What does the nameplate rating mean?

[Warren S.]

Hello, group:
I have a new oven to install this weekend. The nameplate gives it a rating
of 6.4 Kv at 240 volts. By advanced calculus, I get 26.6 amps.

Now my question is, will a 30 amp circuit suffice, or does this thing really
use all 6.4Kv? If so, 26.6 amps is more that 80% of the circuit ampacity.
Should I run a 40 amp circuit instead?
Warren

 

[SQLit]

Hello, group:
I have a new oven to install this weekend. The nameplate gives it a rating
of 6.4 Kv at 240 volts. By advanced calculus, I get 26.6 amps.

Now my question is, will a 30 amp circuit suffice, or does this thing really
use all 6.4Kv? If so, 26.6 amps is more that 80% of the circuit ampacity.
Should I run a 40 amp circuit instead?
Warren

It will when everything is on high and heating. I would run a 40 amp
circuit. Never can tell how often it will be used on high.

 

[Warren S]

Don Phillips wrote

I would refer to the installation instructions as well. It may tell you
what you need to install to maintain the equipment's listing.

The installation instructions were not specific. I have decided to run a 40
amp power supply anyway, since I don't want to cut it that close. Thanks to
those who responded.
Warren

 

[Harry Bloomfield]

Warren S. wrote on Wednesday (21/01/2004) :

Hello, group:
I have a new oven to install this weekend. The nameplate gives it a rating
of 6.4 Kv at 240 volts. By advanced calculus, I get 26.6 amps.

Now my question is, will a 30 amp circuit suffice, or does this thing really
use all 6.4Kv? If so, 26.6 amps is more that 80% of the circuit ampacity.
Should I run a 40 amp circuit instead?
Warren

30 amp should prove to be perfectly adequate.

1. The rating you calculated suggests so.
2. You are unlikely to switch everything on at once.
3. Even when everything is on, the temperature controls will not all be
on and drawing current at the same time.

... And finally 2 and 3 mean that some diversity is allowed for in
cooker supply ciruits within the IEE Regulations. It does sound like a
rather small cooker though.

 

[Romy]

Hello, group:
I have a new oven to install this weekend. The nameplate gives it a rating
of 6.4 Kv at 240 volts. By advanced calculus, I get 26.6 amps.

Wow, 6.4 Kv huh? Mighty powerful oven!


Romy

 

[Louis Bybee]

"Warren S." <[email protected]> wrote in message

Warren, are you sure that it doesn't say Kw and not Kv? It makes a
major difference in the interpretation.

If it is Kw, a 6.4 Kw load operating at 240 volts resistive load will
draw 26.66 amps as you correctly deduce.

While you could operate it from a 30 amp breaker, you may run into
intermittent trip problems with the breaker when the oven is running
at full capacity for an extended period of time. I'd personaly go for
the next higher capacity breaker, be it 40 or 50 amps, but be sure to
size the wire guage accordingly.

For 50 amps, I'd run #8 wire, although #10 may marginally satisfy NEC
requirements (I don't have a copy of the NEC handy here at home).
Another factor is the distance between your distribution box and the
oven, but I'm assuming that it is less than a 50-ft wire run. Realize
that the cost of the wire is likely the least expensive thing in the
project, because that wire will likely be there to provide service for
many years.

Licensed Electricians, please correct me if I'm wrong here, because I
don't want to steer the guy in the wrong direction and most of my
practical experience here is with 3,000 MCM or larger traction power
cables on subways and #24/26 signal and communicatons wiring. I also
generally assume that #14 is used for 15 amps, #12 for 20, and #10 for
30 amps, so I'm not entirely sure that #8 is adequate for a 50 amps
(but didn't want to suggest #6 which many homeowners have problems
working with).

My personal preferance here would be for a 40 amp breaker feeding #8
wire, however I'm not sure if 40 amp breakers are readily availble for
domestic distribution panels, but I know that 50 amp breakers are.

Then too, I'm a control system guy, so what do I know!

Harry C.

Your recommendation of #8 Copper and a 40 amp breaker is most likely correct
for this installation.

There are many variables the OP didn't share with us. Manufacturer's
installation instructions, system supply voltage (not the appliance rated
voltage), method of connecting circuit conductors and their temperature
rating, etc.

Many installers take the amperage figures of the NEC Tables (i.e. 310.16)
under the insulation classifications as the permitted current capacity of a
branch circuit wire. While in some cases this could be the case, often there
are other non-apparent factors that could limit the current allowed for a
specific size conductor. One of many such possibly limiting factors is the
temperature rating of terminating devices. If the terminal temperature
rating happens to be listed at 60 deg., the amp rating of even 90 deg. wire
would be limited to 60 deg.

With the NEC what might appear to be a logically correct choice might be
disallowed by other factors.

Louis--
*********************************************
Remove the two fish in address to respond

 

[Warren S]

Louis Bybee wrote

Your recommendation of #8 Copper and a 40 amp breaker is most likely correct
for this installation.

There are many variables the OP didn't share with us. Manufacturer's
installation instructions,

It just says to connect to a circuit appropriate for the nameplate rating.

system supply voltage (not the appliance rated
voltage),

My Fluke says 241.3 volts

method of connecting circuit conductors and their temperature
rating, etc.

Blue wire nuts at the oven j-box, circuit breaker screw terminals at the
panel. IIRC, 75 degree rating.

Many installers take the amperage figures of the NEC Tables (i.e. 310.16)
under the insulation classifications as the permitted current capacity of a
branch circuit wire. While in some cases this could be the case, often there
are other non-apparent factors that could limit the current allowed for a
specific size conductor. One of many such possibly limiting factors is the
temperature rating of terminating devices. If the terminal temperature
rating happens to be listed at 60 deg., the amp rating of even 90 deg. wire
would be limited to 60 deg.

With the NEC what might appear to be a logically correct choice might be
disallowed by other factors.

I've decided to run #8 THHN in alflex, to a 40 amp breaker. Another poster
caught my error listing the oven's rating at 6.4Kv. It is, in fact, 6.4 KW.

Thank you for your reply.
Warren

 

[Steve Alexanderson]

Wow, 6.4 Kv huh? Mighty powerful oven!

Nope, we know nothing about how powerful it is, just that it has a weird
dual voltage rating.