From my research it’s a couple things:
First just basic mechanical noise: you need to use damping (called Blankets in their terminology) or HVAC “boots” (big vibropods, essentially) etc.... quite similar to TT crowd.
However increased mechanical noise is usually do to the system working under duress / out of spec.
Apparently the precision of the motor run cap capacitance to what’s called for on the compressor is essential. Mine says 70uf 5%.
I bet you after a year or so in FL it’s outside that.
The start mechanism: In many cases the AC is drawing way too much. If your lights dim when the AC kicks in you need a hard start. That sound while not constant is quite annoying and a hard start will reduce this. It has to do with current draw. I haven’t familiarized myself enough with it yet to speak competently.
What precisely is a hard start? Well again, I’m no HVAC technician:... I guess just a potential relay and an additional start cap.
Perhaps these issues due to aging / reduced capacity of the start cap? Usually they are lower quality than a run cap.
I think us maniacs can do better.
Plus savings on a new AC means more Hifi funds.
There’s really knowledgeable diyers on YouTube who keep their HVACs running like a champ for 25 plus years just maintaining what I discussed above plus some normal fan blade oiling etc.
Again, the savings (both monetarily and sanity) potential for just a hundred bucks or so and a half hour of your time is pretty exceptional from what I can see.
First just basic mechanical noise: you need to use damping (called Blankets in their terminology) or HVAC “boots” (big vibropods, essentially) etc.... quite similar to TT crowd.
However increased mechanical noise is usually do to the system working under duress / out of spec.
Apparently the precision of the motor run cap capacitance to what’s called for on the compressor is essential. Mine says 70uf 5%.
I bet you after a year or so in FL it’s outside that.
The start mechanism: In many cases the AC is drawing way too much. If your lights dim when the AC kicks in you need a hard start. That sound while not constant is quite annoying and a hard start will reduce this. It has to do with current draw. I haven’t familiarized myself enough with it yet to speak competently.
What precisely is a hard start? Well again, I’m no HVAC technician:... I guess just a potential relay and an additional start cap.
Perhaps these issues due to aging / reduced capacity of the start cap? Usually they are lower quality than a run cap.
I think us maniacs can do better.
Plus savings on a new AC means more Hifi funds.
There’s really knowledgeable diyers on YouTube who keep their HVACs running like a champ for 25 plus years just maintaining what I discussed above plus some normal fan blade oiling etc.
Again, the savings (both monetarily and sanity) potential for just a hundred bucks or so and a half hour of your time is pretty exceptional from what I can see.
Last edited:
Perhaps we should take a poll of everyone’s AC Startup Current Draw... at least the US folks here.
I believe that’s the most relevant figure in the conversation. Of course adjusted for compressor spec / HVAC size.
I think you all might be surprised to what you mind find, regardless of the age of your AC.
Then comparison between that, compressor labeled capacitance vs measured capacitance on start and run caps as well as startup and running noise ~ 1 ft from compressor without cover in place to remove poor cover coupling from the equation.
YouTube
I believe that’s the most relevant figure in the conversation. Of course adjusted for compressor spec / HVAC size.
I think you all might be surprised to what you mind find, regardless of the age of your AC.
Then comparison between that, compressor labeled capacitance vs measured capacitance on start and run caps as well as startup and running noise ~ 1 ft from compressor without cover in place to remove poor cover coupling from the equation.
YouTube
Last edited:
I believe that is wrong.
Starting needs high current, so a small reactance, so will be the higher uFd.
The Run capacitor value is designed to give, with winding factors, a specific Phase Shift. An AC motor fed single-phase power is like a 1-legged bicyclist, can't start from standstill and is erratic until crank speed is high. A 1-cylinder steam engine was a better analogy to the Old Men. The Run cap approximates a 2-phase power source, and like a 2-cylinder steam engine will spin reliably. I am sure the motor makers have this calculation done right, between basic theory and 40+ years of industry experience. Do not tinker the cap values.
The Hard Start is a bodge. It will INcrease the initial starting current. It is used when low voltage and/or high system fill force the motor to lug a long time at low RPM before coming to full speed.
My well-pump sucks 44A to start and 11A when lifting water 110 feet. This is how electric motors work. At full speed the back-EMF causes less current suckage; at zero speed the suckage is maximum. In my water pump the starting load is "zero": an impeller designed to load-up at 3400RPM has nearly zero load at 0-100RPM. The closed gas compressor may have to start against FULL load. A shop air compressor may have to make nearly full pressure on the FIRST half revolution.
IMHO, your real problem is Florida. It is not a fit place to live. "Nobody" lived in Florida until 100 years ago when Carrier started marketing practical A/C systems. That started the Florida Boom, first for the rich, and now for everybody. But when the hard-worked A/C fails you suffer.
OTOH here in Maine most folks still do not have A/C. Along the coast we have A/C more for humidity than temperature. And at that maybe under 200 hours a year (like a week for you). And my whole-house A/C is less BTU than a Florida window unit for one bedroom. (However I do have several winter heating systems and over-insulation.)
In Penrhyndeudraeth they lack a clue because they hardly ever get the temperature swings of the east coast of America. A little fire on the hearth in winter, a few days of sweat, but mostly very steady and rarely extreme.
You sorry are correct. 5uf run. 70uf start.
But I believe you are incorrect in that a hard start should REDUCE inrush current.
Yes, but in Maine you freeze and all the good looking women have left, presumably following Carrier’s air conditioning units. I’ll take the heat outside and modern science inside, but to each their own.
From what I can tell mostly it’s compressor drawing too much current, which does a multitude of damage- noise, compressor wear, increased electricity bill, wear on other circuits near same breaker location.
So; the solution would be a larger hard start capacitor with a potential relay to switch out of the circuit once it’s running.
Because.... “200% increase in capacitance in a typical 1/15-hp motor approximately doubles the starting torque. However, the running efficiency of the motor drops from approximately 50% to 18%, and serious overheating of the motor results.” Technical explanation: “Hotrodding” AC Capacitor Motors and Gearmotors …At your own Risk | Bodine Electric Gearmotor Blog
So, the run cap needs to stay as precise as possible and we need a 2 cap solution.
The one I’ve sourced for start is 270uf with a 270R 3W bleeder preattached.
Relay (AC on 230V):
Pick Up at: 180-195VAC
Drop Out: 40-105VAC
FLA - 16A
RES- 25A
I believe the relay should switch at~75% or so of the running current and thus not effect running efficiency. Shouldn’t be on for more than 1-1.5Sec.
LRA is the relevant parameter on the compressor (what one wants to reduce). Stands for Locked Rotor Amps. Also called starting inrush, this is the amount of current the motor can be expected to draw under starting conditions when full voltage is applied.
Usually for compressors just 5 or so years old that are running 24/7 in hot climates with hot enclosures are drawing crazy inrush current well above their rated specifications in many cases.
But I believe you are incorrect in that a hard start should REDUCE inrush current.
Yes, but in Maine you freeze and all the good looking women have left, presumably following Carrier’s air conditioning units. I’ll take the heat outside and modern science inside, but to each their own.
From what I can tell mostly it’s compressor drawing too much current, which does a multitude of damage- noise, compressor wear, increased electricity bill, wear on other circuits near same breaker location.
So; the solution would be a larger hard start capacitor with a potential relay to switch out of the circuit once it’s running.
Because.... “200% increase in capacitance in a typical 1/15-hp motor approximately doubles the starting torque. However, the running efficiency of the motor drops from approximately 50% to 18%, and serious overheating of the motor results.” Technical explanation: “Hotrodding” AC Capacitor Motors and Gearmotors …At your own Risk | Bodine Electric Gearmotor Blog
So, the run cap needs to stay as precise as possible and we need a 2 cap solution.
The one I’ve sourced for start is 270uf with a 270R 3W bleeder preattached.
Relay (AC on 230V):
Pick Up at: 180-195VAC
Drop Out: 40-105VAC
FLA - 16A
RES- 25A
I believe the relay should switch at~75% or so of the running current and thus not effect running efficiency. Shouldn’t be on for more than 1-1.5Sec.
LRA is the relevant parameter on the compressor (what one wants to reduce). Stands for Locked Rotor Amps. Also called starting inrush, this is the amount of current the motor can be expected to draw under starting conditions when full voltage is applied.
Usually for compressors just 5 or so years old that are running 24/7 in hot climates with hot enclosures are drawing crazy inrush current well above their rated specifications in many cases.
Last edited:
I may be the only person to have benefitted from a very noisy air-conditioner!! A local public radio station wanted to get zoning variance permission to install a back up emergency generator. A neighboring lawyer opposed the application. A site survey showed the emergency generator with a muffler was quieter than the noise at the site. One neighbor had an air-conditioner that far surpassed any reasonable noise level.
So the variance was easily granted as the noise level would go down during a power failure. The decision might also have been influenced by the radio station could serve a useful purpose by informing folks about what was going on. It seems many folks have battery powered radio receivers, not so many televisions.
Now for on topic, some time back I made an LC AC power line filter that resonated at the power line frequency and placed it across the power source for my office sound system and found it did make a difference. Only precaution is the circulating currents from L to C were in excess of 100 amps.
So the variance was easily granted as the noise level would go down during a power failure. The decision might also have been influenced by the radio station could serve a useful purpose by informing folks about what was going on. It seems many folks have battery powered radio receivers, not so many televisions.
Now for on topic, some time back I made an LC AC power line filter that resonated at the power line frequency and placed it across the power source for my office sound system and found it did make a difference. Only precaution is the circulating currents from L to C were in excess of 100 amps.
That's funny about the generator! Good story.
The Florida population boom started in the 50s. I arrived here in the mid 60s. There was very little A/C then, not at home, not at school and even a lot of offices didn't have it. That started changing for real in the 1970s. I don't know how kids these days cope outside. They are so used the A/C everywhere, that being outside must slay them.
On the flip side, we look forward to winter when we can open up the house and not use A/C. The buzz of the neighborhood compressors is somewhat reduced in the winter, although many people run it even when it's 70F outside. I don't get it.
Are there norms for A/C unit noise? I don't think they are as bad as they used to be, just that there are so many more of them.
The Florida population boom started in the 50s. I arrived here in the mid 60s. There was very little A/C then, not at home, not at school and even a lot of offices didn't have it. That started changing for real in the 1970s. I don't know how kids these days cope outside. They are so used the A/C everywhere, that being outside must slay them.
On the flip side, we look forward to winter when we can open up the house and not use A/C. The buzz of the neighborhood compressors is somewhat reduced in the winter, although many people run it even when it's 70F outside. I don't get it.
Are there norms for A/C unit noise? I don't think they are as bad as they used to be, just that there are so many more of them.
Fun link: Banging, bearings, buzzing HVAC Noise Descriptions & Recordings
iagnostic Examples of Air Conditioner / Heat Pump Compressor, Air Handler, Ductwork Noises
A collection of recordings of HVAC noises and descriptions of what is happening with each.
Pano yes there are, but those are only valid when new. Also depends on quality of install / platform. They definitely don’t cite noise figures after 2 or 10 years of 24/7 use.
Also many people don’t have regular maintenance, which is quite absurd considering it’s the most used / abused item in the home down here.
iagnostic Examples of Air Conditioner / Heat Pump Compressor, Air Handler, Ductwork NoisesA collection of recordings of HVAC noises and descriptions of what is happening with each.
Pano yes there are, but those are only valid when new. Also depends on quality of install / platform. They definitely don’t cite noise figures after 2 or 10 years of 24/7 use.
Also many people don’t have regular maintenance, which is quite absurd considering it’s the most used / abused item in the home down here.
Last edited:
Misspoke twice. One is the fan run cap, one is the motor run cap. No start cap. Scrolls usually don’t have start caps anymore.
You are missing what I’m driving at here. There’s no thought of changing run cap size.
The start cap is connected through a potential relay. It will be removed from the circuit once the unit is up to around 75% run speed. So give or take one second. There’s no danger of motor damage if you size your potential relay properly.
I believe you have this backwards.
Florida is an environment- all of which have various pros and cons. Maine has snow, which requires special considerations. What does the military or aerospace do for harsh / stressful environments? Certainly they don’t say, “Well guys going into space is looking pretty complicated, I guess we’ll just say here.” You figure it out and you heavily derate along the way.
The same AC sold in FL gets sold in Virginia, and likely the same tonnage for a given square footage. Also newer ACs have been subject to serious cost cutting- anything they can do without they chuck. Heck it works to their advantage- you sell more ACs when they break more frequently.
This is a problem with the consumer / capitalist system, not a given climate.
Just like with audio, DIY is a way to get better value out of a backwards system.
Last edited:
I suppose my outstanding questions are:
Because run cap precision is fairly critical, would 2 capacitors in series of double the required capacitance result in less cap variance over time due to the combined voltage rating?
(I believe the max deviation is usually specified on the compressor, usually around 6%, and due to cap aging esp. in harsher environments this could pose issues)
What are the pros and cons of dry vs oil caps?
How to calculate the ideal potential relay for start capacitors based upon ones compressor specification, rather than rely upon “one size fits most” such as the 5-2-1 models for “3-4 ton” or “4-5 ton” units.
My compressor stats are:
Model #: H83R413ABCA
Single Phase
FLA: 21.1
LRA: 150
Charge: 8.75lbs
Voltage: 230/208 VAC
Because run cap precision is fairly critical, would 2 capacitors in series of double the required capacitance result in less cap variance over time due to the combined voltage rating?
(I believe the max deviation is usually specified on the compressor, usually around 6%, and due to cap aging esp. in harsher environments this could pose issues)
What are the pros and cons of dry vs oil caps?
How to calculate the ideal potential relay for start capacitors based upon ones compressor specification, rather than rely upon “one size fits most” such as the 5-2-1 models for “3-4 ton” or “4-5 ton” units.
My compressor stats are:
Model #: H83R413ABCA
Single Phase
FLA: 21.1
LRA: 150
Charge: 8.75lbs
Voltage: 230/208 VAC
Changing the capacitor type is unlikely to reduce the noise. If severe harmonic distortion is affecting the mains supply current, the motor may be noisier and a better capacitor may slightly reduce this noise due to marginally better filtering, but a real filter would work even better, and probably with less total expense. Motor run capacitors should be replaced regularily anyway. On some industrial machines at work we have this maintenance task scheduled every 10 years, according to manufacturer recomandations. Yours seems to be 14 years old, if I read the mfg code correctly, and replacing is a good idea.
On my experience, the only effective way to reduce the AC noise is to choose a unit that is less noisy by design. On my previous home the AC unit was a conventional type installed by a local company that mainly does maintenance / install services for residential and small commercial. The noise was annoying. For my current house, I followed a tip from a friend and I have bought the AC from a company that mainly does custom installations for large venues. They don't usually do small works, but they eventually found time to work on my project in the middle of the winter when they had less standard work to do. The obvious difference I found is that they have a real system designer that does know all the options, and it does not merely try to always sell the same product. The AC compressor I ultimately selected is a uncommon low power Mitsubishi unit with high efficiency and excedingly good mechanical parts. The noise is a small fraction of a conventional unit, and when I touch the housing I barely feel a tiny vibration. This came at a price 3x higher than a conventional system (not mentioning months of delays for the design and for the delivery of the unit), but my noise problem is almost solved. Almost, because the noise from the made-in-china AC unit of my neighbour is higher than the noise from my unit.
On my experience, the only effective way to reduce the AC noise is to choose a unit that is less noisy by design. On my previous home the AC unit was a conventional type installed by a local company that mainly does maintenance / install services for residential and small commercial. The noise was annoying. For my current house, I followed a tip from a friend and I have bought the AC from a company that mainly does custom installations for large venues. They don't usually do small works, but they eventually found time to work on my project in the middle of the winter when they had less standard work to do. The obvious difference I found is that they have a real system designer that does know all the options, and it does not merely try to always sell the same product. The AC compressor I ultimately selected is a uncommon low power Mitsubishi unit with high efficiency and excedingly good mechanical parts. The noise is a small fraction of a conventional unit, and when I touch the housing I barely feel a tiny vibration. This came at a price 3x higher than a conventional system (not mentioning months of delays for the design and for the delivery of the unit), but my noise problem is almost solved. Almost, because the noise from the made-in-china AC unit of my neighbour is higher than the noise from my unit.
Last edited:
The hot-day load is not so very different, Florida or Virginia.
But VA will work hard 3 months a year, FL 9 months.
If FL is 3X the runtime of VA, then if as pcan asserts your "14 year old" in Florida would be like 42 years of use in Virginia.
I hope-for long-long life here in Maine (1/10th the runtime of VA, 1/30th of FL), limited mainly by rust, corruption, and leakage rather than wear.... but not 42 years! That would be like still driving my 1979 T-Bird (RIP).
Pano- OK, I over-stated Florida heat. Agree that A/C has spoiled us. In fact the last straw on the 1979 T-Burd was A/C failure, even though none of the cars of my youth had A/C.
But VA will work hard 3 months a year, FL 9 months.
If FL is 3X the runtime of VA, then if as pcan asserts your "14 year old" in Florida would be like 42 years of use in Virginia.
I hope-for long-long life here in Maine (1/10th the runtime of VA, 1/30th of FL), limited mainly by rust, corruption, and leakage rather than wear.... but not 42 years! That would be like still driving my 1979 T-Bird (RIP).
Pano- OK, I over-stated Florida heat. Agree that A/C has spoiled us. In fact the last straw on the 1979 T-Burd was A/C failure, even though none of the cars of my youth had A/C.
You didn’t over-state Florida heat. It is made worse - much worse - by the humidity. 90 degrees 90% RH puts an incredible load on an AC - takes a lot of energy to bring the temp down.
I did grow in in FL - with no AC. That’s right, none at all. Expend any energy at all and I was just as soaked as if I just got out of the (city) pool. Except I didn’t smell like chlorine.
I don’t know what’s up with the kooky weather we’ve been having in the Dallas area all year. The humidity has been like Florida. Even through the dry season in the summer. The overflow on my AC has been running almost constantly until just the last week or so, creating a mess on the front porch. Both lines have been running like a fire hose. I changed out the cap the year before last so I’ve got about 3 to go - unless this year took two or more off the life. I did come home to a hot house one day last month - but it turned out to just need a reset. I thought four sure the cap went out.... again.
I did grow in in FL - with no AC. That’s right, none at all. Expend any energy at all and I was just as soaked as if I just got out of the (city) pool. Except I didn’t smell like chlorine.
I don’t know what’s up with the kooky weather we’ve been having in the Dallas area all year. The humidity has been like Florida. Even through the dry season in the summer. The overflow on my AC has been running almost constantly until just the last week or so, creating a mess on the front porch. Both lines have been running like a fire hose. I changed out the cap the year before last so I’ve got about 3 to go - unless this year took two or more off the life. I did come home to a hot house one day last month - but it turned out to just need a reset. I thought four sure the cap went out.... again.
Not my suggestion. Title was tongue in cheek. I was concerned with long term stability of the motor run in comparison with dry film type capacitors like those from Vishay.
Yes. The start cap I mentioned.
I don’t believe so.
Incorrect. Has to do with a number of factors, many of which are dependent on the install.
For example wire not rated for enough current to the breaker panel.
Or, in many cases scroll motors now come without start caps, even though the compressor data clearly suggests start capacitors.
Take a look at the data
[url]https://i.imgur.com/PFUwbhm_d.jpg[/url] [IMG]
This can make an excellent machine sound rather noisy on startup and cause major undue wear that will add to noise levels over time.
In my case the manufacturer recommends 330uf start capacitance, but the unit it came installed inside came without one from the factory due to cost cutting.
[quote]
The obvious difference I found is that they have a real system designer that does know all the options, and it does not merely try to always sell the same product. The AC compressor I ultimately selected is a uncommon low power Mitsubishi unit with high efficiency and excedingly good mechanical parts. The noise is a small fraction of a conventional unit, and when I touch the housing I barely feel a tiny vibration. [/quote]
Again, I maintain that competent installation and configuration is more than half the battle. They likely ensured the unit came with the components Im retrofitting.
An A/C is simply a bunch of different modules from different manufacturers slapped together. It should not be considered some kind of unique entity. These manufacturers routinely sub whatever’s available within the general spec they are going for. There’s no master plan involved by any stretch.
The worst noise is from a unit functioning poorly. And, it indicates poor efficiency and is thus ecologically unfriendly. However it goes unattended due to the average persons fear of electricity / HVAC.
But since many of us haven’t benefitted from such a service, it would be wise to approach retrofit solutions in the time being in the best interests of noise pollution and environmental / resource waste considerations. Financial outlay avoidance / corner cutting is not my motivation.
I’m not against a new AC, but in the meantime I’d like to quiet mine and as an intellectual exercise to see how far I can take it.
A start capacitor, a potential relay and some vibration compressor mounts have CUT THE NOISE LEVEL BY HALF AT MINIMUM for the grand total of ~$75 delivered.
It also significantly reduced the start thump at the breaker panel and the led porch lights on the breaker directly next to it no longer flicker momentarily when it kicks in.
I’d call that a win.
This is without a change of the motor run cap (another $25) as it’s presently in transit. I selected a new Genteq (GE) unit. The key in a replacement is that it’s EIA-456 certified. Datasheet: [url]http://www.farnell.com/datasheets/703914.pdf?_ga=2.221101656.1318329357.1538326753-7521282.1538326753[/url]
I also used some marine rust inhibitor for good measure while I was in there and oiled the fan motor.
With some Noico lining the inside and/or a compressor cover I bet it’ll be quiet as a church mouse.
Presently I now hardly hear it turn on from the other side of a door ~8 feet away.
If you want to place bets on it outliving your own or that it’s operating more efficiently I’m all ears but I think the time horizon is prohibitive.
Last edited:
Ed manufacturers are going to aluminum these days to reduce corrosion / leaking. Valves and other parts aren’t a huge headache.
Sure this isn’t a simple one size fits all thing. There’s many areas of potential issue.
For me- my focus was on noise. Also i felt the noise was due to poor operating conditions which were creating rapid wear and using unnecessary electricity.
Nothing will last forever.
But I use 20k hour electrolytics wherever I can, because it’s a small price to pay for less headache later on.
I was able to reduce from 85db to 67db total, after some noico (dynamat) on the compressor and the door. I measured directly next to the other side of the compressor on the air handler.
I think that’s pretty damn good.
Also the frequencies of the noise have changed considerably to something far less irritating to me.
Startup noise has dropped considerably as well, although I forgot to measure it before making changes.
I’ve given up on using dry film caps because of the heat and humidity issues. Genteq is UL rated for this purpose, no need to reinvent the wheel.
Just an update:
Sure this isn’t a simple one size fits all thing. There’s many areas of potential issue.
For me- my focus was on noise. Also i felt the noise was due to poor operating conditions which were creating rapid wear and using unnecessary electricity.
Nothing will last forever.
But I use 20k hour electrolytics wherever I can, because it’s a small price to pay for less headache later on.
I was able to reduce from 85db to 67db total, after some noico (dynamat) on the compressor and the door. I measured directly next to the other side of the compressor on the air handler.
I think that’s pretty damn good.
Also the frequencies of the noise have changed considerably to something far less irritating to me.
Startup noise has dropped considerably as well, although I forgot to measure it before making changes.
I’ve given up on using dry film caps because of the heat and humidity issues. Genteq is UL rated for this purpose, no need to reinvent the wheel.
Just an update:
Also:
All the Motor Run Tube amp folks seem to like ASC caps.... I forget the exact model number that’s usually recommended. I wonder why the Genteqs aren’t used more often? Maybe GE has lost its brand appeal?
From all the data I’ve reviewed the Genteqs seem to have the most rigorous testing / vetting procedure, longest life, etc. I believe they are also cheaper than the ASCs. However, I don’t see them used much.
For the tube amp folks this might be worth considering.
All the Motor Run Tube amp folks seem to like ASC caps.... I forget the exact model number that’s usually recommended. I wonder why the Genteqs aren’t used more often? Maybe GE has lost its brand appeal?
From all the data I’ve reviewed the Genteqs seem to have the most rigorous testing / vetting procedure, longest life, etc. I believe they are also cheaper than the ASCs. However, I don’t see them used much.
For the tube amp folks this might be worth considering.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.