There are two F5B limiters available today. One is Neu limiter from Neumotors and the other is Unilog from SM Modellbau in Germany, more informations are in F5B Equipments New and Used page.

How to use 1750watt/min
You must set the timer on your radio first so that it will show accumulated time of your motor run. Always use power limiter on your practice and always use it till it cut off. This way you know how many seconds this particular set up will run before it cut off. When it cut off you must immediately stop motor switch otherwise it will continue counting time and won’t be able to know exact run time. Record motor run time after the landing before turn radio switch off. Continue this with different propellers and motors to find out each set up’s run time.

How many seconds should I set it.
1750watt/min is the rate of power which works 1750 watts in one minute.
If you use it in 30 seconds you can use 3500 watts.
So with less time we can use more power.
How many seconds do we need to complete full task in real competition?
Most everyone were using 35 seconds set ups in last world championship in Ukraine.
Some took risk and tried 27 seconds high power set up and end up short in duration.
It was a cold (7 to 8 degree C) and raining, Glider doesn’t float well and decelerate more in this kind conditions.
Each competitor had to climb higher than normal and also must set aside at least 5 seconds for duration task.
In case of 35 seconds set up we use 30 seconds for distance task which means less than three seconds motor run in each climb. If you are to try for more than 40 legs you need to fly 6 legs set which require more motor run to climb higher.
This requires 2.5 seconds for 4 legs and 3.5 seconds for 6 legs.
When the condition is bad like last WC in Ukraine even top class flyers could only make 42 to 43 in rain.

Opposite case was when I was practicing in Japan I made 48 legs with 28 seconds set up.
It was clear sunny day with 17 to 18 degree C and good thermal conditions. I checked motor time after the landing it was only 24.1 seconds. Each climb was about 1.5 sec to 2.0 sec. The most important point is less you use the motor run more you can use it for extra legs.

If there is the person use 0.5 second less in each climb he will end up extra 5 second to do one more legs.
In general when the condition is good use high power settings ( stronger pitch prop or longer prop).
And opposite for the bad conditions.