Are they in series?

[zot64]

I have a situation were someone has run from the copper bus inside a panel to there own box, set a 200 amp three phase breaker to run a chiller tower motor (40 hp) they have gone from breaker to starter normal enough...but someone else has come along and added lugs to the top of the starter and continued on to another motor and starter set up....not only have I never seen this before...but it seems that you have then put the motors 'in series'.
My natural assumption is to seperate the two motors to their own circs. Of course cost was an issue so if this "ok" they want to leave it instead of purchasing another three phase breaker.

Any thoughts shared would be appreciated.

 

[bob]

Are they in series? No, but I bet the person that did this broke all of the tap rules.

 

[zot64]

Are they in series? No, but I bet the person that did this broke all of the tap rules.

yes they have done this

 

[steelersman]

I have a situation were someone has run from the copper bus inside a panel to there own box, set a 200 amp three phase breaker to run a chiller tower motor (40 hp) they have gone from breaker to starter normal enough...but someone else has come along and added lugs to the top of the starter and continued on to another motor and starter set up....not only have I never seen this before...but it seems that you have then put the motors 'in series'.
My natural assumption is to seperate the two motors to their own circs. Of course cost was an issue so if this "ok" they want to leave it instead of purchasing another three phase breaker.

Any thoughts shared would be appreciated.

So now perhaps the 200 amp breaker is not enough to power the cooling tower and the other motor that they fed off the chilling tower starter. When you said they came off the copper bus in the panel you make it sound like they just tapped off of it. But they installed a 200 amp breaker out of that panel correct?

 

[zot64]

So now perhaps the 200 amp breaker is not enough to power the cooling tower and the other motor that they fed off the chilling tower starter. When you said they came off the copper bus in the panel you make it sound like they just tapped off of it. But they installed a 200 amp breaker out of that panel correct?

Yes. I have given more detail in the "stumped by C Phase overheat" (I think) post.
thanx for reply though...

 

[LarryFine]

...but it seems that you have then put the motors 'in series'.

You could say that they are physically in series, what we usually call 'daisy-chained,' but electrically speaking, they are in parallel. Losing either load will not de-energize the other, and their respective currents add.

In a genuine series circuit, opening any load de-energizes them all, and the current is the same anywhere around the loop.

 

[jcassity]

You could say that they are physically in series, what we usually call 'daisy-chained,' but electrically speaking, they are in parallel. Losing either load will not de-energize the other, and their respective currents add.

In a genuine series circuit, opening any load de-energizes them all, and the current is the same anywhere around the loop.

yep,,
and what do we know about the poor lil electrons flowing,, source current will get divided across the two motor unless one is newer or stronger than the other.,, either way sounds goofy but yes they are parallel having the same voltage on each branch.

my thoughts are that if the motors are not perfecly wound exacly (which they arent the same impedence likely) that one will dominate the other slightly and the weaker will work harder to keep up.,, more work = more watts, more watts= tripped breaker or heating terminals ect.

Clamp on the legs of each and see who's pulling the most current and take notes, they will probably have issues later unless your current mission your on in the other thread fixes it.

 

[steelersman]

yep,,
and what do we know about the poor lil electrons flowing,, source current will get divided across the two motor unless one is newer or stronger than the other.,, either way sounds goofy but yes they are parallel having the same voltage on each branch.

my thoughts are that if the motors are not perfecly wound exacly (which they arent the same impedence likely) that one will dominate the other slightly and the weaker will work harder to keep up.,, more work = more watts, more watts= tripped breaker or heating terminals ect.

Clamp on the legs of each and see who's pulling the most current and take notes, they will probably have issues later unless your current mission your on in the other thread fixes it.

he didn't say whether or not the second motor was the same size or not. Either way the voltage would be the same since they're in parallel but the current that they both draw together might be too much for the branch circuit conductors. If their both identical motors then I don't think one will dominate the other just because one is before the other. If they both have the same available current then the other shouldn't have to work harder to keep up. And this shouldn't happen since they are in parallel not series.