TEFC (XP) motors with 4oz water in them

[dave676]

We recently purchased (4) direct drive blowers for installation on skids that we then shipped to a customer in New Jersey. We ran some brief run tests in our shop to verify that each blower functioned.

The original submittal from the blower rep included Baldor motors, but upon receipt of the equipment we noted that the supplied motors were Reliance. In addition, three of the motors have two nameplates - one indicating 50HP and one indicating 40HP. The fourth motor had only one nameplate indicating that it was a 40HP motor. We had expected, based on their submittals and the curves for the blower, to receive only Baldor 40HP blowers.

We contacted our rep and were told that the blower manufacturer would not be able to provide the Baldor motors to meet our schedule, so they substituted Reliance. We grudgingly accepted this due to our tight schedule and positive previous experience with Reliance motors. Questions regarding the different nameplates were answered indicating the a 50HP motor was turned down in some fashion to make it a 40HP motor.

Fast-forward to startup at the site - All motors run off of AB VFD's and are outdoors. Each blower was run briefly early in the week to check rotation and set up the VFD's. Later in the week, upon startup, one of the VFD's indicated a motor fault. After much to-do, we got the motor inspected by a Reliance certified shop that indicated that the motor had at least 4oz of water in it. We had a second motor fail with the same symptoms prior to shutting everything down and are now concerned about the other two.

These are TEFC(XP) motors with a weather cover. Word from the field is that the covers were removed to view the nameplates, but the motors were not exposed to rain at any time.

Two questions in order of importance:

1. How could so much water be in a TEFC(XP) motor? The motor repair shop tech said that "there are several paths of entry for water". Any experience with this?

2. What was done with the 50HP motors to make them 40HP motors?

We are trying to get responses to the above from the rep, but are not getting much help (I suspect because we already paid the bill).

Sorry for the length of the post. I will appreciate any help you can provide.

Thanks,

Dave676

 

[jbartos]

Suggestion to dave676 (Mechanical) Dec 16, 2003 marked ///\\The original submittal from the blower rep included Baldor motors, but upon receipt of the equipment we noted that the supplied motors were Reliance. In addition, three of the motors have two nameplates - one indicating 50HP and one indicating 40HP. The fourth motor had only one nameplate indicating that it was a 40HP motor. We had expected, based on their submittals and the curves for the blower, to receive only Baldor 40HP blowers.
///The proper engineering and design, and properly written contractual documents would prevent this. There are many very good electrical engineers and designers on public assistance or on unemployment while poorly qualified are trying to do electrical engineering and design.\\
Two questions in order of importance:

1. How could so much water be in a TEFC(XP) motor? The motor repair shop tech said that "there are several paths of entry for water". Any experience with this?
///There are not supposed to be any openings at that motor. There may also have been inadequate quality control.\\2. What was done with the 50HP motors to make them 40HP motors?
///This may be part of motor derating to obtain lower motor operating temperature. Probably, nothing physical has been done to the motor.\\

 

[electricpete]

Consider a motor enclosure almost sealed but not perfect. Air only flows when there is a differential pressure.

When it shuts down and begins to cool it will draw a vaccum. At this time outside air is drawn in. Condensation may occur during the shutdown period.

Now the motor starts and heats up. Air is expelled. But the location where air is expelled may not be at the bottom where the water is.

Repeat the cycle and more condensation may occur.

I have heard some people recommend that all TEFC motors should have holes drilled in the bottom to allow condensate to drain. If such is the case it would seem it also needs to include a space heater (if outdoors).

This is confusing subject for me and I'm not sure if there is a standard practice. If explosion proof requirements apply of course user should never modify the motor.

 

[dave676]

ElectricPete,

We are providing trickle voltage on the windings of the motor when it is not running.

We only ran these for a short period of time in the field. Have you seen this much water caused by condensation alone?

Thanks,

Dave676

 

[electricpete]

I have not seen it. There is some discusson by Nailen in "Managing Motors". When I get a chance I will re-read that and post back here.

 

[UKpete]

In Europe TEFC motors are the standard (indoor and outdoor) and they are usually fitted with anti-condensation drain holes, usually at least two. These are tapped and the motor is supplied with drain plugs fitted, it is left up to the user which drain plug to remove depending on the orientation of the motor. On indoor applications they are possibly all left in. Maybe this type is not so common in the US, I don't know.

I'm puzzled by your problem, I can only assume that the water was there already as they have hardly had any use. If drain holes are not fitted then maybe the motors are not "fit for purpose" and were specified in a hurry. It may be worth asking Reliance's opinion. Considerable care will be needed if drilling your own holes (obviously).

 

[resqcapt19]

The most common entry point for water is the conduit system and its connection to the motor junction box. It is almost impossible to keep water out of an exterior conduit system, especially if there are vertical sections of conduit that contain couplings. If the motor junction box is the low point on the conduit system I would look at that as the entry point.
Don

 

[Kiljoy]

Is it possible that the manufacturer, being in a pinch, could only get ahold of refurbished motors? Hence the odd size and off brand... Unless exposed to wash down, TEFC motors are generally rated for outdoor use.

 

[aolalde]

Totally enclosed motors are not hermetic, so they allow air interchange with the atmosphere thru shaft-end brackets clearances. Humidity dissolved in air will condensate with temperature dropping below the dew point. Water condensation will reduce internal air volume and the motor breath, filling that space with new ambient air. If condensation temperature remains, more water will condensate ongoing that cycle. I have seen a gallon of water condensation into a TEFC explosion proof motor.

There are internal space heaters and explosion proof drains for this type of motors to prevent water condensation while motors are idle. Unfortunately those should be installed only for the original motor manufacturer, under UL Listed procedures; any modification will void the UL Listed approval.

 

[jbartos]

Suggestion: Visit

http://www.reliance.com/pdf/catalogs/variable_speed/4-sml_dc_app.pdf

for the TEFC features

 

[dave676]

Just thought I'd update this for anyone who was interested. We pulled the remaining three motors and had them sent to a factory-owned repair center. They tore them apart (found no water), replaced two of the motors and rebuilt the third. I haven't been able to get a report from them detailing what the problem was yet, but they did all of the work at no charge - after some badgering - and the blower manufacturer agreed to pick up the tab for the original unit.

Also, the blower manufacturer sent one of their technicians at their cost to the site to assist one of our people for the installation of the new motors and startup.

If I ever get a disposition on those other three motors, I'll post their report.

 

[aolalde]

dave676:

Do these motors have internal space heaters? If so, turn-on them while the motors are idle or in storage.

 

[jbartos]

Comment: Often, Nema enclosure 4 or 4X is opened by drilling a small hole at the bottom to avoid any condensate to accumulate. Water condensate may arrive via conduits and conductors. Apparently, that may have been the case with those motors. Water accumulated inside the motor enclosure via conduits.

 

[aolalde]

JB.
"Drilling a small hole at the bottom to avoid any condensate to accumulate." Is Not Allowed in an Explosion Proof Motor. Special drains UL approved must be installed by the motor manufacturer.

 

[jbartos]

Comment on the previous posting: The NEMA 4 or 4X enclosures are altered by drilling a small hole in them.
The XP motor should not have any opening either. However, what if someone makes that hole in there. Apparently, not all XP environments are of the same danger. However, I agree that the special drains should comply with industry standards. Also, XP electrical installation should be installed properly, i.e. properly sealed.

 

[kassad]

Two Nameplates (50HP & 40HP)
A motor when it is being used with a VFD has to be an inverter duty motor. If, for some reason, the manufacturer has zero stock, motors of a higher rating are used (i.e. 50HP instead of 40HP) but this is only a temporary solution. These higher rating motors are not suitable to run on VFD's. A manufacturer that has built a motor for inverter duty use, never uses 2 name plates. I think that your motors are standard of the shelf motors on which the 40HP nameplates were put to indicate that they were de-rated for inverter use.

Water Entry
If you are using trickle voltage then condensation is left out. Only two ways left. Either water entered at the factory or someone in the field has washed the motor using a water jet. The second option is only true when the motor has no inpro seals (or IP55 seals).It is up to you to decide which one might be obvious. Or if you like conspiracy theory, then the shop knowing that these motors were de-rated (they must have contacted Reliance) and not suitable for inverter duty, made a claim that we found water in them.
It is up to you to judge which might be right.

 

[jbartos]

Comment: Water may appear inside of a motor if the motor terminal box is not tight enough during motor handling.