ONT to be turned off when power cuts?

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jacwlg

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#141188 4-Mar-2014 11:15

Chorus came around and installed fibre at our place a few weeks ago, the last thing the technicians said after the installation was that we should turn off the power outlet for the ONT if a power cut lasts more than 2 hours, or the ONT might blow up when the power comes back.

Anyone can give some sort of scientific explanation to this?

We used to be in a suburb where WorldExchange/Xnet supplies fibre connections (not UFB, not sure what they call it), the fibre modem and all that were built-in with the new house and we never had such warning from xnet guys, only once xnet called up and asked us to restart the modem for update, is that because the technology is different between what xnet does and UFB?

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Vocus

#998660 4-Mar-2014 11:23

Power cuts are often followed by a voltage spike. These can kill electronic equipment. If we have a power cut at home I usually leave one light on (flourescent) so that I know when it's returned, and switch off all the power socket breakers.

Oncop53

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#998693 4-Mar-2014 12:06

All your critical electronic equipment should be on surge protectors anyway. I have had things (router, DECT phone base) fried before after a powercut. Now everything is has surge protectors, including the ONT.
The belkin "sugar cubes" are good.

jacwlg

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#998737 4-Mar-2014 12:52

thank you fellow geekzoners.

I thought it was something specific to the ONT and "2 hours" was some sort of threshold for the device ... :-)

ubergeeknz

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#998757 4-Mar-2014 13:05

jacwlg: thank you fellow geekzoners.

I thought it was something specific to the ONT and "2 hours" was some sort of threshold for the device ... :-)

No idea where the "2 hours" thing comes from. Even a power cut of a few seconds is often followed by a voltage spike.

hyperman

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#999007 4-Mar-2014 18:39

Oncop53: All your critical electronic equipment should be on surge protectors anyway. I have had things (router, DECT phone base) fried before after a powercut. Now everything is has surge protectors, including the ONT.
The belkin "sugar cubes" are good.

mmm belkin "sugar cubes"
gussing you mean surge cubes.....

The views expressed by me are not necessarily those of my employer

Oncop53

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#999034 4-Mar-2014 19:32

hyperman:
Oncop53: All your critical electronic equipment should be on surge protectors anyway. I have had things (router, DECT phone base) fried before after a powercut. Now everything is has surge protectors, including the ONT.
The belkin "sugar cubes" are good.

mmm belkin "sugar cubes"
gussing you mean surge cubes.....

Interesting it looks like they have changed their name to something more logical. When I bought them they were "sugar cubes" e.g.: http://www.trademe.co.nz/electronics-photography/other-electronics/adaptors-chargers/auction-518730666.htm but now surge cube: http://www.pbtech.co.nz/index.php?z=p&p=SURBEL8111&name=Belkin-F9H100vauCW-Surge-Cube-+-$40K-Warranty-Surg
Or was this some typo at a Chinese factory...

Anyway this is what I have done,Sugar/Surge cube protecting the ONT and switch lower left:

coffeebaron

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#999037 4-Mar-2014 19:38

Please setup a video camera (with plenty battery life of course) next time you have a power cut. Post the video of the exploding ONT for us all to see :)

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gregmcc

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#999077 4-Mar-2014 21:05

ubergeeknz: Power cuts are often followed by a voltage spike. These can kill electronic equipment. If we have a power cut at home I usually leave one light on (flourescent) so that I know when it's returned, and switch off all the power socket breakers.

I've heard some stories before, but this takes the cake, do you have any recent examples of these voltage spikes after a power cut?

ubergeeknz

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Vocus

#999154 4-Mar-2014 22:11

Maybe it's not true, I'd always believed it to be the case that surges were common when power was being restored.

webwat

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#1001644 9-Mar-2014 12:27

gregmcc:
ubergeeknz: Power cuts are often followed by a voltage spike. These can kill electronic equipment. If we have a power cut at home I usually leave one light on (flourescent) so that I know when it's returned, and switch off all the power socket breakers.

I've heard some stories before, but this takes the cake, do you have any recent examples of these voltage spikes after a power cut?

Its common knowledge and I'm sure a sparkie could explain the technical reasons for it.

If you don't have a UPS then that would give you more protection than a little surge protector, and with a faster response time too. I don't think it hurts to have both. I do, but we have a scheduled power cut tonight and the UPS/modem will be switched off just so it doesn't wake me up beeping for half an hour at 3am.

Time to find a new industry!

gregmcc

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#1001646 9-Mar-2014 12:35

webwat:
gregmcc:
ubergeeknz: Power cuts are often followed by a voltage spike. These can kill electronic equipment. If we have a power cut at home I usually leave one light on (flourescent) so that I know when it's returned, and switch off all the power socket breakers.

I've heard some stories before, but this takes the cake, do you have any recent examples of these voltage spikes after a power cut?

Its common knowledge and I'm sure a sparkie could explain the technical reasons for it.

I am a sparkie, and the only common knowledge of this is that it is not true.

But I willing to evulate any examples you can provide to support your side of the story

richms

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#1001672 9-Mar-2014 13:25

The surge is in the current as everything in the house is trying to start up at once so pulls a massive amount of current tripping out the main breaker when the power comes back on which is called inrush current.

Nothing there to destroy your gear. It seems when it is a general area outage that the voltage comes back slow enough that the breaker doesn't trip but flick the main switch off and then back on again and its almost certain that the breaker outside will trip off if its winter and there are a few heaters also on as well as all the other equipment.

Possibly the other end of the fiber connection freaks out with all the ONTs coming back on at once which is what they wanted to prevent?

Richard rich.ms

gregmcc

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#1001707 9-Mar-2014 14:26

richms: The surge is in the current as everything in the house is trying to start up at once so pulls a massive amount of current tripping out the main breaker when the power comes back on which is called inrush current.

We are talking about voltage spike here, not current spikes, and in a house I cant imagine a "massive amount of current" been that big that it causes voltage dips, and if it does dip the power then there is an underlying problem of the mains not been big enough.

Nothing there to destroy your gear. It seems when it is a general area outage that the voltage comes back slow enough that the breaker doesn't trip but flick the main switch off and then back on again and its almost certain that the breaker outside will trip off if its winter and there are a few heaters also on as well as all the other equipment.

if main breaker is tripping out (which is unlikely at the main breaker in a house is just a switch and that's it) then there is a problem.

BTW the voltage does not come back slow enough that the breaker doesn't trip, it's either there or not.

and if you are going to start turning your main switch on and off to make the service fuse trip you really are asking for a problem, the main switch in your house is not a load break switch and will eventually fail early if you turn it on and off under high load.

richms

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#1001745 9-Mar-2014 15:23

gregmcc:
We are talking about voltage spike here, not current spikes, and in a house I cant imagine a "massive amount of current" been that big that it causes voltage dips, and if it does dip the power then there is an underlying problem of the mains not been big enough.

The OP was asking about the surge when the power comes back on again. Which is a current surge so the voltage drops, not an increase so no problem for a majority of loads.

gregmcc:
if main breaker is tripping out (which is unlikely at the main breaker in a house is just a switch and that's it) then there is a problem.

BTW the voltage does not come back slow enough that the breaker doesn't trip, it's either there or not.

and if you are going to start turning your main switch on and off to make the service fuse trip you really are asking for a problem, the main switch in your house is not a load break switch and will eventually fail early if you turn it on and off under high load.

The main breaker is outside in the meter box not the inside one which is just a switch. The make you put them in on the 2nd or third call out for a blown pole fuse.

The increase in voltage is slower after an external power outage as everyones houses are full of loads that are pulling their inrush surge, so there is a massive voltage drop in the system.

The only time recenty I have turned the main switch off is when we were painting around one of the panels inside so didnt want it live with the cover off and wet paint brushes around it. On turn on the breaker tripped and had to turn a few circuits off and then it stayed on, then could turn the other circuits on one at a time.

Richard rich.ms

gregmcc

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#1001751 9-Mar-2014 15:45

richms:
gregmcc:
We are talking about voltage spike here, not current spikes, and in a house I cant imagine a "massive amount of current" been that big that it causes voltage dips, and if it does dip the power then there is an underlying problem of the mains not been big enough.

The OP was asking about the surge when the power comes back on again. Which is a current surge so the voltage drops, not an increase so no problem for a majority of loads.

A voltage spike is NOT a current spike, two different things, if the voltage is dropping when the current increases then there is a wiring problem.

gregmcc:
if main breaker is tripping out (which is unlikely at the main breaker in a house is just a switch and that's it) then there is a problem.

BTW the voltage does not come back slow enough that the breaker doesn't trip, it's either there or not.

and if you are going to start turning your main switch on and off to make the service fuse trip you really are asking for a problem, the main switch in your house is not a load break switch and will eventually fail early if you turn it on and off under high load.

The main breaker is outside in the meter box not the inside one which is just a switch. The make you put them in on the 2nd or third call out for a blown pole fuse.

Again the switch in the meter box is exactly that, a switch, if 'They' have required you to fit a circuit breaker in there as well the reason is more than likely the pole fuses are under rated for your load, looks like the power company got you to fix their problem at your cost

The increase in voltage is slower after an external power outage as everyones houses are full of loads that are pulling their inrush surge, so there is a massive voltage drop in the system.

again not correct, there are many rules and regulations to ensure that this should not happen, correct cable sizing for connected loads etc, maximum demand calculations.

The only time recenty I have turned the main switch off is when we were painting around one of the panels inside so didnt want it live with the cover off and wet paint brushes around it. On turn on the breaker tripped and had to turn a few circuits off and then it stayed on, then could turn the other circuits on one at a time.

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