2 - motors running through contacts won't start up

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I know this may complicate the control setup,
but do both motors have to start simultaneously?
Just a few seconds delay could allow both to start.
I realize this complicates the control system, but
this method has saved my crew many problems.
If they must start at the same time, good advice
is given above.

I hope you find a good solution to this somewhat
strange problem. 400 Amp MDP & #8 wire shouldn't be
the the direct cause of your problem. From a remote
perspective, the switch is the likely problem if your
motors run without it.

JR
 
Fan Motor Voltage

Fan Motor Voltage

What is the voltage on these motors? Two speed
was mentioned. And that concerns me as to which
method in the motors dictate the speed. Does the
switch change the motor's lead configuration?
Your solution may be more simple than it seems
(hopefully)

JR
 
JRW 70 said:
what is the voltage on these motors? Two speed
was mentioned. And that concerns me as to which
method in the motors dictate the speed. Does the
switch change the motor's lead configuration?
Your solution may be more simple than it seems
(hopefully)

JR
Click to expand...
I start discussing Joe's project with my help and after a bit they let me know by the WTF looks on their faces that they have no idea who or what Joe's project is even though it is perfectly clear to me.. Detail is what they need.

We know #8 75ft to 5.5 amp motor(s) should not have a VD issue if properly terminated and installed.
QO contactors are not generally on the POS list.
We need details has to what you have and what you want to do.
 
Agree

Agree

This scenario simply does not make sense.
There is something in the load end of these
motors. All of the lead up to the motors should
be solid. 400 Amp service and #8 wire should
be sufficient. In my opinion (which means nothing)
re-check the control end first, and then move
upstream. After all even new cables can have
faults where joined at the manufacturer.
However, check controls and motor leads first
(especially if multi-speed)

JR
 
ActionDave said:
Sounds like the problem is not the contactor but the the wiring to the leads on the motors.

An answer to this question would help.
Click to expand...

OP said the motors run fine when bypassing the contactor, so I don't think wiring to the motor would be the problem.

I'm thinking it's the contactor or how he's using it. I take from his comments that he only has ONE contactor trying to start two fan motors. Now more info is needed such as what type of fans, the brand of contactor, just how the switches are being used, etc.
 
Little Bill said:
OP said the motors run fine when bypassing the contactor, so I don't think wiring to the motor would be the problem.

I'm thinking it's the contactor or how he's using it. I take from his comments that he only has ONE contactor trying to start two fan motors. Now more info is needed such as what type of fans, the brand of contactor, just how the switches are being used, etc.
Click to expand...
I'll say it another way..........it does not sound like contactor is the problem, so I am thinking it is the wires on the poles of the line or the load side of the contactor. It would be very helpful if sparkyrick's question about shoving the contactor closed was answered.
 
I keep coming back to --Are the contactor coils somehow being connected in series when trying to start both motors at the same time?--That would let them pull in separately but not together--I know I know--WAAAAYYY out in left field!!! But it is Monday!!
 
RichB said:
I keep coming back to --Are the contactor coils somehow being connected in series when trying to start both motors at the same time?--That would let them pull in separately but not together--I know I know--WAAAAYYY out in left field!!! But it is Monday!!
Click to expand...

I think it's just one contactor feeding both motors.
 
Check voltatge and current, both line side and load side of the contactor and measure current to each motor as well. Unless voltage measurment shows a very significant drop - then you may not need the current measurement all that bad and need to figure out why you have such a voltage drop.

What type of motors are these? We kind of assume single phase, but are they capacitor start motors, PSC motors, other?

if they are capacitor motors are the capacitors good? If capacitor start - did the start capacitor cut out close after last run?

Seems odd both would have that cut out switch malfunction at same time but still need to rule it out.
 
kwired said:
Check voltatge and current, both line side and load side of the contactor and measure current to each motor as well. Unless voltage measurment shows a very significant drop - then you may not need the current measurement all that bad and need to figure out why you have such a voltage drop.

What type of motors are these? We kind of assume single phase, but are they capacitor start motors, PSC motors, other?

if they are capacitor motors are the capacitors good? If capacitor start - did the start capacitor cut out close after last run?

Seems odd both would have that cut out switch malfunction at same time but still need to rule it out.
Click to expand...
All valid things to consider.......I still say check the wiring first.
 
ActionDave said:
All valid things to consider.......I still say check the wiring first.
Click to expand...

If voltage is really poor then checking voltage while under load at the supply end is next step - if good there then the problem is somewhere between - so check the wiring next. If voltage is poor at supply end then you have other issues upstream or maybe the breaker feeding this is bad.

But then we still have comments about how things work fine when contactors are bypassed - so something is being missed that deals more directly with the contactor IMO. Maybe the power circuit, maybe the control circuit IDK, don't really know what exactly was done when "bypassing" the contactor either.
 
kwired said:
But then we still have comments about how things work fine when contactors are bypassed - so something is being missed that deals more directly with the contactor IMO.
Click to expand...
IMO too.

..... don't really know what exactly was done when "bypassing" the contactor either.
Click to expand...
No we don't, and until we do I am going to believe that the components are not the problem.
 
Jr.

You keep mentioning the two speed part. Are these snap switches
two switches per motor or is there one threeway or single pole double
throw switch per motor switching between the motor low and high speed taps?

It really sounds like a circuit problem. We really need to see your circuit.

Ronald :)
 
Contactors don't make any noise at anytime only when opened or closed. All noise comes from motor. I didn't manually hold in or close contacts, I just spliced through and controlled by breaker and they fired up no problem. Funny thing is I just wired 2 bigger fan motors almost exactly the same in same building and no issue at all with them starting at same time. I know everything leads to my control wiring... I sketched a quick diagram it is attached. Thanks for everyone s effort!!
 

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Is this drawing what you actually wired, or what you think you wired? The way you have your commons drawn, one motor should be working on high (motor 1) and the other working on low (you only have commons going to one motor from each contactor). Is it possible you have the on/off/on switch wired wrong and you're energizing both hi and lo windings simultaneously or energizing them with 230V? Are the commons at both contactors the same phase?
 
Unless I am missing something here (quite possible)
Your high and low configuration seems ok. As stated
above, there is no way the selector switch could cause
both high and low contactors to be energized at the
same time ( is there ? ). Looking at your wiring diagram
briefly, I did not see any gross errors. It might be helpful
to check your selector switch, if nothing else to eliminate
that as the problem. This definately sounds like a control
problem somewhere. Hopefully the solution will present
itself shortly.

Good luck.

JR
 
I am bothered with the Low & Hi speeds being common with each other. I would be inclined to make sure the Hi of M1 & M2 are separated unless they are to be energized. Same with Lo. I lack the education to explain precisely but each of those windings will have some voltage on it and that may be messing with the magnetic fields in each motor.
 
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