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Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1577
Posted: 05:25am 28 Nov 2020
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The first real heat of this summer has arrived here today in sh*tney.
One thing I have been doing for some years and found helpful that others may like to try is putting a water spray on the AC Condenser (Outside) Unit. I use those garden Micro spray misting Nozzles set back a bit from the condenser which allows some evap before the mist is pulled through the core of the machine. Mine is a 15 Ton, double height machine and I use 2 Nozzles with just enough pressure so they spray not stream. They are said to do 3L an hour but I would think I am running them under that with the lower pressure than full mains I turn them down to.
Last year I did a few measurements and found this water spray dropped the exhaust air coming OUT of the condenser by around 20oC which is a substantial reduction. It certainly makes the difference on my ( older) machine between the thing operating comfortably in it's performance curve and well outside it. The water use is minimal, it all seems to evaporate even on Humid days and there is never any puddling around the machine. I have used some plastic paneling on one side of the machine to restrict the airflow so it comes in only from the sides being misted.
My friend whom is in AC says a 20 O reduction of the output air is a big deal and would make the efficiency much better and give the machine a much easier time. No Surprises there, one can feel the difference inside especially on the 45o days we had a good number of last summer.
The other thing I have done which my mate also says makes a big difference is put a solar powered car radiator fan in the manhole blowing air up into the ceiling cavity. In this place it's in the laundry so I can close that off and open the door to let the outside air in. I have not taken measurements but my mate whom is very dismissive of any DIY like this seems to think it should make a big difference to the house temp by not letting the roof cavity turn into an oven and is worthwhile doing.
One way I can see this does work is with the Kitchen tap water. It can become quite warm on hot days where it sits in the roof and warms up. Can take some litres of water to flush that away and get back to the cooler temps. I have noticed with the ceiling fan the temp of the water seems to be reduced which would indicate to me a reduction in ceiling temps.
As I say, never actually measured the temps but it makes sense to me. Instead of giving the air hours of resident time to build temp, circulating it ( and the double fans blow a LOT of CFM of air) would bring it back to ambient. Not cool but much cooler than the still trapped air. The ridge capping of the tin roof has gaps for airflow and to allow moisture to escape so the hot air being under some positive pressure should escape much quicker.
Bing the fans are direct connected to a couple of panels sitting on the verandah roof, the system is totally automated just connecting the panels direct to the fans. The hotter it is the harder the fans blow etc.
The ceiling is double insulated with sarking under the tin which does a good Job and batts in the ceiling but the temps in the roof even on a coll but sunny day are significant.
The fact my learned mate thinks this is worthwhile is good enough for me. Bing I just run the fans off a couple of old solar panels which make it nil cost, no reason for me not to do it.
noneyabussiness Guru Joined: 31/07/2017 Location: AustraliaPosts: 506
Posted: 06:01pm 28 Nov 2020
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I also do the same with aircon. The car aircon when its been sitting a while and you need to remove that built up heat fast, grab the hose and spray the condenser, the water doesn't last long but dramatically speeds up the cooling..I think it works !!
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 02:32am 29 Nov 2020
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At least in my own air conditioner, there is a bung in the lower tray intended to drain the condensate produced by the evaporator. That can have a suitable drain hose connected to it.
If you leave the drain bung plugged, water condensate forms a pool in the lower tray. The external outside fan that cools the condenser is designed to pick this water up and sling it over the condenser.
And that does make a noticeable difference...Cheers, Tony.
Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1577
Posted: 07:06am 29 Nov 2020
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I have been a bit wary of the water rusting the cabinet that houses the outdoor unit but seen no I'll effects. I spose it dries pretty fast once the water is turned off.
I read some time back of a car that used the Condensate from the evaporator to squirt back onto the condenser to help with cooling. Don't remember what car it was, I remember them saying it was the first to do it, Might have been the only one to do it as well.
I know in another application where water misting is excellent at keeping things cool, water injection in an engine. Amazing how much difference that makes. I used to tow a heavy trailer in my old Mercedes W123 Diesel and that would be up in the high end of the temp range on the highway on a cool day and overheating unless you turned on the cabin heater on a hot day.
With the water injection the thing would be normal temp as when it wasn't towing anything. Used about 25L of water an hour constant running but I never was on the highway more than about an hour so was OK. :0)
If you added about 40% Methanol, the thing would run positively cool and pick up a good 15 KMH on the top end and had noticeable better acceleration.
Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1577
Posted: 07:18am 29 Nov 2020
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That's what I tried at first and was impressed with the difference so I made a more permanent setup. The misting uses little water and I am thinking of automating it. Put a temp sensor on the output of the condenser and when the output temp reaches 40oC, have it kick in a watering system solenoid valve for the mains or Trigger a pump from a tank.
I have a 2000L water tank right beside the AC unit so a 12V diaphragm pump might be OK but those things tend to be pretty crap quality and wouldn't last long. I don't think a conventional AC pump would have enough pressure for the nozzles. $30 as a small diaphragm pump costs buys about 12K L of water and I think it would take more summers than I have left to use that amount of water. If it used $30 a season, who cares anyway?
I imagine the temp sensor would cycle the water a bit anyway and probably use less water over all... Not that I'm really concerned about that. Power is nearly free so I'll reinvest in a few bucks worth of water over the summer for our comfort and be quite happy.
I'd still like to toy with the idea of Underground Buried and Insulated tanks. In summer I could run a fan on a radiator and Chill the water and run it back through another radiator through the day. Last night it was still quite warm over night but the night before when the day temp was only about 6o Less, the night temp was 17oC.
Would be good for heating water in winter and storing it but I am putting in a 2500L spa and I'm intending to set that up as a heat store and fire it up on oil for winter heating.
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 07:32am 29 Nov 2020
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It certainly will if the air conditioner is protected from the weather. Its only used during hot weather obviously, so any residual water remaining, evaporates pretty quickly.
I have one installed in my back shed, its installed in the wall of a brick garage with no eaves. In winter it sees the full blast of every rain storm, and stays wet inside....
I have two identical air conditioners of similar age (pretty old), one is pristine, the other full of massive flakes of rust internally, but it still works ! I guess all the most important working bits must be copper or plastic.Cheers, Tony.
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