AC mains startup surge dampener

[FrankenPC]

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?

[Richard Crowley]

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.

[FrankenPC]

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.

True.  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.

[theatrus]

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?

You'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.

[Fank1]

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.

[ManateeMafia]

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.

[Tinkerer]

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.

I 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.

[David Hess]

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.

[calzap]

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

[Monkeh]

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.

lol, NEC quality again.

[richard.cs]

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.

Ok, 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.

[Monkeh]

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.

Ok, that's pretty bad. In the UK we design for <10% drop on a power circuit and <4% drop on a lighting circuit (because you only need a few volts to produce a noticable flicker).

5% and 3%, unless it's changed since I last had a copy to hand.

[Richard Crowley]

lol, NEC quality again.

Perhaps 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.

[Monkeh]

lol, NEC quality again.

Perhaps 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.

But 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..

[Richard Crowley]

But it's okay to have an otherwise unsafe, unreliable, poorly thought out installation, because it only has to comply with the NEC.

What 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.

We can get into the statistics on electrical fires in the US vs other countries again, if you like..

My 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

[Monkeh]

But it's okay to have an otherwise unsafe, unreliable, poorly thought out installation, because it only has to comply with the NEC.

What 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.

And this is an argument against the accepted regulations enforcing basic standards?

We can get into the statistics on electrical fires in the US vs other countries again, if you like..

My 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

You'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.

[ManateeMafia]

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.

[calzap]

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

[David Hess]

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.

I suspect it is just a significant difference in magnitude.  Brushes should not be arcing destructively.

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.

I 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.

[SeanB]

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.

[calzap]

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

[NiHaoMike]

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.

[GiskardReventlov]

Get a new printer? Did anyone suggest that?  Sounds like a broken printer either by design or not.

[David Hess]

Get a new printer? Did anyone suggest that?  Sounds like a broken printer either by design or not.

I 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.

[GiskardReventlov]

@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.