Sorry, I get so much to reply to I don't usually get back to these posts. You need to e-mail me because I may never see your replies & questions. If my memory is correct, around 35 years ago occassionally the compressors had higher BTUH ratings than the condensing units. Laxer49 I just checked your page & my birthday is on Dec 8th, too, I will be 73. Those 10-SEER condensers' used to do real well. If the E-Coil has a leak it should be replaced anyway. Laxer49, If it were me, I would put a New half ton larger BTUH rated Coil in there with a TXV refrigerant control. If you can get a real good deal on a new 10-SEER with that combination & the correct tightly sealed ducts & airflow it should cool okay in the hottest weather. If you want the most cost-effective payback I would do all I could to reduce the radiant & other heat gain as the insulation will also reduce the heating bills. The Installation is the most important thing, it has to be done right! Read & learn allyou can. Funkeruski, I suppose they replaced the evaporator with a matching TXV controlled coil? Everything has to be performed just right & even then if it is real hot & the indoor load is also heavy it may not equal the old unit which would have a larger BTUH capacity compressor on that 4-ton condenser. Those high SEER tests are performed under rather light load conditions. The SEER of a system is determined by multiplying the steady state energy efficiency ratio (EER) measured at conditions of 82°F Outdoor Temperature, 80°F Dry Bulb and 67°F Wet Bulb (near 50%RH) indoor entering air temperature by the Part Load Factor (PLF) of the system. (The PLF is supplied by the government.) IMO, they ought to be tested at 95 or 100-F outdoor temperature. Which SEER do you think will perform better at 100-F plus ambient temperatures, the one with the larger capacity compressor or the smaller one? You could slow the blower CFM down to keep the suction pressure & E-Coil temp somewhat lower, but that also drops sensible capacity some. At 82-F outdoors, the 15 should do real well against the 10. Just my viewpoint. udarrell _ 2007 Here is a link that might be useful: udarrell.com

We are having the same problem with our older "WallMaster" unit by Friedrich. After cleaning both coils, filters, checking thermostat, etc finally broke down and called in a repair person. Sad news was that the compressor is going causing the unit to shut down before reaching the proper temperature. Try all the above suggestions, especially cleaning the filter, and a through cleaning of the units coils (both). Get a good thermometer (an instant read kitchen one will do), and check the difference between the incoming air (front of the unit), and what is being blown out. There should be at least a 12-20 degree difference. If the condenser comes on, but shuts down after about 10 minutes, you may have a problem with motor (condenser), in which case it would be cheaper to chuck the unit and buy new. In fact considering how inexpensive units can be,you may wish to look into getting a new one sooner rather than later. The last thing you want to do is purchase a new unit during a heat wave because your current AC died a slow painful death. If funds are tight check Craigslist for local people selling units. They may not be what you want, but it will get you through the summer, that way you can wait and get a good deal when stores are clearing stock in the late Fall.

No, it's not true. The 20 F number is the nominal delta T or split, the difference between the temperature of the air entering the evaporator coil and the air leaving it. If your house is insulated and doesn't leak like a sieve, you should be able to do better than 20 F split between outdoor and indoor temps. It should do at least as well as the old system, and I'd be upset if it couldn't do 75 when it's 100 out. Phew, I see I just wrote a lot of stuff. It's a little of what I've learned dealing with an underperforming system in my new construction home. Hopefully, you just have a wrong charge problem, or a dirty filter and/or coil problem, as these things are easy to correct. But maybe this will help... How many tons is your system? Give both the evaporator coil and condenser ratings. What exactly did you replace? If it was just the condenser, does it match the evaporator coil? That can be a problem to get right especially if you're mixing manufacturers. You need a tech who can evaluate the system as a whole. Starting with charge, if it's fixed orifice, he must evaluate charge using superheat. If it's TXV, he must use subcooling. No matter what, he should write both numbers down on your receipt along with temperatures and pressures and preferably verify against the manufacturer's specs instead of just using rules of thumb. Beyond getting the charge right and verifying the split is what is expected given the current conditions, which depends on the indoor wet and dry bulb temps, the outdoor dry bulb, and air flow, the main thing to look at is air flow and duct work. However, if it was working fine with the old system, and the new guy didn't mess with the duct work, the problem should be limited to what he did. Still, you should verify your ductwork isn't leaking badly anywhere along its length, from the return through the blower through the coil all the way to the registers. What is the fan speed set to? I have a 3.5 ton system in south Louisiana, and the installer left the blower on High, which gives over 500 CFM/ton and draws air from every hole in the envelope as the return is undersized for that high fan speed. Over the course of several years, including a couple of years at Medium, I found the best setting is Medium Low, which gives about 360 CFM/ton, which works much, much better in this hot, humid climate. You need a competent tech to evaluate these things, select the proper speed, and charge the system properly for it; you can't just reduce the speed without adjusting the charge, especially if you don't have a TXV, as the reduced air flow can cause the coil to freeze up. At a minimum, he should measure external static pressure and look up the nominal CFMs for the chosen fan speed in the manufacturer's literature, and he should write those numbers down for you. (Good luck with that. Out of a half dozen techs over 5 years, none of them looked at air flow, which is incredibly important, beyond sticking a hand up to a register, which is horribly inadequate.) Here are some red flags. If the guy measures temps by pointing an IR thermometer at a register, he doesn't know what he's doing. He really doesn't know what he's doing if he stands under the register for several minutes waiting on the IR thermometer to read lower and lower. To measure temperature at a duct, you need to stick a thermometer through the grill into the duct. If your ductwork goes through unconditioned space, i.e. a stinking hot attic, and it isn't insulated extremely well, at least R8, it is likely picking up considerable heat, which makes measuring the coil split inside the house problematic; you could observe (say) 12 F or 15 F during the heat of the day when it's really 20 F. The best place to measure it is through holes in the plenum or ductwork on either side of the evaporator coil, which will give you a true reading. If it's 20 there but much less as measured in your house, you have a duct insulation problem and/or airflow problem; the lower the airflow, the more heat you pick up.

"The airflow I do not know. The last AC guy that inspected the system reported a liquid line pressure of about 270 psi (the suction line around 70 psi), that after he removed some freon. He said it was OK." "The outside T was around 86 F. The system is from 1996." (10 to 12-SEER) A 122.5°F is a fairly high condensing temp. What was the outdoor temp & what SEER or year would the condenser be? (my question) ----- That is a 36.5°F temp-rise off the condenser; that is way too high; 23 to 26°F would be considered high for a 10-12-SEER condenser. There are a number of things it could be. It probably has a fixed orifice as the superheat is not too high due to the high head pressure feeding the coil faster; could also be TXV controlling @14°F superheat. Check for a dirty condenser coil or the blower motor that is not achieving its rate rpm. If there are major supply duct leaks (temps @registers are very high) that could drop static pressures so low that the indoor blower is delivering too much air through the evaporator. It could have a major return-air leak from the hot attic area. It could be a combination of factors; not just or even two...