The Full Power Balanced 700cx,http://www.krellonline.com/assets/support/0162_020_MAN.pdf
750Mcx, 400cx, and 450Mcx amplifiers need to
be operated from a dedicated AC power line
rated at a minimum of 20 amps.
Please contact your authorized Krell dealer, distributor,
or Krell before using any devices
designed to alter or stabilize the AC power for
Full Power Balanced amplifiers.
I assume the unit uses a NEMA 5-20P plug. Thus you will need a NEMA 5-20R receptacle. A NEMA 5-20R 20 amp receptacle can only be installed on a 20 amp branch circuit per UL, NEC, and most importantly the manufacture of the receptacle.
Krell should of incorporated soft start circuitry in the amp but instead, and I am only guessing here, is telling their dealers to tell their customers to use a 30 amp breaker if nuisance tripping occurs. Bad call.... Subject: Breaker nuisance tripping>http://www.lyntec.com/body_faq-msp.htm
Subject: Breaker nuisance tripping
Do all 20 amp circuit breakers respond to inrush surges the same way?
NO! Circuit breakers have widely varying trip responses depending on their intended use. For most audio power amplifiers you need breakers with a HM rating. The High Magnetic rating allows a substantial inrush current, about double, for the first 100 milliseconds to eliminate nuisance trips. Nuisance trips are common on circuit breakers not rated for High Magnetic duty.
For instance, a standard Square D QO120 breaker will trip with as little as 120 amps in the first cycle compared to 240 amps for a QO120HM.
In Square D, the HM rating is only available for 15 and 20 amp breakers.
The 30 amp QO breakers sustain inrush currents of 300 amps for the first 10 cycles @ 60 Hz, sufficient to light up most of the largest power amplifiers without nuisance tripping.
Instead of using a 30 amp breaker I suggest you ask the electrician who will be installing the dedicated circuit for the Krell to see if the electrical panel manufacture makes a HM 20 amp breaker for the panel.
I would still have #10 awg solid core wire installed for the branch circuit wiring.
Example of an HM 20 amp breaker. http://ecatalog.squared.com/fulldetail.cfm?partnumber=QO120HM
Something else I would suggest if you will not be leaving the amp on 24/7 and will be turning on and off the amp daily you may want to use a heavy duty UL listed 20 amp receptacle. Hubbell manufactures a highly respected heavy duty recept. The Porter Port
is a Hubbell heavy duty recept.
I believe Wattgate also uses a Hubbell. Maybe others....