I just bought a house and found the A/C unit not working. I checked the filters and they were as filthy as you can imagine. I thought I could make the A/C work by simply replacing the filters. No. After I replaced the filters, there was still no cool air. I wonder what has been damaged, if any?
Among other things, the fan motor is not designed to pull a vacuum. Face it, the filters were not the only thing ignored.
If the filters were VERY dirty, the system could have been pulling in air from any leak and/or tear in the duct work.since most is not sealed correctly. This will lead to the evap coil being covered in the same mess that you see on the filters. This will cause: Compressor failure, or fan motor failure.
The compressor can fail due to the evap coil icing over. This leads to liquid refrigerant being sent back to the compressor, and the valves in most units, (piston type) are reed valves. While the compressor may be running, it may not be pumping, and this will cause a lack of cooling. It can also lock the compressor up, and a replacement in either case is the fix. The compressors lock not due to refrigerant lock, but due to the oil being washed off the bearings. Think automotive style crankshaft, turning two pistons at about 1750RPM, or more, bathed in oil, and then the oil is removed. The blower motor may fail, NOT due to load as there is no load with dirty filters, but from lack of load. The motors are designed to run at a particular static pressure, and without the load, the blower speed actually increases, and with lack of air, the unit overheats.
Get a legitimate AC company out to give it the once over, and make sure that they check the condition of the return duct, the evap coil, blower etc... If its all in working order and the compressor is runnning, and the outdoor fan is as well, and they claim its low on refrigerant, find out WHY...as in, if its low, WHY since its a sealed system. A dirty evap coil, or lack of airflow will cause the techs gauges to read low, but the gauges are only ONE tool used to determine if the systems low. If all the tech does is slap gauges on the outdoor unit, and proclaim its low, tell him to take a hike, but be sure to tell him why.....subcool, or superheat, readings HAVE to be taken to determine if the units low. Without those calculations NO ONE can tell you HOW low, or how overcharged a unit may be....and if the previous owners only had someone come out that didnt check the filters, or evap, and they were that dirty, its possible as can be that the tech simply overcharged the system not knowing, (not having the training, or caring enough to check) that the airflow over the evap was reduced.
Have the entire system serviced...and if its over 15 years old, seriously consider investing in a new higher SEER unit, keeping in mind that Jan 1st,
2006, the minimum standard will be 13SEER...tomorrows cheap unit is a higher SEER unit of today, so look into a 14 or better SEER rating, and remember, that if you go that route, if the company does not change out the indoor evap coil, they simply took your money and ran.
Filters are supposed to be dirty. But rarely will a dirty filter cause problems elsewhere. Call a repair man...
Jeff
Dirty, not filthy....and yes, a clogged filter can create all kinds of problem$
It is counterintuitive but "pulling a vaccuum" is easier on the fan than moving air. To see that in action try holding your palm against the intake of a hair dryer. The motor speeds up.
And do that to a CAH and you get a motor that does not last long..
Thus over amping, over heating and burning out.
Yup....
Because now, since the fan is doing little if any work, pretty much all of the electrical energy input translates into core losses and mechanical friction, resulting in excessive heat generation--and with this all happening at a time when there is also an insufficient amount of cooling airflow over the motor, it makes the motor very likely to overheat and fail in a much shorter time period than its design service life.
Amps increase with load.
Your post is right on! Yes of course, a clogged filter can by-pass lint and dirt and create all kinds of high $ problems!
The tech needs to confirm that the evaporator has "an adequate heat-load" through it before the tech even considers checking the charge!
No system will work properly without adequate airflow of sufficiently warm air to vaporize the liquid refrigerant as it is metered into the evaporator coil udarrell.
It is highly unlikely that your problem with your AC not working was caused by the filters being filthy.
Filters being filthy does cause highly inefficient operation though, so they should be changed regularly to lower your utility bills.
Pj
A forced air HVAC blower motor is an induction motor, and spins at about the same speed at all load conditions below the point of stalling. Blower motors sit outside of the conditioned air stream:
Amps increase with load.
Afraid not..and it can be proven with a remote tach. Sorry...matter of fact, every major brand on the market right now, will void the warranty on a motor that fails due to undersized duct, or bad filters.
How long you been in the biz, or are you just pulling up some website to try to be right, cause you are wrong, and so is the site. BTW...there is a reason we carry over 400 different part numbers for AC units and furnaces..
Oh..how many motors you care to see that sit IN the airstream? Havent seen a motor located on the outside of the box..ever. Therefore, you, or the website you pulled that off, is wrong....the motor does indeed sit in the conditioned air stream...and clue.....its even got cooling vents on it...some even have heat sinks. The heat sinks are not there for looks...but give ya a hint why they are there...its for when you have a commercial installation that you are unsure that the filters will be changed on a regular basis, and to protect the motor....GE and Trane used to install them from the factory.
LOL...while you are correct, to a point, tell that to the people that called us today as a 3rd quote...filter got sucked into the evap, they didnt know it.....had been there for 3 years... One new heat pump....it CAN indeed happen, and you would be surprised how many we see that have been run like that, the other techs didnt check things properly, overcharged the unit to the point that the unit was in a floodback condition, and it kills the units.
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Somehow I think the bigger problem here is that the OP didn't get a home inspection done before buying the property. That inspection would have found this problem. Why people fail to do this is beyond me, because it is free in most cases. A routine inspection will usually uncover more than enough problems to get the seller to discount way more than the cost of the inspection.
In a previous article "Steve@carolinabreezehvac" writes: : ;Afraid not..and it can be proven with a remote tach.
If you didn't understand what I meant before, I said this fact contradicts your claim by implication that the motor will not last long because it will spin itself into destruction when the input is blocked:
Your reply: And do that to a CAH and you get a motor that does not last long..
As any speed up from reducing the load will be quite minimal.
Certainly if the motor is completely enclosed and there is no air circulation, the motor can overheat no mater what load was placed on it. If that is the case, that should have been your answer to "blue".
As it is, with the input blocked, and somehow I can get the normal amount of cooling to the motor iself by whatever mean, the motor will run continuously for its designed service life -- because it is not putting out more heat than it is designed to and not running faster than it is designed to.
You are right I am just surfing the web for information, and I have came across several cases where the motor is outside of the conditioned air stream without seeing one that does it differently. You are welcome to post your own link.
If they are in the conditioned air path, I would have to wonder why it was done that way. Certainly the motors themselves are quite rugged and can operate at a temperature far exceeding that expected in the air handler. They have small internal fans and have no problem at all dumping heat into the air even in a hot attic. Why cut down the cooling efficiency of the whole system by, in effect, using the evaportor to cool the motor.
I know what you said, and I say you are still wrong...and I gave you a method to prove it...its one of those tools that a good professional will invest in to make sure your furnace is fully, and correctly operational...but....I doubt you want to go buy one just to prove it...so...believe what you will. Got news for you...block the filter, and the possibility exists you will be putting a motor and a cage in the unit...
hNo...it should not have been.
Care to post YOUR credentials in this line of work? You can post shit off a website all day long, that wont make it right.
Go to
Lemmie guess....you are simply trolling at this point....and you are not in the trade....bah...believe what you want. You have one (by your admission) ancient pos furnace that has a thermocouple..you know...stone age units. Todays units are nothing like that, and if you dont have a clue, and so far, you dont, dont bother a reply.
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;> As you can see, the speed of an induction motor does not vary much :> around its full-load speed over its useful load range. If you increase ;> load on it, it slows down a bit and then stalls. If you take away all :> load, it doesn't go faster than the syncronous speed, which is only ;> slightly faster than the full-load speed. :>
;> If you didn't understand what I meant before, I said this fact :> contradicts your claim by implication that the motor will not last long ;> because it will spin itself into destruction when the input is :> blocked: ; :I know what you said, and I say you are still wrong...
Could you at this point explain what you believe that I have said to be wrong? Was it -
1) An underloaded induction motor will not speed up to the point of self-destruction or significant accelerated wear?2) If the normal operational amount of cooling is maintained to the induction motor (as in the case where the motor is outside), a blocked input (which "Blue" says to have the effect of reducing the load on the motor) will allow the motor to coninue to function to its designed service life?
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