AC mains startup surge dampener - Page 1
Forum section: electronics / projects

author: FrankenPC
author_rank: Unknown
timestamp: April 18, 2014, 11:03:53 pm
content: I need a solution to an AC mains problem I have.This problem is with one circuit in my home. It's a long wiring run for all receptacles in the bedrooms. It's very easy to overload. Well, I put an office in one room and in that office I placed a color laser printer. This printer draws so much current on sleep-resume that is throws my UPS's into a tizzy.AC motors use an A/C cap to assist with short duration start loads. The duration is too fast.A UPS backup system can deliver instant A/C inverted signals on mains loss.What about a design that uses a battery/capacitor bank and an inverter that dynamically disconnects from the mains when the current begins to overload mains capacity? Anyone ever heard of such a device?

author: Richard Crowley
author_rank: Super Contributor
timestamp: April 18, 2014, 11:10:38 pm
content: You wouldn't just put a bandage over Melanoma Cancer.This is a symptom that your power mains wiring is either damaged or insufficient for the loads you are attempting.Have you had the wiring checked? Specifically if there are any junctions that are not perfectly tight, you could be losing power along the way.Seriously, this could be a valuable early-warning of a catastrophic failure that could burn your house down.Or at minimum, you need to do a serious job of reviewing the wiring and perhaps installing an additional branch circuit.

author: FrankenPC
author_rank: Unknown
timestamp: April 18, 2014, 11:14:00 pm
content: Quote from: Richard Crowley on April 18, 2014, 11:10:38 pmTrue. This could be a good excuse to study A/C mains construction. I already know how to repair appliances and HVAC equipment. Why not take it all the way to A/C electrical construction standards and debugging? I'm getting bored with programming anyway.

author: theatrus
author_rank: Frequent Contributor
timestamp: April 18, 2014, 11:57:56 pm
content: Quote from: FrankenPC on April 18, 2014, 11:03:53 pmYou're describing the role of a UPS. Any good UPS will notice mains sagging and switch to the inverter.The inrush should not be sagging your circuit this much, which means its overloaded and you shouldn't be running the printer on it.

author: Fank1
author_rank: Regular Contributor
timestamp: April 21, 2014, 11:43:50 pm
content: The capacitor in the motor is not to hold the voltage up.It's to induce a phase shift in the start winding so the motor will always start in the same direction.Caps on AC don't hold up voltage.

author: ManateeMafia
author_rank: Frequent Contributor
timestamp: April 22, 2014, 04:07:36 am
content: I experienced the same issues as you with a laser printer. The UPS blew its guts out and tripped the breaker. My voltage references depleted their batteries and it cost me a lot to repair.Like the movie 'A Christmas Story' it was one plug too many.I have at least one UPS in every part of my home. Florida gets some bad thunderstorms and I wanted as much protection as possible. One of the things I learned quickly was that any UPS that drops to backup frequently will chew through batteries. The best solution I found was buying units with AVR (auto voltage regulation) in them. You can hear them kick in during the summer, but the batteries rarely get used.You can buy dedicated Tripp-lite or APC AVR units like the LE1200. If your UPS has this feature, you may be able to change the minimum sag voltage before it kicks in.I have also added a couple dedicated branch circuits to my home to handle all my extra gear. I think it was a good investment and may be worth getting an electrician to get you a quote.

author: Tinkerer
author_rank: Frequent Contributor
timestamp: April 22, 2014, 04:53:00 pm
content: Quote from: Richard Crowley on April 18, 2014, 11:10:38 pmI agree with this. One good thing to look into is the age of the wiring. If the building is older, the wiring may never have been installed properly to begin with or with outdated inadequate codes.

author: David Hess
author_rank: Super Contributor
timestamp: April 22, 2014, 05:59:37 pm
content: Some uninterruptible power supplies are much better than others. Even when not switching to backup mode, I have found that cheap ones tend to destroy their backup batteries in short order while they last 5+ years in good ones.While an online UPS might solve the printer problem, I would not consider that a good solution compared to running a separate or second circuit to handle the apparently excessive load.

author: calzap
author_rank: Frequent Contributor
timestamp: April 23, 2014, 03:12:51 pm
content: Chances are the wiring was done to code, but the original design never anticipated multiple electronic devices, some of which can have a sudden current draw, in a bedroom. The key words are "long wiring run" and "UPS's". The bedroom probably has a single 120VAC 15 A circuit or possibly a single 120VAC 20 A circuit. If the former, wiring was likely a run of 14 AWG. In most parts of the US, the NEC is the code for residential wiring. The NEC mentions voltage drop as an informational issue, but it's not part of the code because it's not considered a safety issue. Voltage drop may prevent your equipment from working, but it's unlikely to lead to fires or shocks. Personally, I think this is shortsighted, but that's the way it is.Because voltage drop will almost never cause a fail from an inspector, it's almost never considered in residential wiring (or light commercial either, for that matter). So if you are going to run a bunch of electronic equipment in a bedroom that's some distance from the breaker panel, you need another circuit with wiring that considers voltage drop. If you are in a rental, good luck with landlord paying for it. In that case, beefier UPS's with bigger batteries can compensate, but they'll be getting a good workout. Even in a rental, it may be cheaper to pay for a new circuit. Just putting in a larger breaker on the existing circuit would be dangerous and would do nothing for voltage drop. Basic problem is a lack of copper, and more copper is the best way to fix it.Mike in California

author: Monkeh
author_rank: Super Contributor
timestamp: April 23, 2014, 03:22:48 pm
content: Quote from: calzap on April 23, 2014, 03:12:51 pmlol, NEC quality again.

author: richard.cs
author_rank: Super Contributor
timestamp: April 23, 2014, 03:32:55 pm
content: Quote from: calzap on April 23, 2014, 03:12:51 pmOk, that's pretty bad. In the UK we design for <10%5% drop on a power circuit and <4%3% drop on a lighting circuit (because you only need a few volts to produce a noticable flicker).Edit - This should have been 5% and 3% as Monkeh says. Oops.

author: Monkeh
author_rank: Super Contributor
timestamp: April 23, 2014, 03:36:14 pm
content: Quote from: richard.cs on April 23, 2014, 03:32:55 pm5% and 3%, unless it's changed since I last had a copy to hand.

author: Richard Crowley
author_rank: Super Contributor
timestamp: April 23, 2014, 03:37:31 pm
content: Quote from: Monkeh on April 23, 2014, 03:22:48 pmPerhaps if you misunderstand what the NEC is.From NEC terms, "quality" means FIRE PREVENTION. Not a laughing matter, IMHO.If you house doesn't burn down, then they have done their job. Thank you.

author: Monkeh
author_rank: Super Contributor
timestamp: April 23, 2014, 03:40:07 pm
content: Quote from: Richard Crowley on April 23, 2014, 03:37:31 pmBut it's okay to have an otherwise unsafe, unreliable, poorly thought out installation, because it only has to comply with the NEC.We can get into the statistics on electrical fires in the US vs other countries again, if you like..

author: Richard Crowley
author_rank: Super Contributor
timestamp: April 23, 2014, 03:48:21 pm
content: Quote from: Monkeh on April 23, 2014, 03:40:07 pmWhat world do you live in? Every other thread around here is about shoddy goods/services. You get what you pay for.If you buy a cheap, "bargain" house, the doors squeak and the drawers stick as well.QuoteMy observation is that the overwhelming majority of private home construction here in the New World is "stick-built" (90% wood).UK/Europe has way more construction from masonry modules ("blocks") of an amazing variety. They all appear to be fireproof.I can't remember the last time I saw or heard or read of an electrical-caused fire even here in stick-bullt land. YMMV

author: Monkeh
author_rank: Super Contributor
timestamp: April 23, 2014, 03:54:26 pm
content: Quote from: Richard Crowley on April 23, 2014, 03:48:21 pmAnd this is an argument against the accepted regulations enforcing basic standards?QuoteYou've never seen what a fire does to a masonry building, then. Normal masonry construction methods main contain fire to a degree, they do not survive it.

author: ManateeMafia
author_rank: Frequent Contributor
timestamp: April 23, 2014, 04:37:16 pm
content: From what I understand, there is a requirement that new construction must use Arc-Fault circuit interrupters in bedrooms. As a minimum I would consider having these added if you are worried about overloading the existing wiring.I can tell you that the additional lines I added were necessary considering the amount of equipment I have running at any given time. If you don't already have a whole house surge protector, they are relatively easy to install for additional protection.

author: calzap
author_rank: Frequent Contributor
timestamp: April 23, 2014, 06:13:32 pm
content: Arc-fault breakers are designed to protect against arcing in permanently installed outlets and equipment attached to them. Presumably they would also trip if there was an arc in an intermediate connection along the wiring run. The arc-fault feature doesn't give any more overload protection than a regular breaker, and neither will do anything about voltage drop.I've never seen a good explanation of how an arc-fault breaker can distinguish between arcs that aren't supposed to occur and arcs that occur in a motor with brushes. Presumably the generated waveforms are different, but how? If anyone has a good explanation or link, I'd like to have it.Whole-house surge protectors are useful, but have limitations. Mine get blown-out about every 3 years and cost more than US$100 to replace. However, that's cheap compared to the value of the electronic equipment in the house. They won't provide much protection from a direct lightning strike on power lines near your home; the surge is just too massive. If a surge is generated in the home, it may fry sensitive equipment before it gets to the protector in the panel.Despite the title of the thread, we've been mostly discussing sags rather than surges.Mike in California

author: David Hess
author_rank: Super Contributor
timestamp: April 23, 2014, 07:25:43 pm
content: Quote from: calzap on April 23, 2014, 06:13:32 pmI suspect it is just a significant difference in magnitude. Brushes should not be arcing destructively.QuoteI have never been a fan of this preferring instead to use an online UPS to protect sensitive or expensive equipment but that transfers the problem to the UPS power supply itself although I have never had one fail yet. Presumably they are overbuilt compared to normal off-line power supplies. They also make power conditioners which are essentially the same thing using a capacitor bank instead of batteries and some online UPSes can operate this way without batteries installed. I considered replacing a 60 volt online UPS battery with ultracapacitors as a test but the batteries are more economical.In extreme cases, a ferroresonant transformer would my choice but they are not suitable over a wide load range because of low efficiency at light loads.I have not lost any computer equipment to power surges or sags yet but I do lose about half of my light bulbs every year making high efficiency CFL and LED bulbs a waste of money. If it were not for code issues, I would put all of my lamps on a separate UPS protected circuit.

author: SeanB
author_rank: Super Contributor
timestamp: April 23, 2014, 07:42:50 pm
content: Generally in a motor the arcing is quite well suppressed by the 2 very large series inductors there as the field winding. Other motors have a capacitor across the brushes and a small inductor in series as well for extra attenuation. This reduces the arc noise on the mains quite a lot. If the switch arcs it should trip the AFCI.

author: calzap
author_rank: Frequent Contributor
timestamp: April 23, 2014, 08:09:13 pm
content: It may well be magnitude of the arcs is smaller in brush-type motors than the trip level for arc-fault breakers, but I suspect it's more than magnitude. I have an old hand-held drill that has a pretty good "ring of fire" if you look into the case while it's running, but it doesn't trip arc-fault breakers. I would guess that the main pulses from separated conductors that are arcing would be at line frequency. The pulses coming back down the line from a motor should be several times line frequency depending on the number of windings in the rotor.Mike in California

author: NiHaoMike
author_rank: Super Contributor
timestamp: April 23, 2014, 08:18:49 pm
content: Assuming the wiring is done to code and does not have any bad connections (check that first!), you could try lowering the sensitivity setting on the UPS if there is one. Or if the mains voltage is marginally low to begin with, use an autotransformer to boost it.If you're willing to modify the printer, add a heavy duty dimmer in series with the fuser heater. Start high and adjust it down until the problem is resolved.

author: GiskardReventlov
author_rank: Frequent Contributor
timestamp: April 23, 2014, 08:33:56 pm
content: Get a new printer? Did anyone suggest that? Sounds like a broken printer either by design or not.

author: David Hess
author_rank: Super Contributor
timestamp: April 23, 2014, 08:49:38 pm
content: Quote from: GiskardReventlov on April 23, 2014, 08:33:56 pmI doubt this is a printer problem although it would be nice if they were designed to soft start their fuser heaters to prevent this issue. UPSes usually have problems powering them although you can make up for that with brute size.

author: GiskardReventlov
author_rank: Frequent Contributor
timestamp: April 24, 2014, 01:05:55 am
content: @David Hess, now that you mention it I have noticed the lights dim when a print job starts.I'm not clear on another thing too.Is the UPS a whole-house variety or just for the printer? Actually as has been noted the UPS does sound under powered. But if it's a whole-house maybe there's a fault somewhere else.I was trying to imagine why I'd put my printer on an UPS. But I couldn't come up with much unless the power goes out and stays out but then I'd buy a backup generator if that occurred often.

author: David Hess
author_rank: Super Contributor
timestamp: April 24, 2014, 04:49:15 am
content: Xerographic printers (laser and LED and photocopiers) use high temperature to fix the toner to the paper. It would be wasteful to leave the fuser heater running when idle but nobody wants to wait long before printing either so the heater draws a lot of power while starting allowing it to heat up quickly. The high power is greater than most UPS units can handle so the general recommendation is to operate the printer directly from the AC line. The high power also may cause problems with other equipment on the same AC circuit because of the voltage sag which is what is occurring here.An online UPS large enough to operate the printer *might* solve the problem. They have inverters which operate continuously supplying clean AC to the load which is decoupled from the AC line. Such a UPS would certainly shrug off the line glitch caused by the printer if it was powering other equipment. They are great for cleaning up the power from AC backup generators.Using an online UPS for an entire house would not be very economical and would be unlikely to solve the circuit sag problem caused by the printer anyway. In the past I have considered using one for *just* my house lighting because the dirty power where I am blows out light bulbs at an alarming rate.

author: mzzj
author_rank: Super Contributor
timestamp: April 24, 2014, 10:39:01 am
content: Quote from: calzap on April 23, 2014, 03:12:51 pmNo requirements for _minimum_ short-circuit circuit current on that side of the pond?European regulations specify minimum requirements for short-circuit current to ensure that fuses/circuit breakers react enough fast. Added bonus is the limitation for voltage sag under load.

author: Richard Crowley
author_rank: Super Contributor
timestamp: April 24, 2014, 10:47:37 am
content: Perhaps we are confusing the standards for building wiring with the requrements for the breakers that protect that wiring.

author: richard.cs
author_rank: Super Contributor
timestamp: April 24, 2014, 12:04:41 pm
content: Quote from: Richard Crowley on April 24, 2014, 10:47:37 amUnder the European system there is a requirement to disconnect a fault (assumed to be a L-E short circuit) within a certain amount of time. To acheive this with a given circuit breaker requires that the fault current be sufficiently large compared to its rating and therefore puts limits on the maximum permissible supply impedance. This usually relies on the magnetic part of a circuit breakers tripping characteristic, wheras the thermal part provides the function of protecting against overload.An example:Imagine a 20A cable protected by a 16A trip is subjected to a 30A load. This will eventually (about 200 seconds) cause the trip to open and is sufficient to protect the cable from overheating.Depending on the type of circuit the required disconnection time changes but 0.4s is used in the UK for a circuit that powers normal sockets. That same 16A trip needs an 80A fault current to open in that time and so on 240V mains the total loop impedance must be kept below 3 ohms. A side effect of this is that the circuit then has a maximum volt drop (at 16A load) of 48V which is 20%. In this specific case the 5% requirement is narrower but there are situations where the disconnection time requirement reduces the voltage drop beyond that otherwise needed.

author: calzap
author_rank: Frequent Contributor
timestamp: April 24, 2014, 03:43:24 pm
content: There is a lot of misunderstanding about the NEC, inside and outside the US. The NEC is produced as a model code for electrical safety by a private organization, the NFPA (National Fire Protection Association), whose overall goal is developing codes for fire protection for all types of installations, not just electrical. For example, they also produce a model code for fire sprinkler installations. In and of itself, NEC has no force of law. Under the US federal system, it is up to the individual states whether to adopt it in whole or in part, as it is or modified, or not at all. The states can allow individual counties or cities to adopt it or not. California has adopted most of it, added to it, and requires counties and cities to follow the modified code. Our county inspectors don't look at the NEC if a question comes up during an inspection. They look at the California Electrical Code. Inspection in most (maybe all) states is done at the county or city level except for state or federally owned properties which may be inspected by their own employees.A few examples:My late in-laws lived in a remote, poor, rural county in Colorado. Electrical installations were supposed to be done as per NEC as adopted by the state of Colorado. However, the county was too poor to hire an electrical inspector, so there were none.I once lived and worked on a non-military federal research station. All electrical inspections were done by federal inspectors . Local authorities had no control at all. I don't know what code the federal inspectors were using.The NEC has allowed plastic sheathed cable to be used for residential wiring, and it is the norm. However, at one time, and maybe still, Chicago banned it, so residential wiring had to be done with conduit or flexible, metal-clad cable.----The NEC excludes itself from application to trains, planes, automobiles, ships, mines and wiring on the utility side of meters. There are other model or legal codes for these areas. For example, the model code for electrical utilities is the NESC (National Electrical Safety Code) produced by IEEE. For mines, the federal government has jurisdiction, and codes are developed and enforced by the MSHA (Mine Safety and Health Administration).The NEC is not very detailed on specifications for most types electrical equipment. For example, circuit breakers are broadly divided into instantaneous and inverse time. However, the NEC requires them to be "listed", which effectively transfers responsibility for detailed specs to UL.So, building wiring in the US is really ruled by 51 codes (50 states plus the federal government) which may or may not include the NEC or parts of it. Small wonder there is confusion.Mike in California

author: GiskardReventlov
author_rank: Frequent Contributor
timestamp: April 24, 2014, 04:12:30 pm
content: Quote from: David Hess on April 24, 2014, 04:49:15 amI need to look into one of these, I've heard them called whole-house line conditioners. Or is this something different?I'm talking about an inline AC conditioner for the entire house.QuoteDirty in what way? Your power company is providing poor service?Line conditioner?So the point of the UPS was to attempt to deal with the surge but the UPS is under-sized. I would check the printer to see if there are any low power settings or the like. Something sounds wrong though.

author: StevenB
author_rank: Contributor
timestamp: April 24, 2014, 04:54:53 pm
content: Quote from: calzap on April 24, 2014, 03:43:24 pmNice explanation. I'd like to also add that things get even more complex when you add inspectors in the mix. Their interpretation of NEC can be off the mark, but you are many times at their mercy with little recourse.One example of interpretation gone amuck is the idea of listed equipment (similar to CE marking for Europe). Listed equipment is out of the scope of the NEC. However, that hasn't stopped many an inspector of trying to inspect our permantently mounted (listed) equipment as if it were part of the building.

author: David Hess
author_rank: Super Contributor
timestamp: April 24, 2014, 06:02:27 pm
content: Quote from: GiskardReventlov on April 24, 2014, 04:12:30 pmThey make line conditioners which operate like online UPSes without the batteries but I have never seen one large enough except in an industrial setting to power a whole house and they are expensive essentially being an inverter proceeded by a DC power supply.QuoteThe US midwest gets lightning storms in summer but I also losing power 2 or 3 times a year despite being in an urban area.QuoteLow power is not going to change the surge from the fuser heater.

author: Monkeh
author_rank: Super Contributor
timestamp: April 24, 2014, 06:03:26 pm
content: Quote from: David Hess on April 24, 2014, 06:02:27 pmSome units heat more slowly to a lower temperature and feed slower in 'eco mode'.

author: GiskardReventlov
author_rank: Frequent Contributor
timestamp: April 24, 2014, 06:15:10 pm
content: Quote from: Monkeh on April 24, 2014, 06:03:26 pmThat's the word! Eco. is short for economy and economy is a word that is usually equated to lower cost and lower cost, in this context, equates to low power and low power could also mean lower surge.@David Hess, I looked some years ago for a whole-house line conditioner and recall they were expensive and large.I may have to revisit the state of the art.

author: David Hess
author_rank: Super Contributor
timestamp: April 24, 2014, 06:38:33 pm
content: Quote from: GiskardReventlov on April 24, 2014, 06:15:10 pmIt would be easy enough to test with an AC current clamp.QuoteThis is why I considered moving all of the lighting to different independent circuits so a much smaller line conditioner or online UPS could be used.

author: ejeffrey
author_rank: Super Contributor
timestamp: April 24, 2014, 09:52:39 pm
content: Quote from: FrankenPC on April 18, 2014, 11:03:53 pmIf you had read your printer installation guide it would have probably told you "do not connect this printer to a UPS", and if you had read your UPS manual it likely would have contained the same warning. Laser printers have very high surge currents to heat the fuser roller. Ideally you would plug your laser printer into the surge-only port on your UPS and just avoid overloading the circuit. If you must overload the circuit (bad idea), put everything *else* on the UPS and let it handle the brownout when the laser printer kicks in.