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References: <ea7ebfa5-dcfa-40d8-8170-1089a5dc7146@googlegroups.com>
<CAAxzKbRyMkxswhUYek8zt4RTR772su49YHJ0hT=hffd20Ky...@mail.gmail.com>
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Date: Thu, 18 Oct 2012 14:08:22 +1100
Message-ID: <CAPh9M+GsCVbg91=LSX+eXxMM_A8E_2Zy6xeYjVu9Q_jzmGR...@mail.gmail.com>
Subject: Re: AC fans in series - problem?
From: Stuart Young <cef...@gmail.com>
To: hackerspace_brisbane@googlegroups.com
Content-Type: multipart/alternative; boundary=f46d040714c92a543c04cc4cb332
--f46d040714c92a543c04cc4cb332
Content-Type: text/plain; charset=ISO-8859-1
What may be the case is that by free-running them in parallel you are
getting audible beating as the fans aren't running quite in sync. The
difference only needs to be very small to lead to beating.
By putting them in series they are forced to run in sync due to the peak in
current flow having to go through both motors at the same time.
Fwiw: I have seen fan shelves for cabinets that have 4 x 120 VAC fans, with
2 each in series, then with each series string in parallel. They rewire
them all in parallel for 120V (eg: USA, Japan).
--
Cef
On Oct 18, 2012 1:41 PM, "James Churchill" <pel...@gmail.com> wrote:
> They couldn't be AC induction motors, because halving the voltage
> wouldn't change the speed of them (as the speed is dependent on line
> frequency).
>
> I don't think there's any risk here.
>
> - James
>
> On 18 October 2012 12:34, tjhowse <tjho...@gmail.com> wrote:
> > When you say "AC" do you mean "Air Conditioning" or "Alternating
> Current"?
> >
> > If the former, you should be safe. If the latter, I wouldn't try it.
> >
> >
> > On 18 October 2012 11:59, Spoz <mr.s...@gmail.com> wrote:
> >>
> >> So we got a new server rack at work and the AC fans it comes with are
> very
> >> noisy and we don't need anywhere near the airflow they provide.
> >>
> >> I opened up the unit and there's four fans. If I put two of them in
> series
> >> (so each fan sees half the voltage) they run at a perfect speed for us.
> What
> >> I want to know is, is this a problem? Will they burn out and set our
> office
> >> on fire over the weekend?
> >>
> >> --
> >> You received this message because you are subscribed to the Google
> Groups
> >> "hackerspace_brisbane" group.
> >> To view this discussion on the web visit
> >> https://groups.google.com/d/msg/hackerspace_brisbane/-/0bpuV4BF8V4J.
> >> To post to this group, send email to
> >> hackerspace_brisbane@googlegroups.com.
> >> To unsubscribe from this group, send email to
> >> hackerspace_brisbane+unsubscribe@googlegroups.com.
> >> For more options, visit this group at
> >> http://groups.google.com/group/hackerspace_brisbane?hl=en.
> >
> >
> > --
> > You received this message because you are subscribed to the Google Groups
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> hackerspace_brisbane@googlegroups.com.
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>
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--f46d040714c92a543c04cc4cb332
Content-Type: text/html; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
<p>What may be the case is that by free-running them in parallel you are ge=
tting audible beating as the fans aren't running quite in sync. The dif=
ference only needs to be very small to lead to beating.</p>
<p>By putting them in series they are forced to run in sync due to the peak=
in current flow having to go through both motors at the same time. </p>
<p>Fwiw: I have seen fan shelves for cabinets that have 4 x 120 VAC fans, w=
ith 2 each in series, then with each series string in parallel. They rewire=
them all in parallel for 120V (eg: USA, Japan).</p>
<p>--<br>
Cef<br>
</p>
<div class=3D"gmail_quote">On Oct 18, 2012 1:41 PM, "James Churchill&q=
uot; <<a href=3D"mailto:pel...@gmail.com">pel...@gmail.com</a>> wrote=
:<br type=3D"attribution"><blockquote class=3D"gmail_quote" style=3D"margin=
:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
They couldn't be AC induction motors, because halving the voltage<br>
wouldn't change the speed of them (as the speed is dependent on line<br=
>
frequency).<br>
<br>
I don't think there's any risk here.<br>
<br>
- James<br>
<br>
On 18 October 2012 12:34, tjhowse <<a href=3D"mailto:tjho...@gmail.com">=
tjho...@gmail.com</a>> wrote:<br>
> When you say "AC" do you mean "Air Conditioning" o=
r "Alternating Current"?<br>
><br>
> If the former, you should be safe. If the latter, I wouldn't try i=
t.<br>
><br>
><br>
> On 18 October 2012 11:59, Spoz <<a href=3D"mailto:mr.s...@gmail.com=
">mr.s...@gmail.com</a>> wrote:<br>
>><br>
>> So we got a new server rack at work and the AC fans it comes with =
are very<br>
>> noisy and we don't need anywhere near the airflow they provide=
.<br>
>><br>
>> I opened up the unit and there's four fans. If I put two of th=
em in series<br>
>> (so each fan sees half the voltage) they run at a perfect speed fo=
r us. What<br>
>> I want to know is, is this a problem? Will they burn out and set o=
ur office<br>
>> on fire over the weekend?<br>
>><br>
>> --<br>
>> You received this message because you are subscribed to the Google=
Groups<br>
>> "hackerspace_brisbane" group.<br>
>> To view this discussion on the web visit<br>
>> <a href=3D"https://groups.google.com/d/msg/hackerspace_brisbane/-/=
0bpuV4BF8V4J" target=3D"_blank">https://groups.google.com/d/msg/hackerspace=
_brisbane/-/0bpuV4BF8V4J</a>.<br>
>> To post to this group, send email to<br>
>> <a href=3D"mailto:hackerspace_brisbane@googlegroups.com">hackerspa=
ce_brisbane@googlegroups.com</a>.<br>
>> To unsubscribe from this group, send email to<br>
>> <a href=3D"mailto:hackerspace_brisbane%2Bunsubscribe@googlegroups.=
com">hackerspace_brisbane+unsubscribe@googlegroups.com</a>.<br>
>> For more options, visit this group at<br>
>> <a href=3D"http://groups.google.com/group/hackerspace_brisbane?hl=
=3Den" target=3D"_blank">http://groups.google.com/group/hackerspace_brisban=
e?hl=3Den</a>.<br>
><br>
><br>
> --<br>
> You received this message because you are subscribed to the Google Gro=
ups<br>
> "hackerspace_brisbane" group.<br>
> To post to this group, send email to <a href=3D"mailto:hackerspace_bri=
sbane@googlegroups.com">hackerspace_brisbane@googlegroups.com</a>.<br>
> To unsubscribe from this group, send email to<br>
> <a href=3D"mailto:hackerspace_brisbane%2Bunsubscribe@googlegroups.com"=
>hackerspace_brisbane+unsubscribe@googlegroups.com</a>.<br>
> For more options, visit this group at<br>
> <a href=3D"http://groups.google.com/group/hackerspace_brisbane?hl=3Den=
" target=3D"_blank">http://groups.google.com/group/hackerspace_brisbane?hl=
=3Den</a>.<br>
<br>
--<br>
You received this message because you are subscribed to the Google Groups &=
quot;hackerspace_brisbane" group.<br>
To post to this group, send email to <a href=3D"mailto:hackerspace_brisbane=
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For more options, visit this group at <a href=3D"http://groups.google.com/g=
roup/hackerspace_brisbane?hl=3Den" target=3D"_blank">http://groups.google.c=
om/group/hackerspace_brisbane?hl=3Den</a>.<br>
<br>
</blockquote></div>
--f46d040714c92a543c04cc4cb332--
Message from discussion AC fans in series - problem?
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