New 1/2 house A/C time

[Who]

Better size matching equals longer run times equals more dehumidification...

[JasonG]

Part of the reason you're getting better dehumidification and lower elec consumption is the coil depth.
Newer units have more surface depth so the air is in contact longer and touches more coil.
You should see what a 6 pass commercial unit can do !
With the variable speed fan you will have a hard time meetering watt usage. If it makes a slight whine as it speeds up and down or ramps smoothly not just "changing gears" it probably is running off a Variable Frequency Drive. Unless you have some real good equiptment or its running at 100% it will give some weird readings.
Look inside the unit for a bok around 6"X8" with a display on it. You may be able to scroll the display to show amps or watts, think of it like a scan gage for an elec motor.
That said, your electric bill proves the savings !

[elhigh]

If your AC guy won't go for the multispeed systems, dump him. You're close to a big city, there's plenty of AC contractors that will do the work. Louisiana is so hot, so humid that AC isn't a luxury as much as it is a life safety feature there. There's bound to be someone that will take the job.

I do some AC around here, read up on the websites for the AC manufacturers. You could do a lot worse than a mini-split system, some of the SEER ratios will blow your mind.

Also: if you have a hot space that adjacent to conditioned space, now someone - think it's Rheem - is building a heat pump water heater. It looks like a regular water heater with a coil hat, really tall. Rheem recommends placing it in an attic, getting hot water plus a cool attic, cool roof and cool ceiling all on the same bill. Can't hate that. Works like a regular resistance water heater when ambient drops too low.

[Xringer]

I've got to agree on the Min-Split. Just make sure it's an Inverter type.
Bushless DC motors is the only way to go..

Sanyo 24KHS72 AC/HP DIY install project - EcoRenovator

At last we've had a few warm days(80s) to test out the cooling function of the Sanyo.
WOW! This thing is cooling down the whole house with ease.
It's like having Central Air.. Without all the fuss..

On the high-humidity mid 70s days, it looks like the cost is going be about 70 cents a day..
I'll start a new log when the real cooling season starts..

[gone-ot]

+1 on variable speed blower, permits adjusting airflow rate to match A/C thermal-cooling capacity.

[Xringer]

The Sanyo inside unit blower fan only runs at a few fixed speeds, but the outdoor unit
has DC speed variable compressor motor and main fan motor.
When we only need 4,000 or 5,000 BTUs (instead of 24,000), those outdoor motors slow way down..
My power use meter shows 350 to 450 watts a lot of the time.
When the system goes to idle, it uses about 60 watts, as it very slowly
circulates a small amount of air past the temperature sensor in the indoor unit.

When it detects a rise in temperature, it comes back on and slowly starts
using more power until it gets up to a peak of 800 to 1,400* watts
(for 8 or 10 seconds) and then starts slowly stepping down until
it's back down to the 350-450 watt range.

*Note:
Max power peak depends on the indoor and outdoor temperatures.

This Sanyo works way better than my old 18,000 BTU Kenmore AC,
and so far, it seems to be using about 1/4 the power.
Plus that Kenmore sounds like a jump-jet is landing in the driveway.

[slowmover]

Another note My A/C guy said that my ducts are undersized (volume/ time) for 4 tons of air; *just* large enough for 3 tons of air. Not sure if that affects de-humidification; but it was definitely affecting the load on the old blower motor (drew just under 1000 watts). I want to test the new blower motor draw when I get a chance.

Of course the funny thing is the guy who commented about the duct size; was the guy who designed + installed the ducts in the first place.

You hit on it right there. Most contractors are only "okay" in the sense that they have to work with existing ductwork . . and my money and reading says that this is where the real problems/solutions lay. Even brand-new houses, supposedly energy-efficient (more than band-aid work) seem to not be as good as they could be. The explanations I've read mean to me that to build from scratch down here in pretty-much-needs A/C year-round-land that one might as well start enquiring about certified engineers and be willing to pony up the cost.

No matter the system type, you gotta deliver and retrieve. And much of it appears to be in the ducting. Computational-hydrodynamical-National Security-Agency-teraflop-number-crunching applies . . yeah, okay, an exaggeration. Much is known and formulated. But even more is lost in translation from scientists to engineers to contractors to homeowners.

Most of us are just not going to rip out the walls/attic/basement and re-configure room layouts for "the perfect system". Much as we'd like to. (Worst part about most post-war houses down South is the lack of basements to run ducting . . that, naturally, is better in 160F attics. With loss rates of 30% common after five years. Or, higher. On "energy efficient" designs).

I haven't read up on this in a few years, but I have owned five houses the past six years so have had time to install, repair, maintain central HVAC of differing ages and quality; on my own and with pro's. The ducting leaks are a huge, straightforward thing to fix. A genuine PITA. Worth a third of the A/C bill every month to get right.

Aeroseal Air Duct Sealing - w/o air duct cleaning, mastic, air duct dust

is an interesting service/product to look at.