home a/c efficiency

The high pressure here isn't an efficiency problem, it is as equipment strength problem. The higher the pressure, the heavier and stronger the equipment must be to hold the pressure.

 

It’s not just the strength of they quit meant there efficiency part comes in the ratio of high side pressure to low side pressure.
Remember our 12 Arlo side used to travel somewhere between 24 psi for medium temp air-conditioning and are high side pressure would be between somewhere 130 psi to 170 psi depending on the ambient temperature of the day and humidity. The R1 34 system would be about 21 psi on the low side and 130 psi to 190 psi on the high side . Almost none of these numbers are valid when you started to introduce veritable displacement compressors and veritable fan speeds. Been using pressures were totally useless and not valid . With R410 refrigerant your low side pressure will be about 120 to 130 psi and your high side pressure will be about 270 psi to 390 psi in on 110° day you might even see 600+ psi .
Now let’s get in the CO2 your low side pressure might be 700 or 1100 psi and your high side pressure might be 1700 to 2400 but even these numbers will change whether it’s fixed piston displacement or a completely automated system with inverter technology on both fans and compressor with high-efficiency condenser and evaporator‘s will completely change the numbers and efficient ratio. Pardon any spelling errors I’m using voice to text.

 

Last I checked this was a Prius forum. As Prii owners we have a quite advanced ac systems, with inverter driven variable speed compressors that allow maximum cooling with the engine off and a thermostat that is dynamically corrected for solar gain. One of my favorite features of my Prius v is its oversized ac system compared to the standard hatchback. It also has a “hepa” filter timed option that many don’t realize exists. Of course it can ramp down for low loads and is highly reliable.

Bisco, “high speed” home systems with small ducts are more commonly know as high velocity systems. I don’t think small adjustments make that much difference in home ac but larger setbacks can be a problem for heat pumps in winter. As suggested in the continuing dialog, managing humidity can be as important as regulating temp. Some residential thermostats and their connected systems do have humidity setpoints and control. Allowing auto over cooling for humidity reduction is the simplest logic employed followed by slowing down fan speeds slightly. You are effectively performing the overcooling strategy manually. More advanced two and multistage compressors coupled with variable speed blowers can essentially dial in the desired temp and humidity.

Minisplits typically are poor in humid environments, have poor filtering and require more time consuming cleaning regiments to avoid clogged up blower wheels. They are effective for that new addition, a garage or other unique loads such as shops. In a whole house application they often leave smaller spaces like walk-in closets and bathrooms poorly conditioned. Generally they are cheaper than a small central system that has good filtering and ducts.

Load calcs for cooling are typically a best guess and are usually omitted by the majority of the contractors.

Multistage systems allow long runtimes in lower capacities while ramping up to as much as 120% nameplate btu when needed. Optimum? Yes, at the expense of complexity in an industry that does not seek a “Toyota” level of reliability while maintained by residential techs who don’t understand power electronics and have none of the advanced “Techstream” style scanners. So some residential ac companies avoid inverter based systems and usually shotgun repairs when necessary. Commercial and industrial ac operations are entirely different. The bigger applications require engineering by job which then ensures proper equipment selection, distribution, commissioning and maintenance. Most of the innovation trickling down to residential have long been employed in commercial and industrial. But with a much higher price point.

Finally, flammable gasses like propane used for refrigerant are only allowed in small amounts, usually several ounces max. As a result you see them in small refrigeration applications.

 

Still, I prefer the inexpensive option of using small window and through the wall contained units. They require very little maintenance and last for over 10 years or more.

They are not bathed in a high humidity corrosive environment like the steel housing of a heating and cooling furnace. Without AC, I've seen gas fired heating units and handlers last 30 years or more.

 

Window units are the low cost option and usually are just replaced if they fail. They inherently support zoning based on placement. Properly executed central units will keep the indoor humidity/dewpoint low and prevent condensation in the summer, which can be a major problem in many areas of the home. Mold is a significant concern when dewpoints are allowed to get high.

 

That's the caveat, "property executed." Installers have the incentive to sell higher tonnage units to increase their profit margin, especially when an uninformed home owner wants it. Temperature rise and continuous running for several hours during the hottest part of the day, is more efficient for removal of humidity. Many homeowners, however, believe in error that short on-off periods are better.

 

Mini splits nowadays have all the features of a normal residential split system they have options of large high static pressure ducts that you can install Merv 16 five or 7 inch deep pleated filter in systems with excellent humidity control the outdoor units can turn all the way down. The LG residential 6 ton unit I’m installing right now The main high static pressure unit is roughly 60 inches wide 27 inches deep and 15 inches in height and weight is just about 200 pounds this is not your on the wall little plastic dinky mini split. On top of that you have the capability of adding 130% over outdoor rated indoor head capacity. Four spot cooling in very small rooms they now offer little tiny cassette mounted or wall-mounted 4000 BTU heads that can take care of a small closet for changing or somebody’s bathroom in a remote location at the other end of the house. You could have one outdoor unit and you can have nine indoor air handler‘s all been serviced off of one piece of pipe in one long shot through your house just like your water that goes to your multiple bathrooms in multiple kitchens off of one pipe system. If you have a multi story house that has a basement that gets a little too cool and damp even for the summer time while you’re using all your energy to cool the upper part of the house that is hot you do energy recovery by taking that very same gas it types it down a third pipe to your air handler in the basement to keep the basement warm and dry. Without using any extra electricity because it’s the waste heat that would have been discharged out of the condenser coil instead it gets re-routed and pumped down to the needed air handler in the house for heating . There is no American made heating system on the market that I can even come close of doing this .
As for text stream level of diagnostics yes they do have this they have had it on the larger commercial units for the VFR (variable flow refrigerant ) you plug in your laptop and use the software interface exactly like you do Toyota tech stream. I myself own the mongoose Bluetooth wireless text stream adapter for my Toyota so I don’t even have to plug-in a wire from my car to a laptop it’s all wireless . Exactly the same for the modern minisplits they have Bluetooth wireless diagnostics or over ethernet or online . But it comes down to a lot of the old texts this technology scares them and a lot of the young tax who are not well educated who shot gun replace parts don’t want to touch the stuff and when they do they often break it we have a Lotta problems with incompetent installers trying to turn defective units in for warranty when the problem is the person who installed the unit improperly and do not understand the technology .
And for those very rare ones in about a decade when your temperatures exceed your national average temperature for a few days the systems also have the ability to ramp up their compressors 130% over rated output for short periods of times during the heatwave.
As for the bigger commercial variable refrigerant flow systems they only advertise that you can add 130% over outdoor rated condenser of indoor air handler‘s here in United States they allow more overseas on the LG units that I sell and install. But because I do my own load calx and I engineered the piping layout within very specific to detail I submit my plans to LG engineers and they have given me permission to take my indoor air handler’s capacity up to 200% over outdoor condensing capacity so long as any one time I do not try to exceed 100% this comes in excellent play when you’re in large buildings that never have over 70 or 80% occupancy and the majority of floors or rooms are empty. American engineers for the American typical split systems and what they’re trying to do this would be just a fantasy or a pipe dream for them to even believe such a thing as possible because they’re so far behind the times .
I started installing the large Panasonic variable refrigerant systems over a decade ago I did the first installation for Northern California is Panasonic commercial training facility in San Francisco. But LG had better service and parts and I switched over to LG large commercial and small residential units and now my son just y but LG had better service and parts and I switched over to LG large commercial and small residential units and now my son just installed the large commercial variable refrigerant system in the training facility that he designed and put together for FUJITSU in Oakland . We have not installed the American made common air-conditioning or heat pump split system in well over a decade and we would not go backwards to installing the stone age technology that my grandfather installed it would be like going backwards to having to light our houses with candles and cranking our engines on our car to start them in the morning.
In the new energy-efficient mini split systems are so energy-efficient you can run them off of a small set of small solar panels. with the American made split systems you would need a small solar farm that would take up your entire roof and the backyard

 

lech,

You appear to know a lot about HVAC. That's great. I want to read your posts but, unfortunately, they drive me nuts and I can't get past the first paragraph. Are you using some type of voice to print software? You've got to come up with a better format for your posts, or at least read through them and correct the wording, etc. If I'm giving up, I would venture that many others are also.

 

Yes unfortunately I am using a voice to type program on the Apple iPhone and I usually do these on the fly while I’m working performing another task sorry I don’t edit keep the time down to a minimal because of the amount of work I have to do. I’m definitely not a book writer or a English major far from it.
I have read through them and I have fixed them occasionally but there’s so many errors it drives me nuts trying to fix them. Just pretend I’m a foreigner and English is my second language and I’m not very good at it . Lol

 

It's not an issue at all. I read and write a lot of technical engineering documents and rewrite them for the layman.

Everyone who is hear is of foreign ancestry. Those who migrated here across the and bridge from Asia were also foreigners.

Those who came first often denigrate the new comers. It is been proven scientifically that 99.9% of humans have the same genome. Most Europeans are even part Neanderthal.

 

Putting in more paragraph breaks would be a big help.

 

For the same reason, most readers will skip your lengthy novels.

 

…but for those who expend the effort, there’s some neat stuff to learn. Well worth the price of admission.

@lech auto air conditionin Don’t let ‘em get you down, keep posting!

 

I want to meet the 0.1% of humans who do not have the same genome as the rest of humans. Though I predict if such "person" does exist we wouldn't call him/her a human. lol

I am sure you wanted to say "99.9% of the human genome are identical".

 

People should also keep in mind that Neanderthals were at least similarly intelligent as us, possibly even slightly better. (Their average brain size was slightly larger, though their known samples fit completely within our sample range. Archeological evidence for the era is similar.) We just don't know how much or little difference there was.

But the archaic view that Neanderthals were dim witted and less intelligent than us was clearly the direct result of old racist attitudes about skull shape. That racism has been fairly well removed from the science, but persists in popular culture. We shouldn't perpetuate it.

Other commentary has pointed out that when Neanderthals and modern humans are compared, it appears that we have many of the same 'domestication syndrome' traits that domesticated animals have compared to their wild cousins. Neanderthals would be approximately the wild version of us. Our domestication may have allowed us to live together in much larger groups and cities and societies, rather than keep to smaller bands and tribes as the Neanderthals apparently did. Our 'superiority' may just reflect the power of our much larger societies, not any inherent better intelligence of the individual members.

 

I may have linked previously to this Smithsonian 'exhibit'. Lots of detail, so wander around when time and curiosity permit:

Ancient DNA and Neanderthals | The Smithsonian Institution's Human Origins Program

There is certainly potential to recover more DNA from 7 extinct Homo species.

Human Family Tree | The Smithsonian Institution's Human Origins Program

 

My points were relative to residential. As I suggested above “...most of the innovation trickling down to residential have long been employed in commercial and industrial. But with a much higher price point.”

I would argue that variable capacity residential systems with traditional ducted air handlers are now available from all of the traditional brands. Trane and Carrier represents quality as does Mitsubishi. But they can not legitimately be called “minisplits” even if one can add an extra cassette on them. In my area, Mitsubishi vrfs are often employed in the largest custom homes but with traditional ducting, filtering, humidity control and indoor air quality accessories.

As you know, the hvacr industry has no universal diagnostic protocols like traditional automotive, utilities or pipelines enjoy. So making diagnostic tools affordable to the local ac tech (as opposed to a factory tech) is not there yet.

Certainly commercial variable refrigerant flow (vrf) ducted systems are not new but smaller versions that are within the reach of homeowners is recent. Most are in their first generation and arguably are not as robust as they will become, largely due to their low cost and unprotected inverters. Right now the wise buyer will include the ten year parts and labor warranty for residential variable capacity systems. Better things are sure to come in subsequent designs.

 

Thanks for on-topic post