AC repair question

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I had a problem with my AC units. I thought it was the freon which was too low. The AC guy came out and said that he first recommended cleaning the outside AC units, at $80/unit. His partner says that my units look clean. He says that they should be cleaned every year. So he takes off the top casing, washes it with a lawn hose, sprays on an A/C cleaner (sodium hydroxide based), and washes it off. $300 later, he says that the freon needs to be added too. Ok, another $150 later the problem is solved. I got the feeling I was hood winked and robbed. Two questions. Is washing and cleaning the units standard practice? Is it even necessary to do it once a year? On my old house, I haven't cleaned them in 3 years and never noticed a higher than average bill for not doing so. How much efficiency is lost by not cleaning the units? The repair guy quoted 50%, but I made a smart ass remark like 5%/yr.
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I had a problem with my AC units. I thought it was the freon which was too low.
CY: yeah, everyone says that.
The AC guy came out and said that he first recommended cleaning the outside AC units, at $80/unit. His partner says that my units look clean. He says that they should be cleaned every year. So he takes off the top casing, washes it with a lawn hose, sprays on an A/C cleaner (sodium hydroxide based), and washes it off.
CY: Hope he left the cleaner on long enough to foam up. I've worked on plenty of units that "look clean" but aren't. You have to get the system running, and check some temperatures to find out if the coils need cleaning.
$300 later, he says that the freon needs to be added too. Ok, another $150 later the problem is solved.
CY: Hope he left the system running long enough to dry out, afterwards. The evaporative cooling can throw the numbers and pressures and temperatures around a bit.
I got the feeling I was hood winked and robbed.
CY: I can imagine that.
Two questions. Is washing and cleaning the units standard practice?
CY: Yes, it is.
Is it even necessary to do it once a year?
CY: Depends how much dirt and dust they pick up. I think that most cases, every 3 to 5 years is good.
On my old house, I haven't cleaned them in 3 years and never noticed a higher than average bill for not doing so.
CY: Well, if you take the energy bill from three dirty-coil years of use, they will be about the same. Clean the coils, and the energy bill should go down.
How much efficiency is lost by not cleaning the units?
CY: I've seen 100% loss of efficiency in units that were dirty, but looked clean. I worked on one that was simply not cooling the house at all. After cleaning, it worked great. The home owner was talking about replacement, but was willing to let me clean it and see if that helped. It did.
The repair guy quoted 50%, but I made a smart ass remark like 5%/yr.
CY: The repair guy was a lot too low.
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Deodiaus wrote:

We recommend cleaning the outdoor condensing unit once a year for a straight AC and twice a year for a heat pump. The evaporator coil, "the cold part inside" should be checked at the same time and cleaned if necessary. If you change your filters regularly, you should have no problems with the evaporator. I always tell customers to turn the AC off when you are cutting the grass because the dust and grass clippings will be sucked into the fins clogging them up. You should keep hedges and landscaping plants away from the outdoor unit. A lot of folks will pile mulch and bark around the AC unit and that's a bad idea too. I like to see a bed of pea gravel or rocks around them and the grass/weeds pulled from around the units. Air flow, air flow should be the AC mantra especially in this hot weather.
TDD
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wrote:

Some increase in use of air heat pumps here; noticing that most of them are now mounted at least a foot above ground and often on some sort of hard pad, not surrounded by bushes, flowers and other junk that can shield them. Also in winter homeowners seem to make make sure snow does not pile up against them. Since a heat pump is just an AC in reverse and in fact can be used as AC in summer and is airflow device that makes a lot of sense. After all no one (one hopes) would block off the radiator of a motor- vehicle and then complain it wasn't cooling the engine properly! Here in our windy climate that blows dust, autumn leaves etc. around it would also makes sense to clean outside coils regularly.
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I dont think you got hoodwinked. He was acting in your best interest ; yes, the condensor and evaporator DO contribute to efficiency if they are clean because maximum heat transfer takes place thereby increasing cooling capacity over dirty coils, decreasing amp draw due to the compressor not working as hard, making the units life expectancy theoretically longer, and making your space cool faster/better dehumidified. Now that you know how to clean the coils, you can do that yourself each year prior to startup so it functions at peak performance.
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BTW, I have a follow up question. I am buying a AO Smith DL1056 1/2 HP Direct Drive Blower Motor motor, which needs a 10 mF capacitor (according to manufacturer's specs), but the AC guy put in a 7.5 mF cap. Any reasons why he would do that other than that's what he had available (because he had to make a special run to grainger anyway?
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wrote:

It will likely work, but it is almost certain he got that because it was all that was available or because he thought it was the right animal for the job.
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Can't think of any.
--
Christopher A. Young
Learn more about Jesus
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The motor I had in there is http://americanhvacparts.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=MOT2426003&Category_Code sco-luxa which as you can see here also comes recommended with a 7.5 MFD cap, but the manufacturer suggests 10 MFD.
God is Dead -Nietzsche
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http://americanhvacparts.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=MOT2426003&Category_Code sco-luxa
That's a much better capacitor than the crap plastic ones we have in EU;_) I have no idea why they recommend 10 uF, since the website has a link to a GE 7.5 uF, and the electrician put a 7.5 uF.
Gott ist tod. (your signature in German). (Pronounced toont).
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Tzortzakakis Dimitris
major in electrical engineering
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The other issue came up when I was looking at the new motor. The one I had was a one speed motor. The new one is 3 speed. Ok, which speed should I choose? High, med, or low? I guess a high speed will give you more circulation, but consume more electricity. Any estimates on how much this will affect my energy consumption? Should I just punt and chose medium speed? -- God is Dead and I know German!
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Look at the nameplate on the old motor. The rated speed should be there. Choose the same (or closest) speed on the new motor and wire it up accordingly. Make sure the new motor is wired to turn in the same direction as the old motor. The capacitor hookup will determine the direction of rotation. Rotation is always specified when looking at the shaft end of the motor. Energy consumption will be modestly different on different brand motors, but the difference will probably be negligible if the HP rating is the same, regardless of the speed.
Cheers Dave M.
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Bull Shit!

If it is a reversible type motor, there will be 2 wires to change.

Again Bull shit. Have you ever looked in a motor catalog and wondered what they mean when it says CCW Lead End?
Don't make statements not true that can cost somebody aggravation or money.
Stupid Rookie
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Care to post a reference to a catalog page that says that?
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Talking to a friend who is an electrician, he told me that maybe just the capacitor might be of the wrong capacitance. The problem with buying one off the shelf is that its tolerance might be off enough to throw the engine off. Does anyone know how to calculate the torque for an engine with a capacitance? I use to know this 30 years ago, but now, don't even know how to google this question properly!! Using a 7.5 MFD cap did not work. I tried a 10 MFD cap, which worked for 10 mins. BTW, I found a cheap motor at https://www.plumbersstock.com/product.html?partNumber 476 Does anyone have experience with this brand, PARTNERS CHOICE ??
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wrote:

They are called motors. Your credibility has taken a dive.
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It sounds as though you are in over your head, and it's time to get a qualified, experienced person to take over the job.
A residential air system blower motor should work about the same with a properly rated AC capacitor of 7.5uF or 10uF value (for a motor that's marked for either a 7.5uF or a 10uF), with only a small difference in motor speed. These motors are typically PSC permanent split capacitor type motors, and may be reversible, but may be designed to operate more efficiently/cooler in one direction.
The motor you referred to is not a cheap motor, it's just not an exessively inflated priced motor. New surplus blower motors can be found at numerous surplus dealers for about $30 or less, plus shipping.
-- Cheers, WB .............

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Wild_Bill wrote:

<snip>
why would the speed change?
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Speed changes in PSC motors when the value of the capacitor is changed. Not a major speed change for the previously discussed values of 7.5uF to 10uF.
For the theoretical explanations, try a book with a detailed section on Permanent Split Capacitor (PSC) type AC motors. These motors have been used for deades and are still presently utilized in many applications from fans and blowers to fractional HP gearhead motors.
PSC type motors differ greatly from split-phase capacitor start motors.
-- Cheers, WB .............

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I found one for $65 shipped at: http://boatandrvaccessories.com/43587.htm
Does anyone know where I can buy one for $30?
ps1. I am interested in the start capacitance, (the motor makes the humming sound trying to start up). ps2. my friend the electrician is not the same as the AC repairman and not the same as the earlier guy who put in the 7.5 MFD cap (which seems to be the one that the sites sell with it [A.O. Smith recommends 10 MFD]). ps3. The reason I was looking for the calculations is that I can see how sensitive they are to a change in capacitors.

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