The t-stat is in the master bedroom on the wall opposite where the ceiling supply vent is in the room (~8 feet apart) and directly beneath a small return vent. Additionally, it's next to the bedroom door going into the hallway where the main return vent is located. I'm not sure what the CFM is on the air handler but when the unit turns on there is a very noticeable "breeze" that can be felt around most vents and it's particularly noticeable in around the t-stat. We set the temp at 68F and leave it alone and there's not humidity control. The t-stat in the old system (where I didn't notice frequent cycling with this t-stat) was located in a hallway under a large return vent and with no supply vent anywhere near it - supply vents were in bedrooms only. The air felt the least conditioned here I guess because of the large return vent above the area. I feel like the nighttime cycling has to do with the t-stat's 1F tolerance combined with it's close proximity to a supply vent. In other words, outside air temp is 70F meaning not much cooling is needed but with the 1F temp tolerance it's enough to kick the system on only to produce a cold draft and very quickly drops the temp to 68F and kicks it off. It kicks on at again at 69F and off at 68F. That's why I was wondering if a t-stat that would allow me to adjust that to say 3F would be better? If set the t-stat at 68F it would take additional time for the temp to rise to 71F before the system turned on again.

The contractor probably does not want to recalculate the load calculation because he may find a mistake and then you will use it against him. The calculation is probably correct. I am a little skeptical about the duct loss. What he has seems low. I would want an explanation on how that number was generated. There could be an additional 0.5 ton of loss that is missing just in duct losses. I am also concerned that this is the first time he has installed this equipment and in 5 trips he has not been able to solve the problem. When you talk to American Standard, tell them the contractor is having problems getting the equipment to work correctly. Installation issues are not their problem. Let them know you have a load calculation and the unit size is matched to the calculation, but the equipment does not seem to working as per the spec sheet. Tell them it is a new installation and with new duct work. Hopefully they will work with you and send someone to inspect the system.

Similar situation happened when I helped my nephew and his girlfriend (now wife) move to a different apt a few years ago. First the A/C wouldn't run at all. Maintenance found a breaker had been shut off. It then turned on but the output airflow was very weak to the point that I doubt it would flutter a ribbon at any of the registers. Was a hot day in May and the apt never cooled down for the hours I was there. I told nephew something is seriously wrong, call maintenance again. A couple months later when I had opportunity to ask about the situation, he said there had been a problem, maintenance fixed it and now it gets COLD in there (in Austin TX, so plenty hot summer weather).

Common Causes of a Constantly Running System. https://www.air-conditioning-ductless.com/ Dirty evaporator coil. Did you forget to have your air conditioner serviced this spring before you turned it on for the summer? If so, the evaporator coil may be covered with dirt and debris, impeding the cooling process and making the unit work harder to cool your space. This can happen even if it was cleaned a few months ago, and the unit is in a location where it picks up a lot of grime, like near a restaurant kitchen. Frozen evaporator coil. If your unit is blowing warm air from the supply vents in addition to running constantly, it may have frozen up. Turn the air conditioner completely off, and call in a professional right away to diagnose the cause and prevent further damage to the system. Clogged air filter. When your system’s air filter is full of dirt and debris, the flow of air is restricted, which can impede the functioning of your air conditioner. Without enough air flowing over the coils, the system can’t remove humidity and cool the air to the set temperature, so it keeps running when it shouldn’t. Restrictive filters. Even if your air filter is new, you may be using one that’s too restrictive for your system (such as one designed to remove pollen and allergens). For better air flow, use a filter with a lower MERV value. Low refrigerant charge. If you don’t have enough refrigerant in the system, probably due to a leak in the coils, your unit can’t cool the space. When this happens, the unit will keep running as it works harder. In this case, you need an experienced HVAC service professional to find and repair the leak and restore the refrigerant to the correct level. Faulty thermostat. If your thermostat is not working correctly, the unit doesn’t know to turn off even when the temperature is reached. Check your thermostat to see if the actual temperature in the space is below the set point. If it is, there’s a good chance that the thermostat may need replacing. Leaky ducts. Especially if you have older ductwork in your building, you may be losing cool air through leaks in the ducts. The joints may not be sealed, or the insulation may be gone. If enough cool air escapes, the temperature in your space never reaches the set point and the system will keep running. Dirty or blocked condenser. Just like the evaporator coils on the inside, the condenser coils on your outdoor unit also need to be cleaned, possibly even more so since they are exposed to the elements. The flow of air can be impeded by dirt and debris from the air, but also from accumulated leaves or even animal or insect nests. A good cleaning using professional products and tools will take care of this problem. Blower motor and fan issues. If your blower motor is not producing enough air for your system, or the fan is running at a low speed, that can cause the system to lose enough efficiency to make it run too much. Adjusting the fan speed can solve the problem. A layer of grime on the fan blades can also slow it down, so again you may just need a good cleaning. Incorrectly sized unit. Have you recently renovated your space or rearranged the layout without changing your air conditioner? It’s possible that your unit is no longer adequate for the needs of your space. Bring in a certified HVAC professional to do a load calculation, taking into account the design, size and needs of your building as well as windows and sun exposure, insulation and more. Many of these issues can be taken care of, and even prevented entirely, with regular maintenance of your equipment. What’s more, neglecting this task can be costing you in many ways that you haven’t considered. To learn more, download a copy of our helpful guide to Calculating the Hidden Costs of Poor HVAC Maintenance.