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Connecting Two Generators Without Transfer Switch

03/06/2016 2:11 AM

Dear all,

I need your help. There are two generators, say A and B which are intended to operate 12 hours alternately.of B (out put of course ).

the plan is to connect three phases of breaker A to breaker B. When Gen A is used, breaker B would be open and vice versa. But neutral is directly connected from Gen A to Gen. B.

What I understand is that if the generators are not grounded (neutral point), there won't be any problem. But if generators are grounded, the current would take all the paths i.e. neutral conductor + earth.

Is my understanding correct? Please advise. Thanks

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#1

Re: Connecting Two generators without transfer switch

03/06/2016 2:32 AM

No, what you propose is dangerous and probably in violation of the electrical codes in your location. You need a better understanding of neutral, earth, bonding, and the electrical codes that govern their use.

Another question would be how you intend to perform the switchover between machines. Unless you are willing to interrupt the load, you will need to have some form of synchronization in place otherwise you will have to ensure that both breakers are never closed at the same time.

The help you need is from a local electrical engineer familiar with what you are trying to accomplish.

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#2
In reply to #1

Re: Connecting Two generators without transfer switch

03/06/2016 2:48 AM

Thank you. I agree it's dangerous. We have no problem with the interruption. If we make sure that both breakers aren't closed simultaneously, then is it safe?

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#3

Re: Connecting Two generators without transfer switch

03/06/2016 4:35 AM
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#4
In reply to #3

Re: Connecting Two generators without transfer switch

03/06/2016 5:53 AM

Thanks a million!

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#5

Re: Connecting Two generators without transfer switch

03/06/2016 8:53 AM

why do I think I'll be seeing Lyn's picture if the guy in a shower of sparks soon?

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#6

Re: Connecting Two Generators Without Transfer Switch

03/07/2016 11:51 AM

Totally wrong!!

You are listening to the wrong people.

You also need a lot of training and knowledge that you simply don't have.......

Let me say that if you do this wrongly, one or both of the generators could fly through the air for hundreds of meter.....it could kill many people.....just for starters.....

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#7

Re: Connecting Two Generators Without Transfer Switch

03/07/2016 12:50 PM

Shipboard use of A/C generators involves switching loads from 1 generator to another while running. At no time could we completely shut down power to the ship's electrical system when changing over.

The procedure is quite standard in that the idle generator is started, brought up to speed and allowed to warm up to assure no mechanical issues, speeds are matched up, the unloaded generator remains with its fields unexcited, synchronization is achieved,and then and only then is the oncoming generator's Main breaker closed to bring it on line with little to no-load. If synchronization is not done properly, as noted above, you can literally have your generator tear itself off it's foundation. Load is then gradually transferred to the on-coming generator until it has full load and then the other Main breaker is thrown to disengage the then idle generator from the electrical system.

We had no "Transfer switch" other than the 2 or 3 Main Breakers on the Control Panels. (3 when it was normal to have 2 - 50% units on-line at all times). The terminology of the grounds being between each generator as almost unusual is strange in of itself since all generators are grounded to each other by some means. Aboard ship, they are both bolted to the frame of the ship and therefore an effective ground is established through the hull framing.

This is a very condensed procedure and it has been some time since I've actually had to do it but others may review and add any steps that I've missed.

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#8
In reply to #7

Re: Connecting Two Generators Without Transfer Switch

03/07/2016 1:34 PM

Same thing with tactical communications in the field. Generators were transferred over like that all the time. Each generator had a synchronizing panel with the two classic white lights.

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#9
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Re: Connecting Two Generators Without Transfer Switch

03/07/2016 2:01 PM

Somebody gave you an off topic for some obtuse reason, maybe because you didn't get it exactly right, but FAR better than the OP understands it!!!

I have "negated" the off topic for you with a GA!! So you should be back to zero.....

It would appear that someone else understands the technology required even less than the OP does...... but thinks he's clever!!

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#10
In reply to #9

Re: Connecting Two Generators Without Transfer Switch

03/07/2016 2:11 PM

Thanks. It has been awhile but certainly not "Off Topic" and should be close.

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#11
In reply to #10

Re: Connecting Two Generators Without Transfer Switch

03/07/2016 3:12 PM

It was!!

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#12
In reply to #11

Re: Connecting Two Generators Without Transfer Switch

03/07/2016 8:07 PM

Well, there. I just made it a bona fide GA. Because it is.

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#13
In reply to #12

Re: Connecting Two Generators Without Transfer Switch

03/07/2016 8:42 PM

Me too.

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#20
In reply to #10

Re: Connecting Two Generators Without Transfer Switch

03/08/2016 3:31 AM

I meant that it was very close, sorry!!

My previous answer was not clear!!

Spinco, you now have 4 GAs!!!

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#15
In reply to #7

Re: Connecting Two Generators Without Transfer Switch

03/07/2016 10:30 PM

Thanks! Actually, there is no plan to run these two in parallel. One generator would be used 12 hours per day and the rest of the time, it would remain shut.

The alternate is that each time the other generator is needed, cable from main DB would be removed from the first genset and connected to the other. What we are trying to do (as I mentioned in the question) was to reduce the hassle. So there is no reason we would run both generator as the same time or we wouldn't want any interruption (it's OK even if we have no power for an hour :) )

Thank you

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#16
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Re: Connecting Two Generators Without Transfer Switch

03/07/2016 10:55 PM

Well then, problem solved.

Carry on.

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#17
In reply to #16

Re: Connecting Two Generators Without Transfer Switch

03/07/2016 10:57 PM

I don't know whether it's pun or you really mean it

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#18
In reply to #17

Re: Connecting Two Generators Without Transfer Switch

03/07/2016 11:08 PM

I meant it. But there is never a unanimous opinion about anything here.

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#19
In reply to #18

Re: Connecting Two Generators Without Transfer Switch

03/07/2016 11:14 PM

Thank you! Much appreciated.

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#21
In reply to #7

Re: Connecting Two Generators Without Transfer Switch

03/08/2016 8:53 AM

Having spent 20+ years in the Navy, both shipboard and land based, and paralleled generators more times than I can remember, your explanation is great.

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#14

Re: Connecting Two Generators Without Transfer Switch

03/07/2016 8:52 PM

Me three

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Andy Germany (4); Brave Sir Robin (2); Fredski (1); LOCKDUKE (1); lyn (4); magnetic_flux (5); RAMConsult (1); rickmoore69 (1); Spinco (2)

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