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Home > Archive > Alternative Power sources > November 2005 > Generator
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| I noticed in a post sometime back that a man was having a problem trying to
use the 240 v. from his generator to run into his house and split it into
two 120 v as you would on a standard residential service, seems the 240 v
was OK as long as it was being used on the water pump or any balanced load,
as he tried to branch it out with the neutral and two legs in order to run
misc. appliances , the load was no longer balanced and the generator let him
know it, wondering how common this problem is , Mfg. of generator didn't
seem very helpful, was actually thinking of using the same setup myself,
wonder if someone else has had the same problem ?
Thanks in advance
Phil
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| How about getting a 240 to 120 CT iso xfmr that will handle the KW?
| |
| Ecnerwal 2005-11-10, 12:21 pm |
| In article <dkuk4h01n4@enews2.newsguy.com>, "Phil" <pdl@imaginenet.net>
wrote:
> I noticed in a post sometime back that a man was having a problem trying to
> use the 240 v. from his generator to run into his house and split it into
> two 120 v as you would on a standard residential service, seems the 240 v
> was OK as long as it was being used on the water pump or any balanced load,
> as he tried to branch it out with the neutral and two legs in order to run
> misc. appliances , the load was no longer balanced and the generator let him
Well, I have not had the problem, at least using the 120V outlets on my
welder generator (which, insofar as I know, are connected to the same
two windings that make up the 240V outlet on it), but there is a simple
solution - connect a transformer to balance the load - both Trace and
Outback make them. About $300 with an encosure, $200-240 if you have an
electrical box (large enough that) the raw transformer can sit inside.
--
Cats, coffee, chocolate...vices to live by
| |
| Pete C. 2005-11-10, 2:21 pm |
| Phil wrote:
>
> I noticed in a post sometime back that a man was having a problem trying to
> use the 240 v. from his generator to run into his house and split it into
> two 120 v as you would on a standard residential service, seems the 240 v
> was OK as long as it was being used on the water pump or any balanced load,
> as he tried to branch it out with the neutral and two legs in order to run
> misc. appliances , the load was no longer balanced and the generator let him
> know it, wondering how common this problem is , Mfg. of generator didn't
> seem very helpful, was actually thinking of using the same setup myself,
> wonder if someone else has had the same problem ?
> Thanks in advance
> Phil
I've not seen or heard of this issue with small generators before.
My 5kW generator which is just over 20A per leg, has a 30A outlet and
one of the sides of the windings over wound to handle the 30A. If you
pull the 30A from the single leg and nothing from the other side it's
very unbalanced and still has no issues.
I'd expect that anyone seeing this apparent problem may have problems
with their neutral and/or ground or may have a large load on one leg
that has a startup surge the generator can't handle.
Pete C.
| |
| Bruce in Alaska 2005-11-10, 4:21 pm |
| In article <LawrenceSMITH-EEB933.11063010112005@news.verizon.net>,
Ecnerwal <LawrenceSMITH@SOuthernVERmont.NyET> wrote:
> In article <dkuk4h01n4@enews2.newsguy.com>, "Phil" <pdl@imaginenet.net>
> wrote:
>
>
> Well, I have not had the problem, at least using the 120V outlets on my
> welder generator (which, insofar as I know, are connected to the same
> two windings that make up the 240V outlet on it), but there is a simple
> solution - connect a transformer to balance the load - both Trace and
> Outback make them. About $300 with an encosure, $200-240 if you have an
> electrical box (large enough that) the raw transformer can sit inside.
There are a couple of things going on here that need to be addressed.
First, Was the OP saying that his genset 240Vac outlet really putting
out just 240Vac, or was there a neutral connection also brought out, so
that it was 240/120Vac-three wire? Did the OP really connect his 240Vac
genset to the panel with a true 240/120Vac-three wire connection?
If a 240Vac-three wire connection was actually made, then the only
unbalance problem he should have incountered, would be, if he exceeded
1/2 the total continious power rating, on either leg.
If he actually just had a 240Vac-two wire connection with no neutral,
then he is a DUFUS, and shouldn't go near electricity, unless it is
D-Cell Powered.
Most if not all current production gensets that have 240Vac connections
DO bring out the neutral, (CenterTaped) connection to the plug.
If the OP was complaining that he couldn't get full rated power from
his genset due to unbalanced loading from a proper 240Vac-three wire
connection, then a Balancing Transformer may solve his problem to
some extent. He could connect the Primary side in 240Vac-two wire,
or 240Vac-threewire, and as long as he connected the secondary side
via 240Vac-three wire, would get the the full power he is seeking,
except he must take into account the size of the transformer, so that
it could handle the higher amps per leg on the higher loaded leg,
without overheating or overcurrent on the transformer winding for
the loaded leg. (5Kw genset would need, say 8Kw transformer)
Also you would have to consider the losses inheirant in the transformer
conversions.
In my Powerhouse, I generate all my Prine Power at 240/120Vac-three wire
and feed a 240/120Vac-threewire Panel. One of the Loads on that panel
is a 10Kw 240/120Vac Transformer that then feeds a 120Vac subPanel.
One of the loads on the 120Vac subPanel feeds the Trace4024 Inverter.
this setup places the Trace 4024 across both Legs of the genset in a
balanced situation, rather than loading only one leg if no transformer
were used. I try to keep my Leg to Leg 240Vac loads within 5 amps
with my 20Kw gensets. In the cabin, the only 240Vac load is the Dryer
and that is feed of the 240/120Vac Panel directly, so the House 120Vac
Inverted Feed, feeds both legs of the House Panel in 120Vac-two wire
fashion.
If anyone would like a complete disscription of my Power System, just
email me offlist, and I will forward a text file to you of the complete
system.
Bruce in alaska
--
add a <2> before @
| |
| Bruce in Alaska 2005-11-10, 4:21 pm |
| In article <1131626473.639986.149520@g44g2000cwa.googlegroups.com>,
"BobG" <bobgardner@aol.com> wrote:
> How about getting a 240 to 120 CT iso xfmr that will handle the KW?
>
Well not quite, If one would like to use the total output power
of a 5 Kw genset with a 50% load unbalance, the transformer would
need to be oversized to say 7.5 or 8Kw, to handle the excess current on
the higher loaded leg.
Bruce in alaska
--
add a <2> before @
| |
| Pete C. 2005-11-10, 4:21 pm |
| Bruce in Alaska wrote:
>
> In article <1131626473.639986.149520@g44g2000cwa.googlegroups.com>,
> "BobG" <bobgardner@aol.com> wrote:
>
>
> Well not quite, If one would like to use the total output power
> of a 5 Kw genset with a 50% load unbalance, the transformer would
> need to be oversized to say 7.5 or 8Kw, to handle the excess current on
> the higher loaded leg.
>
> Bruce in alaska
> --
> add a <2> before @
I think you missed something. If you put a transformer with a 240V input
across the 240V output of a generator, the generator will see a balanced
load regardless of what is done on the transformers output. There is no
neutral used on the input and therefore there can be no imbalance
between the only two legs of the circuit.
Pete C.
| |
| Ulysses 2005-11-10, 4:21 pm |
|
"Pete C." <aux3.DOH.4@snet.net> wrote in message
news:43738E04.1E0183F7@snet.net...
> Phil wrote:
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>
> I've not seen or heard of this issue with small generators before.
>
> My 5kW generator which is just over 20A per leg, has a 30A outlet and
> one of the sides of the windings over wound to handle the 30A. If you
> pull the 30A from the single leg and nothing from the other side it's
> very unbalanced and still has no issues.
>
> I'd expect that anyone seeing this apparent problem may have problems
> with their neutral and/or ground or may have a large load on one leg
> that has a startup surge the generator can't handle.
>
> Pete C.
I'll often run a 3/4 HP pump or air compressor from just one leg but I
usually try to balance it by running relatively equal loads. When it's cold
the compressor has a hard time starting.
| |
| Pete C. 2005-11-10, 4:21 pm |
| "Pete C." wrote:
>
> Bruce in Alaska wrote:
>
> I think you missed something. If you put a transformer with a 240V input
> across the 240V output of a generator, the generator will see a balanced
> load regardless of what is done on the transformers output. There is no
> neutral used on the input and therefore there can be no imbalance
> between the only two legs of the circuit.
>
> Pete C.
Ok, reading your other post I see that you were referring to imbalance
on the transformers center tapped output. In this case however they
indicated a 240V to 120V transformer which I take to mean a 2:1 step
down transformer vs. a 1:1 isolation transformer using a 240/120V center
tapped output. If it is indeed a 2:1 step down then you again have no
imbalance and no need to oversize the transformer, you will get the full
generator kW/KVA minus 1% transformer loss at the output with no
imbalance.
Pete C.
| |
| Vaughn 2005-11-10, 8:21 pm |
|
"Phil" <pdl@imaginenet.net> wrote in message
news:dkuk4h01n4@enews2.newsguy.com...
>I noticed in a post sometime back that a man was having a problem trying to use
>the 240 v. from his generator to run into his house and split it into two 120
>v as you would on a standard residential service, seems the 240 v was OK as
>long as it was being used on the water pump or any balanced load, as he tried
>to branch it out with the neutral and two legs in order to run misc. appliances
>, the load was no longer balanced and the generator let him know it, wondering
>how common this problem is , Mfg. of generator didn't seem very helpful, was
>actually thinking of using the same setup myself, wonder if someone else has
>had the same problem ?
First of all, if you have (for example) a 10 KW generator, you are allowed
a maximum of 5 KW from each side. Unless you have a single, large, 110 load,
this will likely never be an issue. Several have correctly mentioned using
transformers to balance the load between the two sides of the generator, but
reserve that as your last option to achieve balance, not the first.
Are you going to connect this generator to your house via a transfer
switch? If so, just arrange your home circuits so that you end up with vaguely
the same load on each side of the line. Ideally, your house may be pretty close
already.
The EmerGen switches http://www.nbmc.com/emergen/ , come with a wattmeter
on each side of the line that are handy for managing total load and load
balance.
Vaughn
> Thanks in advance
> Phil
>
>
| |
| Bruce in Alaska 2005-11-11, 3:21 pm |
| In article <4373A104.745C7695@snet.net>,
"Pete C." <aux3.DOH.4@snet.net> wrote:
> Bruce in Alaska wrote:
>
> I think you missed something. If you put a transformer with a 240V input
> across the 240V output of a generator, the generator will see a balanced
> load regardless of what is done on the transformers output. There is no
> neutral used on the input and therefore there can be no imbalance
> between the only two legs of the circuit.
>
> Pete C.
No Pete,I didn't miss anything. You missed the main problem of the
current imballance on the secondary side of the transformer would put
that leg of the secondary overcurrent if the transformer was sized the
same as the generator. Just as if there was no transformer in the first
place.
The problem is the current imbalance between legs of the load causes
overcurrent situations on what ever is driving that imbalanced load.
It doesn't matter is it is a generator or transformer, if they have the
same power capacity rating, and that unbalance puts overcurrent loads on
any one leg.
Bruce in alaska
--
add a <2> before @
| |
| Bruce in Alaska 2005-11-11, 3:21 pm |
| In article <4373A29C.FE88546E@snet.net>,
"Pete C." <aux3.DOH.4@snet.net> wrote:
> "Pete C." wrote:
>
> Ok, reading your other post I see that you were referring to imbalance
> on the transformers center tapped output. In this case however they
> indicated a 240V to 120V transformer which I take to mean a 2:1 step
> down transformer vs. a 1:1 isolation transformer using a 240/120V center
> tapped output. If it is indeed a 2:1 step down then you again have no
> imbalance and no need to oversize the transformer, you will get the full
> generator kW/KVA minus 1% transformer loss at the output with no
> imbalance.
>
> Pete C.
Exactly, Now your cook'en with gas........ I guess my answer didn't
exactlly specify that I was talking about 240/240 rather than 240/120
Transformer......
Bruce in alaska
--
add a <2> before @
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