On Tuesday, October 22, 2019 at 8:26:04 PM UTC-4, Commander Kinsey wrote:
On Wed, 23 Oct 2019 01:17:39 +0100, trader_4 wrote:

On Tuesday, October 22, 2019 at 5:16:19 PM UTC-4, Commander Kinsey wrote:
On Tue, 22 Oct 2019 20:43:19 +0100, trader_4 wrote:

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,

It's not a window unit, it's not shaped to fit a window. But it has one inside part and one outside part, so works in the same way.


Well, IDK what exactly you had. But you and Danny were comparing it to
a mini-split. A mini-split can and often is just two pieces one inside,
one outside. Some will support more than one inside unit. So, what you
say isn't a mini-split sounds like one to me, so far.

The word split suggests you get at least two indoor units.

Maybe to you, but not to the industry, the companies that build and
market them. The "split" refers to the fact that it's not a single
unit in a window type AC, the condenser and evaporator are in separate
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

In the USA perhaps. Other countries like the UK (where I live) don't have regulations on AC efficiency.

That's quite shocking, what with global warming and all the other things
being regulated and controlled in Europe as a result.

Global warming is bull****, and we don't use much AC. Eventually we'll use heat pumps for heating, then no doubt they'll introduce tree hugging bull****. But having left the EU, we might not.

and they go up to 20 and beyond. Window units are rated in EER,
and he may be confusing the two ratings.

No, this one lists SEER and EER.

[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.

I assume what Danny was saying is if running it on full blast, then the coils themselves will get very cold and hot, hence make it run less efficiently. Best to run a big engine slowly than a little engine fast - Top Gear (a UK motoring program) ran a test where a Toyota Prius drove as fast as possible round a race track, and a large BMW followed it. The BMW used less fuel!

Yes, I agree and have no issue with that. But I've never seen a system
where it runs on one minute, then off four. When it's not that hot outside
the AC runs long enough to drop the temperature down about a degree.
If it's mild outside, the inside temp isn't going back up a degree in
just four minutes. Now would anything close to a working, realistic
system cool off the place in just a minute, even on a mild day. Running
for 5 mins, then being off for 30 mins or an hour is what you see.

Agreed.

If you have a two stage unit, it will run more frequently at the lower
output on mild days. That helps move more air around, equalize temperature,
get more humidity out, etc. But the problem is that two stage costs
considerably more, I looked at it, decided it was not worth it.