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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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  1.  
    Chinese made 24v RGB garden lights. I've got 6 of them. The ones that are facing upwards are fine but after 3 years the ones pointing down (with the cable entry pointing at the sky) have all got water inside and failed.

    I'd assumed just an LED failure but in one the circuit board was fizzing and running hot so not good.

    The 'Chinese identical' replacements (obviously a different factory - finish is different, circuit board arrangement inside different) I'm thinking of filling with silicone sealant in an attempt to keep the water away from the electronics. Is there likely to be any issue with that?

    Obviously I should have bought 'pond' lights that are completely waterproof but too late now as I've got the replacements.
    • CommentAuthorbarney
    • CommentTimeAug 8th 2019
     
    Depends where the water is coming from

    Very well sealed (but not perfectly airtight enclosures will breath due to heating (when the luminaire is on, and cooling - this draws in air, which contains water vapour which condenses out when the casing is cold

    It's a bit counterintuitive, but higher IP ratings don't necessarily solve the problem

    The fact that the upward facing ones are fine and the downward facing are not suggests the luminaire body is OK but the ingress is via the cable gland - quite possible any condensed liquid on the "upwards" is readily draining away - but on the downwards the lens/cover etc is stopping any draining action

    If these are cheap and cheerful units, tray a small drain hole in the lowermost point first and see if the problem goes away-

    Regards

    Barney
  2.  
    I'll post some photos. Construction means a hole at the lowest point isn't really going to work. There are nice silicon seals where each of the sections join - the cable gland is definitely the weak point.

    The new ones have a round circuit board that fills more of the cavity (rather than the little flat one in heat shrink...)

    Quite a reaction from 24v and aluminium bodies... I had just one of the upward ones fail really early on. it must have had a short to the case as the aluminium spike basically dissolved away...
    • CommentAuthorCWatters
    • CommentTimeAug 11th 2019 edited
     
    Edit: Oops. I see these ideas have already been posted.


    It can be a nightmare sealing electronics against water ingress. If there is any air in the fitting it will expand and contract as the temperature of the lamp changes. When the air expands it will most likely escape, then when it cools water can be sucked back into the fitting - if its in the right place.

    My guess is water is sitting on the cable gland long enough to get sucked in. Instead of trying to totally seal up the gland it might be better to fit some kind of cover so rain can't fall onto it while allowing the gland to be ventilated.

    In some cases drilling a drainage hole can work better than trying to seal it up even better. The hole allows air in/out so there is no pressure difference to push water in past the gland.
  3.  
    I tried sealing the new ones with silicone (inside and out) and they failed almost immediately. Should have tested them first as not sure as to why. Red in two f them never worked, third failed after 10 minutes of messing. Green then failed in one as well. Maybe I disturbed wires, or silicon damaged circuits or caused overheating (though why would that only affect one colour of LED?)

    So, scrapping those and have bought some simple white spots which also look like they' have a cable seal issue....
    • CommentAuthorRobL
    • CommentTimeAug 12th 2019
     
    You could try conformal coating - that's the usual way electronics is made to cope with intermittant condensation issues. Conformal coating at its simplest is spray on clear varnish, rated according to how it performs electrically and what temperatures it should work over. You can buy conformal coating from Farnell or other electronic suppliers, but if it's not super critical (24V is not) I would expect any spray on clear varnish to help a lot. Clean the pcb first (boiling rainwater / or deionised water is usually good for cleaning), leave to dry. Spray on 2 or 3 coats at different angles of the varnish to get into all the nooks & crannies, leaving to dry between coats.
  4.  
    For the pointing down lights it might be worth mounting a small funnel sealed to the cable with silicon goop just above the cable gland so that it acts like an umbrella shedding the water off the cable entry.
  5.  
    Not having a lot of luck with this...
    Most of the outdoor spots seem to be sold as 12-24v. The ones I bought seemed to indicate from the listing that they would work at 24v but turned up marked 12v AC (which was odd). Connected them momentarily to test and they worked, seemed bright.

    Installed and they failed. Tested the spare one and left connected to 24v and it soon failed as well.

    My knowledge here is sketchy - does the voltage matter for an LED? That there are different LED strips sold for 12 and 24V suggests it does, but then why are these sellers marking them as 12-24v?

    Any suggestions on what to buy?
    •  
      CommentAuthordjh
    • CommentTimeAug 13th 2019
     
    I bought a simple mains-connected outdoor spot that uses a GU10 lamp. There are loads available.

    Strictly, it's the current that matters for an LED, so you could run it on a higher voltage by adding a resistance in series with it or increasing the one that's already there. I'd ask the supplier if it claims to be intended for 12-24 V but burns out on 24 V and return it if there isn't a good explanation.
  6.  
    If they are marked as 12v ac then that is what you should run them at. If they were marked 12 - 24 v then I would expect them to function at anywhere between those voltages. What the marketing boys put on the advert / specification sheet may be different to what you actually get and if what you get is marked 12v then I would expect problems at 24v.

    If it is worth the trouble you would probably have a claim because what you were sold was either not what you got or was sub-standard and failed instantly. Either way there would be a claim if you could economically pursue it.

    Oh and for electronics voltage matters. Often you will get a bit of kit that can take a range of voltages but this will have a voltage control /limiter built in to it.

    What to buy? buy quality from a reputable source. Or buy cheap and take a gamble on getting problems and then work out if chasing the claim is cost effective.
  7.  
    >>What to buy? buy quality from a reputable source

    Easier said than done these days with certain stuff. eg the construction of these https://www.lighting-direct.co.uk/garden-24v-3w-led-spotlight-kit-4-lights.html looks no different

    Given I'm now on white led's there shouldn't be much to go wrong. An LED that works at the stated voltage in a watertight casing.
    •  
      CommentAuthordjh
    • CommentTimeAug 14th 2019
     
    Simon Still quoth: "Easier said than done these days with certain stuff. eg the construction of these https://www.lighting-direct.co.uk/garden-24v-3w-led-spotlight-kit-4-lights.html looks no different"

    Well those are IP44 rated so will probably be OK with the light shining upwards but not downwards. They are not guaranteed to work with rain falling on them, only splashes.

    There are low voltage IP65 spike lights but they don't seem to be cheap! e.g. https://www.thelightingsuperstore.co.uk/products/bayville-led-textured-black-low-voltage-outdoor-spike-light-8310
    • CommentAuthorCWatters
    • CommentTimeAug 14th 2019
     
    +1

    Even if you find IP67 rated lamps I personally wouldn't assume the cable gland is waterproof. If water can sit on a seal it can be sucked past it.

    You may find that IP67 lamps designed for replaceable MR16 LED/Halogen bulbs are cheaper and possibly more reliable than dedicated/sealed LED units.
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