Electric Cost

[ma]

Hello all, I tried to get an answer by searching Usenet but I didn't see a matching issue.

About 2 weeks ago we replaced our 20+ year old 10 SEER, 3.5 ton Carrier condenser with a Trane 14XLi, 14 SEER 3.5 ton. Didn't change the attic unit.

Since then I have been monitoring electric usage, and I, not only don't see a drop in usage, but a few days I saw an increase.

We live in Houston, and is June and all, but I compare usage to last year in June, and on average we used

82-83 KW-HR a day then, and we are using 84-86 KW-HR now.

All other usage habits have not changed at all.

Our total living area is about 2100 sq. ft. with walls & attic being 20+ years old. But these attributes have not changed for either condensers.

Why going from an old SEER 10 to new 14 SEER does not provide a little relief from high electric bill?

Outside temperature runs about 92 to 94 with 60% RH. We keep inside at 76 and I admit the old one couldn't keep up with 76 and let it rise to 79 to 80 inside, but the new one keeps up with the setpoint of 76, but runs most of the time costing us 84-86 KW-HR every day!

Sorry if turned out to be a long post.

Thanks in advance for any type of guidance.

Mike

[Oscar_Lives]

The new one sounds bigger and may use MORE electricity than the old one. Set the new one to 80 degrees and compare apples to apples.

[udarrell]

All high SEER claims may not prove to be as claimed. (?) Was the evaporator a match to the new 14 SEER? What refrigerant control does it have TXV or piston-flow-rater? - udarrell

[Colbyt]

You may not achieve your rated SEER since you did not replace the inside evap coil. Even if you do you are going to need to look at the energy bills for the entire season, that is the S in SEER.

Hopefully one of the HVAC guys will explain this better.

Colbyt

[udarrell]

No two years' seasons are identical. (SEER the S is Seasonal) However, you might be able to get a general idea if you kept detailed records for each month over two or three year periods of time.

If it already had a match-able coil with a TXV refrigerant control, no changes would be needed. The probability may not be too great, though.

[Joseph Meehan]

In addition to the comments already made I would like to add that you have at most two weeks of data. How hot was it during those two weeks as opposed to the base period? (I believe that is measured in degree cooling days).

[Steve B.]

They get the additional SEER ratings with a combination of the outside unit and the coil in the attic. Replacing only half and you will be luck to still get 10 SEER out of it as you now have a mismatched system. It's kind of like putting a new Honda engine in a '65 Cadillac and then expecting it to get 30mpg... Just not gonna happen.

Steve B.

[Stormin Mormon]

That's like getting a new engine for your old 70's truck and wondering why you don't get the mileage of a 05 model.

You oughta replaced the attic unit, and get a TXV coil, too.

[ma]

I am so overwhelmed by the many replies I received. Thanks everyone who enlightened me.

After reading all the replies, it sounds acceptable to me. Evaporator is a 4 ton Carrier, and is about 7 years old.

I guess I need to average out at least one complete seasonal cycle to compare and make allowance for old evaporator.

Thanks again. I feel a little relieved of agony.

Mike

[SQLit]

The specs on a/c's are pretty specific. If you expect the seer rating you install MATCHED equipment. That means compressor and air handler are matched to provide the rated performance. The old 10 SEER air handler has just taken you back to 10 SEER.

If not changing the air handler was your decision, OUCH>>>

Call your contractor and see if there is a upgrade coil that can be installed in the old air handler cabinet. I have never heard of one but that does not mean that some one is not making them.

Sorry if this is really negative.

[Wes Stewart]

So if I take an old stick shift 1/2-ton Chevy truck with a carbureted

350 in it and replace the engine with an LS-1 5.7 L, I shouldn't expect any gain in performance or fuel economy? Interesting.

[Steve B.]

No you shouldn't expect much improvement if you replace the engine (outside compressor unit) and leave the existing 3 speed transmission (air handler/evaporator). The new four speed overdrive transmission is where a lot of your savings comes from

Steve B.

[Wes Stewart]

No, the improved BSFC that derives from better fuel metering, reduced friction, higher combustion efficiency and the lighter weight are where the improvements come from.