Water mist help cooling my AC condenser unit

[RickCyin]

I have done experiment on my home a/c unit.

I went to Home depot and purchase water mist system for your porch they use this thing on desert areas.
So I had bright idea that if i install this guys around my condenser unit and when compressor comes on it turns on mist. i figure it cools condenser faster help compressor work less hard.
but that’s not the case, when mist turns on my supply air temp went up instead i expected temp. should go down.

Is this normal or I'm missing something here, I know theory of how a/c works.
Please someone explain. Thanks.

[Octopus]

Don't take this the wrong way, but thats a bad idea.

[midhvac]

Don't take this the wrong way, but thats a bad idea.

Agreed

[mud]

Well it could be a good thing if the unit is too small. Once its completely trashed the op can get a properly sized unit. just sayin!

[jpsmith1cm]

In theory, you are correct. Misting the condenser WILL help out the unit, especially if you are in a dry climate.

Here is where the problem lies.

What ELSE is in the water? What does water do when it gets mixed up with electricity? What happens to metal that is continually exposed to water?

Just some food for thought...

[Kevin O'Neill]

Water mist will lower the head pressure. But with some metering devices, overall freon flow will be reduced, lowering total cooling.

Besides the lime in the water will be deposited on the coil, clogging it. Then you need a new coil. Ususlly not a good idea.

[sammyray]

Here in Texas the hard water can cause deterioration to fins of condenser coils.

[rojacman]

Water mist will lower the head pressure. But with some metering devices, overall freon flow will be reduced, lowering total cooling.

Besides the lime in the water will be deposited on the coil, clogging it. Then you need a new coil. Ususlly not a good idea.

hey Kevin , could you elaborate on your statement "overall freon flow will be reduced , lowering total cooling"........does misting the condenser make that large of a difference to the unit subcooling to affect its performance????? I was going to post about fouling the condenser also . at o'hare airport we found a rooftop full of units that were repainted But no one told the workers not to paint the coils , subject for a different thread.........Jack

[Kevin O'Neill]

A piston metering device controls Freon flow with pressure difference. Spraying water on the outdoor coil lowers the head pressure. Therefore lower pressure difference, therefore lower flow through a fixed oriface. Therefore less cooling. However efficiency can go up, so compressor amps drop. If you use water spray, you will need to add Freon to get enough cooling.

If you have a TXV, you will have less trouble.

[Wheelbaron]

Freezer with a cap tube will do the same thing. Clean that coil with water for a few min and the system pressure will drop too low and the metering devise no longer has enough pressure behind it to cause expansion, and you nave less cooling. I.E. the evap that was frozen over will start to melt.

[Caribb Tech]

hey Kevin , could you elaborate on your statement "overall freon flow will be reduced , lowering total cooling"........does misting the condenser make that large of a difference to the unit subcooling to affect its performance????? I was going to post about fouling the condenser also . at o'hare airport we found a rooftop full of units that were repainted But no one told the workers not to paint the coils , subject for a different thread.........Jack

I have done a lot of research on these misting systems. I like to do my homework first before offering items to clients. I have worked with another company who swears by these misting units. Yes, it does work and increases efficiency and reduces power consumption. I can confirm this with all the power recording and power analyzing we had performed. The client was extremely happy! However after returning only 3 months later to perform our PM's on the chiller, we discovered a mass of complete rust! the entire unit frame and coils were oxidized and rusted. The costs of repairs were much more significant than the costs savings. Maybe when someone comes up with a glycol (non-corrosive) system I will entertain this idea again.
Regards
Caribb Tech

[timtanguay]

hey Kevin , could you elaborate on your statement "overall freon flow will be reduced , lowering total cooling"........does misting the condenser make that large of a difference to the unit subcooling to affect its performance????? I was going to post about fouling the condenser also . at o'hare airport we found a rooftop full of units that were repainted But no one told the workers not to paint the coils , subject for a different thread.........Jack

Most systems are designed for a 90F design day temperature, corresponding to a saturated condensing temperature of ~120F (on standard efficiency coils). Metering devices are calibrated to work best at these specs. Metering devices work off of a pressure differential between the high and low side. If your head pressure is too low, then refrigerant flow suffers. You can kind of think of it as a push-pull kind of effect. This is why, in areas like Coastal British Columbia, where you are lucky to see 10 days a year reach 90F we have condenser fan cycling, which artificially raises the head pressure.

[energy star]

We have a company around here that swears by these things. Even goes on the radio touting how they will lower your energy bill by a large percentage. He said you can go inside feel the difference in the air temp as soon as you turn it on and then go watch your electrical meter spin less.