Hi Gang,
We moved in to new (to us) house last August. Prior owners told us they didn’t use a/c much, real frugal folks. When we went to use it I noticed a loud rumble and it ran continuously.
When I checked it out I found two things wrong; a belt on the fan that was probably original…big chucks missing…new belt cured most of the rumble. Second, the cooling coil was an iceberg! Thawed it out and found an VERY dirty coil, and a metal mesh filter that would probably stop a fly, but not much of anything smaller. Took my time spraying it with cleaner and rinsing… think I did a pretty thorough job. Replaced filter with a pleated media type. Worked fine the little we used it.
First startup this spring was last night, pretty sure it ran all night, so I checked it out this morning. An iceberg…not as big as before, but surface ice on at least 1/2 of coil. What I can see of it still looks clean and clear…thawing out now.
To the point of post, what would cause ice-up, assuming clean coil. Secondly I’d like to eliminate the remaining fan rumble. It appears to fasten directly to the plenum so what ever vibration is there telegraphs into ducts (galvanized). Motor mounted directly on fan housing, fan on rubber mounts, bronze bushings on fan shaft. Is there such a thing as a precision bearing fan or maybe flex coupling into plenum to reduce telegraphing? Any ideas?
I’m all ears! err…make that eyes, I guess.
PJ
Whatever you can do or dream you can,
Begin it
Boldness has genius, power and magic in it. Goethe
Replies
Coil ice has 2 basic causes. Too low of air flow or low freon.
One possible solution to the noise problem is add stifeners to the sheet metal where the blower attaches. And they do have flexable boots that can be used to isolate the furance from the ductwork.
Yeah, unless the fan is a manually-adjusted variable-speed unit, you have low freon.
Re the vibration, a cheapo partial fix I learned many years ago is to glue cheap linoleum scraps to the ductwork.
Did you use a foaming type cleaner on the coil???
You'd be amazed at the amout of crud INSIDE of a coil. Are the fins on the coil flattened at all. Closed off cells will affect the air flow. A coil comb will help you there.
With the amount of crud you found I'd go for a reclean. Use an alkiye based foaming agent... Boil out, so to speak, the core of the coil...
Caution with the cleaner, it's caustic...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming....
WOW!!! What a Ride!
Edited 6/4/2004 1:47 pm ET by IMERC
Had same problem on new unit , it was freon leak
A dirty blower will hurt yur air flow and cause it to be out of balance. See if it is a slide out model, if so, great... Usually all that is holding them in is a couple of screws or bolts.. Take it out back and clean it. This would be the time to inspect the bearings / bushings. Best time to change them out if need be...
After the blower is cleaned and it turns freely mark a fin with a felt tip. Moved the fin to the 2 o'clock posistion. Let go. Does it stay put where you left it or does it move on it's own. Repeat for 4, 6, 8, 10 and 12 posistions. The blower may be out of balance and resonating. The pulley could be out of balance.
While yur there spin the blower and see if the pulley runs true or wobbles. Wobble is most lilely from bent pully or bent blower shaft or or worn bearings. Wrap a pull rope on the pulley and start yur engine.
Check the drive pulley. Is it fixed or adjustable??? Worn out??? In alignment with the blower pulley??? Is motor askew slightly??? Belt too tight or too loose???
Do all this maintenence and it still freezes up... Low freon is the next problem to take care of.... then we get into do you have a leak.
PS. Check the isolation bushings on the compressor. Are they in good health. So far everything covered you should be able to do except fot the freon. Save yurself some bucks and improve the efficientcy of the unit....
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming....
WOW!!! What a Ride!
Edited 6/4/2004 1:59 pm ET by IMERC
you may also need a new blower wheel.
grainger sells them $30 or so.
Thanks for the input, everybody
Iceberg mostly melted. Shined a light through coil, looks clear over the 60% or so I can get my head inside to see. I did spend the time to do it right when I cleaned it last August...I dislike doing things twice. Looks like a visit from the freon man is in order. Do they purge and recharge like a car A/C? What might I expect to spend? Is it normal to lose some amount of refrigerant over a period of several years, or should I be looking for the leak?
I'll pull the fan and give it a tune-up, and damping the tinny plenum I'm sure will help, too.
We'll be replacing this in 2 or 3 years and noise like a fan droning is one of my many (who me?) pet peeves. Are there manufacturers that pay attention to keeping the noise down, or is that largely up to an installer? BTW, this is an A/C only, the house has radiant ceiling heat that I'll disable when we start remodeling. So the replacement will likely be a furnace and A/C combo unless I go to floor radiant heat or...or...who knows! Anyway, I'll be seeking the combined wisdom here when that's closer at hand.
I've been told that the direct-drive fans are quieter than belt-driven. No personal experience, though.
I kinda like having a noisy fan so I can turn it on when NFH is having a party, or just outside with his boombox.
Peter
Just had the same exact problem, as others, low freon was the cause.
Woodworkers Supply (I think) has a modular belt for a table saw...links of red plastic/fabric that you buy by the foot...everyone who has tried it (not me yet) says that it reduces the belt noise and vibration on the saw. Might be worth a try.
When you get around to looking for a new heat source, see if you can install a heat pump outside unit...I thinkn they use the same coil inside, so if you can stop the noise problems maybe you can replace fewer parts.
Whenever you are asked if you can do a job, tell'em "Certainly, I can!" Then get busy and find out how to do it. T. Roosevelt
I had a Lennox furnace in my previous house called a "whisper quiet" unit. Made in 1994, don't know if they still make them. It was fairly quiet, couldn't hear anything upstairs, but what they did was get rid of the draft inducing fan. Made me a little nervous that I might get a back draft some day, but it had all kinds of safety switches on it to prevent this.
Update for any that are interested: got on the schedule to have A/C checked for refridgerant...two weeks out. I did pull the fan out and apart to do what I could to quiet it down. Real pleased with results.
Turns out motor has oil cups I didn't see before. Judging from the coil condition I found before, I'll bet that's the first oil it's had in a while. Replaced the fan shaft bushings with precision bearings ($22), replaced the stamped fan pulley with a balanced cast iron unit from Grainger ($16) and put some panel damping sheets on the fan body and plenum ($21). I had some pieces of sorbothane vibration damping left from another project and sandwiched that beteen motor base and fan.
Made a huge difference. The only noise now comes air movement through registers. Now that I've satisfied my obsessive need to build a better mousetrap, we just need to make that air cool...
Thanks for the help.