On Tuesday, October 22, 2019 at 2:32:30 PM UTC-4, danny burstein wrote:
In op.z92p4mxowdg98l@glass "Commander Kinsey" writes:

Just had a reply elsewhere that said the USA 13 minimum SEER only applie=
s to split units, and that most single units are much lower. Any reason=
why split units would be more efficient?

A bunch of reasons:

1: "mini split" units tend to be inverter controlled,
with variable output cooling/heating. There's more
efficiency with a five degree temperature drop [a]
than a 20 degree one.

2: the mini splits aren't wasting energy pumping all
that air around through ducts. Also, less leakage
in places where, well, the conditioned air is leaking..

I assume by single units the poster was referring to window units,
not central AC, because he claims that most single units are much
less that 13 SEER. You can't buy a central AC that's less than 13 SEER
and they go up to 20 and beyond. Window units are rated in EER,
and he may be confusing the two ratings.







[a] standard units have the compressor (cooling part)
fully on or off. The thermostat will kick it on
and, well, off as needed.

Not true with two stage AC or heat pumps.




Hence if you only (for simplified example) need 5,000
BTUs/hr to keep your place cooled down (let's say it's
only a tad warm outisde) and your system is rated with
a 24,000 BTU (two ton) output, it'll cycle on for one
minute, then off for four, on for 1, off for 4. Rinse,
cycle, repeat.

If it's not that hot outside, then the inside temperature,
once lowered, isn't going to bounce right back up again in
just four minutes. Typically it would run briefly a couple
times an hour.