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How to Store Your Electric Motors Off-Site - HECO

November 11, 2021

It’s the middle of the night and a key motor in your facility broke down. Every hour of delay is costing thousands of dollars. You pull a drop-in spare from on-site storage and it doesn’t work. It was ice cold when you pulled it out, the bearings are making odd noises, and it looks like a forklift dented its enclosure. How can you keep that from happening to you?

Two words: off-site storage.

Goals of Offsite Storage

There are certain things that off-site storage should always accomplish. First, and perhaps most importantly, it should ensure that your spare electric motors are ready to go when needed. Keep in mind that just because you have a spare motor doesn’t mean it’s ready to be dropped in as replacement. This is best accomplished through a combination of (1) proper climate control, (2) documented PM (Preventative Maintenance), and (3) existing plant audit reports that audit deficiencies and observations.

It’s not uncommon for a forklift to inadvertently ram a stored electric motor or pump, and the damage isn’t announced or discovered until that spare pump or motor is needed during a plant emergency. This is another goal of off-site storage of spares: preventing accidental damage to key spares.

Key Considerations for Proper Storing of Electric Motors

Let’s consider some important factors for storing your spare motors — proper storage techniques go well beyond finding a convenient place to put them.

Temperature Regulation

Electric motors must be stored above the dew point.

I was called to a local glass plant around 10PM on Christmas Eve because a motor pulled from their just completed outdoor storage building flashed and shorted out immediately upon energizing with 480 Volt 3 Phase Power. Next, they tried a stored 2nd, and then a 3rd new motor — all producing the same catastrophic results. When only one spare motor was left, they called me for an emergency plant visit.

I brought out the Megger and discovered that the new, freezing cold motor megged, i.e., shorted to ground. We picked up the motor, brought it to the shop, removed the end brackets, and water came out of this new TEFC motor!

Water had condensed in the motor because it had been stored below the dew point and the water had no way to escape. We baked the stator windings dry, replaced the bearings, reassembled the motor, and returned it early Christmas morning!

In short, motor storage temperatures should be between 50 to 90 F.

Optional Electric Space Heaters

There are optional electric space heaters you can use with critical motors in storage. Their function is to eliminate moisture and ensure that the temperature does not fall below the dew point. These space heaters should always be energized if they are on your motor. They can be added as inexpensive options when specifying new electric motors, and I highly recommend them. They are very low energy consumers and are very beneficial to the health of your motor.

Humidity Control

Humidity should always be less than 60%. Avoiding high humidity levels aids in maintaining high megger readings and significantly reduces the problem of surface rust. Make sure you check with your provider concerning their climate control standards.

Preventative Maintenance

Stored spares and other apparatus require proper PM. This includes megging the stator windings and rotating the motor shaft periodically so that the shaft is left in a different position than before. This PM should also be carefully documented.


Let’s talk about vibration.

A local manufacturing plant stored all electric motors on-site. One day, the new spare 800HP Mill Motor was needed to replace the old Mill Motor in operation. After two days of a difficult motor removal / installation, the motors were swapped out, only to discover that the new stored motor had bad bearings!

The Plant Engineer called me; our EASA Accredited Motor Service Center performed vibration analysis and determined that the bearings suffered from false brinelling. So I looked at the in-plant storage location to gather further data. This motor, the most critical in the plant, was stored on the concrete floor in a busy corner where frequent, heavy forklift traffic shook the foundation. Add to that the fact that the shaft had not been turned during storage.

The motor was pulled and off it went to our motor shop for new bearings and a stator winding analysis (no megger testing had been done on the spare for years). We were able to get it running again, but the removal/recondition/reinstallation cost did not approach the astronomical loss of production cost! From that time on, this customer has become an enthusiastic supporter for off-site storage!

Indoor Storage

One of the fundamentals of apparatus storage is that it must occur indoors. Outdoors there is no way to control temperature, humidity, and precipitation outdoors. However I personally know of one exception to this. I have a good friend who is the CEO of an EASA Accredited Electric Motor Repair Facility in San Diego, CA. Due to the constant climate in San Diego, he stores customers’ electric motors outdoors where they are still protected from rain and other perils and has never had an issue.

Lubrication Verification

Your off-site storage facility should monitor the elapsed time during which the motors are stored. Keep in mind that the additives in grease break down even when the apparatus is not used, so the old grease should be purged and replaced with compatible grease every 3 years.

Choosing a Motor Storage Provider

There are also three things to consider when choosing a motor storage provider. First, spare motors should be stored at a provider that guarantees a predetermined time between your call and asset delivery. This not only minimizes costly downtime but also gives a dependable window of time to get things running again.

In addition, the storage provider should have peril insurance. Before choosing a motor storage provider, request a copy of their peril insurance to be sure your assets would be adequately protected. Off-site storage cost is generally billed monthly or annually, based upon the square feet of storage space required. For some, the cost may be off putting but it is analogous to a utility: you are simply paying for an essential service.

Finally, it sounds so basic and simple, but ask yourself this: do you trust the company offering to store your apparatus off-site? Do they have a proven record as a quality oriented service provider, or is their reputation based on offering the “cheapest” price? Do they maintain an EASA Accredited Service Center? The positive answer to these questions will provide the peace of mind you need to move forward boldly with off-site storage without looking back.


Do you pay for Cloud Storage? Why not just buy a bigger hard drive, a more sophisticated server, and the skilled IT staff you’d need to support it? Or does it make more sense to empower professionals to care for your data, and ensure your assets will always be available while you and your staff deal with matters directly related to your expertise?

It makes sense that moving your storage to the cloud eliminates the cost of hardware and maintenance. And removing the capital expenditures and associated salaries to maintain all of that can translate into significant cost savings–just like storing your spare motors off-site!

If you are looking for a trustworthy, reliable off-site motor storage provider, look no further than HECO. We are an EASA accredited shop that meticulously follows industry best practices for storing and managing your spares, from temperature regulation to lubrication verification.

Contact us today to learn what we have to offer. At HECO…it is All Systems Go!

Posted in Equipment Management

Equipment and identification of electric motors