I appreciate the responses. These are molded case thermal magnetic breakers used for distribution on a data floor. We have been having some problems with breakers failing on the instantaneous test. Some of them would pass if the 40 - 30% was used but not the 25 - 25% tolerance. The question was to clear up what I perceive as a contradiction in the stated information. Some information that I have read on one of the manufacturere's web sites that stated the most important thing, under an instantaneous situation, was for the breaker to trip as testing equipment and techniques can create different results. That probably is true on the high side but becomes a little more problematic on the low side, where most of our breakers are failing. There is the fact that there is not a large startup surge with this equipment so they may be OK, but that doesn't change the fact that with written industry standards of testing in place, that if something did happen to cause a nuisance trip, management would not be very happy with us relying on our own opinon as to what is acceptable. Another problem we are having is breakers that trip without the handle moving to the trip position. Some of the data equipment does not alarm if one of the power sources goes down. This creates a problem with dual corded equipment when we de-energize a panel to install new whips. We now have to physically check the breakers of the alternate source panel to make sure none have tripped without us knowing. This is a little unnerving as some of the breaker handles have a very light touch. We are considering going to a different brand breaker, on our new distribution equipment, along with branch circuit monitoring.
Thanks again