Had a problem with a motor starter which blew up about a month ago. The electrician that came out said it was a fault starter and needed to order a new starter. The replacement starter was installed yesterday and it also blew up. The electrician was confident it was the starter but now he was back to square one. We went up to the roof to check the exhaust fan and it was fine both physically and electrically, he tested the wiring with the fan removed from the circuit and results were 3k ohms between red and black phase everything else was open. Is this the problem I asked? He said yes. He then checked the isolation switch and it looked fine. He removed the switch from the circuit and test the wiring again with the switch removed from the circuit. It tested clear. Now he test the HUBBELL HBL7810D switch and the switch was reading 3k ohms between two phases. Has anyone experienced this problem with ease switches...we have several of these switches installed.
Exhaust Fan Starter blown apart!
- Thread starter Rickyeve
- Start date
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kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
As far as the switch goes, might just be a case of things happen. Sounds like you have more available fault current than the contactor can handle and/or poorly selected overcurrent protection.
Cow
Senior Member
- Location
- Eastern Oregon
- Occupation
- Electrician
Is he using a megger?
This is what I'd be using.
This is what I'd be using.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
190406-0939 EDT
Rickyeve:
I suspect that you are a manager and do not have an electrical background. You need your electrician to be the one on here doing direct communication.
As presented your question makes little sense other than to say you have a problem.
Always the best way to communicate information is directly from the person directly involved with the problem and the person expected to solve the problem. In general, if I was called by a process engineer and told such and such was a problem on a particular machine, then when I actually got to the plant, and talked to the people directly at the machine I usually got totally different information about the problem. Still might not be real good information, but better than second hand.
What seems to be your case is that you have an exhaust fan, controlled by a starter, and that the starter blows up. I don't know what blows up means. What part or parts of this starter failed? Did the starter really blow up into a lot of small pieces or just fail in some internal manner? If it really exploded it would involve a lot of energy. I suspect failure was in some internal way that the starter fails to close, or possibly always remains closed. Is this an electromechanical starter, or a solid-state unit? 3k ohms may or may not be of significance. 3k at 120 V is 3.6 W. Not much heat.
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Rickyeve:
I suspect that you are a manager and do not have an electrical background. You need your electrician to be the one on here doing direct communication.
As presented your question makes little sense other than to say you have a problem.
Always the best way to communicate information is directly from the person directly involved with the problem and the person expected to solve the problem. In general, if I was called by a process engineer and told such and such was a problem on a particular machine, then when I actually got to the plant, and talked to the people directly at the machine I usually got totally different information about the problem. Still might not be real good information, but better than second hand.
What seems to be your case is that you have an exhaust fan, controlled by a starter, and that the starter blows up. I don't know what blows up means. What part or parts of this starter failed? Did the starter really blow up into a lot of small pieces or just fail in some internal manner? If it really exploded it would involve a lot of energy. I suspect failure was in some internal way that the starter fails to close, or possibly always remains closed. Is this an electromechanical starter, or a solid-state unit? 3k ohms may or may not be of significance. 3k at 120 V is 3.6 W. Not much heat.
.
ptonsparky
Tom
- Occupation
- EC - retired
I suspect you are right on both counts with the correction to short circuit protection.
iceworm
Curmudgeon still using printed IEEE Color Books
- Location
- North of the 65 parallel
- Occupation
- EE (Field - as little design as possible)
Ricky - I don't have a clear picture as to what exactly happened.
My translation:
- The circuit is 3 phase, we don't know the voltage.
- The Hubble 7810D is a local disconnect up next to the fan motor. (just a guess, the 7810D could the the starter disconnect)
- There is a remote located starter, overload block, fused disconnect. The contactor has a fused disconnect and overloads is not mentioned, but surely must have.
- The existing (first) contactor blew up either while running, or on energization. "Blew up" means the contactor fragmented, with broken pieces ejected with significant force.
- A second contactor was installed. It "blew up" either while running, or on energization.
- The motor was disconnected and the Hubble 7810D disconnect measured 3Kohms between two poles (DVM?)
Here is what I am missing:
The HBL7810D should be protected by Class J fuses. I attached the cut sheet. Those fuses should be opening long before there is any arc fault (This assumes the starter blew up from arc fault damage)
3Kohms between two phases is not good. However it is not enough to cause any short circuit current damage. Consider that even at 480V, 3K ohms is only .16A. And since this measurement was after the second starter failure It is not getting worse.
Two things.
1. Keep the electrician away from the work until the fault is determined - no more guessing. "Blowing up" one starter is bad. Blowing up a second starter is not conceivable. Why didn't the fuses open? That needs to be figured out - before the circuit is energized again.
2. Come back and talk to us. There is a large knowledge base here. They can and will help.
(edit to add) Whoops forgot the attachment
the worm
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
190406-1208 EDT
Now it may appears that the word "starter" really means a small 3 pole single throw switch. Possibly the 4k ohms is a measured resistance between two of the switch poles. This could mean severe arcing occurred within the switch creating a carbon path between two poles.
Did the switch really explode causing particles to fly out of its casing? Has a failed switch been opened and the point of failure been looked at?
Unlikely a new switch failed in the same way as the original switch. If so, it would likely imply a design or manufacturing defect. Such a defect is unlikely. Thus, it implies a major short on the load side of the switch.
As mentioned above by iceworm correct fusing is required.
.
Now it may appears that the word "starter" really means a small 3 pole single throw switch. Possibly the 4k ohms is a measured resistance between two of the switch poles. This could mean severe arcing occurred within the switch creating a carbon path between two poles.
Did the switch really explode causing particles to fly out of its casing? Has a failed switch been opened and the point of failure been looked at?
Unlikely a new switch failed in the same way as the original switch. If so, it would likely imply a design or manufacturing defect. Such a defect is unlikely. Thus, it implies a major short on the load side of the switch.
As mentioned above by iceworm correct fusing is required.
.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Ice, Gar - the Hubbell switch mentioned is local disconnect at the motor location according to OP. It was removed and tested and had 3Kohm between two poles. OP seemed to mostly be asking if those switches are prone to having problems.
I don't know exactly what the starter "blowing up" means, but would assume there is a controller (most likely magnetic contactor and overload protection) that was damaged in some way. If so one has to question if it is rated for available fault current and/or if there was poor selection of overcurrent protection.
Cheap 9 amp IEC contactor tapped onto a circuit with a 50 amp + overcurrent device - that contactor may be the weakest link in the circuit and first thing to open under the fault he had. Might not been the contactor but rather the overload assembly that failed.
I don't know exactly what the starter "blowing up" means, but would assume there is a controller (most likely magnetic contactor and overload protection) that was damaged in some way. If so one has to question if it is rated for available fault current and/or if there was poor selection of overcurrent protection.
Cheap 9 amp IEC contactor tapped onto a circuit with a 50 amp + overcurrent device - that contactor may be the weakest link in the circuit and first thing to open under the fault he had. Might not been the contactor but rather the overload assembly that failed.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
190406-1407 EDT
The first post is so unclear that we don't know what failed and in what manner.
Considering the Hubbell switch only.
If the switch was open at the time of failure, then practically nothing but a lightning strike would cause arcing and resulting carbon damage.
If the switch was in the closed state at the time of failure, then a dead short on the load side of the switch could cause the switch failure.
If the switch failure occurred during switching, on or off, then it is the wrong switch for the job, or there was an excessive load on the switch at the time of switching.
The title of this thread is "Exhaust Fan Starter blown apart!". To what is the title referring?
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The first post is so unclear that we don't know what failed and in what manner.
Considering the Hubbell switch only.
If the switch was open at the time of failure, then practically nothing but a lightning strike would cause arcing and resulting carbon damage.
If the switch was in the closed state at the time of failure, then a dead short on the load side of the switch could cause the switch failure.
If the switch failure occurred during switching, on or off, then it is the wrong switch for the job, or there was an excessive load on the switch at the time of switching.
The title of this thread is "Exhaust Fan Starter blown apart!". To what is the title referring?
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kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Some things are not clear. The fact the Hubbell switch is an isolation switch near the motor was fairly clear. The fact the 3kOhm fault that was measured went away when the switch was removed from the circuit seems to be reasonably clear there was a fault in that switch. Whatever it is he is calling the "starter" seems to be the main controller - it apparently could not handle the fault current for some reason.
Is likely that 3 Kohm turns into less resistance with operating voltage than it maybe is with a digital meter test voltage applied to it. In Canada - operating volts might even be 600.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
190406-1653 EDT
Likely there is something close to a dead short on the load side of the Hubbell switch between the two lines that pass thru the two poles where 4k is read.
240 A at 120 V would be 1/2 ohm.
My guess is that this switch could possibly handle 24 A ( 5 ohms at 120 V ) continuous when not being switched, probably much higher. Note: I am saying not switching. From the Hubbell specifications values one has to assume the values are good life time for switching inductive loads. This does not tell us much about heating under steady state closed conditions.
.
Likely there is something close to a dead short on the load side of the Hubbell switch between the two lines that pass thru the two poles where 4k is read.
240 A at 120 V would be 1/2 ohm.
My guess is that this switch could possibly handle 24 A ( 5 ohms at 120 V ) continuous when not being switched, probably much higher. Note: I am saying not switching. From the Hubbell specifications values one has to assume the values are good life time for switching inductive loads. This does not tell us much about heating under steady state closed conditions.
.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
More details are necessary if you want help. Motor HP, FLA and voltage? Starter details / brand / failure mode? Wire size? How is that Hubbell switch mounted / protected? This could be anything from a completely mis-designed system to a bug crawling into the switch housing and getting fried between poles.
iceworm
Curmudgeon still using printed IEEE Color Books
- Location
- North of the 65 parallel
- Occupation
- EE (Field - as little design as possible)
guys and girls -
May I gently suggest we leave this one alone until the OP responds.
No sense scaring them off
May I gently suggest we leave this one alone until the OP responds.
No sense scaring them off
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Which still shouldn't have "blown up" the starter if designed for the conditions present.
- Status