Any electricians aboard ??????????????????

[mopar_man]

I have a chance to pick up a couple of Cat diesel emergency  generators . They are like new and for cheap .  They are 208 v and three phase .My house is 120/240 and of course single phase .
My question is .....how do i get the voltage to 240 or do i drop the 208 voltage down by means of a transformer to 120 per leg and then pick off two legs for my house . I have a 12kw right now and its 120/240 v and three phase and I just pick off two legs and run my house perfectly for the last 20 yrs. This is not full time thing its just for power outages .
Any help would be apppreciated before I pull the trigger . 

[2Gunz]

This is prolly a pass.

The big problem is that your home is single phase and the generator is 3-phase.

And that will make it difficult to balance the load.

Then there is the voltage......  which actually could not matter at all as long as you have no 240 Volt appliances.


Anyway, possible?  Sure..... But I dont see it worth the headache even if they are free.

[2Gunz]

And to answer more directly...

The voltage needs to get up to 240  phase to phase.

And as far as using just 2 of the 3 legs....

it will be fine wilth low load/no load, but as soon as you start loading it up it will under or over crank.

[khodne]

Unless you know a Electrician or a Lineman that you could hire to help I'd pass. 

120/208 is a from a Y transformer bank is not used for residential.  The 208 from a Y bank is 208 phase to phase. 

120/240 three phase is a Delta transformer bank and contains a a Wild Leg (208).  A Delta bank is 120/120/240/240/240 with the 208 being from the far transformer to ground. 

The Delta banked three phase generator that you have been using is made to supply your 120/240, 240 three phase and also a 208 to ground Wild Leg commonly used as a "lighter".

http://www.industrial-electronics.com/images/elecy3_20-9.jpg

http://waterstorage.tpub.com/TM-55-1930-209-14P-9-4/img/TM-55-1930-209-14P-9-4_134_1.jpg

[mopar_man]

Thanks for the replys . I have been running my house during power outages this last 20 yrs with the genset i have which is a 120/240  3 ph genset . No problem running anything even my computers and all electronic gadgets . I just use two of the three legs plus the neutral and feed into my main service .  the problem with this new one is the 208 voltage. I guess I could get a step down transformer from 208 to 120v and still take off two legs plus neutral . I have had no issues as to the engine not running smooth or drop outs or anything . My dad ran our service station off it when we had a major power outage which lasted 5 days . we ran our gas pumps , compressors, ramps, and welders and lighting and even electronic cash registers and never had any issues, I guess i will have to talk to somebody at some of the large electrical outlets aand get their opinion too.

[mopar_man]

Unless you know a Electrician or a Lineman that you could hire to help I'd pass. 

120/208 is a from a Y transformer bank is not used for residential.  The 208 from a Y bank is 208 phase to phase. 

120/240 three phase is a Delta transformer bank and contains a a Wild Leg (208).  A Delta bank is 120/120/240/240/240 with the 208 being from the far transformer to ground. 

The Delta banked three phase generator that you have been using is made to supply your 120/240, 240 three phase and also a 208 to ground Wild Leg commonly used as a "lighter".

http://www.industrial-electronics.com/images/elecy3_20-9.jpg

http://waterstorage.tpub.com/TM-55-1930-209-14P-9-4/img/TM-55-1930-209-14P-9-4_134_1.jpg

So what you are saying is that this  is not practical to purchurse for residential . ?

[khodne]

Twenty years ago I was looking at a similar situation as you are now.  If what you have is working now, I don't see that it would be worth the cost/benefit. 

It can be done but you'll need to convert your 208 phase to phase to 240 phase to phase on two legs.  It can be done but I have never heard of or seen anyone do it.  Cost/Benefit is heavy on the side of cost.

[2Gunz]

Unless you know a Electrician or a Lineman that you could hire to help I'd pass. 

120/208 is a from a Y transformer bank is not used for residential.  The 208 from a Y bank is 208 phase to phase. 

120/240 three phase is a Delta transformer bank and contains a a Wild Leg (208).  A Delta bank is 120/120/240/240/240 with the 208 being from the far transformer to ground. 

The Delta banked three phase generator that you have been using is made to supply your 120/240, 240 three phase and also a 208 to ground Wild Leg commonly used as a "lighter".

http://www.industrial-electronics.com/images/elecy3_20-9.jpg

http://waterstorage.tpub.com/TM-55-1930-209-14P-9-4/img/TM-55-1930-209-14P-9-4_134_1.jpg

So what you are saying is that this  is not practical to purchurse for residential . ?

Its not meant for residential.

But if you dont put 240 volt appliances on it.... and it doesnt overcrank/undercrank because its unbalanced..... you might get years of service out of it.

[2Gunz]

Oh and I failed to mention before.....

There might be a switch to change from 3 phase 208 to single phase 240.  And it also might be possible to retap the genny windings to provide single phase 240.

[J.Bond]

My 30 KVA Onan is set up so you can tap it, Double Delta, Series Delta, Parallel Wye and Series Wye. Wiring Double Delta gives you 120-240 single phase, everything else , gives you three phase. Check your wiring diagram on the unit, you should be able to make those changes.

[mopar_man]

My 30 KVA Onan is set up so you can tap it, Double Delta, Series Delta, Parallel Wye and Series Wye. Wiring Double Delta gives you 120-240 singe phase, everything elese , gives you three phase. Check your wiring diagram on the unit, you should be able to make those changes.

Thanks Mr. Bond i'll see if I can find out if it can be changed . 

[mauve66]

maybe it would be easier to move somewhere there are no power outages.................

[mopar_man]

maybe it would be easier to move somewhere there are no power outages.................

LOL wouldn't think about it . I live on an island , North America's unknown paradise .

Anyway Got to look at the tag on the gen .  there are three blocks on the tag for configuration  .......WTE,     DELTA      ZIG ZAG   . The "X" is in the block  WTE.
I am assuming that WTE is the way the gen is wired.
What does WTE mean ??/

[J.Bond]

Are you sure that it's a T and not a Y, anyways, here is my wiring schematic, might help you understand your diagram.

[mopar_man]

Thanks for the diagram . So what does this mean thats its a "WYE" configuration ?

[J.Bond]

Look at the two lower WYE configurations, you can see the   Y   The Delta configurations are triangular. If you can configure your windings to 220 volt Delta, not a Series Delta ( second from the top ) It should give you 120/220. There is a communicator line that will have to be changed out in your control panel. That should be listed on your wiring diagram.

[2Gunz]

He should be looking for 120/240.

110/220 is the old US standard.