[time-nuts] External cooling fans - source

[Van Horn, David]

In the US, I have seen line voltage as low as 70VAC and as high as 145VAC. 
That's what I design to.
The power companies say different, but my meters don't lie.


-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Jeremy Nichols
Sent: Tuesday, December 19, 2017 9:20 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] External cooling fans - source

I put a small external fan on my 5370B, which keeps the heat sink at a reasonable low temperature (Time-Nut content) -but- (Nixon segué) the power company here also runs the voltage all the way up to the limit (126VAC) because "many of our [rural, like me] customers are all-electric and the load tends to pull the voltage down during times of peak use." The voltage got so high I finally put a recorder on it and walked the results into their office. In response, they attached their recorder to my connection and ran it for a couple of weeks before agreeing with me. Then they reluctantly turned the transformer down a notch so we stay below 126VAC now.

Jeremy

On Tue, Dec 19, 2017 at 5:44 AM Bob kb8tq <kb8tq at n1k.org> wrote:

> Hi
>
> Yes, this *is* a bit off topic. Sorry about that … I’m sure it’ll 
> never / ever happen again :) …. ummm …. today ….
>
> The voltage that supply feeds are set to is as much a public relations 
> issue as a technical one. People would routinely complain “the lights 
> are to dim”.
> Voltage
> gets bumped up. Complaints drop off. Eventually you are right at (or 
> as you observe marginally above) the max limits. Since the power 
> company is paid by the watt, the added power usage (if any) is not a 
> big deal. The call outs for checks
> *are* a big
> deal to them ….. complaints impact the metrics by which they are judged ….
>
> Bob
>
> > On Dec 19, 2017, at 12:48 AM, Dr. David Kirkby <
> drkirkby at kirkbymicrowave.co.uk> wrote:
> >
> > On 18 December 2017 at 23:11, Charles Steinmetz 
> > <csteinmetz at yandex.com>
> > wrote:
> >
> >> From time to time, the subject of external cooling fans comes up -- 
> >> for example, in discussions of the HP 5370A/B with their steaming 
> >> hot heatsinks.  I have several times recommended very quiet, all-metal, 4"
> desk
> >> fans as ideal for the job, but have not been able to suggest a source.
> >>
> >
> > For what it is worth, my 5370B run very hot, which forced me to 
> > check my mains voltage as I knew every time I had done a quick 
> > measurement, the voltage was above 230 V. So for a few days I logged 
> > the voltage, and
> found
> > it was consistently high. The maximum permitted here in the UK is 
> > 253 V, but I measured mine at 255.x volts. It was the heat of the 
> > 5370B that forced me to contact the electricity supply company (UK 
> > Power Networks), who logged the voltage for 4 days. I have a 3-phase 
> > supply here, which is unusual for a domestic property, but each of 
> > the 3 phases was
> consistently
> > high. I managed to get the supply company to reduce the voltage by 5%.
> That
> > made a *significant* difference in the heatsink temperature of the 
> > 5370B, and a significant difference to to the exhaust temperature of 
> > my HP 70000 series system.
> >
> > I'm not saying an extra fan is not a good idea, but it is certainly 
> > worth ensuring the mains voltage is not too high. I was told by UK 
> > Power
> Networks
> > that they aim for 245-250 V in rural areas - this is despite the UK 
> > is supposed to be 230 -6%/+10%. On equipment with linear power 
> > supplies, a
> few
> > extra volts can lead to a significant increase in the amount of heat 
> > the regulators produce. 10% extra voltage does *not* equate to 10% 
> > extra
> power
> > dissipation, but considerably more.
> >
> > I found quite a reluctance on the part of the UK Power Networks to 
> > reduce the voltage. Even though it was was on average more than 5% 
> > high, the technical manager who took ownership of the problem only 
> > wanted to reduce the voltage by 2.5%, despite they could easily 
> > reduce it 5%. Luckily,
> when
> > the engineers came to adjust the supply voltage, (which they do by
> changing
> > the taps on the 11 kV primary), I managed to convince them that 
> > there
> were
> > very few properties on the transformer, and the furthest was an old
> couple
> > that used very little electricity. So they did reduce it 5%, which 
> > is the maximum they could. But they warned me that if there were 
> > complaints of
> low
> > voltage, they would have to increase it 2.5%. Luckily for me, nobody 
> > locally noticed the reduction in mains voltage, and it is still on
> average
> > over 230 V.
> >
> > It would be interesting to know how low the AC input can go on a 
> > 5370B before the regulators fail to regulate. Given they are the 
> > sort of instrument one might want to run for long periods, running 
> > one on a UPS, with a transformer to reduce the output of the UPS, 
> > might not be such a
> bad
> > idea.
> >
> >
> >> Charles
> >>
> >
> > Dave
> > _______________________________________________
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