Amp and preamp on same outlet?

03-09-15: Ct0517

03-06-15: Jea48
Edit to my last post.

Do you know the ampere rating of the circuit breaker mounded in the back rear panel of the amp? 15 amp? 20 amp? Do you know if it is a magnetic trip breaker only?

@Jea48

I received info from Patrick Bresnahan at Krell that these are 50 amp breakers.

I provided some info in my previous post about how it works.

Cheers
Ct0517

Ct0517,

Thank you for taking the time and finding out the rating of the breaker.

50 amp breaker.... 'IF' we are to assume the breaker handle rating of the breaker is 50 amps that could explain the power consumption max rating given in the Krell owner manual.

6000 max. watts / 115Vac = 52.17 amps.

‘IF’ , The 700CX amp has two 4kva power transformers.
4000VA, watts, / 115 = 34.8 FLA primary amps, secondary fully loaded for each transformer. (For purposes of transformer rating only).

Note, this assumes there is not any other current limiting fusing after the load side of the rear panel 50 amp main breaker of the Krell amp for each power transformer primary winding.

Secondary fuse protection could/would limit the amount of power that could be drawn from each power transformer as well.

The 50 amp rear panel breaker limits the max FLA combined total possible connected load of the two transformers by a little over 80%.
34.8 X 2 = 69.6 X 80% = 55.68.

So what else limits the mains 115Vac power for the 700CX amp? The branch circuit breaker in the electrical panel. Though remember the branch circuit is meant to protect the branch circuit wiring not what is connected to it at the wall receptacle. It is the manufacture's responsibility to select the proper NEMA plug for the FLA load for his equipment. If he say the equipment should be connected to a 20 amp circuit then his equipment must not draw more than 16 amps FLA. The plug on the end of the cord shall be a NEMA rated 125V 20 amp plug. PERIOD!

So far I have resisted giving any, "what if", happens in this thread concerning the Krell 700CX.

So if the branch circuit feeding the amp is 30 amps, what if there is a ground fault event anywhere in the 120Vac power wiring inside the amp, including the hot side fed of a primary winding of one of the 4kva transformers, to the safety equipment grounded metal chassis of the amp? Will the ground contacts of the plug/wall receptacle combo be able to handle the ground fault current that will travel back to the source, the electrical panel? If the receptacle and plug are NEMA 30 amp rated and UL and or CSA Listed then yes the equipment ground contacts of the plug and receptacle will be able to handle the possibly extremely high current the 30 amp breaker can supply until it reacts to the ground fault load current placed on it and hopefully trips open and breaks the ground fault circuit.

If it's a NEMA 5-15P plug/5-20R receptacle connection who knows? Not the manufacture of the devices. Not UL or CSA.
And I would be willing to bet Krell doesn't know either.
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Edit.

Though remember the branch circuit is meant to protect the branch circuit wiring not what is connected to it at the wall receptacle.

Should read,

Though remember the branch circuit breaker is meant to protect the branch circuit wiring not what is connected to it at the wall receptacle.
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Jea and Jmcgrogan, I thought you two already knew that you can't teach a pig to sing, and I'm certainly not going to try.
03-09-15: Mrvordo

I never said that.

Pig singing.
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I agree with Mrvordo!, he has the krell 750MCX mono amps with 30 amp breaker!, he knows first hand this works on our monster amps!

Edit post, 03-09-15: Jea48.

So if the branch circuit feeding the amp is 30 amps, what if there is a ground fault event anywhere in the 120Vac power wiring inside the amp, including the hot side fed of a primary winding of one of the 4kva transformers, to the safety equipment grounded metal chassis of the amp? Will the ground contacts of the plug/wall receptacle combo be able to handle the ground fault current that will travel back to the source, the electrical panel? If the receptacle and plug are NEMA 30 amp rated and UL and or CSA Listed then yes the equipment ground contacts of the plug and receptacle will be able to handle the possibly extremely high current the 30 amp breaker can supply until it reacts to the ground fault load current placed on it and hopefully trips open and breaks the ground fault circuit.

If it's a NEMA 5-15P plug/5-20R receptacle connection who knows? Not the manufacture of the devices. Not UL or CSA.
And I would be willing to bet Krell doesn't know either.

Quote
"Will the ground contacts of the plug/wall receptacle combo be able to handle the ground fault current that will travel back to the source, the electrical panel?"

It should have been obvious but I should have included the plug/wall receptacle Hot contact connection as the Hot brach circuit conductor that is connected to the Hot contact of the receptacle is feeding the high current, caused by the ground fault event, back to the source, the electrical panel, through the safety equipment grounding conductor. "Houston, we have ignition!"

Also in case it was not clear my load calculations, in the post, were for possible FLA full load of the two 4 KVA power transformers. I have no idea what the actuals loads could be. If Al couldn't figure them out from the Krell specs given, I assure you I can't. I did try to find a wiring diagram for the amp on the net without any luck.

03-09-15: Ct0517 post reminded me again from a previous post of his the rear panel 50 amp breaker has a pair of wires for hard wire remote control of the breaker. Just a guess, and that's all it is, the 50 amp breaker has a shunt trip solenoid that when energized will mechanically trip the breaker open. The shunt trip circuit could be controlled through relay contacts of relays that are controlled from each channel of the amp. This could be part of overload protection for the two power amplifiers of the amp. A wiring diagram of the amp's overcurrent protection would be nice.

For those interested, a look inside the Krell 700CX

It's just a shame Krell did not put a 30 plug on the end of the power cord to began with.

The power of electricity
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