Twayne wrote:
In ,
bud-- typed:
Twayne wrote:
A "Class 2" xfmr is simply a double-insulated transformer
without an earth ground on its plug, nor a polarized plug.
A "Class 1" xfmr requires a third wire, the earth ground
pin on its plug. The "Class of xfmr is a UL/CSA et al
classification which approves the xfmr and nothing else as
safety approved.
The primary characteristic of class 1, 2, and 3 power
sources is that they are power limited. There is a
specified maximum voltage, current and power you can get
from the source. For a class 2 24V transformer the max
current is 8A - the maximum current you get if you short
circuit the transformer.

I think you're confused between class definitions for Safety and what the
NEC defines; they are different.

I think you're confused about nearly everything.

Class 1, 2, and 3 CIRCUITS are classified as remote-control, signaling, and
power-limited circuits in the National Electrical Code (NEC).

Limiting the discussion to class 2, which many people are familiar with
(thermostat, doorbell):

Class 2 circuits are class 2 because they are _powered by a class 2
power supply_.

Class 1 and 2 Power Supplies determines the insulation PROPERTIES of a power
supply and there is no Class 3. To the layman, they either need the third
ground wire or not (1 & 2 respectively).

So if I buy a UL listed class 2 transformer, according to you, it is not
power limited and can not be used to power a class 2 circuit. What a
bizarre idea. Make that a stupid idea.

No class 3? UL category XOKV - "TRANSFORMERS, CLASS 2 AND CLASS 3".

The 8 Amp limitation IN NEC has nothing to do with UL/CSA et al
classifications. A transformer can output any current it can be designed for
as long as it meets the insulation and overvoltage/current test
specifications and meet the safety requirements.

That will surprise UL.

Class 1, 2, 3 as used in the NEC as you can see above is quite different.
While saftey is of course a concern, simply limiting an output to 8 amps
would not deem it to be "safe". The NEC is concerned with wiring, and the
Safety is concerned with safety. Two different worlds. A google for UL
1459 might be enlightening for you.

It might be a lot more enlightening for you.

UL 1459 is "Telephone power supplies" (and has probably been withdrawn).
You are probably the only person that thinks we are talking about
telephones.

Class 2 transformers are listed under UL 1585, "Class 2 and Class 3
Transformers." (There is that pesky "class 3" again.) They are power
limited "in accordance with ANSI/NFPA 70, ‘National Electrical Code’ (NEC)"

Some other standards may be applicable such as UL 1310, "Class 2 Power
Units" which also comply "with Class 2 voltage, current and volt-ampere
limits as specified in ANSI/NFPA 70, 'National Electrical Code'."

Note the reference to the power limits in the NEC.

Information is from the UL White Book.

Again you are posting nonsense.

Four months ago, in a thread about utility PF correction caps, you told
HeyBub "next time I'll be a lot more careful."
Obviously not.
Again.
G

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bud--