Evaporative Air Con (not happy!)

Brent · 27-02-2007, 01:41 PM

Hi all.

This has been bugging me all summer, so I'm seeking the experiences of any forumites who have ducted evaporative air conditioning in their houses.

We have evaporative air con at our place (Brivis unit), and I'll be buggered if I reckon that its not the most overrated method of cooling ever devised. Yep, I know... it relies on air movement rather than absolute cooling of a regrigerated air con. However, it seems if its sub 30 degrees outside, you get a nice, calming temperate breeze through the house, however, when you NEED air con is when its 33 degrees and upwards, and this is when it really struggles. I can barely get the inside air temp less than 28 degrees if its mid to high 30s outside. The breeze out of the vents never really seems 'cool'...just temperate. Almost muggy.

Is this normal? I've stuffed around with changing the angle of the ceiling vents, opening more windows, less windows, higher fan speeds, lower fan speeds, the works. Yep, I know that ambient humidity also affects it, but even on hot & dry days, its performance is ordinary.

PS. Unit is about 3 years old and was serviced last summer.

These are apparently very popular, so, does anyone else have similar issues?

Thanks,
Brent.

GXL078 · 27-02-2007, 01:46 PM

I am surprised you can still use it with the water restrictions. Don't these things use a heap of water?

apolloxbgt · 27-02-2007, 01:50 PM

They need to be serviced every year,the pump's tend to clog up otherwise.
Not a hard job at all,pull off a side cover,then one of the filters and you will see the built up gunge inside in the tank,clean it all out and bob's your uncle.

Brent · 27-02-2007, 01:51 PM

Quote:

Originally Posted by xcgxl

I am surprised you can still use it with the water restrictions. Don't these things use a heap of water?

They do use a bit, but then given that my wife and I are not in the house for 12 hours a day during the week, and don't have a family, I really don't care if it uses a bit whilst its on.......

ratter · 27-02-2007, 01:52 PM

I have it at home also and it is SH!T. Thinking about changing to refrigarated air con

Brent · 27-02-2007, 01:54 PM

Quote:

Originally Posted by apolloxbgt

They need to be serviced every year,the pump's tend to clog up otherwise.
Not a hard job at all,pull off a side cover,then one of the filters and you will see the built up gunge inside in the tank,clean it all out and bob's your uncle.

Hmmm. I might have to get up on the roof and take a look at it and give it a clean as you suggest. Now, where did I put those spare roof tiles.........

:

angelfury · 27-02-2007, 02:03 PM

i've got refridge aircon, and hate it. i hate having the house closed up, and i hate that it gets so cold. i'm going to get evaporative which my dad has - his house is never over 25 degrees, no matter what the temp outside. EXCEPT for when it's muggy or humid, then it's not the best.

i can't remember his brand, but i reckon it's the best thing since sliced bread!

goXF · 27-02-2007, 02:03 PM

evap wont cool as good as refig but it is lot cheaper (electricity wise) to run. On a 40degree day we can keep the inside temp at about 30 - still hot but way better than 40!!

sgt_doofey · 27-02-2007, 02:05 PM

Evaporative air-con is not very effective if the outside humidity is high. There is too much moisture in the air and it doesn't evaporate properly not providing the cooling effects. I noticed that on hot, dry days, evap cooling works well. On more muggy days, it goes to hell and just makes you uncomfortable.
Refrigerated air-con is much better and is not affected by humidity in the air.

4.9 EF Futura · 27-02-2007, 02:11 PM

Yep humidity will really reduce their ability. Lol, not in Darwin or FNQ are ya??

And as well as cleaning filters, the unit on the roof needs to have its covers replaced at the start of winter.

Brent · 27-02-2007, 02:14 PM

Hmmmm. I've asked others about this same issue, and have also got a variety of responses. I'm starting to wonder if some people (like me) have a cooling unit that's a little too small for the house area, whilst others who reckon its the duck's guts have the larger cooling units.

The one I have is angled on the bottom so that it matches the slope of the roof. This obviously would mean less surface area of the cooling pads as compared to the larger units you sometimes see on some houses which are more elevated from the roofline, but which are perfectly square in shape.

Cooper69S · 27-02-2007, 02:15 PM

evaporative is (or was) fairly popular here in perth because its usually pretty low humidity although lately its been humid a bit more than usual. when its hot and dry they work ok, but i still went for refrigerated because at least you can have some control over the temperature. the comment that refrigerated systems get too cold is pretty common but increasing the temp is pretty easy - you don't have to leave it set at 18 degrees...
and with the inverter systems becoming more common they're not so expensive to run any more...

Brent · 27-02-2007, 02:16 PM

Quote:

Originally Posted by 4.9 EF Futura

Yep humidity will really reduce their ability. Lol, not in Darwin or FNQ are ya??

And as well as cleaning filters, the unit on the roof needs to have its covers replaced at the start of winter.

In Melbourne (bayside suburbs). What covers are you talking about? There's the cooler pads, then there's the plastic side covers, and that's about it. Do you mean to just ensure that there's no leaves, dirt etc blocking the vents on the unit itself?

4.9 EF Futura · 27-02-2007, 02:20 PM

Quote:

Originally Posted by Brent

In Melbourne (bayside suburbs). What covers are you talking about? There's the cooler pads, then there's the plastic side covers, and that's about it. Do you mean to just ensure that there's no leaves, dirt etc blocking the vents on the unit itself?

Yeah mate just the covers that basically block everything - stops leaves and dirt from getting in and prevents all the water from entering (rain only really a big problem when the unit not being used for months at a time).\

Lol... shouldnt think relative humidity in melb would be a prob

Outbackjack · 27-02-2007, 02:27 PM

Out here where the climate is extremely dry, they work brilliantly. In any kind of humid environment, they are very ordinary. Cant understand why they would install one other than in a dry climate.

Brent · 27-02-2007, 02:33 PM

Every second house seems to have one around where I am, and as a rule, Melbourne is rarely humid (aside from last week).

Wish I just had a reverse cycle unit instead, because not only would it cool better, but I'd be able to use it for heating too. Currently have ducted gas heating and I'm considering building my own underwater gas pipeline from Bass Strait direct to my house...........would be cheaper than my winter gas bills!!!!!

fairmont1998 · 27-02-2007, 02:45 PM

Evap air cond can't compare to refrigerative air cond, but they can be pretty effective.
First perform some maintenance on the unit.
Get up on the roof and remove all the pad assemblies and hose them out gently until the water is clean. If they are the celdek cardboard honeycomb looking ones, go gently. They are fragile and very expensive to replace. If the pad frames have a water trough on top with holes in it, clear all the holes. Check your water piping from the pump to the top of the unit, clear any holes, fix any leaks.
Drain the unit and clean out the water trough, using a tube and syphoning it out after scrubbing it works well. Check the pump basket, if fitted, is clean. If the unit has a bleed tube set the flow rate to a slow trickle. If the unit doesn't bleed, salt builds up, reducing effectivness.
Set the water level in the trough. Too low and the pump will starve, too high and it will dump water when you turn it off, or overflow all the time.
Also check your pads are fully wetting. If there is only a small dry area of pad, efficiency will reduce quickly, as all the air passing through that bit of pad is not cooled at all.
Jump in your ceiling and look for loose ducts/air leaks.

If all this checks out, you may possibly have an undersized unit.

Brent · 27-02-2007, 03:12 PM

Fairmont1998, thanks for all of that.

I think that the water levels seem to be OK, as the unit waits for the pads to wet before starting automatically, and I hear the 'hissing' noise of the water from time as the unit tops up the hold tank. When turning it off, water is automatically dumped from the unit (not heaps of it though). I've never heard the pump labouring or anything. So, if I need to check the water trough level, is this done by sight, or is there some technical way of doing it?

The air volume doesn't seem to be an issue. if I turn the fan speed up there's a lot of air mass coming from each vent in every room, so I don't think that I'm losing air pressure anywhere. Its more a case of the air temp itself not feeling at very cool.

I'll hop up there anyway and check all those things. Wouldn't be surprised if the pads have a build up of dust, pollen, spider webs etc on them.

**GasoLane** · 27-02-2007, 04:22 PM

We've got evap here and when it's 35c+ outside it's around 25c inside but like Outbackjack says they work best in low humidty areas.

Check the water flow through the pads, which should be cleaned every year or so.

Is the unit big enough for the area it has to cool? I've seen quite a few houses with very small evap units on their roof.

fairmont1998 · 27-02-2007, 04:25 PM

There is a standpipe in the trough, check your water level against that, as you have a small trough due to the sloping design of the unit, I'd aim to keep the water level about 10-15mm from the top of the standpipe. Also, as you mentioned the unit has a dump facility, you probably won't find a bleed tube in it, don't worry about that if its not there.

miitch · 27-02-2007, 04:39 PM

Just drop a crapload of ice cubes inside the water trough and it'll make worlds of difference

fairmont1998 · 27-02-2007, 04:44 PM

Quote:

Originally Posted by rocket.

Just drop a crapload of ice cubes inside the water trough and it'll make worlds of difference

That's a myth and makes no difference.

MightyXR6Turbo · 27-02-2007, 04:57 PM

Quote:

Originally Posted by rocket.

Just drop a crapload of ice cubes inside the water trough and it'll make worlds of difference

There are three factors that control rates of evaporation. Remembering that all the water can do is absorb the heat, the air doesn't absorb the cool.

1. The higher the wind speed, the higher the rate of evaporation.
2. The higher the temperature, the higher the rate of evaporation.
3. The lower the humidity, the higher the rate of evaporation.

So really, if you are pumping ultra cold water through an evaporator, it is probably going to be less effective since the temperature surrounding it will be greatly lower. Obviously wind speed is dictated by your fan speed, and well its fairly obvious that it wont work when there is higher humidity since the air is too saturated.

Evaporative airconditioning is totally crap compared to refridgerative.

XR6-VCT-2000 · 27-02-2007, 05:38 PM

Honestly , i used to work for Brivis , and lets just say i wouldn't purchase one !, refridgerated aircon for me any day. The pads in them are rubbish and constantly clog up with dust etc, there is allways 'some' old water left in the unit ( even though they say it fully drains ). If there is even the slightest tadd of moisture in the air then forget about them working propperly. They're usually ok for really dry areas , with low humidity , and thats about it.

Brent · 27-02-2007, 05:42 PM

Quote:

Originally Posted by XR6-VCT-2000

Honestly , i used to work for Brivis , and lets just say i wouldn't purchase one !, refridgerated aircon for me any day. The pads in them are rubbish and constantly clog up with dust etc, there is allways 'some' old water left in the unit ( even though they say it fully drains ). If there is even the slightest tadd of moisture in the air then forget about them working propperly. They're usually ok for really dry areas , with low humidity , and thats about it.

I have a sneaking suspicion that you're somewhat close to the truth...........

**GasoLane** · 27-02-2007, 05:45 PM

Quote:

Originally Posted by XR6-VCT-2000

Honestly , i used to work for Brivis , and lets just say i wouldn't purchase one !, refridgerated aircon for me any day. The pads in them are rubbish and constantly clog up with dust etc, there is allways 'some' old water left in the unit ( even though they say it fully drains ). If there is even the slightest tadd of moisture in the air then forget about them working propperly. They're usually ok for really dry areas , with low humidity , and thats about it.

You couldn't get much drier than here... well, maybe Outbackjacks, but they work well here. Ours is an old one with the straw type (is that the right word?) not the air filter pad type.

Bucket · 27-02-2007, 06:33 PM

Yea, Got one here in WA...It does Jack on a Hot, Humid day...about as useful as a wet sock.

Bisazc887 · 27-02-2007, 06:46 PM

Refrigirated is the only way to go in this sun burn hot country which is of little help to you now

Outbackjack · 27-02-2007, 06:49 PM

A mate of mine lives on 10acres out here in the desert. His house is a monster. He has evaporative aircon. Last week it was 45c out side and a pleasant 23c in the house. These units can be very effective, but only in a VERY dry climate. Anywhere else is a compromise.

fairmont1998 · 27-02-2007, 06:51 PM

Quote:

Originally Posted by GasOLane

Ours is an old one with the straw type (is that the right word?) not the air filter pad type.

You have what is called 'wood wool'. The original wooden pads were made of Aspen, which can absorb its own weight in water. Now they are made of cheaper timbers, which don't perform as well as Aspen pads.