Which UPS?

[Scott Allen]

On 14 June 2012 10:32, James Knott <james.knott-bJEeYj9oJeDQT0dZR+AlfA at public.gmane.org> wrote:
> Scott Allen wrote:
>>
>> Emphasis on "we're talking the typical North American home here", thus
>> assuming a typical small retail UPS.
>
>
> I was referring to industrial systems, as used in telecom and data centers
> where all UPS is truly that.  No relays to switch output.

Fine, but your statement that started this whole discussion between
you and me was:
"I'd have to question why having both in the same package results in
higher efficiencies of the order you claim."

Which I assumed was referring to the only thing that you quoted from my message:
Scott Allen wrote:
    With a 48VDC output UPS powered by mains AC:
      - While on mains (most of the time):
    UPS needs to convert 120VAC to 48VDC at, let's say, 85% efficiency.
    The 48VDC PC power supplies above are 70% efficient but let's say we
    find one that's 85%. UPS 85% and PC 85% is 72.25% overall.

as compared to my given calculations for an AC output UPS.

Given the terms that I had spelled out: that I was talking about a
home system and my stated assumption that the AC output UPS has no
loss while the line is up (due to using a relay), what, exactly, about
my claim are you questioning?

If you're arguing the fact that PC/UPS systems using DC supplies in
the PC can be more efficient than feeding AC to the PCs, then you
should have said something more like:
"Your claims are valid, for a small home UPS/PC setup, but in other
situations DC powered systems can be more efficient."
rather than questioning my claim.

I would then have agreed with you.

-- 
Scott
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