Misting AC unit?

[steve308]

Tried the search feature but nothing came up so....Has anyone installed an AC misting system? They are all over you tube and it seems to make sense (at least to me) but before I waste my wife's hard earned money I thought I'd check here.

Worth it? Pros/cons.

Thanks in advance.

 

[PelicanPines]

There are ways to prevent it but... consider mold.

 

[bobbyjean]

eh....think if used for a short time it's ok....but ... the hardness of your water supply is a big factor.
If it's an old system running high head pressure's on very high temp day's-go for it .....otherwise i would avoid
i would check capacitor's,amp out fan motor and wash condenser coil.....
if you have an oscillating sprinkler you could try that first and save your benjamin's

 

[yeldogt]

My memory was that misting played with the pressures and did not result in significant savings .... if the water was cold it actually put some systems into the too cold area.

My guess would be the VS systems would be better able to take advantage --

 

[LS6 Tommy]

Using sprinklers on the condenser are a bandaid for an old, inefficient coil. Don't do it on a properly working unit. It will overcondense.

Tommy

 

[theoldwizard1]

Misting systems DO work ! All commercial building use them, but there are some caveats !

• You want well filtered water with very little mineral deposits. If not, you are going to just build up "stuff" on the coils and make them even less efficient.
• Do NOT recirculate the water ! Make sure you have adequate drainage around the A/C pad. 4" deep gravel under and 4" out from the pad would be good. Capturing and reusing the water can lead to mosquitoes and various othe BAD things (Legionella).

 

[yeldogt]

Misting systems DO work ! All commercial building use them, but there are some caveats !

• You want well filtered water with very little mineral deposits. If not, you are going to just build up "stuff" on the coils and make them even less efficient.
• Do NOT recirculate the water ! Make sure you have adequate drainage around the A/C pad. 4" deep gravel under and 4" out from the pad would be good. Capturing and reusing the water can lead to mosquitoes and various othe BAD things (Legionella).

The problem I remember is that a properly operating unit has a standard range of temps and when hit with water it will fall out of that range. It's just like how HP's can remain almost as efficient as the temps drop.

The ability of the system to give up a specified amount of heat is not dependent on the ambient temp as much as the design temp.

comercial systems are running at much higher temps and pressures

 

[bonneyman]

Water on a condenser coil does work (Rheemaire's in the 60's-70's had air and water cooled condensers), but the problems typically outweigh the advantages. The mineral content of the source water, increased rusting of equipment, added cost of water, clogging of the water distribution system, etc. negate most advantages unless the unit is designed for it.

Rheemaire's had a stainless steel pan under the compact condenser coil, but the rest of the unit was just enameled steel - and they rusted profusely. Every year the coil had to be descaled with muriatic acid - then neutralized - and the water nozzles clogged constantly. The water pumps were belt driven, meaning another part to wear out and fail on the hottest day of the year. When they worked they were fairly efficient for their time but by 1980 or so they were discontinued as municipalities started hitting high water use customers with surcharges, basically eliminating any electric cost savings.

 

[tfinniii]

Works best with low humidity.

 

[eddieK]

Tried the search feature but nothing came up so....Has anyone installed an AC misting system? They are all over you tube and it seems to make sense (at least to me) but before I waste my wife's hard earned money I thought I'd check here.

Worth it? Pros/cons.

Thanks in advance.

Great idea if you don't mind rotting the outdoor unit out.

 

[theoldwizard1]

Cheap alternative. Rig up some kind of tarp to keep the sun off the unit. It still needs LOTS of air flow !

 

[steve308]

Thanks for the input. The system(s) I saw advertised all had a mineral filter and either a flapper or 24volt thermostat triggered mist engagement function but I was not sold on it's true savings and if in fact they truly worked as advertised. I think I'll pass.

 

[LS6 Tommy]

Misting systems DO work ! All commercial building use them, but there are some caveats !

• You want well filtered water with very little mineral deposits. If not, you are going to just build up "stuff" on the coils and make them even less efficient.
• Do NOT recirculate the water ! Make sure you have adequate drainage around the A/C pad. 4" deep gravel under and 4" out from the pad would be good. Capturing and reusing the water can lead to mosquitoes and various othe BAD things (Legionella).

Nope. NO commercial equipment uses gimmicks like that unless it wasn't sized correctly. Ever. Most municipalities do not allow "once through" use of water for cooling, either. It must be recirculated or used in a closed cooling system.
If you have a need for it, your system was undersized from the word go and the nitwit that sold it to you is trying to tell you it's a benefit to cover their asses for not sizing it right the first time.

Tommy

 

[rlitman]

Misting systems DO work ! All commercial building use them, but there are some caveats !

• You want well filtered water with very little mineral deposits. If not, you are going to just build up "stuff" on the coils and make them even less efficient.
• Do NOT recirculate the water ! Make sure you have adequate drainage around the A/C pad. 4" deep gravel under and 4" out from the pad would be good. Capturing and reusing the water can lead to mosquitoes and various othe BAD things (Legionella).

SOME commercial buildings (bigger ones) use wet chillers. Many others use dry coolers. In humidity prone areas, wet cooling doesn't buy much power savings, and there are many other costs associated with we cooling. More importantly, wet cooling coils are constructed to withstand more corrosive environments than the typical air conditioner condensor coil (although heat pump coils are built to run wet some of the time). Wet chiller coils have increased fin spacing to account for accumulation of debris and scale (and for easier cleaning), and either shorter service lives, or thicker walls.

Back to the DIY approach, you can make it work using the condensate water. Many window ACs take advantage of this. It will be dirty water, and will build up mold, but it will not build scale or be corrosive.

Cheap alternative. Rig up some kind of tarp to keep the sun off the unit. It still needs LOTS of air flow !

A tree would be better. A tarp, even arms length away may have a serious negative affect on airflow.

 

[Trey T]

grayfurnaceman on youtube did a test on it and the conclusion was NOT RECOMMENDED.

His test was not comprehensive and not representative of many units simply because his condenser is likely more cleaner than your average unit, which we often neglect to clean. If your condenser fins are plugged up and the misting dislodge it, the misting device will help; however, that's foolish.... pay a tech to clean your condenser.

Cleaning the condenser can dramatically lower the operating pressure and lower the operating amperage. So clean it properly by taking off the fan and spray from inside-out.

 

[bonneyman]

Cheap alternative. Rig up some kind of tarp to keep the sun off the unit. It still needs LOTS of air flow !

Or build a unit shield like this. Keeps the sun from directly hitting the coil fins, but allows free movement of air through the latticework.

 

[LS6 Tommy]

Shade makes little to no difference on air cooled equipment. If you can reduce the ambient air temperature your condensing unit is exposed to, then you can make a difference.

Tommy

 

[bonneyman]

Shade makes little to no difference on air cooled equipment. If you can reduce the ambient air temperature your condensing unit is exposed to, then you can make a difference.

Tommy

Mine makes a little difference. Since the coil fins are black, direct sunlight beating on them between 2 and 5PM makes the coil alot hotter. The shield prevents that. I haven't measured PSI and amp draw differences but the electric bill is about $10 less per month. Won't make me rich, but I'm happy.

 

[rlitman]

...Since the coil fins are black...

If your coil fins are black, then they need cleaning. Anyway, the metal cover that protects the fins also creates their shade.

 

[Trey T]

It's a good idea to keep the condenser in the shade to lower the coil temp and operating pressure. I don't know how much, but qualitatively, it's a very good practice. If it's placed on the east side of the home, giving it a shade is not needed.

Air flow trumps shades though. So keep the coil clean.

 

[garagelogician]

I rigged up a janky misting system when my leaky condenser was failing (low on charge and R22 was getting expensive). It kind of helped for a couple of days until the HVAC guys could come and install a new unit.

I wouldn't do it for any reason other than that. Too many variables, too many potential problems.

 

[LS6 Tommy]

Mine makes a little difference. Since the coil fins are black, direct sunlight beating on them between 2 and 5PM makes the coil alot hotter. The shield prevents that. I haven't measured PSI and amp draw differences but the electric bill is about $10 less per month. Won't make me rich, but I'm happy.

Without pressure and amp readings before and after on the same day you put up the sun shield, all other info including average electrical bill is irrelevant. Rooftop units have zero shade. Condenser coils are aluminum. If they're black, they need a serious chemical cleaning.

All that being said, it certainly cannot hurt to put the unit in the shade. Makes it nicer for me to work there when I replace the condensing unit after the misting system corrodes the condenser coil...

Tommy

 

[brewchief]

Condenser coils are aluminum. If they're black, they need a serious chemical cleaning.


Tommy

Some residential coils are black from the factory, Lennox had some as well as Amana.

 

[LS6 Tommy]

Some residential coils are black from the factory, Lennox had some as well as Amana.

I stand corrected.

Tommy