I have a problem

[JesseFrank]

For 3 times in the past week it has happened that my pc and the microwave have lost power for a single second at the same time.

Nothing else in the house, that I can check, seems to be affected by this power loss.

PC and microwave are on a separate breaker, which in turn are each on a separate main circuit with each their own RCBO. No breaker trips.

On the breaker from the microwave are also the other kitchen plugs, which I can not really know if the lost power, but the clock from the microwave resets.

On the breaker from the PC is also the ceiling fan in the office, which would drop out and the light switch on in case of a sudden power loss, but this doesn't happen.Also the monitor, which would show it's reset clock when restart, but also this doesn't happen.

I have tried to switch off either breaker separately to see if the other item loses power, but this is also a negative

Other appliances in the house which have a clock that resets or a warning signal when power has lost, are seemingly not affected either.

I have single phase electrics at my house.

Where do I start to look ?

[IMHO]

Sounds like it's a bad joint in the wiring, or pehaps something has chewed on a wire... first place I'd be looking is all the junction boxes in your ceiling space.. be careful though, do it with the main breakers all off

[JesseFrank]

For sure it must be 2 different junction boxes, so if that is the case it would be an unbelievable coincidence that 3 times they both have the problem at the very same time.

[bankruatsteve]

Voltage surge?

[JesseFrank]

I have surge protectors on each main circuit, but I guess that other appliances would be affected also in case of a surge protection.

As a test I have even tried switching the beaker with the PC, fan and monitor connected, off and on as fast as possible, and each time all three items are affected.

[Deke]

I have surge protectors on each main circuit, but I guess that other appliances would be affected also in case of a surge protection.

As a test I have even tried switching the beaker with the PC, fan and monitor connected, off and on as fast as possible, and each time all three items are affected.

An automatic recloser operation on the 22 kV distribution primary happens much faster than you can operate a circuit breaker. There is no delay in the first reclose attempt so if the fault is cleared, the circuit is reclosed "instantaneously"; that is in something on the order of 0.04 seconds. I suspect that this is what you are experiencing.

[JesseFrank]

I have surge protectors on each main circuit, but I guess that other appliances would be affected also in case of a surge protection.

As a test I have even tried switching the beaker with the PC, fan and monitor connected, off and on as fast as possible, and each time all three items are affected.

An automatic recloser operation on the 22 kV distribution primary happens much faster than you can operate a circuit breaker. There is no delay in the first reclose attempt so if the fault is cleared, the circuit is reclosed "instantaneously"; that is in something on the order of 0.04 seconds. I suspect that this is what you are experiencing.

But I assume that a 0.04 second power cut would also not restart my pc and reset the clock on my microwave ?

[Deke]

I have surge protectors on each main circuit, but I guess that other appliances would be affected also in case of a surge protection.

As a test I have even tried switching the beaker with the PC, fan and monitor connected, off and on as fast as possible, and each time all three items are affected.

An automatic recloser operation on the 22 kV distribution primary happens much faster than you can operate a circuit breaker. There is no delay in the first reclose attempt so if the fault is cleared, the circuit is reclosed "instantaneously"; that is in something on the order of 0.04 seconds. I suspect that this is what you are experiencing.

But I assume that a 0.04 second power cut would also not restart my pc and reset the clock on my microwave ?

Maybe not. There might be enough capacitance in those pieces of equipment to keep them going for the less than two cycles it takes for the recloser to operate.

[Spoonman]

Sounds like a brown out. Put your PC on a UPS.

[JesseFrank]

A brown out would in my opinion not affect only the same two devices each time. I have plenty of devices with a digital clock throughout the house, so they would all reset at the same time .

[Spoonman]

Up to you then.. don't put a UPS on your PC. I await your "why did my PC die" thread.

[Crossy]

+1 on the brown-out theory.

The two devices being affected are evidently the most sensitive to power glitches.

A low cost PC PSU running near its load limit may not last even a few skipped cycles, use a UPS.

If you have low energy lighting it may not even flicker and you almost certainly wouldn't notice the fan doing anything untoward.

[JesseFrank]

Not necessarily, a low cost PC PSU running near its load limit may not last even a few skipped cycles, use a UPS.

If you have low energy lighting it may not even flicker and you almost certainly wouldn't notice the fan doing anything untoward.

The PC is definitely not running near it's limit when using only the browser. The ceiling fan is on a light switch and has an electronic remote control.

When I switch on the fan i have to use the remote to close the light and start the fan, so losing power for just a second will stop the fan and switch on the light.

I have several skyboxes in the house, which when they lose power for a second restart. This doesn't happen.

An security system which switches to battery power and will give me a warning which I have to manually reset that there was a power loss. Doesn't happen

My monitor, which is on the same breaker as the PC should reset it's clock when losing power. But doesn't happen.

The only item that reset at the same time, and each time, is the microwave which is behind a different RCBO at all. If it was on the same RCBO I would know where to start looking, now I'm completely in the dark.

[Crossy]

My money's still on brownouts Jesse.

We're not talking about long failures, just a few missing cycles or a period of low voltage that most kit will happily bridge over, your microwave and PC seem to be particularly sensitive.

Without power monitoring kit it's difficult to come to any better conclusion.

Get a UPS, with a desktop PC you need one anyway.

EDIT Do you have a means of measuring your supply voltage, it could already be low making your PSU work even nearer its limit.

[JesseFrank]

My money's still on brownouts Jesse.

We're not talking about long failures, just a few missing cycles or a period of low voltage that most kit will happily bridge over, your microwave and PC seem to be particularly sensitive.

Without power monitoring kit it's difficult to come to any better conclusion.

Get a UPS, with a desktop PC you need one anyway.

EDIT Do you have a means of measuring your supply voltage, it could already be low making your PSU work even nearer its limit.

Just measured and it fluctuates 219/220 v.

To go on the bad connection in a junction box as IMHO suggested.

The plugs that are involved are all on the same stretch of wall . Is it possible that regardless that they are on different RCB and RCBO's that they have a wire in common ?

[Crossy]

The plugs that are involved are all on the same stretch of wall . Is it possible that regardless that they are on different RCB and RCBO's that they have a wire in common ?

It's quite possible that they are sharing a neutral back to the distribution box (not good practice but common here) and that has an iffy connection. Finding that iffy connection (if of course it exists) will be a challenge.

Task A, determine if the outlets do indeed share a neutral, this will require some power off testing with your DMM (disconnect the neutrals in the distribution box and use a long traily lead).

That said, if one is on an RCBO then a borrowed neutral should be apparent as the device will trip often (or not stay engaged at all).

[bankruatsteve]

Still sounds like over-voltage to me where just your microwave and PC have the electronics to shut down for that. (?) Maybe check the MOV's in your suppressors as they will burn out with extended over-voltage.

[JesseFrank]

The plugs that are involved are all on the same stretch of wall . Is it possible that regardless that they are on different RCB and RCBO's that they have a wire in common ?

It's quite possible that they are sharing a neutral back to the distribution box (not good practice but common here) and that has an iffy connection. Finding that iffy connection (if of course it exists) will be a challenge.

Task A, determine if the outlets do indeed share a neutral, this will require some power off testing with your DMM (disconnect the neutrals in the distribution box and use a long traily lead).

That said, if one is on an RCBO then a borrowed neutral should be apparent as the device will trip often (or not stay engaged at all).

Both of them are on a separate RCBO and Ive never had an RCBO or any other breaker trip as long as I moved in.

Finding the neutral in the distribution box will be a bigger problem I guess, since my system is single wire.

To find the iffy connection however will be no big problem since the power plugs of both devices are located within 5 meters from the distribution box and involve only 3 or 4 junction boxes.

[JesseFrank]

Still sounds like over-voltage to me where just your microwave and PC have the electronics to shut down for that. (?) Maybe check the MOV's in your suppressors as they will burn out with extended over-voltage.

My surge protectors give a green sign. When they are burned out they will give a red sign.

[Crossy]

Both of them are on a separate RCBO and Ive never had an RCBO or any other breaker trip as long as I moved in.

Finding the neutral in the distribution box will be a bigger problem I guess, since my system is single wire.

To find the iffy connection however will be no big problem since the power plugs of both devices are located within 5 meters from the distribution box and involve only 3 or 4 junction boxes.

The neutral for each circuit must go back to the RCBO (not the neutral bar) so it should be easy to verify.

Open up each JB and look for signs of something getting hot (tape peeling off), do this with the power off, we don't want anyone touching bare copper.

Do the RCBOs trip on pressing the 'Test' button?

[JesseFrank]

Both of them are on a separate RCBO and Ive never had an RCBO or any other breaker trip as long as I moved in.

Finding the neutral in the distribution box will be a bigger problem I guess, since my system is single wire.

To find the iffy connection however will be no big problem since the power plugs of both devices are located within 5 meters from the distribution box and involve only 3 or 4 junction boxes.

The neutral for each circuit must go back to the RCBO (not the neutral bar) so it should be easy to verify.

Open up each JB and look for signs of something getting hot (tape peeling off), do this with the power off, we don't want anyone touching bare copper.

Do the RCBOs trip on pressing the 'Test' button?

Test button on the RCBO's works.

So since PC and Microwave are on different RCBO's, it is just a case of disconnecting the neutral from 1 RCBO, and if the any appliance on the other RCBO also stops working there is a shared neutral ?

All junction boxes have wire nuts.

[Crossy]

If you have RCBO's that stay engaged and trip on 'Test' you likely don't have shared neutral.

The possibility is significantly reduced that you have a single dodgy connection that's causing this.

Are the RCBOs next to one-another in the distribution box? Check all terminals are tight.

Otherwise I think we're back to undervoltages.

[JesseFrank]

RCBO are in different distribution boxes .

[Spoonman]

Brown out.

[Forkinhades]

Sounds like a brown out. Put your PC on a UPS.

This is indeed your best Option

[JesseFrank]

Sounds like a brown out. Put your PC on a UPS.

This is indeed your best Option

The UPS protects the PC, but it doesn't solve any possible issues .

[Forkinhades]

^ Issues lie with the PEA/MEA it would seem, not much you can do about that.

[JesseFrank]

^ Issues lie with the PEA/MEA it would seem, not much you can do about that.

Possible, but it sounds strange to me. I have had brown outs in the past, but always with the result that everything in the house would reset.

What I experienced the past 3 " brown outs " with only the same 2 appliances resetting has happened 2 times within 1 hour last week and yesterday for the 3rd time.

By the way my house is pre-wired with the idea to have a whole house UPS in a central location which provides protection to certain zones in the house.

I'm still looking for an affordable UPS or inverter. Any suggestions ?

[Forkinhades]

^ Indeed experiened exactly the same last week? You in Pattaya by any chance?

In answer to your question, to put your supply on a UPS is just not going to happen, unless you spend spend spend

Best solution is to put indiviual circuits that you deem you want to protect on the UPS

I just have all my IT equipment, and it works very indeed.

[JesseFrank]

^ Indeed experiened exactly the same last week? You in Pattaya by any chance?

In answer to your question, to put your supply on a UPS is just not going to happen, unless you spend spend spend

Best solution is to put indiviual circuits that you deem you want to protect on the UPS

I just have all my IT equipment, and it works very indeed.

I'm East of Pattaya.

All connected appliances together would require 2.5 kVa to run smoothly, but they are split up in 3 equal circuits .which start from a central location.

The reason I pre wired the house like this because I provided for extended power losses, but the longest I have experienced in the past 3 years is 1,5 hour, and that was maybe 2 times only.

Edited June 3, 2014 by JesseFrank