confused about 20 amp power cables

@ditusa while you can clearly buy such a cable, for a receptacle  the code states...

• A single receptacle installed on an individual branch circuit shall have an ampere rating not less than that of the branch circuit. 

So my interpretation is that the plug and socket on a cable should be of the same rating, because the cable is just an extension of that branch circuit.

I think it is one of those grey areas that will only be judged in the event of a catastrophic failure unfortunately.

Regards, steve

@williewonka said:

A single receptacle installed on an individual branch circuit shall have an ampere rating not less than that of the branch circuit.

True, not less than. The single receptacle installed on an individual branch circuit can have an ampere rating greater than the ampacity rating of the branch circuit. Therein a single NEMA 5-20R (20 amp) receptacle can be installed on a 15 amp branch circuit.

As for this:

NEC 210.21 (B)(1)

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@ditusa said:

First, the discussion is in regards to a 15A male plug of a power cord with a 20 female IEC connector. NEC is not involved.

The power cord @ditusa Linked in his post may not be a Listed power cord. There are ones just like it manufactured that are Listed. UL Listed.

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@ditusa - thanks for that info. Its interesting that UL allows this practice. Goes against everything I was taught in college in the UK, but that was some 50 years ago 

So I guess it boils down to personal preference as to how safe a person would like to feel using a power cable of this design.

Personally, I would err on the side of caution and change the plug to a 20 amp model.

Regards Steve

 

 

@erik_squires said:

Check the fuse rating on the back of your amp. It’s probably a lot less than 20A. :) I don’t have access to the manual but I saw an image which specified 1500W on the back. This should be around 12 Amps. A 15A circuit is generally rated to 1800W, a 20A circuit for 2400, so definitely a good thing you are using a 20A circuit!

No fuse on the back of the amp. Fuses are inside. Accessed from removing the bottom cover of the amplifier. I couldn’t find anywhere on the Net what the ampere rating is for the fuse(s).

I don’t have access to the manual but I saw an image which specified 1500W on the back. This should be around 12 Amps.

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This should be around 12 Amps.

Agree. 1500W/120Vac (nominal) = 12.5A

On HiFi Engine Web Site you can access the owner’s manual. Listed in the specs it says AC power consumption max 1500 watts. Not sure exactly how the 1500W max power consumption number is applied. Max continuous watts???. I don’t think so. There is only one power transformer. 1000Va, 1KVa.

@blisshifi said:

I am an authorized T+A dealer, and I can tell you that the most powerful fuse in the unit is 10A,

I take him at his word.

YouTube video. The Formidable T+A 3100HV Integrated Amp from Germany

The power transformer in the amp is a 1000Va "torodal" transformer.

Two 500Va 115Vac primary windings. For the U.S. the two windings are wired in parallel. 1000Va. Using the data given on the transformer.

Available FLA = 1000Va / 115Vac = 8.7A

U.S.connected 120Vac nominal AC mains amps, 1000Va / 120V = 8.3A.

Available short term overload of the 1000Va transformer??? Just a guess, there is a rated overload percentage. (service factor). Look at the specs for head room for 8 ohm and 4 ohm max power ratings.

The amplifier has to have a soft start circuit, imo, to limit inrush current. If not the electrical panel circuit breaker would see a dead short on turn-on of the amplifier and trip on its short circuit protection.

So back to the overload protection AC line fuse in the amplifier. 10A, I assume slow blow.

IF the FLA is 8.3A the fuse was sized at a little over 120% of 8.3A. (Good chance the circuit designer of the amplifier sized the power transformer at 80% of the of the FLA of the amplifier. That leaves 20% head room for playing/listening to music with high dynamic music passages.)

It would be nice if a reviewer took the time to measure the AC line current at power output clipping.

From the owner’s manual specs:

Output Power* (Peak)
8 ohm 380 W
4 ohm700 W

Peak is not max continuous output power.

Just for a rough AC mains current draw calculation using 4 ohm 700W.

700W / 120V = 5.8A + unknown loses.

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Bottom line... why the 20 amp IEC inlet connector? Better contact surface area???

Beats me why it was used.

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@blisshifi -- Hi, yes I am that person. Nice to know that you worked with Michael. I will put the PS 3000 on my "down the road list". Next stop for me is a speaker upgrade :).