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    Variac's on sale right now at Circuit Specialists in AZ

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    deepee99

    Posts : 1646
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: Variac's on sale right now at Circuit Specialists in AZ

    Post by deepee99 on Tue Aug 01, 2017 2:56 pm

    I'm just thinking I'll run a drop-cord to Grand Coulee dam. Got enough cable for that Smile
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    Kentley

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    Location : Worcester, MA

    Re: Variac's on sale right now at Circuit Specialists in AZ

    Post by Kentley on Tue Aug 01, 2017 8:46 pm

    Re: U.S. AC Power acceptable variation.
    There seems to be widespread dissension about the actual allowable variation in the line voltage. Some say +/- 5%, which would give 114-126. Others claim the actual regs specify +/- 10%, which would yield 108-132. It seems logical to assume (!!!) that the latter set of ranges is the one adhered to. Right now, my line AC is an all-time low of 113VAC. I doubt that bringing this to the attention of National Grid would elicit any response other than a quiet yawn.
    This situation (low line voltage) has led me to a workable solution, possible only because my ST-120 was built with the time-delay relay. The Weber WS-1 SS rectifier is designed with no sag resistors. So my B+ voltage as measured on the driver board is pretty close to the center of acceptable range -- 386 VDC -- the range is 370 - 410. And the bias pots are generally around 10 o'clock.
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    Peter W.

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    Join date : 2016-08-07
    Location : Melrose Park, PA

    Re: Variac's on sale right now at Circuit Specialists in AZ

    Post by Peter W. on Wed Aug 02, 2017 8:03 am

    https://www.cdw.com/shop/products/Tripp-Lite-1000VA-800W-Line-Interactive-UPS-Sine-Wave-120V-Rackmount-2U-TAA/1923328.aspx?cm_cat=GoogleBase&cm_ite=1923328&cm_pla=NA-NA-TRI_BA&cm_ven=acquirgy&ef_id=WUgmggAAAKtl5okB:20170802113356:s&gclid=CjwKCAjw8IXMBRB8EiwAg9fgMBoz0yS-m4ApcExYGxNmXe24JTqUyNy1SkFLHpnitwuGwWn68dVXXBoC1skQAvD_BwE&s_kwcid=AL!4223!3!47988697099!!!g!64450928333!    

    Does not seem overly complicated nor particularly expensive to me for the basics - if one's power is as bad as described.

    National Standards:   https://www.pge.com/includes/docs/pdfs/mybusiness/customerservice/energystatus/powerquality/voltage_tolerance.pdf  A little bit dense to read, but the potential for variation is considerable.

    Those of you at some distance from the source, in areas where there has been considerable growth, you are at particular risk, as suppliers have raised the voltage in the distribution lines so that existing conductors can carry additional capacity. Meaning that you may be running at the limit of the local step-down transformers.

    I will state, again, for the record, that variable  autotransformers, while better than nothing, are not designed to create a steady-state output, but to drop (or raise) input voltage at some proportion to the setting of the transformer. They also can be a source of noise, and if run constantly at anything approaching their load rating will get hot. Note that the largest risk of an VAT is the wiper - a small graphite button (if quality devices, otherwise a simple copper/bronze leaf-spring) that carries the entire load. Hence the need for significant over-sizing if used as a constant control.

    We are blessed with "good" power - inasmuch as we are in a very old neighborhood with almost no additional development since 1900 - so the increase in load has been relative to additional consumers - central AC, appliances and so forth, not 300 new houses on the same distribution line. But if I were in an area with such wild fluctuations as described here, I would go with a decent line-conditioner. Were I to be into belts, suspenders and Velcro, I would feed such a conditioner through a heavy-duty VAT at say.... 118 V or so as a midpoint.  And let the LC handle the rest. We get about 118 V as our steady-state at the wallplate here. Even mid-summer when the AC load is at its highest.

    You pays you money, you makes you choice. What is appropriate for my location is unlikely to be entirely appropriate to yours.

    On Kill-A-Watt meters - they are about as precise as a diesel engine, and that is no big deal when one considers their basic purpose, which is a snapshot of actual consumption at any given location at any given time *relative* to a previous future or time. Does anyone here remember the term "speedometer error"? This was the amount of slop expected in the typical automotive speedometer that the "Cops" would typically permit a drive before pulling one over for speeding. In Pennsylvania, for one example, the 'courtesy' was about 15% of actual speed. A study was done in about 1968/9 or so, and it was determined that at a cost of about $0.02 per car, this error could be eliminated, or reduced to a variation based on tire wear (really). Two things happened: The automobile industry howled that this cost would be excessive across total production (about 9,000,000 units in the US alone - $180,000. Really?), and the AAA howled that this would cause all sorts of unjust arrests for speeding. Never happened. Look at the Kill-A-Watt meter as a similar device. It is only as accurate as it must be. A Fluke Meter is designed to be accurate - and costs accordingly.


    Last edited by Peter W. on Wed Aug 02, 2017 10:23 am; edited 1 time in total (Reason for editing : Punctuation.)

    tk125

    Posts : 1
    Join date : 2017-06-01

    Re: Variac's on sale right now at Circuit Specialists in AZ

    Post by tk125 on Wed Aug 02, 2017 4:27 pm

    deepee99 wrote:
    slate1 wrote:
    Peter W. wrote:
    deepee99 wrote:  >>SNIPPAGE<<
    Bite the bullet, get a studio-grade Furman. They have some solid-state internals but basically are just a great big multi-tapped autoformer and your gear will see a pure sine wave, clamped at 121 VAC regardless of line voltage. Plug it into a manual-reset GFCI and run all your gear off of it. Cheapest insurance on the planet.

    Yep.

    Just to be clear - the Furman units, like the P1800 regulate to approximately 120v +/-5v as long as the input voltage is between 100-140v.  The APC H15 Conditioner (which I own and has been very reliable) provides close to the same level of regulation (120v +/- 5% between 102-132v) at a fraction of the cost.  Neither of the devices, however, will keep me consistently under the 123v I'm trying to achieve with the APC providing potentially up to 127v.

    I understand and appreciate the lack of surge protection, but in the end though, the variac seems like it would be a better choice for accurate voltage regulation, although requiring more "maintenance" - I'm wondering if I shouldn't just plug a kill-a-watt P4400 meter into the variac to get a better quality reading than the analog sweep meter?  (you'll have to google it - won't let me post a link because I haven't been a member for 7 days)

    Simply set the variac to 117v before powering up the amp and I believe  I'm set.  Also wondering if I should just plug the variac into the APC H15, providing surge protection, or just straight into the wall which, granted, would leave me exposed to spikes.

    The cheaper Furmans, like the 1800 models, do indeed have a 5-volt slop factor, which is still pretty good. I use an 1800 in the den to protect a combination of tube pre-amp and s/s amp.  Furman's studio grades, such as the SPR-20i I use in my all-tube main system have a 1-volt variation (off 121) within the input voltage range you mentioned. Believe me, I spent hours with their English-as-first-language-speaking tekkies before dropping 2 large on it. All I can say again, the sumbitch does its job.
    If you're going to drop $30 on a kill-a-watt, why not add another $70 and get a Fluke, which will give you far greater accuracy and utility. And again, you can "set" your Variac to 117 VAC (based on 120 VAC line voltage at the time) if your line voltage has a momentary spike to 130, the Variac will be right behind it at 127 VAC.
    And to preach to the choir, if you don't have a manual-reset GFCI plugged into your wall outlet, nothing will save you from spikes, up or down.
    BTW, Welcome to the board. I'm one of the noisier ones here, so take whatever I say with a grain of salt.

    I also use the Furman SPR-20i. I plugged it into my Variac and ran the input from 113V to 126V, and it controlled the output voltages over that range between 118.5V and 121V. I did discover that it responds a little faster when the input voltage increases vs when it is decreasing. Don't know why and neither did Furman. I also asked them why I got readings of 118.5V when it is supposed to output 120+/-1V. They said they thought the unit was working fine. What it is doing is switching taps on a big toroidal autoformer using SCR switches (for slient switching), which is also why you get good RMS output. I'm not hung up about the 0.5V discrepancy since it's a lot better than watching my line voltage go down to 115v on a big air conditioning day here in the south, vs 123V at night. Mine keeps the line at 118.5 to 120, and my tubes are happy!

    RE: the Kill-a-Watt accuracy. I measured the Variac output and the Furman output with a Keithley 2015 DMM and compared it to the Kill-A-Watt. The KAW is generally about 0.7 to 0.8V low all the time. I compared my Keithley to a couple other hand held DMM's I have, and they compared within 0.1V in general on the 120V scale. I use my Keithley as my standard.
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    deepee99

    Posts : 1646
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: Variac's on sale right now at Circuit Specialists in AZ

    Post by deepee99 on Wed Aug 02, 2017 5:26 pm

    tk125 wrote:
    deepee99 wrote:
    slate1 wrote:
    Peter W. wrote:
    deepee99 wrote:  >>SNIPPAGE<<
    Bite the bullet, get a studio-grade Furman. They have some solid-state internals but basically are just a great big multi-tapped autoformer and your gear will see a pure sine wave, clamped at 121 VAC regardless of line voltage. Plug it into a manual-reset GFCI and run all your gear off of it. Cheapest insurance on the planet.

    Yep.

    Just to be clear - the Furman units, like the P1800 regulate to approximately 120v +/-5v as long as the input voltage is between 100-140v.  The APC H15 Conditioner (which I own and has been very reliable) provides close to the same level of regulation (120v +/- 5% between 102-132v) at a fraction of the cost.  Neither of the devices, however, will keep me consistently under the 123v I'm trying to achieve with the APC providing potentially up to 127v.

    I understand and appreciate the lack of surge protection, but in the end though, the variac seems like it would be a better choice for accurate voltage regulation, although requiring more "maintenance" - I'm wondering if I shouldn't just plug a kill-a-watt P4400 meter into the variac to get a better quality reading than the analog sweep meter?  (you'll have to google it - won't let me post a link because I haven't been a member for 7 days)

    Simply set the variac to 117v before powering up the amp and I believe  I'm set.  Also wondering if I should just plug the variac into the APC H15, providing surge protection, or just straight into the wall which, granted, would leave me exposed to spikes.

    The cheaper Furmans, like the 1800 models, do indeed have a 5-volt slop factor, which is still pretty good. I use an 1800 in the den to protect a combination of tube pre-amp and s/s amp.  Furman's studio grades, such as the SPR-20i I use in my all-tube main system have a 1-volt variation (off 121) within the input voltage range you mentioned. Believe me, I spent hours with their English-as-first-language-speaking tekkies before dropping 2 large on it. All I can say again, the sumbitch does its job.
    If you're going to drop $30 on a kill-a-watt, why not add another $70 and get a Fluke, which will give you far greater accuracy and utility. And again, you can "set" your Variac to 117 VAC (based on 120 VAC line voltage at the time) if your line voltage has a momentary spike to 130, the Variac will be right behind it at 127 VAC.
    And to preach to the choir, if you don't have a manual-reset GFCI plugged into your wall outlet, nothing will save you from spikes, up or down.
    BTW, Welcome to the board. I'm one of the noisier ones here, so take whatever I say with a grain of salt.

    I also use the Furman SPR-20i.  I plugged it into my Variac and ran the input from 113V to 126V, and it controlled the output voltages over that range between 118.5V and 121V.  I did discover that it responds a little faster when the input voltage increases vs when it is decreasing.  Don't know why and neither did Furman.  I also asked them why I got readings of 118.5V when it is supposed to output 120+/-1V.  They said they thought the unit was working fine.  What it is doing is switching taps on a big toroidal autoformer using SCR switches (for slient switching), which is also why you get good RMS output.  I'm not hung up about the 0.5V discrepancy since it's a lot better than watching my line voltage go down to 115v on a big air conditioning day here in the south, vs 123V at night.  Mine keeps the line at 118.5 to 120, and my tubes are happy!

    RE:  the Kill-a-Watt accuracy.  I measured the Variac output and the Furman output with a Keithley 2015 DMM and compared it to the Kill-A-Watt.  The KAW is generally about 0.7 to 0.8V low all the time.  I compared my Keithley to a couple other hand held DMM's I have, and they compared within 0.1V in general on the 120V scale.  I use my Keithley as my standard.
    For reasons known only to Furman, the voltage reading on the meter is what it's seeing coming from the wall. Set the meter to amperage and that will indicate what it's putting out. That's why I just leave the toggle on the amps reading. The amperage gauge tells you what the total load actually is, regardless of input voltage. If that starts to wobble a bit, you've probably got a tube or component about to go pear-shaped.

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    Re: Variac's on sale right now at Circuit Specialists in AZ

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