AC repair question

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.

Reply to
Deodiaus
Loading thread data ...

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.

Reply to
ilbebauck

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?

Reply to
Deodiaus

Probably what he had on hand. The effect depends on the type of motor, in some cases the capacitor is there just for power factor correction, and in others it creates a phase shift for one of the two windings. In the latter case, a lower value capacitor will result in slightly less horsepower.

Reply to
James Sweet

The motor I had in there is

formatting link
as you can see here also comes recommended with a 7.5 MFD cap, but the manufacturer suggests 10 MFD.

God is Dead

-Nietzsche

Reply to
Deodiaus

? "Deodiaus" ?????? ??? ?????? news: snipped-for-privacy@a36g2000yqc.googlegroups.com...

formatting link
which as you can see here also comes recommended with a 7.5 MFD cap,

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).

Reply to
Tzortzakakis Dimitrios

In all liklihood, depending upon the motor, the capacitor is just used for startup. The result will be less starting torque. For a blower, the starting torque requirements are minimal. For a compressor, however, considerable starting torque may be necessary.

Without a capacitor, there is no starting torque. The motor will run in whichever direction it is started if that were possible,

Bill

Reply to
Salmon Egg

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!

Reply to
Deodiaus

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.

Reply to
Dave M

I've never seen a capacitor start motor used with a blower, they're for applications like air compressors that require high starting torque, which a blower does not.

What I have seen are shaded pole and PSC motors, generally 1/4HP and smaller are shaded pole, while larger or higher quality are PSC. The capacitor on a shaded pole motor is just for power factor correction, while that for a PSC motor creates the phase shift.

Reply to
James Sweet

Depends. Higher speed will extract heat from the heat exchanger more efficiently, but will also result in more noise and higher power consumption. If your ducting is nice and big, then the higher flow can be an advantage, but if it's marginal to inadequate as is the case with many houses, turning it up high will mostly just make more noise.

If it's the same horsepower as the old motor, you'll probably want it on high, but you could try medium and see if it's significantly quieter while still keeping the temperature out of the furnace or heat pump within spec. Many of the setups I see run the medium speed for heating with a gas furnace, and switch to high for A/C.

Reply to
James Sweet

On a multispeed motor the rated horsepower will only be at the maximum speed. The lower speeds will be less horsepower with correspondingly less electrical consumption. If you replace a 1/2HP single speed motor with a 1/2HP 3 speed motor, the highest speed of the 3 speed motor will be the same as the only speed offered by the single speed motor. That is assuming of course that both motors have the same number of poles, which you want to be the case if you are replacing one with the other.

Reply to
James Sweet

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

Reply to
Big Bob

Care to post a reference to a catalog page that says that?

Reply to
PeterD

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

formatting link
anyone have experience with this brand, PARTNERS CHOICE ??

Reply to
Deodiaus

They are called motors. Your credibility has taken a dive.

Reply to
TheQuickBrownFox

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 .............

Reply to
Wild_Bill

Actually, where do I find a site with the physics of starter windings on motors explained. 30 years ago, I had someone explain this to me in a class, but I have forgotten it all. Any good descriptive web sites??

BTW, does anyone know of cheaper motors on the web?

formatting link
above site lists some substitute motors, but some just hang my browser .

Reply to
Deodiaus

Actually, this is a good intro discussion.

formatting link
The motor did not rotate when I put in a 7.5 MFD cap. It worked for about 10 mins for a 10 MFD capacitor. It was making a squeaking sound, before it cut out. I am trying to figure out if it is a simple repair in the starter winding and return the motor, or if I need to replace the motor.

BTW, I look at this as a learning experience. So, unless I fry myself or the house, nothing is lost. I have messed up things in my life, but I think I have fixed many a things too.

I know the difference between an engine and motor. An engine turns mechanical energy into electricity. A motor turns electrical energy into mechanical. You can usually run one in reverse to get the behavior of the other.

Reply to
Deodiaus

The capacitor in this discussion is a Run capacitor, not a start capacitor. Your progression to this point has been backwards.

When the motor hums instead of starting, it's not because the value needs to be 8.645789uF, it's because the motor is not wired properly.

You need a qualified, experienced person to take care of the installation.

-- Cheers, WB .............

Reply to
Wild_Bill

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.