On 9/12/2022 3:51 PM, TimR wrote:
> On Monday, September 12, 2022 at 3:57:13 PM UTC-4, bruce bowser wrote:
>> On Monday, September 12, 2022 at 3:18:46 PM UTC-4, danny burstein wrote:
>>> In <qCJTK.33643$x5w7...@fx42.iad> Mark Lloyd <not....@all.invalid> writes:
>>>
>>> [snip]
>>>> A lot of older people say 110/220. It seems to mean the same thing as
>>>> 120/240. I've also heard 115/230, 117/234, 118/236, and 125/250 (always
>>>> a 1:2 ratio),
I understand 120/s40 to be the "system" voltage - nominal voltage at the
service.
And 115/230 (or maybe 110/220) to be the "utilization" voltage - at the
equipment. Mark says his AC compressor/condenser is marked 208/230 (208
would be nominal system voltage - a violation of this convention, but I
don't remember seeing 200/115).
>>> And, of course, 120/208 ...
>>>
>>> (Don't ask >>
>> 120/208 is usually OK for 120v. 208v merely lacks a neutral, but its
OK. And many panels have current-limiting fuse capacity.
In a "208/120" volt 3-phase system "120" should always be good for 120.
A "current-limiting" fuse is fast acting, and for high current faults
melts and clears before the current reaches its first peak - the
let-through peak fault current is significantly lower than with a slower
fuse. Bussmann FRN fuses are common current-limiting cartridge fuses
that fit in normal cartridge fuse holders.
>
> We wired a housing area with 120/208 because we got a good deal on a bunch of AC units that needed 3 phase. I guess anyway, wasn't my decision. But I got the angry phone calls from people whose clothes dryers took forever, and ovens heated slowly. I wouldn't put 3 phase anywhere I didn't have to (in the US) because of problems with harmonics.
>
Some large apartments have 208/120 3-phase coming in and 2 phases go to
each apartment - 208/120. A 240V appliance on 208V will heat slower -
208/240=87% but the effect is squared - 75%. A relatively small
buck/boost transformer can boost to 240. A 240V motor shouldn't be used
on 208 unless the nameplate says 208/230.
Not obvious which harmonic problem. Some harmonics on different phases,
which can be caused by power supplies, can add on the neutral instead of
cancelling.