Air Conditioning - new unit can't keep up - power bill sky high

Hello,


I have a question about a new system keeping up with the "load" and a sky high bill.

We are in Orlando FL area - 95 degrees high most days since June, sometimes 90.

About June 18th of this year, we have recently purchased and have had installed an new Trane xl-14i system. The company we worked with was said to have a good reputation an provided pretty good service. We replaced a 15 year old Carrier system that was oversized (5 ton) , mis-matched with fan-coil, and had ducting problems. The new system is a Trane xl-14i (3.1 ton) with a matched fan-coil unit installed up in the attic. All the parts are new. We also fixed the ductwork around the returns and outputs. The engineer did what seemed to be a complete load analysis for our home (2300 sq ft - wood frame - dbl glaze wood frame windows etc). We recieved a print out of the calculations and went with their size recommendation. Also, we have only lived in this 25 year old home for 1 year.

Problem is that on the hotest days, when it does not rain, the temperature in the house starts to rise. We like the temperature to be 79. By 3-4 pm the temp is rising to 81-83. Of course the outside compressor unit has been runnng all afternoon. The temperature does not come back down until after sundown. There is another problem which is even worse, our sky high power bill is now even higher!

Our company's engineers did double check their install and calculations. They did point out that we were missing some insulation in the attic, which we promptly repaired, although it did not solve the problem. (plumbers several years ago moved several big fiberglass quilts and did not replace them). With the problems noted I am wondering if we needed a bigger unit?

Now I have heard from others that this could be considered normal on the hotest days. Is it? Would an undersized unit cause the power bill to go up? I just spent an awful large amount of money and 1.5 months later I do not know if things are right. The power bill was a real shocker!

Thanks for considering our problems.

If you leave it run 24/7 at about the same setpoint you should be able to achieve no less than 20º difference from the out door temp. When they did the load calculation they should have figured in the lack of insulation in the attic. Do you have an attic fan to get air moving up there?

3 ton sounds close for that size house but being in Ohio is different than Fla.

You do want long run times on the a/c to get the humidity out of the house but if it's not reaching setpoint at all and running constantly your electric bill will be high.

Also, we have only lived in this 25 year old home for 1 year.
So you dont know what the bills where in years past?
Think you have FPL there . Give them a call and get back bills for 2 years and see what they paid with that 5 ton in there. Ill bet it was high. Down here insulation helps a lot should have a about a R 38. Dont say about the vents up there in the attic if you have the right amount for vent in and vent out . A power vent fan in the attic pays down here.
dbl glaze wood frame windows etc).
Dont help if the sun hits them, only help in the winter
I dont know why they didn't try and sell you a X L16i or the XL19i for a higher SEER on the units. Also a hot water recovery unit thats 8 months of free hot water down here.
This will sound different but true. I ran my home here through the PC at my shop in Missouri. It takes a 1/2 ton more of AC up there than it does down here. Up there we run only about 3 months. Down here I run about 8 months.
A 3.5 ton in 2300 should do it . But if you dont see it you dont know.
One other thing, you might get a amprobe and check the units amp draw outside and inside." You have" checked all other electric lines and anything electric in the home .

My .02 cents

ED ;)

Hey,

Thanks mattison,

Thanks Ed Imeduc

FPL - now Progress Energy did share the old bill data with me. We are stil in line with them? , but they were all pretty inconsistent.

I am getting conflicting information about the attic fan. Someone else suggested that if the insulation is good ( and I believe it to be ) a fan wont do much to help for the AC performance. The cost of running the fan would outweigh the benefit. I actually just recently bought one from the Depot, but have not installed it yet.

I am pretty sure I must have another energy hog here somewhere too, can't ID it easily. The only appliance left to change is the hot water tank (9 years old?)


Thanks for the consideration