Rockyboy1, Room thermostat locations could be part of the problem.

That short cycling must be brought under control!
Garyg & others can provide you with some help, too.

Read my last post a few minutes ago on the "100 Degree Day thread below." You can do a ton of reading on my linked Web pages on the other thread(s).

I have Hands & finger problems, I can only do so much typing at one time. udarrell _ 2007

new home construction/insulation qualities..

4200 sq ft with 7.5 tons

ask to see in writing the load calcs both heating and cooling for each zone...

Ductwork sizing correct......pure guess that short cycling caused by unit going out on high pressure protection switch every 4-5 minutes then when pressure goes down unit comes back on. Or could be as simple as kink in copper tubing to unit...Agree with udarrell--- short cycling not good. Do have Carrier rep come out if your dealer can't locate the problem.

Thanks for the suggestions. So everyone agrees that we are talking about short cylcling which isn't a good thing. I did talk with the GM about thermostat locations. Each one is under a return vent (ceiling) and he claims that is the correct location. They are in very similar locations on each side of the house. He had a temp gun and pointed out that the temp around the smoke detector in the ceiling above therm was at 80. Said we still had some insulation issues but I don't see how that would have such a big influence on the cycling. A few more interesting points:
1. This is a spec home that is built in several neighborhoods. Thermostats are in the same place in all of them but GM claims each home is sized independently.
2. Temp reading on therm never changes during cycle. Always reads our set point (77). Digital therm I put next to it reads 76.6. Shouldn't the therm go up and down?
3. Funny that you should mention copper tubing because they recently came out and jiggled the run in this attic because it was touching the sheetrock creating an annoying hum. After that, the hum went away. Still, last Saturday, the tech came out and claimed the pressures/voltages/amp etc were within specs. However, he did say he found the system to be overcharged and he corrected it.
4. I know it is apples to oranges but.....the neighbor has a similar set up (same builder/ac company)but around 5000 square feet. Electric bills just came out and theirs was about $40 higher than ours. Not a big deal but they keep their therm @ 72 (ours 77) and they have a new pool and a 1.5 hp pump has been running 24/7 for the past month. Just makes me go Hmmmmmmmm.

I would ask to see the manual J load calculations. Your units are almost certainly oversized unless your house is 1/2 glass I cannot imagine needing 7.5 tons of air in any 4200 square foot home.

My home is 5500 square feet and I have 5 1/2 tons of air per manual J.

Wow. What a difference in climate makes. Koold...Here in Phoenix, the basic rule of thumb is 400 sq. ft. per ton. I have a 2600 sq ft. house (single level) and a 3.5 ton and 3.0 ton units.

Contractor SWEARS that the units are not oversized but that is what the system is acting like. No manual J calcs, says he has been doing this for a long time. He also says design temp for Oklahoma City is 95. Until our tropical storm (yes, tropical storm Erin) this weekend, we had been above 100 for about two weeks straight so I am thinking the unit should be running all the time....at least in the heat of the afternoon. I have heard that my stat setting may be too high. I don't see how that makes any difference unless the system was sized to hang meat on a 95 degree day. Carrier rep is coming out with the general manager and one of his technicians this week. Would it be unreasonable to ask that they do manual j calculations to justify what they installed?

If you improve the insulation it will make the situation worse so I don't understand why he brings that up. You say the 3.5 ton unit runs continuously in the hottest part of the day. That sounds good so it doesn't seem like you have a problem there.
You do set the tstat a little higher than most. I would say 74 is normal. The next really hot day set both tstats at 74 and see what happens. You didn't say anything about noticing the humidity in the house is high so I'm not sure that the units are that oversized.
Maybe your thermostat is the main problem. Most tstats even out the on & off times more than you are experiencing. Maybe you have a cheap builders grade tstat that is no good.

Contractor did mention the stats so I may let them change them out if they offer. I am pretty sure they are cheap builders grade. Digital but not programmable. All the enviro folks would roll over if they found out my ac won't run correctly unless I lower the thermostat to 74...or lower:-)

Lowering the tstat to 74 on the hottest day will help determine if the units are way oversized. The tstats may still be the problem. Do you have any humidity problems?

No humidity problem that I know of but I don't have a meter that measures that. I turned down the stat to 74 yesterday afternoon while I was working outside next to the unit. The outdoor temp was around 92 or 93 but that dang unit cycled all day long. 15-20 run, 5 off, back on again. I can see run times, but I don't see how the temp in the zone rises so fast that the stat turns the system on again. It is almost like it is running on a timer instead of temp readings.

Just a thought, but if you are even slightly mech/elect inclined, you could swap the thermostats & see if the problem moves with the stat. Just label the wires & put them back on same marked terminals. Very simple.