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Author Topic: Voltage drop under load  (Read 1975 times)

mikenash

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Re: Voltage drop under load
« Reply #15 on: September 21, 2018, 09:31:51 AM »
Hi Hugh
I'm going to order a proper multi-meter with hz function today. I will also recheck the rpm and increase the voltage to about 240v. The vessel for the water holds about 50l it has a diaphragm so the pump didn't have much to do. I have been looking at small generators on the interweb and it seems you can buy 120/240 v 3600 rpm generators which is really confusing for me. This was an old generator when I got it for cheap but it was running at 3600 and making power with no ill effect before I checked the revs so maybe thats as it should be? A little knowledge is a dangerous thing in my case!

P

I have a 5kVa gen head here that's 20-years old.  3000 RPM for 50 Hz (actually recommends 3150 RPM unloaded).  And 3600 RPM (actually 3750 unloaded) for 60 Hz

Johndoh

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Re: Voltage drop under load
« Reply #16 on: September 25, 2018, 03:15:15 PM »
So I did a load of checks and tests and reread all the posts here. Seems ajaffa et al was on the money. The vessel for the pump is 10 feet for the generator the extension lead is 50 feet and about 42 feet was coiled. Rookie mistake on my part, thanks to all
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glort

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Re: Voltage drop under load
« Reply #17 on: September 25, 2018, 03:56:32 PM »

For anything remotely high load, always pays to use the shortest lead possible.
Doubly applies when leads are normally made from Pissy little 1.0mm cable.  The " heavy Duty" ones available here with 1.5mm conductors are not much better.

Johndoh

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Re: Voltage drop under load
« Reply #18 on: September 25, 2018, 04:26:43 PM »
Glort the things you can learn on forums like this are staggering. Like I posted earlier my house was wired for a heavy duty water pump but the connection was never used. My "electrician" has wired a connection to it that simply backfeeds to the house. I have to turn off the main switch before connecting the generator bit of research says he lied and I DO need a changeover switch. Grrr
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Barenburg

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Re: Voltage drop under load
« Reply #19 on: September 25, 2018, 08:10:51 PM »
That clearly depends on the definition of need.

1. Need to make it Fool Proof?  yes
2. Need to meet code? probably
3. Need it to work correctly when tended by a competent person?  no

Johndoh

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Re: Voltage drop under load
« Reply #20 on: September 25, 2018, 08:49:16 PM »
That clearly depends on the definition of need.

1. Need to make it Fool Proof?  yes
2. Need to meet code? probably
3. Need it to work correctly when tended by a competent person?  no

I was reading somewhere that you shouldn't backfeed power with the breaker switched to off? I am allegedly the competent person however I like to do things as well as I can. The guys on here know that I know very little about electricity and I no nothing of the code in Ireland the chap that did the wiring for me is a qualified electrician. I only recently got the generator on electric start it's now connected to a solar charger so battery will always be charged. I'd just use the pull start but I'd like it easy for the missus. If she forgot to throw the breaker....
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glort

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Re: Voltage drop under load
« Reply #21 on: September 26, 2018, 04:21:26 AM »

The whole thing about having to have isolator/ change over switches for the safety of line men working on repairs is one of the great parroted idiot mentalities on the net far as I'm concerned.

The moral High road ignorants purport that if you have a generator running, it will energise all the wires from outside your property to claims I have seen of 5 Miles away.  What a complete and utter crock of shit!

When the power fails, everything in your home does not automatically shut off, many things will stay connected ready to kick on the second there is power.
If there was a power faiure and you connected a genny, in order for the linemen to get zapped, Your genny would have to power everything still connected to the mains.  Every chance that could be most of the homes in your street at very least. I don't know how big these brainwashed zealots think most peoples backup genny is but I would guarantee there are very few people in the world that have a back up genny capable of powering their whole street. Even if they did, the max power they could provide would be limited by the lines connecting their property to the street.  More likley, the wiring between the genny and the household mains is going to be a much lower rating than that so the load any genny could carry without instantly tripping when connected is very limited.

Maybe the break in the line is just up the road and the isolation is 5 Homes. Has your genny got the grunt to run all the fridges for instance when they kick on or pumps and other things that would still be connected and ready to go?  Not a chance in hell or anything like the safety zelots make out.
Good chance at some point there will also be a transformer on the pole still in circuit. You think your little home genny is going to be able to energise that even if it has no load?  If you are isolated and the next place is a way down the road, the impedence and resistance of just powering the grid lines are going to be enough to knock out most home size gennys if not all.

There is also one big flaw in this paranoia.....
It's standard practice for any power work far as I can tell in the western world, to clamp the Lines before touching them and doing any work.

 They get a Big metal bar and securely bolt it across the wires to create a dead short so the lines are dead even if they are some how energised.
That is to stop any active current as well as anything being connected and energising the lines while work is being done.  Not always possible to disconnect the lines from everything so this is a simple, easy and standard practice. If people think their genny has the grunt to blow through a 1" Copper bar across the mains lines, They must have quite a grunty beast in the back shed.

 I have pointed this out before and then the zealots say something moronic like " If there is even a Million to one chance someone could get zapped...."
There is better than a Million to one chance they will get cleaned up and killed in a motor vehicle accident going to and from work and a much greater chance of them having some other accident in the high risk work they do so a million to one chance would be a lot better odds than things the moral high grounders are blissfully ignorant to. Typical internet brainwashed safety sissys.


It is because your genny could be trying to power everyone elses home in the street you do need an isolator or change over switch. "Lineman" safety is an idiotic ignorance.

I can imagine the Load that would be dropped on any generator when you connected not only the live circuits in your house but maybe the ones in the homes either side as well or 10 others in the street. Thing is going to trip immediately unless your back up genny happens to be a 60Kva driven by a 6 cyl Diesel and the whole thing weighs 2.5 Ton. Of course no matter what other loads you would be connected to, most people probably don't want to be powering all their Neighbors places in the street for too long anyway.

Also if there was a short on the mains lines like a tree had taken wires down or one was grounded, you may not be able to get your genny to connect through the short or RCD tripping out.  For these reasons you need a disconect of some sort.  Flipping the main switch would be enough but if the genny is hard wired you need to be able to connect it.
Suicide cables (lead with male plugs either end to connect outlet to outlet)  are another internet paranoia but at least there is sound reasoning behind the discouragement of their use. Never a good idea except in absolute emergency's and every possible precaution taken with them.

Change over switches can be had in automatic, remote and Manual these days and are not that exy.
They are a good idea if you want to be able to back feed but not for the reasons most sensationalists on the net will parrot over and over as usual, without bothering to think though what they are saying.

I'm afraid I have little respect for Regulations and " qualified" sparkys. Yeah, of course, as you always have to state the obvious, there are good ones out there but unless you know someone personally, you first time at least with one is always a risk.
I have done a LOT of my own wiring here and my sparky mate tells me a lot of it is not up to regulation because I have too MANY breakers and wired in heavier duty circuits than is allowed.  Work that one out.

Here, a lot of circuits can be fused at or above the rating of the wire. All my fuses are undersized so they will well and truly be the first things to trip.
I live here. I'm in no rush to get to the next job or do things to the minimum standard. If it takes me all day to do something and I spend double what I could have, so what?  I can always go to bed and lie awake at night as I do thinking about anything and everything rather than if my wiring is going to cause a fire.

I know my limitations and that even if I do stuff up, there is an under rated breaker at the start of everything I have done that will trip way before anything causes any problem at all.
When there is stuff that's out of my league, I get my sparky mate in...... Who generally looks at what I have done, shakes his head and walks off laughing at the over the top way I did things telling me I didn't have to go to all that trouble.  Worth every minute and cent to me. 

I have found plenty of wiring here that is dodgy but is the original wiring that would have been done by a licensed sparky and then passed by a building inspector.  So much for worrying about what the Unqualified hacker did..... Who as it was came along and fixed the things that should have never been done in the first place.



Johndoh

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Re: Voltage drop under load
« Reply #22 on: September 26, 2018, 08:30:23 AM »
So my system is ok apart from the changeover switch I need in case the wife plugs in the generator without throwing the breaker?

I did a little research and made a few calls yesterday. In order to fit the changeover switch you have to remove the main fuse coming into the house. This fuse has a lead seal on it so you have to notify the electricity company that you broke the seal so they can come out to re seal it and inspect the work. A qualified electrician cannot do this unless he is registered as well as he has to sign off on the job.  This is part of the code so retired electricians can't do this job as  obviously they forget a lifetimes work the first day the collect their pension.

A 125 amp switch is only about 40 so I will order one this week. The cable leading from the generator to the changeover switch has to be 20 square (wtf does that mean?) and it has to be installed "properly" which I assume means attached to the walls or buried underground? I have a feeling all this is going to be very expensive.
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glort

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Re: Voltage drop under load
« Reply #23 on: September 26, 2018, 11:20:14 AM »

20 square would be 20 sq MM conductor area. Commonly known here as 6mm.
In 240V, depending on your regulations and installation, that's good for around 100 Amps or 24 KW.  Usually depends on the length of the run back to the board as well. Further you go the more resistance and the larger the cable required to keep both the heat rise in the cable and the voltage Rise/ drop within the limits.  Try to push too much power down the line from solar inverter in the shed back down the too far away main circuit at the house and you end up with 259 at the solar inverter and 241 at the other end..... So I'm told...... I'd never have a problem like that......   :angel:

I was looking to put 6mm up the back but it will depend if I can get that up the conduit.  4mm will be OK for the house arrays when I get it done because the run back to the box will be much shorter.  I also want to put 2 Circuits for 2 arrays on 2 seperat phases so the load on each will be a max of 5 Kilo. 4mm will be heaps for that anyway.

How far do you have to go with this? 6 MM and above starts getting exy here.
Installed properly is probably the all encompassing term for meeting regulations. this will pertain to where the cable is run, switched and fused, depth of burial if it has to be, Conduit rating for in ground and UV exposure if that comes into it, securing, grounding and so it goes.
Sound a lot but most of it is a given.

If you are going to need a trench, might save a few bucks if you dig it yourself. Then again, if they have a ditch witch, probably wont take long and may be worth paying them.

I'd also look at a control panel for the genny.  You'll need it to be isolated at both ends of the line most likley But I'd be looking on fleabay for meters that tell you amps, volts, frequency as a basic.  You can get cheap meters like the all in ones with the inductive sensor which I have a few of and seem very good over the couple of years I started using them or you could get individual meters in digital or analogue for aesthetic reasons.

If you want to impress your friends and put Look hot to the Mrs, at least once, throw some of those industrial looking warning/ indicator lights on the panel along with some equally unessacary as well as required switches. You can put a Light on the main sub  board switch which has little purpose other than to indicate connection to the mains and  make the whole thing look good and elevate your apparent technical prowess to operate this  very technical looking bit of gear with all the switches and gauges and lights it has.
You can have another switch and an indicator light ( they come in 5 Colours, I bought 5 of each and they cost less than a buck apiece) that turns the meters on.  Not in any way required but if you are going to do this, may as well have all the fun and satisfaction you can with it and milk it for all it's worth!  :laugh:
Another breaker and indicator for the starter for the engine and a volt and amp meter for the battery charging circuit and so it goes. With a bit of imagination and a little cash, you can have something that will have people in awe and asking how on earth did you learn how to work all this complicated machinery?

For bonus points, add one of those big red emergency shut down slam switches and a couple of Knife switches... the more old school and scary looking, the better! Also Don't forget to print off and laminate some of those " DANGER- High Voltage " signs and Others like " Authorized Personnel Only" and
" safety equipment must be worn at all times".

You don't need to know about this stuff for family and friends to think you are an electrical god!  ;D
My friends and Family think all my mucking around with electrical stuff is because I'm in a hurry to meet god, or the other fella, but that's a different and less creditable perception you would be better to avoid.  :embarassed:

By the same token with all of this, you can set up a remote starter that will require no more instruction to the Mrs than " If the lights go out, press this" and mount it on the kitchen wall. 
.
Heres a couple of pics for inspiration for your control panel of awe!  :laugh:










ajaffa1

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Re: Voltage drop under load
« Reply #24 on: September 26, 2018, 12:08:36 PM »
Hey Johndoh, yes a cross over switch is the way to go, not expensive nor difficult to wire up. you can legally do all the work yourself except for rerouting the incoming mains supply. I wired dozens of houses in the UK and just paid an electrician to test it and connect it. Cost for testing/connection was about 300. For what you are doing probably 100. Not too drastic and you get a certificate confirming compliance in the unlikely event that something goes wrong. Probably a good idea to send a copy to your insurance company so they can`t wriggle out of their responsibilities should something bad happen.

Bob

Johndoh

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Re: Voltage drop under load
« Reply #25 on: September 26, 2018, 08:08:30 PM »
The yard is concrete so the cable will have to go inside a conduit under the eaves, I like Glort's control panel idea but really simplicity is all I want a few lights tv etc. I dont have many visitors they want my good coffee, the same bastards that give me weak instant coffee, they want to borrow stuff (I refuse). I will put it all in the hands of a spark that's still registered and I'll be covered. I kinda miss the little Kohler petrol generator and the exntention lead with 2 sockets, TV and a standard lamp.
« Last Edit: September 27, 2018, 09:47:09 AM by Johndoh »
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ajaffa1

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Re: Voltage drop under load
« Reply #26 on: September 27, 2018, 09:42:52 AM »
Hey Johndoh, don`t pay a sparky to fit conduit and pull cable. Doing that bit yourself will save you a fair bit of money. Just let him do the clever bits at each end. I expect he is probably getting a considerable trade discount on cable and conduit, ask him to drop off the gear and tell him you`ll call him when you`ve done the donkey work.

Bob

Johndoh

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Re: Voltage drop under load
« Reply #27 on: September 27, 2018, 09:53:24 AM »
Hi Bob

I saw on a different forum that you need to have the spark modify the cable you plug into the generator but it didn't say how why etc? Something to do with earthing it. The generator is earthed to 4 x 1m iron rods each about 2m apart.

thx Paul
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ajaffa1

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Re: Voltage drop under load
« Reply #28 on: September 27, 2018, 12:43:30 PM »
Hi Paul, not sure about the earthing issue. Here in Australia the regulations are a bit different but I still like to go with what I used to do in the UK. I have one ST2 7.5 KVA generator, It has it`s own earth stake connected to the Generator head then the top box and then cross bonded to the engine and fuel tank.

There is an original Lister SOM control box in the shed, this has three 6 mm squared wires feeding it, two for AC current and one for earth.

I have a distribution board connected to the output from this setup. It has it`s own earth stake which is also connected with 6 mm cable to the control box.

From there the (6 mm) 2 live/neutral cables and earth cables run underground to the house distribution board where they link up with a cross over switch and another earth stake which is bonded to the previous two.

From there I have a feed going back to the shed to provide lighting/power etc. I have another distribution board with another earth stake.

So to make this as simple as I can: the generator requires connection to an earth stake with any parts separated by non conductive materials cross bonded. All distribution boards should have their own earth stake. All earth stakes should be connected to one another through the earthing bars in the distribution boards.

I strongly recommend that you water the area around the earth stakes prior to any testing by the local electricity authority if the weather has been dry for more than a week or two.

Bob

glort

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Re: Voltage drop under load
« Reply #29 on: September 27, 2018, 02:24:23 PM »

Earthing regulations like many things electrical are a dog's breakfast here.

I'm pretty sure there is something about NOT earthing gennys but I can't remember if that is portable types or Fixed ones. One would think that fixed machines would need to be but I forget what portables are not suppose to even though most I have seen have an earth terminal on them for grounding.

I also know that the earth is supposed to be able to carry the current of the live and neutral sides.  I have cable up the back that is made here ( and recently bought) that seems thinner than the other 2 conductors so......

There are also regs for the size of the earth rod in Length and depth.  Earthing to buried water pipe is no longer allowed.... for sound reasons.

I had a metal covered trailer years ago I had computers in and covered events with.  We had a problem at one place where were were getting a strong buzz when we were getting in and out of the trailer and touched it.  Sparky mate was there and I got him to come look. Shut it down and went through the wiring  I had done and couldn't find a thing.  Tested the trailer with a meter and there was power going through it.
I had a steel rod in the trailer I used for staking an awning so I pounded that in the ground and clamped a pair of jumper leads between it and the trailer. Problem solved.

Mate said I don't know what's going on but I'll look at the thing again during the week.
Shortly after we heard someone saying things in the canteen were playing up.  We both wandered over to have a look and heard of things going weird. Mate and I knew what it was.  We went round to the fuse box, were looking at the wiring and I discovered the earth connection looked like it had been broken off the ground rod by someone  dropping a metal bin on it.  We reconnected the Wire, went back to the trailer, removed the jumper cables and all was fine.

Mate thought it was probably something amoung the old equipment in the wet kitchen creating a path from one of the live wires and somehow back feeding maybe through the neutral wire.   Bloody lucky no one including us in the trailer outside got fried.
Mate went to his vehicle, found an RCD and made a donation to the club by installing it.

After that I put and RCD in the trailer as well and always grounded the thing wherever we went.  Sometimes it was to a nearby metal fence post, a metal rail or I used the metal rod. A lot of these places we went were old dodgy places and some had their own gennys so I was wary after that.
The whole trailer was aluminum and I spose we would have been fine inside but having one foot in and one out was the danger.

You sound like you have yours well covered Bob.  Never too much of a good thing like that in my book either.