Switching Between Two Generators, No City Power


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Old 11-06-13, 01:11 AM
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Switching Between Two Generators, No City Power

Hello all. I hope someone can give me a simple and somewhat inexpensive solution. I am in Africa but can get things from States so a Stateside supplier/link is okay. I am in a 220v environment. I have two generators, one a very good diesel 16Kva, the other a very simple Chinese diesel 10 Kva. I just need to be able to switch manually between them. I need to be able to start up one , let it come up in temp for a minute, then switch over to it and shut down the other for rest.I have both in place but only the 16Kva wired to my business running a 60 yard 6mm cable to my breaker box. The 16Kva is 3 phase, 10 Kva single phase. Thank you in advance.
 
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Old 11-06-13, 01:30 AM
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Is your load three phase or single phase? If three phase then there is no way that you can use the single phase generator.

If your load is single phase there MAY be a way but it WILL involve some pretty sophisticated switching.
 
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Old 11-06-13, 04:27 AM
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Use a transfer switch.

Note that if one generator is single phase, the panels and position of the transfer switch must be arranged so 3 phase loads are ineligible to receive power when the single phase generator is selected.

You may not allow to be energized two of the three legs of a 3 phase device using a single phase supply.
 
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Old 11-06-13, 05:47 AM
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I have a three phase main switch (breaker box) in my business. I do not have any heavy duty high consumption appliances or machinery. All my outlets are single phase as I understand...just typical outlets. As I am told here in this town, the single phase generator will work once wired into the 3 phase breaker box on one of the phases. My problem is 1. Do I need to run a separate cable to the breaker box from the single phase generator and put the switch at the building or put the swithc in the gen house? 2. Can I just wire my 3 phase 6mm cable to a switch at the gen house, then connect the switch to my 3 phase gen and my single phase gen, understanding the load limitations of the single phase gen? I am only using the single phase gen for low or medium draw appliances like medium sized refrigerators, audio equipment, tv's. Thanks.
 
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Old 11-06-13, 06:42 AM
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Is your 3 phase generator 220 (or 240 volts or 208 volts) phase to phase or is it 220 (or 240) volts wye phase to neutral with 380 (or 415) volts phase to phase? Or something else?
 
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Old 11-06-13, 06:56 AM
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I am in Africa but can get things from States so a Stateside supplier/link is okay.
If you are in Africa, why did you put down Texas, USA as your location in your profile?
 
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Old 11-06-13, 12:34 PM
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I am a Texan. I invested in a business in Africa. I am looking for advice and was hoping I stopped at the right place. It's not easy being in the middle of nowhere with no certified techs anywhere to be found so I appreciate your understanding. As far as I see on my panel readout the output is 415v, 50hz. It runs all my appliances perfectly but I need the single phase 10Kva as a backup to my main generator to give it a rest and not be sitting in the dark. maxsbarandgrill.com
Thanks for helping me but I still don't know how to do the switch or where to acquire the proper switch.
 
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Old 11-06-13, 01:25 PM
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Checked your website, you really are in Africa!!! It says you deliver, can I place a delivery order?
 
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Old 11-06-13, 01:32 PM
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There is no simple or easy answer to your question. A lot depends upon exactly how your system is currently wired. You really need an electrical engineer on site to assess what you have and how best to proceed.

In the first post you stated:
I am in a 220v environment.
Now you post that:
As far as I see on my panel readout the output is 415v, 50hz.
That would imply that you have one, or more, transformers changing the voltage. We do not know what the voltage at the point of use is nor do we know if you have a multi-voltage system. we do not know if you have a three-phase panelboard or three single-phase panelboards. We do not know what loads you need to have energized by the single-phase generator or if these loads can be easily isolated in whatever panelboards you may have.

What you have asked is how you can connect a single-phase generator in place of a three-phase generator and the simple answer is you cannot. Generally the voltage, frequency and number of phases must be the same on both generators to make an "easy" transfer of power. Since that is not the case here you have many conditions that you must compensate for and this will NOT be easy. Truth is, it MAY be impossible depending on several conditions.
 
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Old 11-06-13, 02:36 PM
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It appears to me that all you need is a transfer switch (three phase or single phase) to accomplish what you need. The trick is finding the right one. That way the two generators will not be energizing your electrical system at the same time. This is likely not going to be inexpensive. But, lets back up for a second.

What is the voltage at your receptacles? Check this with a meter.
What is the output voltage of your two generators, and is it three phase or single phase? This info should be on the nameplates of the generators. You can post model #'s too.
What electrical panels do you have, what is their voltage and amp rating? Is all your electrical equipment from the states?
 
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Old 11-06-13, 04:38 PM
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Tolyn and Allan, he states that one generator is three-phase and the other is single phase. He states he is in an area of 220 volts but never states whether or not all the various loads are at that voltage. He later states that the three-phase generator outputs 415 volts but never states if it is a delta or a wye connection. He never states the voltage output of the single-phase generator. He never states what transformers, if any, are in the system and he never states whether any of his critical loads are three-phase.

Now you know as well as anyone that you cannot supply three-phase loads with a single phase generator. You know that you cannot connect a generator with a different voltage to a system designed for 415 volts by merely using a transfer switch. You know that connecting a single-phase source to a three-phase panelboard is not easy.
 
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Old 11-06-13, 04:56 PM
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Usually the basic single phase loads are randomly connected to one of the three phases so there really is no way to even use a transfer switch. In theory.... the transfer switch have would to combine all three phases into one single phase line. If the loads were all the same voltage as the generator it may work but read on.

In Africa the basic power is 230v or 240v 50hz to neutral. So if the generator was listed as 410v that wouldn't work on any basic item.... like lights, computer, appliances.

Intermediate A/C systems, if single phase, could use 410v. but you would have to turn everything else off.

So in my opinion you cannot use a single phase 410v generator on your system.
 
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Old 11-06-13, 06:02 PM
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I understand and agree with everything both of you (Furd and PJmax) have posted. I however think the OP is not giving us all the info we need, or is just confusing us with the wrong info. This is why I posted that we need the Exact specs off each piece of equipment and maybe we can help him out.

You could, in theory, hook up a single phase power source to a three phase panel. One leg would just be dead. Since this place has no city power, I am suspecting that it is well in the "bush" and he is just trying to get by.
 
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Old 11-06-13, 11:08 PM
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I however think the OP is not giving us all the info we need, or is just confusing us with the wrong info.
EXACTLY!

I do not for the life of me understand why some posters think it is necessary to dribble out information one item at a time rather than giving us the whole story in the initial post.

Max, you need to tell us EVERYTHING about your system. What is the voltage on the single-phase generator, Do you have a dual-voltage system, what appliances require three-phase power, what is the connection diagram on the three-phase generator (wye or delta), how many wires from each generator, how many circuit breaker panels do you have, do you have ANY transformers in the system and if yes, then how many and how are they connected? What appliances do you want to run from the single-phase generator and are any of them three-phase?

Pictures of everything might help us to help you.

Now, IF everything that you want to run from the single-phase generator already operates on single-phase, and IF all of these items are in a separate single-phase panel that is fed from one leg of the three-phase panel, AND the voltage from the single-phase generator is the same as is applied to this single-phase panel THEN connecting the single-phase generator should be fairly easy. However, if ANY of the above is not true then it will be significantly more difficult and maybe even impossible without a large outlay of money.
 
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Old 11-07-13, 01:17 PM
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Okay guyz. Thank you for all the feedback. Let me gather more details and repost here. By the way. Some of you as knowledgeable and kind as you are clearly missed some info from my posts. Some of you said I didn't say "x" when actually I did. But some of you have identified some info I left out so let me get back to you and I appreciate the advice.

Best,
Max
 
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Old 11-07-13, 01:23 PM
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On a thread this long when you come back it would be better if you just re-answered the questions some missed the answers to so all the info is in one place.
 
 

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