HVAC system w/ongoing issues: outside temp reading is low & we're on resistance

-- I posted last month but could not log in but just as well- I should start a new string. My previous posts were under "Second Puron Dump in a month, now what?" We have a 5T Amana heat pump and air handler system installed in August of 2013. It is probably too big since we took the second floor off and put a 3T unit upstairs. A number of posters suggested this was an issue. But there is lots more going on.
On 12/7/2014, we had a system lockout. We were told it was a leak, later told the leak occurred as a result of a faulty outside fitting and possibly the wrong braze had been used in the installation. It was repaired, we were charged $697 for a freon recharge but not charged for labor or parts. On January 2, 2015, we had another system lockout. This was repaired 1/20; they replaced both inside and outside TVX (valves). We were told the outside value probably got sticky when the freon was dumped and the service manager likes to replace both valves at the same time. By the time the service manager got home on 1/20, we had another lockout, due to pressure. They came back the next day and the service manager installed a return and (?) another vent in the basement duct work to solve the pressure issue. Sorry I am not able to explain this better.
It seemed to be working fine but I noticed the last several days that the control panel reading of the outside temp was showing about 15-20 degrees lower than it actually was outside. This was especially apparent today when it read 20 degrees - it was really 40 degrees and we were running on resistance heat! Now I am especially sensitive to running on resistance heat since we received the biggest electric bill we ever had with all the service issues over the past month- over $1,000 - (and were keeping it cool knowing we were on resistance). At 40 degrees outside, we never used resistance heat as I recall.
I am wondering this: If the system is reading the temp outside as 15-20 degrees lower than it actually is, would that cause the resistance heat to kick on? We don't know enough about HVAC to know the answer to that very basic question. It feels colder with resistance heat - plus I hate wasting the money. Maybe this is a simple control panel programming issue?
I really thought we had a few years of no expense except two annual cleanings. So disappointing.
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replying to John, hlthcr2000 wrote:

We're on our way to a diagnosis- The heat pump is a frozen block of ice! I thought of that while trying to sleep with the fan running all night. I'm beginning to strongly dislike this system! Isolated malfunction or are the sizing experts going to relate this to duct work?
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John wrote:

I am no HVAC expert. Since you mentioned Puron, your system must be Carrier? Puron system runs in higher pressure compared to old Freon system so leak is more prone when not installed correctly.
You said outside temp. reading is lower than actual. IMO, this is the cause of electric heat running too much defeating the purpose of heat pump. Maybe the sensor is located in a wrong place or it is out of calibration? Have it better checked out asap. I live in cold climate so my cooling need is barely 3 months or so in a year. I have high SEER Carrier Puron unit. Since it's install. ~6 years ago. I have zero issues Accompanying high efficiency NG furnace also been trouble free..
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On Wednesday, February 4, 2015 at 11:50:25 PM UTC-5, Tony Hwang wrote:

I think he's just using "puron" to refer to the new refrigerant. Which is in many brands now.
I really can't imagine have a 5 ton and a 3 ton system. The house must be huge.
Because the thermostat shows the outside temp I'm inclined to suspect the system uses the outside temp as a factor in determining when to augment with resistive heat. So I'd get that fixed. Most likely the sensor but could be a board.
It sure sounds like there has been one long saga of trouble. I'm betting on an improperly sized system plus a bad install.
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