I had an early 1980's 8 HP, 28" Hi-Vac with grass catcher. I loved the performance, simplicity and readily available parts for this machine. Its biggest drawback was an overly sensitive (and dangerous clutch). However, the clutch design rendered the mower able to climb a hill like like a bulldozer. When it finally died about 20 years ago, I replaced it with a Snapper 14.5 HP, 33" Hi-Vac. What a mistake!! This mower is obviously a product of some CEO's family member's freshly minted, clueless MBA. (check this out) The addition of poorly engineered safety devices and other basic modifications have reduced Snapper rear-engine rider mowers to the classification of "junk". The corporate CEO's should be castrated for reducing the once-iconic, highly reliable Snapper rider into a cheap pile of useless junk. All of the foregoing is based solely on my experienced-based opinion, FWIW.

joepiccaso53, I think the primary reason is cost, I haven't seen any literature to suggest that aluminum is any more efficient than that of a copper coil: like specifying exactly the difference in efficiency from Coil A that is copper versus Coil B that is aluminum and that is the only difference from one coil to another. I do have literature that says just configuration of the equipment can have a mild impact on efficiency. But only mild meaning like 1% more or less efficient than some other configuration. So not enough to make it ecconomically viable to only do it one specific way. Like vertical only installs vs horizontal only. I have had plans to revisit and remake that video to show further what I believe to be the problem as I have cut the ends of the coils to reveal the tubes that have an uneven surface roughed up if you will with what looks like to be the edge of a file on the inside of the tubes that run thru the evaporator coil. So with all these peaks and valleys inside the tube of the coil the part that seals the tube in a multitude of places is very thin amount of metal. From that perspective it's not hard to imagine where the leaks are forming when the coil indicates leaks inside the fin pack area of the coil and not at the ends of the coil where they are typically chemically sealed in the case of all aluminum coils. This (the roughed up inner tube area) is essentially I believe to create more surface area, causes the refrigerant to tumble thru the coil absorbing more heat from return air blowing across said Evap coil. They were doing this sort of thing with copper coils prior to switching to aluminum. What difference does it make if failure is a given anyway? I mean you can argue copper failed incredibly easy and copper costs more etc. If the coil has a leak it's not going to operate efficiently anyway. Also they used aluminum back in the 80's for evaporator coils I just don't have any video to show that. Often the failure with those was the connection point from aluminum to copper was merely a compression type connection which would fail and no good way to fix it (meaning it wouldn't leak refrigerant) -- refrigerant was much cheaper then like incredibly cheap. The technology to meld the two metals together copper line set to all aluminum coil is leaps and bounds better than the 1980's variety, but the aluminum coils just fail elsewhere. If I had discovered some coil or some method to avoid failure wouldn't that be something to hang your hat on? If you look to that video I posted: I literally show you that aluminum coil failed all along the bottom of that coil. It's an upflow coil. Meaning the condensate waste water it creates is all along the bottom of that coil. Why are these clues important? I believe they show why there is failure and why there will always be failure. That condensate water the coil creates is what is doing it at least in this particular example. Refrigerant leaks can happen due to other reasons besides as I also demonstrated in the video.

North Texan, I'm sorry, but your point #1 is simply not correct. A gas tankless is about 92 % efficient (condensing model) any time it is running. It is that efficient because it extracts enough heat from the flue gasses that it takes the gases below the point of condensing the water vapor - and thus even gets the latent heat in the water vapor. That's true any time it's running. It's not an average between "low efficiency and off" as you suggested. Condensing gas tankless water heaters extract so much heat that they vent with plastic vent. There are 82% non-condensing units that vent with stainless steel, but the vent is so expensive it makes more sense to use a condensing unit and vent with PVC. BTW: Condensing gas furnaces work on exactly the same principle. Standard gas tank heaters are about 60% efficient and can't get much better than that. The reason is that they must leave the flue gases hot enough to rise up through the atmospheric vent (hot gases rise). Atmospherically vented (standard) gas water heaters also have higher standby losses and air infiltration / exfiltration issues. There is a 3" flue up the middle of the tank that is open to the sky 24/7. They also take their combustion air from the conditioned air in the house and dump it outside requiring makeup air. Most gas tankless units get their combustion air from an outside intake. I think that you are confusing the issue of input requirements for a tankless heater. A tankless heater (gas or electric) has to heat water very quickly - and thus the input requirements are massive (a typical gas tankless is 200k btu/h vs 40k btu/h for standard gas tank). An electric water heater is almost 100% efficient already - and an electric tankless doesn't improve on that any. Electric tankless saves about 3% on standby losses. I have no idea where you got point #2 - but since point #1 isn't right, Point #2 is also not right. There is a significant cost to retrofit to gas tankless. In new construction the cost difference should be about $500 or less. I can't really comment on the payback because the install costs are so out of whack. In my view, atmospherically vented gas water heaters should be off the table - just as atmospherically vented gas furnaces are no longer available. I would never recommend whole house electric tankless. The operating cost savings (3%) aren't enough to justify any of the additional service requirements. There is no discernible payback. They don't generally produce enough GPM either. There are much better solutions for homes without gas - such as hybrid heaters. Electric Point of Use units can make sense in some situations, but not whole house electric tankless.

It’s a very easy and inexpensive plant, live. That’s a lot of money, and I don’t know if it’s a good deal.