HVAC problem (undersized unit)

[Peace_Maker]

As I said the wife's cousin said the duct work and insulation is good. I checked the attic just now I saw no noticeable leaks, the insulation was good, there are vents at roof peak, and the soffits are not covered. We have double pane windows and the kitchen vent has a flapper.

 

[Stephen]

I have one 5 tons and a 3 tons at my 3500sf house, last month's electric bill was $256 with OG&E.

 

[TJay74]

I work for OG&E, there has not been a rate increase in almost 2 years now and even then there is no rate increase that would cause a bill to spike this much. If I had the OP address I could pull the kwh usage and probably point a finger better, most builders will under size the system. Ideal Homes does it on their houses, we live in one. I keep the AC at 71° and my largest bill this year on our 2500sq ft house was $120.

I was told the reason for the under size is it causes the HVAC to run longer, longer runs times are more efficient as the compressor uses the most electricity at start up. Once it is running the load and usage is a lot less. A1 put our system in and they even say it is under sized by a 1/2 ton for our size house, but they also confirmed as to why the builder did it this way as well.

OP what all major appliances do you have running in the house? Age of those items? Fridge, stove, washer, dryer, deep freeze, TV's, hot water tank and so on.

 

[_CY_]

out side evaporator? a pro would know the difference between an evaporator and a condenser

oppss did a typo .. so what ..

most consumers are not aware of sticking 410 TXV problems usually on 2-3 ton units with Copeland compressors, which are used by several brands. problems started early summer of 2014 .. usually this happens within a few months after startup.

bulletin from Emerson ..

from Trane's bulletin:

For TXV’s that exhibit a low suction pressure (<95psig) and high superheat (>30°F) an
oil additive, MJ-X (CHM01005) needs to be added into the refrigerant system. This oil
additive has been shown to dissolve the sticky debris on the push pin and spring
assembly of the TXV, freeing up the movement of the push pin.

 

[Peace_Maker]

I work for OG&E, there has not been a rate increase in almost 2 years now and even then there is no rate increase that would cause a bill to spike this much. If I had the OP address I could pull the kwh usage and probably point a finger better, most builders will under size the system. Ideal Homes does it on their houses, we live in one. I keep the AC at 71° and my largest bill this year on our 2500sq ft house was $120.

I was told the reason for the under size is it causes the HVAC to run longer, longer runs times are more efficient as the compressor uses the most electricity at start up. Once it is running the load and usage is a lot less. A1 put our system in and they even say it is under sized by a 1/2 ton for our size house, but they also confirmed as to why the builder did it this way as well.

OP what all major appliances do you have running in the house? Age of those items? Fridge, stove, washer, dryer, deep freeze, TV's, hot water tank and so on.

I'll pm you my address. We lost everything in the 2013 tornado so everything is new minus the fridge which was new in 2-13 and my laptop, and we have two older style tvs that were donated in the kids rooms. No freezer, and the hw is gas. One of my neighbors works for OGE and he confirmed no major rate increases, he says he uses smart hours which we do not and his bill is $150.

My wife stays at home with our daughter so maybe lights and tv's on during the day is the reason for the high costs. I do have four kids so maybe all the phones charging and the tv's being on is the culprit?

 

[NikatKimber]

I work for OG&E, there has not been a rate increase in almost 2 years now and even then there is no rate increase that would cause a bill to spike this much. If I had the OP address I could pull the kwh usage and probably point a finger better, most builders will under size the system. Ideal Homes does it on their houses, we live in one. I keep the AC at 71° and my largest bill this year on our 2500sq ft house was $120.

I was told the reason for the under size is it causes the HVAC to run longer, longer runs times are more efficient as the compressor uses the most electricity at start up. Once it is running the load and usage is a lot less. A1 put our system in and they even say it is under sized by a 1/2 ton for our size house, but they also confirmed as to why the builder did it this way as well.

OP what all major appliances do you have running in the house? Age of those items? Fridge, stove, washer, dryer, deep freeze, TV's, hot water tank and so on.

This is my understanding as well. A slightly undersized unit runs longer; but this is typically a good thing as the A/C does two things: cool the air, and remove moisture (lower humidity). An oversized unit will cool the air quickly, but not remove as much moisture, resulting in the house not feeling as comfortable as an undersized unit running longer.

My guess is that something is wrong with the unit (too much or too little freon, heat exchangers (evap or condenser) blocked, etc); or poor insulation; or something other than the A/C like the other appliances or such.

 

[dennishoddy]

This is my understanding as well. A slightly undersized unit runs longer; but this is typically a good thing as the A/C does two things: cool the air, and remove moisture (lower humidity). An oversized unit will cool the air quickly, but not remove as much moisture, resulting in the house not feeling as comfortable as an undersized unit running longer.

My guess is that something is wrong with the unit (too much or too little freon, heat exchangers (evap or condenser) blocked, etc); or poor insulation; or something other than the A/C like the other appliances or such.

Or, you could have had a contractor in your ceiling doing some renovation work that decided to unhook a run of pipe in the attic, folded it over 90+ degrees, kinked the pipe, and then installed it back to the ceiling vents.
Don't ask me how I know this.
Just last Month, I figured out why the back of our house was so much warmer than the rest of the place. Had some AC guys come in and replace the pipe, so life is good now.
Oh yeah, when he installed the bathroom vent, he took all of the insulation around the unit and threw it to the side of the eve. It was 14" cellulose to start with, and when he got done, there was about 3" left. Insulation folks coming this week to reshoot it.

 

[sedona]

3 tons sounds a little undersized for a 1900 square foot house.I have a 4 ton unit in a 2100 square foot house and I keep the thermostat at 74.Last months bill was 150.

 

[technetium-99m]

My place is only 1,800 sf. We had 3 different HVAC guys out when we were looking at replacing our unit. They all noted that our 3 ton unit was undersized for the house. We had 2 recommendations for a 4 ton and one for a 3.5. We went with a 4 ton and haven't paid an electric bill over $175 yet. Previous bills were $350 or so during the hottest months with the 3 ton system running for 18-19 hours per day.

Get an HVAC guy you trust and go with his recommendation, we wish we did the change out earlier.

 

[twoguns?]

You got some really good advice here.....
And then some you should ignore
It's not always out of refrigant, pipe is Not ductwork, and under sizing the unit to keep it running is just..Crazy
Your unit is undersized or not installed correctly or your blower speed is set too low
Call a reputable H\A company and they will fix it......buy guns here......
Unless your house is a custom, the smallest unit that could legally be put in it.......was put in it
These days they're using 500 sq ft per ton, rule of thumb is 400 or 1 cfm per sq foot, I've never seen 600, which would seem what yours is getting close too
Anyway, it seems a window unit or maybe even a mini (there Still expensive) would work....Good Luck and hug your HVAC guy.....he prolly needs it this time of year