Author Topic: Voltage drop under load  (Read 1974 times)

Johndoh

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Re: Voltage drop under load
« Reply #30 on: October 09, 2018, 03:20:27 PM »
I had another spark out to do a quote. He told me 16 square cable would be fine for what I want. He said he would have to do tests on the negative wiring before he could do a quote. No clue what he means there. He thinks the backfeed I currently have would be fine reckons the less the state knows about what you do the better! He also suggested I dispose of that "dirty, noisy fcuking thing" and just use a small petrol inverter generator with a cable through the window for tv and lights. He's full of ideas anyway
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BruceM

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Re: Voltage drop under load
« Reply #31 on: October 09, 2018, 06:53:46 PM »
Electricians vary greatly and in many states and countries have almost no technical training to speak of.  In my state not even a HS diploma is required.  Some have completed their apprenticeship managing to learn almost nothing.  Others with interest and aptitude may be much more knowledgeable on power hookups than the typical engineer.

There is no such thing as negative household wiring.  Perhaps he said neutral and you heard negative.

Johndoh

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Re: Voltage drop under load
« Reply #32 on: October 09, 2018, 09:48:21 PM »
Electricians vary greatly and in many states and countries have almost no technical training to speak of.  In my state not even a HS diploma is required.  Some have completed their apprenticeship managing to learn almost nothing.  Others with interest and aptitude may be much more knowledgeable on power hookups than the typical engineer.

There is no such thing as negative household wiring.  Perhaps he said neutral and you heard negative.

Could be neutral he spoke quite fast and there was a lot of expletives! He is a registered qualified spark, he has to be to sign off on the work and he has to break the seal on the main fuse to do the work. That's illegal here in Ireland unless youre registered etc, I'm sure people have done it but I try to stay on the + side of the law however thin the margin is. It might be down to me if he was a chancer.
« Last Edit: October 09, 2018, 09:59:35 PM by Johndoh »
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glort

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Re: Voltage drop under load
« Reply #33 on: October 09, 2018, 10:51:37 PM »

There is no such thing as negative household wiring.  Perhaps he said neutral and you heard negative.

I have heard 2 solar installers now call leads from panels " The Plus and the Minus wire" .
If positive and Negative is too technical for them, not people I would have touch anything I own.

Quote
eckons the less the state knows about what you do the better! He also suggested I dispose of that "dirty, noisy fcuking thing" and just use a small petrol inverter generator with a cable through the window for tv and lights. He's full of ideas anyway

The first part about letting the state not know about what you are doing is both encouraging and worrying at the same time.
The bit about having a petrol Generator with a lead going through the window concerns me.  Does he not want the state to see or inspect his work?
For a sparky to say put a lead through the window seems odd to me.  If you told him you want to run a genny for money saving then it's going to be a more permanant thing. If you said you want it for blackouts then I can understand.

Golden rules is 3 Quotes. Maybe you'll get 3rd time lucky with these guys?

Couldn't agree more with Bruce about sparkys. They tend to have very limited knowledge here in that they are like Doctors in a specialty. They know domestic or industrial or whatever they do but VERY little else. Not met one yet that I could talk to about IMAGS although they have heard of it but know  nothing about them.  Same with a lot of other DIY type things.  They know well what they do every day but outside that, zero.

There is a rule here about breaking the seals on the main Fuses. It's so you can't rewire the meter connections so they run backwards or put a jumper before the meter etc.  No one really gives a damn. Very rare to see Fuses with the seals still on them in older places.  Even meters. 2 of mine are unsealed and were when I got here. Just pulled my main fuses when I wanted to re wire the board... technically Illegally.

The place here has 3 phase, 2 meters are analouge so I can back feed them with my solar and run the meters backwards. The 3rd has an electronic meter which I can't  with the off peak hot water ripple switch built in.  I took everything I could off that which just left the 3rd leg of the 3 phase AC.  Everything else is on the other 2 phases.
Technically that's illegal because the load is supposed to be spread over all 3 phases to balance the loads and consumption.

The stupidity is it's rare now unless asked, for new homes to have 3 phase. It's all on the one phase and there is no regulation for which phase you use.
It's more than possible a whole street could be on the one phase with the other 2 untouched.  The fact the connections are basically random is what they rely on for balance. often the 3 phases are brought down from the pole to the home but only 2 are connected on the board.  The loads I have on each of my 2 phases are still well under the load rating of each phase which is 60A but because the load on the 3rd phase is the lightest with only the air which would only pull about 3 Kw max, Technically it's not compliant.

Funny enough, the real loads I put on my system are not in fact draw but backfeed. I regularly push back at a higher rate than what I ever draw through the meters because all my Big loads are done though the day and the solar feed offsets them in the circuit so there is much less going through the meters and often that's still a small backfeed rather than draw.  When I have nothing doing and doing high solar output as I have recently, there is a load more power going back through the 2 phases which they are connected to that what is ever pulled through them. Only appliance with and decent load that's likley to be used when the solar is not running is the electric stove and the 2 ovens.  They are split phase anyway so are unchanged from the original 2 phases they were wired to and share that load as they always did.

There are a lot of rules and regulations with power but at the end of the day in practicality, it tends to come down to the beliefs and preferences of the guy doing the work.

Johndoh

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Re: Voltage drop under load
« Reply #34 on: October 10, 2018, 08:39:13 AM »
Glort I think he meant that power outages are usually short lived in Ireland and they don't happen all that often. The state here is very hands on as in hands on wallets, they want a cut of everything earned and an annual "inspection fee" for everything else. A friend built a house 15 years ago and the wiring for the generator was installed during construction. This was during the celtic tiger era when construction standards were self certified by the builder and there were no government inspections so in his case they don't know that it's been done.

Another quote might be a plan as #2 spark wasn't cheap although he does seem to know what he's doing. Can anyone explain (in laymans terms) about the issue with the neutral wires? Is it an extra money thing for the spark? 
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ajaffa1

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Re: Voltage drop under load
« Reply #35 on: October 10, 2018, 09:50:12 AM »
Hi Johndoh, I think I understand what your sparky is concerned about. The grid system in Europe works with a neutral wire that you can safely touch without getting electrocuted. The positive/live wire goes from about +350 volts to -350 volts giving 240 volt RMS. If you touch this wire you will probably die.

Depending on the generator you have and how it is configured you could have a system in which the positive wire goes to +350 volt and then the negative wire goes to - 350 volt, still 240 volt RMS, but any piece of equipment in your house that has been earthed to neutral (a very common practice in modern electrical consumables) will become live and kill you.

Bob

Johndoh

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Re: Voltage drop under load
« Reply #36 on: October 10, 2018, 10:30:33 AM »
Hi Bob
Thanks for the info I understand about 25% of it. So could my house be unsafe backfeeding? Is there a way to fix this problem if I have it?
Paul
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glort

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Re: Voltage drop under load
« Reply #37 on: October 10, 2018, 10:37:19 AM »

Depending on the generator you have and how it is configured you could have a system in which the positive wire goes to +350 volt and then the negative wire goes to - 350 volt, still 240 volt RMS, but any piece of equipment in your house that has been earthed to neutral (a very common practice in modern electrical consumables) will become live and kill you.


How would this happen Bob?
As in wiring between 2 Phases  instead of a single phase and neutral?

ajaffa1

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Re: Voltage drop under load
« Reply #38 on: October 10, 2018, 11:25:01 AM »
Hi Guy, there is a very simple way to check, Fire it up and then put a volt meter between the neutral and the earth, anything more than a couple of volts and you have a problem.

Yes wiring between two phases could cause this. Had a similar problem in UK hospitals years ago where they had three phase power. somehow they managed to split the phases so you had one phase on one side of a corridor and another on the other side of the same corridor. A whole load of cleaners got hurt using powered floor polishers, they were fine until they bumped the polishers into one another and then all hell broke loose.

Bob

ajaffa1

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Re: Voltage drop under load
« Reply #39 on: October 10, 2018, 12:15:03 PM »
Hey Paul, I`ll try to explain this in as simple terms as I can. Try to imagine a water pump that pumps water from a well and then changes direction and pumps it back again. (How AC current works) The well is the neutral and depending on which way the water is flowing determines positive or negative pressure. (+350 volt, -350 volt could be +350 psi then -350 psi) Any piece of equipment that is connected into that pipe will be able to draw power. However you set this up there is never any pressure in the well (neutral). If you cut the pipe you will get wet from the pumped side but nothing from the neutral, well side.

Now try to imagine the same system without the well. A sealed system in which you pump water around a loop and then you reverse the pump and pump water in the opposite direction. Any piece of equipment plumbed into this system will be able to extract energy but there is no neutral point. If you cut the pipe you are going to get wet from both directions until the water feeding the header tank runs out.

Hope this helps,

Bob


glort

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Re: Voltage drop under load
« Reply #40 on: October 10, 2018, 01:12:39 PM »
Yes wiring between two phases could cause this. Had a similar problem in UK hospitals years ago where they had three phase power. somehow they managed to split the phases so you had one phase on one side of a corridor and another on the other side of the same corridor. A whole load of cleaners got hurt using powered floor polishers, they were fine until they bumped the polishers into one another and then all hell broke loose.


Geez! That does not bear thinking about! Even if they are 10A fused, you are going to have double that being 10A from each side when they met. And of course only one side is going to be fused, so for a split second.... BAM!  Scary to imagine!
Seems to me they would be lucky just to get hurt.  I'd think death would be a much stronger possibility.

It would seem then that the generator would have to be suitably wired.  Many units can be either in Wye or Delta but the house wiring, depending on how it was done may not be compatible with that. If you had the genny wired in Delta, that's going to give you the live neutral because you are jumping across the phases.  Not sure about the house wiring but it would seem to me that the genny would have to be checked to be running in Wye and if not, if it could be from the engine speed or gearing POV as well as the frequency.

More to consider here than what I have previously thought about.

Johndoh

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Re: Voltage drop under load
« Reply #41 on: October 10, 2018, 01:13:26 PM »
Hi Guy, there is a very simple way to check, Fire it up and then put a volt meter between the neutral and the earth, anything more than a couple of volts and you have a problem.

Yes wiring between two phases could cause this. Had a similar problem in UK hospitals years ago where they had three phase power. somehow they managed to split the phases so you had one phase on one side of a corridor and another on the other side of the same corridor. A whole load of cleaners got hurt using powered floor polishers, they were fine until they bumped the polishers into one another and then all hell broke loose.

Bob

I will do this later on is there any way to resolve this problem if I have it? Suddenly the portable generator with an extension lead doesn't seem that bad!

I just checked there's 283 volts between neutral and earth
« Last Edit: October 10, 2018, 01:27:40 PM by Johndoh »
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glort

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Re: Voltage drop under load
« Reply #42 on: October 10, 2018, 01:15:28 PM »

Do you know if your Genny is single or 3 phase?
Not sure that it matters, I think the problem can exist either way depending on how they are set up.


Johndoh

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Re: Voltage drop under load
« Reply #43 on: October 10, 2018, 01:19:12 PM »

Do you know if your Genny is single or 3 phase?
Not sure that it matters, I think the problem can exist either way depending on how they are set up.

Id guess single Glort but I'm not sure. I saw a smaller generator for sale locally it's got thee yellow 115v and blue 230v but it's 60hz

https://www.adverts.ie/heavy-machinery/generator/16432361
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BruceM

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Re: Voltage drop under load
« Reply #44 on: October 10, 2018, 01:52:45 PM »
The shock potential for a neutral/240VAC system is double that of the US split single phase residential hookup.  I'm glad we have only 120VAC (+/-180V peak) to earth.  Also makes my 120VDC system more practical with only 10- 12v batteries.

I suppose the European power connectors may be part of the problem Bob brings up if they don't have a separate safety ground for metal appliance bodies and/or don't have the neutral keyed.  An obvious safety concern you would like to think your electrical code has well covered so the apprentices wiring things don't electrocute too many people.

The common worldwide use of multiple earthed neutrals for secondary distribution ala the US WYE system is a travesty of bad engineering and is the cause of HUGE amounts of AC current flowing through the earth and aquifers.  It causes home ELF magnetic field levels to be 100x higher than it should. (As clearly demonstrated by measurement of residential areas with Delta power and transformer isolation for each home's secondary derived neutral.) The situation is so outrageous that when Zipse queried large groups of electrical engineers, 85% of them believed that he must be wrong about multiple grounding and WYE violation of transformer isolation, as they felt no self respecting engineer would do such a thing in violation of basic good electrical engineering practice.