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Author Topic: More generator questions  (Read 612 times)

Johndoh

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More generator questions
« on: October 22, 2018, 09:31:06 AM »
Can anyone explain (in simple terms) what a bridging wire in the generator earth is and how to do it. I'd also like to find out the output of the alternator there is no labels or plates on it. I only have a multimeter. Thanks
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mike90045

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Re: More generator questions
« Reply #1 on: October 22, 2018, 04:54:41 PM »
I can't tell you.   There are many variables. How is the load wiring set up?  Does the generator have a Earthing Bolt ? What does electrical code in your city specify ?  Is there an existing Earthing Rod connected to a electrical panel?

So many things, it's not simple. You don't want a hazard and you don't want a ground loop.

BruceM

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Re: More generator questions
« Reply #2 on: October 22, 2018, 05:23:55 PM »
If the generator is to be powering circuits through the main circuit panel, the earth/safety ground connection should be there, at the panel, and connecting to the generator chassis. So your generator hookup would need a ground, a neutral and one or two hots. (Two if split phase).

Generally electrical codes try to avoid multipoint grounding and the ground loops that result.  Pity the same sound approach doesn't apply to the power co.

The safety issues of a transfer switch or other should be studied and considered. 

Johndoh

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Re: More generator questions
« Reply #3 on: October 22, 2018, 05:32:29 PM »
I was reading somewhere that there should be a jumper cable between neutral and earth in the plug going into the generator if its connected to the house.
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BruceM

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Re: More generator questions
« Reply #4 on: October 22, 2018, 06:11:16 PM »
It is preferred/best to have the Neutral to Safety Ground (earth) connection done at only one point- at the main meter panel.   If you connect to a sub panel this becomes more clear- the sub has neutral and safety ground busses separate - so that there is only a single point connection of neutral to earth at the main meter panel.   

Normally the neutral is low enough voltage to not kill anyone, so people get sloppy about neutral to safety ground shorts and the average home usually has a few...which do often cause elevated ELF magnetic fields.  But done properly, the safety ground should never carry current unless clearing a fault (tripping breaker).  The rules of the electrical code attempt to provide this but there is a great deal of misunderstanding and sloppy work out there.


Johndoh

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Re: More generator questions
« Reply #5 on: October 22, 2018, 08:31:48 PM »
It is preferred/best to have the Neutral to Safety Ground (earth) connection done at only one point- at the main meter panel.   If you connect to a sub panel this becomes more clear- the sub has neutral and safety ground busses separate - so that there is only a single point connection of neutral to earth at the main meter panel.   

Normally the neutral is low enough voltage to not kill anyone, so people get sloppy about neutral to safety ground shorts and the average home usually has a few...which do often cause elevated ELF magnetic fields.  But done properly, the safety ground should never carry current unless clearing a fault (tripping breaker).  The rules of the electrical code attempt to provide this but there is a great deal of misunderstanding and sloppy work out there.

And in simple terms? I really want to connect it to the house rather than running an extension cable through a window. If it's safe I'd leave it. BTW it's 230v system
« Last Edit: October 22, 2018, 09:25:59 PM by Johndoh »
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BruceM

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Re: More generator questions
« Reply #6 on: October 22, 2018, 11:25:32 PM »
Connect the neutral to your generator neutral, the panel ground to your chassis ground.

Do you have just a single phase 230V and neutral or two hot legs with 460V between them (aka split phase)? Just interested in power configurations around the world.

How are you switching between grid and generator supply for your generator backup circuits?
How sophisticated you get might depend on whether the wife might need to use it alone.
I think idiot-proofing and best safety are wise choices. 




Johndoh

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Re: More generator questions
« Reply #7 on: October 22, 2018, 11:43:16 PM »
My connection to the house was wired by a retired electrician. In Ireland domestic power is 230 volt single phase and he was backfeeding power into the house until the generator started putting voltage between neutral and earth. I got another alternator its different brushless type and I don't want to connect it to the house if it's going to kill someone. It's going to cost me the best part of a grand to get a changeover switch and wiring installed and certified by a spark. I really only understand the engine side of power generation so legs and phases are beyond me. I would like that the wife could throw the changeover switch walk to the shed and press the starter on the generator. She had a few goes but she wouldn't remember to turn off the power at the meter so thats out of the question.
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glort

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Re: More generator questions
« Reply #8 on: October 23, 2018, 12:44:12 AM »

Tying Neutral to ground is a major no no here and strictly forbidden with anything.  It sounds bad practice to me anyway even though the power co's do it.
It's certainly not allowed to be done by the end user here.

I would just mimic the house wiring.  Neutral to Neutral, Live to live, earth to earth.  Here they would also want you to ground the genny frame with it's own ground rod rather than have any fault have to go all the way back to the box... which again to me makes sense.
 Is there a reason to do the wiring any other way and tie the neutral to ground?  I know it's done some places but does not sound right to me.

As far as the change over switch, I know there are automatic's  ( ATS) but I'm not sure if they would work the way you want.  To my knowledge when the mains power fails they switch to the generator to isolate the mains. I'm not sure they will switch if you still have power but they maybe able to be set up so they could.

With a simple 2 pole switch, you could have it in the mains box and wired so it's one or the other.  Mains or Generator power but never the 2.... which would cause a heck of a problem.... but only for a split second. If thats what you have and the mrs is running the genny while still connected to mains power, You could wire a warning light and an alarm so if the genny is running and the power connected, it activates as a reminder to turn off the mains.
Few ways you could do this but a simple 2 pole relay would probably be the simplest and easiest.

Just wire it to a couple of Car horns in the shed.... she won't forget again. :0)

Just to get it clear in my thick head again, you are doing this so at night you can change to the genny  when you are watching TV and just running a few lights to save some euro on your power bill?

If this is correct, I'd advise you do the maths on this.  Your power consumption and therefor savings will be very low as you are not drawing any current to speak of.  You might want to go and look at your meter at the time you'd start the genny and then again when you'd be going to bed and look how much power you have used. Do it over say a week to get a better averaged idea.

Work out what that costs you, I'm betting 1-2 Kwh from what you say, then divide that into the 1000 quid it's going to cost ( minimum)  and see how long that's going to take to repay.
Even if you are on .5 euro per KWH, that's 2000 hours of power.  If you use say 2 Kwh a night which sounds high for some lights and TV although youd probably have the fridge kick  in as well, then that's 1000 Days  it's going to take to BREAK EVEN, let alone get ahead. On 2000 hours there is oil changes and maintence on the Genny and I'll guarantee a break down or 2 of some kind that might only take a minor repair but if you can't do it or need a part...... So you might want to add another 100 days at least to that number. You have a second hand engine and alt so their life expectancy is a real unknown but 2000 hours plus is a decent amount of time and certainly not a given that the machinery will hold up.

All up you are already at 3 years or close by to even come near getting ahead. ..... and then to do that you are going out and changing switches and starting gennys in the feezing cold, pissing rain etc in the middle of winter which for me would grow old real effing fast. 
You probably earn next to nothing like the rest of the world on your money sitting in a bank but it just may be that you'd get a better return with your money  that way than investing in a change over switch to run a genny.

The other thing, and this is not coming Just from my pet bias, is to look at solar panels. If you have a spinny meter doing a bootleg setup with those will  put you a lot further in front.  To achieve the same savings in power per day you could probably go with 4-5 250W panels and generate more power than you'd use at night and therefor be in front.

The things will sit there and do their thing and you don't need to change the wiring or get anyone in, you don't need to go out and change  switches and start ( and turn off) generators and the Mrs does not have to remember to do anything.  You put them up and forget about them and they do their work.
Go check once a week to just make sure the inverter is ok as they will fall over in 5 years or so but probably a lot longer if you are under driving them on the panel side. I would guarantee you shitty weather or not, you WILL get a far better and infinitely easier return with panels that make a difference on your power bill than you would on a genny.

The other thing would be an off grid system with panels and batteries. You are not going to need a lot to satisfy the power you say you want and you could easy hard wire an inverter back to a couple of outlets in your house so those sockets were independent of the regular house wiring.  Benefit of this would be on sunny days you'd be able to run other loads as the panels would be taking the load in effect and not draining the batteries at all so you could have your cake  during the day and eat it at night off the reserve as well.
I know power is expensive BUT, pretty much without exception anywhere in the world, if you have mains power connected it's impossible to use a generator to make it cheaper yourself even with free fuel.

I DO mean to piss on your parade with this idea now and up front before you spend money you won't get back.
Seems to me 1000 euro+ upfront is a LOT to spend to save maybe 1 euro, at the wild outset, 2 euro a day and not a good investment of you money either way.  I know you would do all this and then say , Oh, the bill is really no different, we spent all that money and stuffing around for nothing.

If you are sold on the " romance" of this idea as we all get carried away with just wanting to do something from time to time, I'd HIGHLY recommend you Stick to the lead through the window for at least one billing Cycle and see how much you do save off the bill and more importantly, how motivated you are at the end of it to be going out and starting gennys and switching them off every night as well as fking round finding and prepping the fuel and servicing the machine. Do you have a reliable supply of WVO lined up yet or got any in reserve?  Not much point to all this if you find you can't get the fuel or you really don't like mucking round with it and if you think for a split second you can do anything but go backwards at 100 Mph using diesel, you would be very mistaken.

Might be that I'm a tight arse and am very careful before I spend Money, especially when the goal is as an investment to save it, but you might just be a bigger tight arse than me which makes a wise an informed decision to do this and spend the money even more important.    :laugh:
Wouldn't like to see you dissapointed and out of pocket because there were things you didn't realise and no one pointed them out to you.

Johndoh

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Re: More generator questions
« Reply #9 on: October 23, 2018, 01:12:20 AM »
Glort it would probably never pay for itself as it would only be used during occasional power cuts. We wouldn't have more than 48 hours without power in a year unless there was a bad storm. I just like the idea of having power whilst my neighbours are sitting cold in the dark!
There's not enough sunlight here to justify fitting solar panels and in all honesty I could probably manage ok with a car alternator and an inverter a setup we talked about some time ago I could finish fixing up the LR1.

I have 4 steel rods each 3 feet in the ground and about a yard apart, I was thinking I could use this as an earth from the generator? The backfeed option is still available and we are a middle aged couple family all grown we tend to be at home or away together especially in the evenings/night.

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glort

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Re: More generator questions
« Reply #10 on: October 23, 2018, 01:59:28 AM »

If blackouts are all you want to address, ( we don't get nearly enough of them here to satisfy my generation proclivities  :( ) for 1000 quid I'd be sticking to the lead through the window.... but like I said, I'm a tightarse!
There is nothing like the morbid satisfaction of explaining to the neighbours why your lights are on and the rest of the street is in total darkness. An opportunity I haven't got to experience nearly enough.

Then again here, the guy next door would just pull out the generator he has in his caravan.... or go in there and watch TV and have a hot shower and be done with it all together.  :0)

The rods should be perfect for earthing.  I think 2 or 3 Ft in the ground is the standard here so they would have to be fine.

dieselspanner

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Re: More generator questions
« Reply #11 on: October 23, 2018, 07:14:29 AM »
+1 for Bruce's point ref the wife!

A guy I met when I had a Dutch Barge added an inverter, on his boat, with strict instruction to his wife that only himself was allowed to plug into the shore (mains) power as it would be possible to backfeed the inverter was it not disconnected before hand.

After a couple of months with no problems they pull alongside and he announces he'll make a cup of tea. knowing he would fill the electric kettle and the swap out the inverter the Missus gave him a minute then plugged in the shore power cable.

Unfortunately he'd gone for a leak first.

The bang when the mains power blew the inverter was enough to soil his underwear apparently. the good news was that the toilet was at the other end of the boat from the said inverter.

I did as Glort suggested and fitted a second circuit for the inverter fed sockets, OK. it means pulling the plug out of the socket and putting it back in the mains fed one but it completely removes the possibility of a cock up of expensive, if not dangerous proportions.

Cheers
Stef
Tighten 'til it strips, weld nut to chassis, peen stud, adjust with angle grinder.

Johndoh

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Re: More generator questions
« Reply #12 on: October 23, 2018, 08:55:02 AM »
Thanks guys I will earth the generator to the rods and call it done! Small high speed diesel was very cheap, even with the replacement alternator and I want to use the power it makes. If I'm going to be in charge of the main breaker switch then backfeeding should be safe enough? It's close to the house and kinda noisy with the window open but that's not a bad compromise. I might try to modify the air intake to quieten it down I need to get some information on doing it and again it has to be cheap. Glort if I remove the standard air filter and extend the pipe to the intake is that how it's done?
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glort

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Re: More generator questions
« Reply #13 on: October 23, 2018, 09:38:43 AM »

You could try it that way Paul. If you used the standard air box, I would try to have it on a flange to a much larger diameter pipe that will act like a Plenum and reduce the gas speed which will help quiet the intake noise.  You can also add a new muffler to the intake and stick the air box on the end of that.
Myself, I'd be looking for a larger car intake from a wreckers. They have a large airbox, a filter size you will never need to replace and often a lot of baffling to cut the noise down. Going oversize will always make a significant reduction in racket.

Is the machine housed in a shed?  If so, you could look at Building a box around the thing with a baffled intake and output for the cooling air and possibly direct the intake and exhaust to the far side of the building from the house. If you enclose the machine it a good idea to bring cold air in from outside the enclosure otherwise you are basically generating a heat loop by sucking hot air in and through the machine which will make it run hotter.

If it has electric start, you could also get a radio switch off fleabay and wire the thing up so you ( or the mrs) could just press a button and off the thing would go.

Johndoh

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Re: More generator questions
« Reply #14 on: October 23, 2018, 10:19:48 AM »
So Glort do you think if the generator is earthed it's safe enough to connect to the house? I have some flexible pipes i can try on the air intake when I get the chance thanks for help and advice!
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