Here is the info on the system and also on the load calc:

In your opinion, can this unit be adjusted to get us down to 72-73 inside while its 90-94 outside, or do I need a 5-ton like I originally asked for?

Do you feel that 90 degrees is reasonable outdoor and 75 indoor ?

No, I would say more like 92-73 to cover for hot days and BBQ's with a lot of people coming in and out of the house.

"In your opinion, can this unit be adjusted to get us down to 72-73 inside while its 90-94 outside, or do I need a 5-ton like I originally asked for?"

I'm just a homeowner with a crappy system and Ive spent the last 3 weeks learning as much as I can. I would defer to the experts that question. I think the most cost effective approach would be to make sure there are no air leaks in the system or your house

Ive heard that you can slow the blower motor down to carry colder air into the house, but you run the risk of freezing the coil and getting fewer air changes. I'd talk to your contractor or another contractor if you have a poor relation with the guy who installed the unit

Matt,

The calculation says a 4 ton is sufficient when it is 90 degrees outside and you want to cool the house down to 75 degrees. So the problem could be the data entered into the software is wrong, the installation is bad, or both.

My thought is a 4 ton system would be sufficient. A degree or two inside or outside should not make that big a difference. I see a note at the bottom about large glass areas. Is there a lot of direct sunlight coming in? Are you able to block the sun with blinds?

I never saw a response to my question about the air handler and duct work. Are they installed in the attic? If yes, what R value is the flexible duct work and does the attic have adequate ventilation?

Without seeing the load calc results in writing and knowing the design temps used for cooling both in and out, I am not convinced a real problem exists.

IMO

Mikehome: the handler is in a closet in the main house but the ducts are in the attic. Not sure the R value of the flex. Tigerdunes: the calcs I took a picture of are different from what you are asking about?

matt: there are more values in the calculations that could be provided such as the cooling load of each room in btu and the number of CFM needed by each room. However the design temp was in the image.

I dont know that there is a "problem" with your system. If the system delivers the design temp then it is working.

The fact remains you are unhappy/uncomfortable. I think your contractor should have consulted with your regarding the desired indoor temp before doing the load calculation.

BTW: at this load size (46402), a 47000 BTU unit is going to run full time at 90* outdoor and 75* indoor.

I would use 94*outdoor with 72*indoor and recompute.

As suggested, you probably have additional losses going on in the attic.

Having the variable speed blower is helping with the humidity removal. Is this a 2-stage condenser?

Is that outdoor temperature from your own temp sensor or from the internet?

Not sure about the condenser. I will send pics tomorrow of the rest of the calc pages.

I also agree you should get the charge checked and make sure the TXV Is properly set

Your dealer should rerun the man j load calc using 73 inside, 95 degree outside. I suspect it will push you over the 4 ton cooling BTUs but not by much. The question though should be about your comfort and if you are getting good dehumidification. Comfort R settings should be checked. Refrigerant charge should be checked. Cooling loss from ductwork should be checked. Again, I would concentrate on whether home is comfortable.

IMO

What vent (supply) temps are you getting. Stick a thermometer in the vent in your bedroom. Then stick it in vent (return) at the filter. You can get meat thermometers at the grocery store.

Our attic is not very sloped at all, maybe 4 feet from bottom to top so it is very difficult to move around especially since I'm 6'3". The outside temp reading is set to be reading from our own temp sensor, not the Internet. I'll check the temp readings today from the vents, the other day a few of them were reading 58 but some others were like 64. I will confirm today and also check the temp in the return filter area. The tech said he was coming out this weekend to re-adjust the unit. What should I be asking him to do?

The more I look at the two photos above, the more I am thinking this is an installation problem and not a size problem. For all we know the load calculation was done completely wrong, but it happened to generate approximately the right answer. If that is the case then it is still a garbage in, garbage out calculation.

The house is comfortable, but the OP wants it at 73F. Not unreasonable and there should be no problem reaching it a 9:19PM at night.

Have the contractor return and do all the items suggested so far. You need to understand how and what ducts were installed in the attic.

Here are a few more pics from the plans:

Here's a few interesting pics:

51 degrees at the registers seems pretty good to me. I would get a good analog thermometer or a good digital meat thermometer and calibrate it by sticking it in boiling water and make sure it is 100 and then test some ice water and make sure its close to 32. Make sure you measure the temperatures when it is at least 80 degrees outside that reflects the true load on the system ( I cant tell what the outside temp is, looks like 83) Your temp difference seems to be about 16 degrees which is not terrible but I would expect something like 20 degrees for a new system. your T-stat says you are close to 73 that's not far off from where you wanted to be

Your delta t is about right. You must have air leaking. Get a can or expandable foam insulation and go to work, electrical outlets, phone and cable inlets. Feel around your air handler for leaks, and use aluminum tape where leaking. Silicone around you vents and windows. Look for gaps on the doors.

I which my supply was 51*

Why is thermometer reading 67 at the return and 76 at the thermostat, while the thermostat itself reads 73? Supplies going through a 120 degree attic coming out at 51 degrees? I am skeptical.

Do you have a reliable temperature gauge you can place in various parts of the house?

ceiling vent is supply? and its 51F?

It came from supply.

The pictures I took happened to be when a storm had passed and it was overcast. The outside temp was only 83 and the attic was probably quite a bit cooler than what it normally is during the heat of a sunny South Florida summer day. That's only a 10 degree difference. I'm going to need a 20 degree drop in temp on hot days

Head to Publix for a meat thermometer to verify your IR temp.

My installer came and adjusted the cfm on the handler to 412 instead of 400. When I asked him if he could recalculate the load calc he said it had to be 90-75 per the South Florida guidelines or something of that nature. I'm clueless. Should I contact the American Standard rep?

Well 412 CFM cant be the total CFM maybe that is per ton.When the temperature is below 90 you should be able to get below 75.

Yeah, I think it was 412/ton. It was set to 400/ton which is the standard setting.

Did the adjustment help? The faster the air flows over the coil their is less time for the heat to transfer from the room air to the refrigerant. On the other hand more air is moving through the house which may help. It is certainly a balance. Did he use any special tools to measure the airflow in each room or install dampers in order to balance the system?

I need to wait until a hot day. It's been overcast and only 83 out. He did not check airflow.

Whats the temp indoors at 83 outdoors ? You can always set it at 50 and see how low you can go...but its alomst 6pm your time so I guess it wouldnt be accurate anyway.

Yeah, I've got it at 73. I need to get it low when it's 93 out.

I don't see how reducing the air flow by 2.5% is going to solve the problem.

We increased airflow. The air coming out was cold enough but not enough of it was coming out.

I would be interested to see what the temp coming out the registers are now. I suspect the increased airflow is slightly warmer than before maybe just a half a degree or so.

Oh and just another thought. If the increased airflow does the trick you might consider trying to balance the system to get the most out of your system. By balance I mean measure the CFM of each room/register and adjust it to deliver exactly what you need or add some more to warm rooms etc. Hope that adjustment was all your needed!

Sorry, I misunderstood about the air flow adjustment. I will restate my comment.

I don't see how increasing the air flow by 3% will solve the problem.

I say this because you are missing the design temperature parameters by a lot. I could be wrong, but I think you will see very little change in performance.

Did the contractor take any other measurements? How many times have you called him back to fix this?

This may actually be a case where undersized. I sure you hvac dealer will make it right.

Did the airflow adjustment fix the issue?

I'm waiting for a hot day to see how it does. Mike_home, he has been back 5 times to make adjustments. This is a 20 seer unit and he had to take a class just to be qualified to install it. He keeps checking with the American Standard rep and then tweaking things, none of which have helped significantly. I don't understand why he won't rerun heat load calc. He told me the standard for this area is 90-75. Any reason for him not to want to re-calculate? Do I need to contact the Am. Standard rep?

I'd guess either there are regulations saying that you need to use certain temperature or he doesn't want to risk the possibility that it results in recommending a larger unit.

Its been 100 plus here in Texas , can you send some cooler weather over this way?

Your return looks small for a 4 ton. Adding another may help.

My house in TX is 2,350 sq ft (9' ceilings with two areas 10'). 5 ton Carrier 1-speed heat pump, basic 12 SEER (2004). Two 20"x25" returns. It can cycle at 78°F to 76° setpoint with 100°F+ outdoor. Probably could maintain 72°F, although I haven't tried it because $$$.

I'm going to contact Am Standard and get some customer service.

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.

Thanks Mike, of course, we already paid the installer, so I don't have much to hold against him. I'm hopeful that Am Standard will send someone out.

Matt5487, what was your outcome years ago?