Eveporator Fans Tripping

My customer has 3 single phase 230v AC eveporator fans fitted in a freezer room. They are all connected in parallel.
They are ebm model S4E350-AP06-59. The rated current draw is 0.58A @230V 50Hz.They all have a 4uf run capacitor installed. These fans have been working trouble free at an amperage setting of 2.2A of the overload setting. Today the overload has been tripping and has to be reset every 5 minutes.Amperage draw is 0.9A on each of the fans.
Total amp draw is 2.7A voltage is 222V.These fans are 3 months old.There is no ice build up on the eveporator to cause a blockage of the blades.There was an storm last night.Could lightning have caused the capacitors to go faulty? Any thoughts on this anyone.I am on my way to measure them and check for any shorting down to earth. I have increased the overload to 3.2A and the fans have since been running for 2 hours.
Cheers,
Feeze

Just returned from site. The capacitors are fine 3.8uf.Winding resistance +-78ohms each in parallel about 24ohms-within spec. None of them are down to earth. I am bewildered.

Feeze.

Hi Feeze :)

It might be worth checking any cable joint boxes for ingress of moisture,(which im sure you have allready :) ).
The switchgear may have been damaged contactors,overloads.Check for clean supply in and out of the contactor/OL,and all connections are sound,what is controlling the fans?ie electronic controller or relays.
Is there anything else on the circuit for the fans,and was the earth leakage reading taken at the motor end or the control panel etc end,with appropriate electrical segregation methods taken.

Best regards.Mark :)

Hi
If you can take a reading at the motor end terminals of voltage and current If there is any earth leakage before the motor then it would show up as a difference. A volt drop of around 50v might be the cause.(I have not worked this out just an estimate).Also the motors fan blades may be too big for the motor or may have too many blades.
Regards
Peter

Quote:

---

My customer has 3 single phase 230v AC eveporator fans fitted in a freezer room. They are all connected in parallel.

---

Quote:

---

Total amp draw is 2.7A voltage is 222V.

---

Or did i read it incorrectly.

Hi Feeze.

I usually connect it to a 3 pole contactor, 3 phase, one for each fan, -0- to all 3.

this way you can find out the faulty one real quick.

Check all the connections and the fan bodies for excessive heat.
Dirt on the blades can draw more currant.

Chemi :)

Thanks all for your prompt input.
Mark,
Moisture does not seem to be the problem however I will recheck when I go to site tomorrow.
Let me give you a background history of this installation.
The installation was done by me some 3 years ago and I have been maintaining it since.
The original evaporator was fitted with 3phase motors which kept on burning out. I tried to trouble shoot the reason why but the fault did not menifest itself when ever I was on site.
Replacing motors under guarantee was becomming expensive
and I was advised by other technicians to opt for single phase motors. I did so and modified the wiring as follows:
I looped the wiring of the stop/start Danfoss overload protector so that all 3 phases were connected in series.
Only the red phase is connected to the overload which then feeds the contactor. The contactor is then feeds the fans.A separate neutral is fed directly to the fans.This setup has been working fine for about 3 months-no burnt motors and no overload trips.
All connections are sound.
The only questionable thing I found was the voltage drop through the overload- voltage in 226v Voltage out 224
Voltage in to the contactor 224 voltage out 223
Voltage at motor terminals 222v.
There is nothing else connected to the circuit except that the defrost heaters share the same neutral but I dont see this as a problem.
The earthleakage was taken at the motors.
I will megger the cable tomorrow.
An electronic controller switches the contactor.
Yes Mark the fan motors are single phase motors rated at 230v with a rated amperage draw of 0.58A at50Hz. However they are each drawing 0.9A and the voltage measured at the motors was 222v.The fan blades do not have any obstructions nor are they dirty.

Peter,
The fan motor and blades are sized correctly as they are a complete assembly manufactured and supplied by Ziehl.
Voltage drop from contactor to fans is 1 volt.

Chemi,
I may have to consider your suggestion of connecting each fan to a seperate phase with a separate circuit breaker for each motor.What amperage and curve circuit breakers do you suggest.
Cheers,
Feeze.

Voltage drop across the contactor could be due to partially burnt contacts - clean or replace ??

Also, is the lubricant of the motor bearings still there; is it the correct lubricant; are the fans easy to rotate ? Stiff bearings will increase drag/amperage.

Quote:

---

Originally Posted by Feeze

the fan motors are single phase motors rated at 230v with a rated amperage draw of 0.58A at50Hz. However they are each drawing 0.9A and the voltage measured at the motors was 222v.The fan blades do not have any obstructions nor are they dirty.

---

Have you actually measured amps through each motor independently at the motor, or divided the total by three? Simultaneous over-amping would indicate to me a line problem, rather than a motor problem. Is the voltage taken at the motors with reference to the actual common neutral or to an equipment ground?

I would look for a problem in the common supply or neutral legs depending on where you are measuring. Is 50Hz verified?

The 3-phase motor problems may have been related if fed with the same circuits currently in use.

Rog

Have you actually measured amps through each motor independently at the motor, or divided the total by three?

Yes, I have measured the amps independently at each of the 3 motors.

Is the voltage taken at the motors with reference to the actual common neutral or to an equipment ground?

Voltage is measured between line and actual neutral.

Is 50Hz verified?

I must admit that I did not check the frequency, will check tomorrow. Actually there has been major power problems in the city this week so you may have a point to consider here.

Also, is the lubricant of the motor bearings still there; is it the correct lubricant; are the fans easy to rotate ? Stiff bearings will increase drag/amperage.

These fans are sealed units and are not serviceable. They are virtually brand new so I doubt that the problem lies here however I will check tomorrow.

Thanks
Feeze.

Quote:

---

Originally Posted by Feeze

Voltage is measured between line and actual neutral.

---

At the starters or at the motors?

Also, any other motors in the facility over-amping?

Rog

Quote:

---

Originally Posted by RogGoetsch

At the starters or at the motors?

Also, any other motors in the facility over-amping?

Rog

---

I have quoted various voltage readings all at differant locations and all of them were measured between actual neutral and live.None of the other motors are tripping.

I was planning to go to site today today but it is raining so the site visit is posponed. I called the customer however and he says that the fans have not tripped again.They have now been running for about18 hours. I feel that if there was a short circuit it would not have run this long and am inclined to think it may be a poor connection in the common power feed.
I will report back later.

Thanks Guys,
Feeze

Hi All,
The evaporator fans have not tripped now for over 2 weeks and I was still not been able to put my finger on the culprit.
I guess I will have to wait this one out until the fault manifests itself permanently. When I have any further info I will give you feedback. Thanks all for your input.
A note to nighter1 Please grow up - your comments appear to be that of an immature person. (I notice that they have since been deleated )
Regards Feeze.

Thanks for the update Feeze.

One final thought, I know that the fans had tripped in your presence but has there been any voltage fluctuation on site that may had caused the trip due to increased amperage ?

There has to be a faulty connection, burnt contacts, or undersized wiring somewhere. Most likely it is the same fault that destroyed the 3 phase motors, and will likely destroy these motors, too.

The fault will run hot, so you might try finding it with an IR thermometer.

The fans have still not tripped however despite been extremly busy with other breakdowns I made a special effort to return to site today to follow up this problem. This is what transpired:
I rechecked all connections and found no problems there.
I disconnected the live and neutral at the electrical control box outside the freezer room ie at the compressor which is situated outside the building and meggered the cable. The cable appeared to be fine.
Now here is something interesting I wish to share.
This plant has developed a gas leak which I have been battling to trace for I while now. I eventually decided to use the ultraviolet method of tracing the leak.
Since I had no joy with the electrical problem I proceeded to check the evaporator for leaks with my cliplight blue diode ultraviolet flashlamp.
The electrical connection box cover happend to be open.
When the blue light fell on the cable feeding the fan motors I noticed a discoloring at the point where the outersheet was stripped of. This discoloring was not visible with normal light.
On closer inspection I noticed the the insulation of the live wire had a cut. I then realised that there must have been a intermittent arcing between the earth wire which is a (bare wire) and live.I stripped the cable further back and insulated and cut off the offending wire.
I think I finally nailed the electrical problem.
I am suprised that the megger did not reveal this fault.
The use of the ultraviolet light as a tool to find this kind of fault was by pure accident. I still havent found the gas leak but I am estatic to have solved the electrical one.

Regards,
Feeze

:cool: Wish i could help with solution but it sounds like everthing has been checked. All the boys have come upwith good theorys. I question the cause being a nicked wire, an occasional arc could be the cause of O/L trip but Im still trying to work out why 0.58 amp motors are all drawing 0.9 amps thats a worry. Have you checked with another tester? Are the run caps correct most of these motors i have come across use a 2uf cap. I think you indicated 3.8uf, a larger cap can increase amp draw. Some manuf. use same motor (PSC) for several different watts output by simply specifying different size run caps.

Quote:

---

Originally Posted by coolkev

:cool: Wish i could help with solution but it sounds like everthing has been checked. All the boys have come upwith good theorys. I question the cause being a nicked wire, an occasional arc could be the cause of O/L trip but Im still trying to work out why 0.58 amp motors are all drawing 0.9 amps thats a worry. Have you checked with another tester? Are the run caps correct most of these motors i have come across use a 2uf cap. I think you indicated 3.8uf, a larger cap can increase amp draw. Some manuf. use same motor (PSC) for several different watts output by simply specifying different size run caps.

---

Sorry coolkev, I forgot to mention that I rechecked the current draw today with a RMS Fluke ampmeter and the total amperage was 1.85amps.

Cheers,Feeze

I would imagine it was more than just nicked. If it shorted to ground even momentarily, then it was burnt. And in order for it to cause the increase in amperage it would have to be resistive. Being resistive it overheated, which is what caused the discoloration.

I found a similar thing today while commissioning No.3 chiller.

The previous 2 chillers went online without any problems but this one kept tripping the overload on one of the fans due to excessive current draw.
Now, you would think that 12 identical fans would have similar current draw characteristics, but no, this one was tripping like mad. Checked and double checked and could not find a fault. The current draw was just over the max setting of the overload so I bypassed the overload to see what would happen and for how long it would run, and , hey presto, something I didn't expect happened.
The total draw amps started to decrease. This must be due to a very tight motor ( close tolerance engineering ) suddenly getting " run in ".

Anyway, all's well now :)

Have you checked the amps with a true RMS meter against a normal meter you may have power problems.
wesmax

Quote:

---

Originally Posted by wesmax

Have you checked the amps with a true RMS meter against a normal meter you may have power problems.
wesmax

---

The last time I was on site I used a true RMS meter to take my readings. All previous readings were taken with a normal amp meter.
No, I did not take readings with both meters at the same time.
Please explain how taking the two readings at the same time could reveal power problems.

Regards,
Feeze.

by using two meters the common meter will tell you the amps in the cct assuming incoming power is in good shape and has a good wave form, the true RMS will read the actual amp draw with good or bad incoming power so if they read the same there is no problem but if your reading on the true RMS meter is higher you have a problem with the incoming power. the is coming power can be tested with a Amprobe AM 111 meter this will show you the wave form.
wesmax

as i saw in the post it is a freezing cell, if the air gets cold the amps will rise as the air gets thicker.
try:
raise temp of evaporator above 0 and check amperage.
i would think fanblades are for cooling not for freezing.
or just leave the door open for a while and if the amps drop enough you will have your answer.
also check if all fans are running same direction.
if motors are normal for 60 Hz and now running on 50 Hz fans should also be reduced or calculated at 60Hz and not calced to 50 Hz.

as i work on ships i can change frequency easily and have done this to check calcs you will be ameged to see the amp dropping about 50% when going from 60 to 50

Quote:

---

Originally Posted by wesmax

by using two meters the common meter will tell you the amps in the cct assuming incoming power is in good shape and has a good wave form, the true RMS will read the actual amp draw with good or bad incoming power so if they read the same there is no problem but if your reading on the true RMS meter is higher you have a problem with the incoming power. the is coming power can be tested with a Amprobe AM 111 meter this will show you the wave form.
wesmax

---

Well Guys 2 months mave gone by and the fans have not tripped since.
I was on site a few days ago and remembered Wesmax's comment regarding using 2 different amp meters, so I took some readings and this is what I found:
Common meter : 2.1 amps
true RMS meter: 1.95amps
The common meter read slightly higher than the true RMS meter.
How would you analyse this result Wesmax?
Regards,
Feeze

Glad to hear that all is still running Feeze; hopefully whatever you have done, corrected or prayed for has worked !!

Thanks Brian_UK,
Appreaciate your good wishes.
Regards,
Feeze