AC unit question

[mem]

This weekend I hosed off the compressor unit (I think) of our central AC system. As I did this, some of the metal fins were so corroded that they just crumbled, leaving the coil exposed. A few questions:

1) What is the purpose of the fin-like material around the coil?
2) Will the AC still work -- it has been very inefficient the last few years
3) Any thoughts on what will be more cost effective in terms of purchase price and operating costs -- replacing the central air, or buying a few window units? This is a manufactured home, I suspect the insulation is not the best.

TIA

[Windy in Kansas]

The aluminum around the coil acts as a heat sink to draw heat away from the tubing and dissipates it into the air moved by the fan.

While performance will deteriorate from the missing fins the AC should still work. Whatever corroded the aluminum may have also corroded the copper tubing, assuming it is copper instead of aluminum tubing.

[tyusclan]

If the unit is old enough to corrode the fins on the coil the efficiency wasn't all that great to begin with. Certainly nothing close to the efficiency of today's newer models.

I would suggest replacing the unit. You will very likely recoup the cost of the unit in power savings pretty quickly.

A unit the age of yours would most likely not have a SEER rating higher than 10. The minimum today is 13. I wouldn't recommend going any higher than 14. There are higher ratings available, but the cost is so much more that it takes a great deal longer to recoup the cost in power savings.

[Harry Chickpea]

Since your fins are corroded anyway... you can do something that will TEMPORARILY make the unit far more efficient. Buy a patio mister and micron water filter (to keep the mister from clogging). These mister nozzles use about 1 or 2 gallons of water per hour.

That works out to about 1000 gallons per month of water, which is usually cheap. Set the mister to spray on the coil and forget about it. What will happen is the water will cool the refrigerant faster, and the air temp around the outside coil will be closer to the dew point temperature than the actual temp., reducing the head pressure on the compressor.

For those who think this a great idea - normally IT IS NOT. You can get a similar effect by using a foam or aspen shavings filter and keeping it saturated with water, but you do NOT want water on a good coil, as it will simultaneously build up an insulating layer of lime, and corrode the aluminum.

The situation here is unique, and a substantial amount of money can be saved until the coil can be replaced.

[hunter63]

Do have a male dog? Sounds crazy but they lift their leg and potty on it, will rot the fins real fast.
Did you use a power washer (doesn't sound like it, but never hose off with washer).

Anyway it will be hard to fix, possible to replace just the coil, but high buck.
You can't hardly get a condensing unit (the name of the complete unit w/compressor, fan and coil + controls) in 10 seer any more.
Start saving your money for a new unit.

[agmantoo]

mem,
I live in humid and often hot NC. I have rental property some of which are double wides. In the past it has been expensive to me and expensive to the tenants through the utility bills to be comfortable Summer and Winter. Several years ago I became aware of PTACs, package terminal air conditioners. It was about the time that package terminal heat pumps were becoming popular to those that are aware of what they really are. Two friends of mine that are also landlords were interested in a cheaper means of providing heat and cool and for a lower utility expense to the tenants. We decided to try the package terminal heat pumps with strip heat. http://ptac4less.net/shop/product_in...8dfa2f6feeeb6c Since making the conversion to these units it has been a win win situation. I strongly suggest you give one of these units consideration to replace your ailing AC. I recently spoke to one of the tenants in a double wide regarding his utility bill and he was literally elated. He told me that his utility expense was much less than he had in a condo and that his reduced utility expense made it much easier to pay the rent which I was glad to hear. I think you too will be pleased should you decide to get one.

[mem]

Thanks y'all for the input.

Yes, I do have male dogs and I'm sure that they are part of the problem.

I know that things vary around the country and with conditions, but does anyone have any idea of a reasonable ballpark figure to buy a new unit and have it replaced? Is this something that a competent do-it-yourselfer can do (I've seen a couple units advertised on Craigs list -- or is that a terrible idea).

Agmantoo --- are the units of which you speak hard wired into the home's electrical system? They are more attractive than window units. How many units for approximately 2000 square feet?

Thanks again

[Harry Chickpea]

You generally can't do it yourself, due to the freon laws. Just the outside coil, drier, and a recharge - guessing somewhere between $800 & $1500. Window units are almost always less expensive to buy and operate. There is no reason why they have to be mounted in a window, I've seen through-the-wall installations that keep the windows clear.

In a split unit, you automatically have the expense of two fans instead of one, the air has to be driven against the restriction of the ductwork, some cool is lost through the ducting, so right there you have some major factors. Additionally, window units sling the condensate water over the hot side coil, reducing head pressure, while central unit do not do this. Add in that you can control rooms individually, are never completely out of air, and a brand new replacement is less than $200 when a repair of a central unit can run much more than that and only replace one component. The downside is the fan noise and upgrading wiring. Central AC is quiet, room ACs are almost always noisy.