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 <[email protected]> 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 < > [email protected]> wrote: > > > > On 18 December 2017 at 23:11, Charles Steinmetz <[email protected]> > > 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 > > _______________________________________________ > > time-nuts mailing list -- [email protected] > > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- Sent from my iPad 4. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
