[time-nuts] Re: Has Line-Frequency Timekeeping Become Less Reliable in the U.S.?

[Geoff Van der Wagen]

We have home inverters that can run in off-grid mode, albeit 3Hz faster 
(to discourage other inverters from trying to feed in). Our oven and 
microwave both gain time rapidly in that mode. Counting mains cycles is 
still cheaper than a crystal.

The desire for mains timekeeping is not strong any more - everyone's 
paying much more attention to a time-synced iThingy than their oven.

Geoff VK2WA


On 16/7/26 15:02, Larry McDavid via time-nuts wrote:
> Nope. All appliances I've checked count mains cycles; this includes 
> three microwave ovens, a kitchen oven and an air fryer. I've set them 
> accurately and watched the minute turn over simultaneously on the 
> several kitchen appliances, concurrent with a very old digital, 
> single-chip clock that also counts line cycles. They all run slow or 
> fast equally. Mains cycle count is no longer maintained. By a lot...
>
> I do have two nightstand clocks that count oscillator cycles; one runs 
> slow, one fast.
>
> Only my GPS clocks (and GPSDO) are accurate. WWVB clocks vary a few 
> seconds until they reset after midnight. Except for two BPSK WWVB 
> clocks; those reset throughout the day due to 100X 60 KHz receiver 
> decode sensitivity.
>
> These are solid, empirical data.
>
> Best wishes,
>
> Larry McDavid W6FUB
> Anaheim, California (SE of Los Angeles, near Disneyland)
>
> On 7/15/2026 3:06 PM, Jim Lux via time-nuts wrote:
>>
>>
>>
>>
>> Â  I would think that ovens, appliances, and the like don't count 
>> cycles any more.  They all have microcontrollers in them, and they'd 
>> count oscillator cycles.
>> Even my 20 year old bedside clock doesn't use line frequency (because 
>> it has battery backup, it can't).
>>
>> Yes, my grandmother's old stove with the clock built in, manufactured 
>> some time pre-1960, certainly is line frequency dependent.
>> A washing machine with a mechanical timer perhaps.  But the old 
>> microwave oven I have in the garage that has a "turn knob to set 
>> cooking time" uses a *mechanical* spring wound timer.
>>
>> Is there anything that uses line frequency as a time standard any 
>> more (other than weird stuff like PDP-11's using line frequency for 
>> RTC input)
>>
>> Older timeclocks controlling lighting (the ones with the pegs to turn 
>> and off) probably use synchronous motors. Same with the household 
>> timers that one might use for holiday lights.
>>
>> I note that in a new installation for lighting controls, almost 
>> invariably, for exterior and sign lighting they're required to be 
>> "astronomical" timers that know when sunrise and sunset are. (CA 
>> TItle 24, ASHRAE 90.1) (or photodetectors). And for interiors, 
>> they're required to be able to automatically deal with holidays and 
>> daylight saving time. That pretty much means the old mechanical 
>> timers have limited uses.
>>
>>
>>
>>
>> On Wed, 15 Jul 2026 15:15:10 +0000, "Thomas D. Erb via time-nuts" 
>> <time-nuts at lists.febo.com> wrote:
>>
>> I recently came across information suggesting that the way the North 
>> American power grid handles accumulated time error may be changing, 
>> and I had not realized this was even being discussed.
>>
>> Historically, synchronous clocks-and some electronic appliance clocks 
>> that count the 60 Hz AC waveform-benefited from long-term 
>> grid-frequency correction. Although the instantaneous frequency 
>> varied slightly, accumulated error was corrected so that these clocks 
>> remained reasonably accurate over time.
>>
>> Does anyone here know the current status of Time Error Correction on 
>> the different North American interconnections?
>>
>> More specifically, are traditional synchronous clocks now likely to 
>> accumulate noticeable long-term error? And what about microwave 
>> ovens, ranges and other digital clocks that may use AC zero crossings 
>> rather than a crystal or real-time clock for their time base?
>>
>> I initially saw a reference to an April 14, 2026 NERC/FERC action, 
>> but on looking more closely, that appears to concern retirement of 
>> BAL-002-WECC-3, a contingency-reserve standard-not BAL-004 time-error 
>> correction. NERC still lists BAL-004-WECC-4, Automatic Time Error 
>> Correction, as active in the Western Interconnection.
>>
>> I would be interested to hear from anyone familiar with current 
>> utility frequency-control practices, particularly in the Eastern 
>> Interconnection.
>>
>>
>> Thomas D. Erb
>> o: 508-359-9684
>> p: 508-359-4396 x 1700
>> f: 508-359-4482
>> a: 97 West Street, Medfield, MA 02052 USA
>> e: tde at electrictime.com
>> w: www.electrictime.com
>> Tower & Street Clocks Since 1928
>>
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