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Monday 8 September 2014

Recommend current limits for treadmills

Recommended Treadmill Current Limits 

(Part 2 of a 2-Part report. Click here for Part 1)

Further to my previous post, I have now completed some more work to help validate the most appropriate trigger point settings for the Treadmill Saver.

Treadmill Saver is a new product designed to alert gym operators when (a) essential treadmill preventative maintenance is required and (b) when excessive electrical current is being consumed. 

Treadmill Saver is a convenient visual indicator as to the condition of your treadmill and can save you energy and help prevent breakdowns. Of course, it will only work effectively if it is set up correctly. The purpose of this experiment is to determine the most appropriate trigger points. 


In speaking with my gym manager, our feeling is that our treadmills will on average be running at 10kph. Therefore, we chose to measure the current in the loaded and unloaded condition at 10kph on each of our treadmills. For info, I ran on the machines for the loaded test and I weigh 91kgs. For comparison, we also measured the current at maximum speed of our Life Fitness T9i treadmill with a new PowerBelt and platform (20pkh).

The results were as follows:

Technogym Excite (not new belt and deck but running well with light wear):
3.3A loaded
2.3A unloaded

Life Fitness 9100 (not new belt and deck but running well with light wear):
3.5A loaded
2.5A unloaded

Life Fitness T9i (new belt and deck and fresh application of silicone oil)
3.8a loaded
1.9a unloaded

Life Fitness T9i at maximum current draw at 20kph (top speed)
8.8a loaded*
3.9a unloaded

*Very difficult to run on for more than a about 5 seconds!


I conclude that all of our gym treadmills are running at, or close to, their optimum condition. Therefore, it would be appropriate to set the Treadmill Saver amber warning set point to be slightly higher than the optimum so as to avoid false triggers.  I would recommend a +20% current drift from optimum which would make the amber set point about 4A.

For the red set point, it would be desirable to choose a threshold which is somewhat higher than the amber set point but not so high as to allow the machine to operate continuously outside of its maximum operating parameters. Based on the current draw at top speed of the Life Fitness T9i, the maximum current draw (maximum speed in the loaded condition) is 8.8A. However, we found that it is not possible to run at 20kph for more than about 5 seconds. Therefore, it is reasonable to suppose that the design criteria used for treadmills is actually based around a continuous current (speed) rating rather than a peak current (speed) rating and so I suggest 6A is a realistic set point for red.

Therefore, I would recommend an amber (maintenance overdue) set point of 4A continuous and a red (stop using) set point of 6A continuous. 

The Treadmill Engineer
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