that might come in one of those timed atomiser set-ups....similar to the flyspray thingies you can buy at Pick@Pay.

    Another consideration might be a small ioniser you could mount in the cupboards. These thingsare widley available andcheap enough nowadays to be found in pub toilets. I'm not sure how effective Oł is as a mould inhibitor but it's widely used for deodourising and sterilizing and in high prolonged concentrations it's toxic to humans as well. Maybe Dave has better info on these ideas, I think Rentokil and other pest companies supply the ionisers.
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    Gold Member daveob's Avatar
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    Thanks for the replies.

    Apart from the de-humidifying to combat mould, the other benefits would be better health, and year round climate control - air filtering, heating / cooling as required, relief from mid summer humidity, etc.
    Watching the ships passing by.

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    Diamond Member wynn's Avatar
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    In El the humidity is not that high all the time.
    I have found that ceiling fans are a great way to cool you down, three settings for differing requirements, more fans in larger areas.
    As far as the cupboards go perhaps sealing them from the atmosphere and using something like a light bulb to circulate warm dry air (like a biltong dryer) will keep the humidity therefore mould inside the cupboards down?
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    Site Caretaker Dave A's Avatar
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    Quote Originally Posted by wynn View Post
    s far as the cupboards go perhaps sealing them from the atmosphere and using something like a light bulb to circulate warm dry air (like a biltong dryer) will keep the humidity therefore mould inside the cupboards down?
    Sealing them is a bad idea - good ventialtion is a critical part of reducing mould. But the light bulb certainly helps.

    I'm scratching my head as to why Daveob is having such a problem. Normally once you've got the ventilation side of things sorted out, that's the end of the miff smell problem.

    The only thing I can think of off the top of my head is a particular mould that is known to cause problems in car airconditioning units. It is quite persistent and takes a special treatment to clear.
    The trouble with opportunity is it normally comes dressed up as work.

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    Gold Member daveob's Avatar
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    Hi Dave A

    Ventilation does seem to play a big part of it. Our cupboards doors do seem to close really well, so maybe I should be looking at some ventilation holes in the cupboards. However, that won't solve the problem in the house in general. The only place we don't seem to have a problem, is in my office, and I can only think that because of all the computer equipment generating extra heat that raises the temperature and lowers humidity.

    As far as ventilation in the house is concerned, we do have all the windows open all day ( we're home during the day ) and only close up late afternoon when the wind starts howling. However, with the high humidity from outside, and reduced air flow behind furniture, the mould seems to keep reappearing.

    So the logic of my thinking, is to put in the system to reduce humidity, so irrelevant of air flow and temperature, the mould would be unable to grow. That way, we don't have to sit with a gale force wind gusting through the house just because we need the windows open. Living on the top side of a sea facing hill means that we generally get a lot more wind than many other properties that are surrounded by walls and trees.

    The other big plus factor, for me, would be the ability to control the climate in the house, which during summer, would be most enjoyable, and during winter, could even be used to lift the fresh 15 / 16 degrees up to a better level around 22 degrees ( by automatically re-directing the cooled dry air via the warmer cooling fins before returning to the house ).
    Watching the ships passing by.

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    Site Caretaker Dave A's Avatar
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    Quote Originally Posted by daveob View Post
    Our cupboards doors do seem to close really well, so maybe I should be looking at some ventilation holes in the cupboards.
    A vent at the top and the bottom of the doors (or perhaps somewhere more discreet if that's an option) would probably help.

    Quote Originally Posted by daveob View Post
    The other big plus factor, for me, would be the ability to control the climate in the house
    That's why I haven't said much so far. Your understanding of the miff problem seems spot on, so really the discussion is about achieving a viable climate control system. And on that, I'm just an interested observer
    The trouble with opportunity is it normally comes dressed up as work.

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    Gold Member daveob's Avatar
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    Sitting in the dentists rooms yesterday, I was browsing a magazine ( Popular Mechanics, I think it was ). There was a 'solar house' project in there, and what caught my interest was an adaptation of what I already have. The dehumidifier bags. Turns out that the active (only) content is Sodium Chloride - a safe product, and I'm reasonably certain that it is this which is contained in the dehumidifier bags. But at nearly R40 for a 1kg bag, you can get the identical thing in bulk buckets from the pool shop for less than half the price.

    A bit of googling and I found that if I were to place the flakes in a box, with an inlet fan ( small 12v PC cooling fan will suffice ) and an outlet, the fan will blow air from the room over the flakes. They absorb moisture, lowering the RH, and dissolve. What I didn't know, was that if you heat the resultant slush ( side burner ring on the new outdoor gas braai would work perfectly ) then the water evaporates and crystals re-form - and can be used again and again.

    So armed with this knowledge, I set off to the hardware shop and purchased the Sodium Chloride flakes and a small PC fan. Will be fixing the fan to a spare small black storage box tomorrow and hope to report back with the reading from the hygrometer in a few days time.
    Watching the ships passing by.

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