Internal "wall wart" and UL/CE compliance?

[har...@hallikainen.com]

I'm finding that we're spending many thousand dollars on UL testing
for safety when we are using a UL listed open frame power supply, a UL
listed power switch, a UL listed power inlet, and a few pieces of
wire. Meanwhile, I can buy a "wall wart" external switcher for $10 or
less that is UL listed.

So, the questions are:

1. If we were to use a UL listed enclosed power supply with an
integral AC inlet (think of a desktop supply for your laptop computer)
and place it inside our product with a hole in the rear panel allowing
access to the inlet, could we substantially decrease the cost of
testing for compliance? This would be similar to the power supplies
used in desktop computers where the supply is totally enclosed. Just
DC wires come out one side and an AC inlet shows through the rear
panel of the PC.

2. If we could reduce compliance testing costs through the use of
such a power supply, who manufactures supplies like that in the 30 to
50 watt range? Or, should we just stick a desktop supply inside our
product and provide brackets that keep it from flopping around in our
cabinet?

THANKS!

Harold

[proso...@gmail.com]

On Apr 4, 12:31 pm, "har...@hallikainen.com" <har...@hallikainen.com>
wrote:

This is a tough question to answer. I guess a prime question would be:
Do you want or need to have the UL mark on your final product. If yes
then UL will still need to evaluate this power supply for use in your
product. Most of these power supplies do not meet Class 2 requirements
so equipment connected to them could still be considered to need
evaluation to comply with the requirements of the standard.

Cheers,
Nick
www.easycomplianceguide.com

[har...@hallikainen.com]

Thanks for the response! I'm not quite sure what "class 2" is. Is it
electrical shock resistance (perhaps double insulation and a high
hipot test) or fire resistance (over temperature shutdown or similar),
or power output limit (limiting fire creation capability of connected
equipment), or some or all? I'm just looking for ways to reduce the
testing costs for UL listing of a device. I heard my employer was
charged $16k to test a device with a UL listed power supply, UL listed
power inlet/line filter, and UL listed power switch. Everything else
was low voltage on the power supply output. I understand that each of
these components must be used within their limits (there was a
question as to whether the power switch would handle the power supply
inrush current). But, I look at a typical PC power supply that has all
the line connected components sealed in the box. If we were to use
something like that (but down in the 50W area), would it decrease our
testing costs? If so, who makes supplies like that (that would just
stick out our rear panel and provide us with "safe" DC inside the
box)?

What else can we do to reduce testing costs?

THANKS!

Harold

[Brian]

If you do not understand what a 'Class 2' power source
is, you probably should not be doing any sort of
evaluation of safety requirements.

For IT equipment, a Class 2 source is supposed to
provide limited voltage, current, and power under both
normal and some fault conditions. Electrical codes have
other requirements for class 2 sources and associated
wiring, depending on the intended end use.

Also, for use in North America, there are other
agencies, such as TUV Rhineland and CSA, that will
provide prompt and cost-effective safety assessment and
certification services.

[har...@hallikainen.com]

On Apr 8, 1:55 am, Brian <not_here@no_where.com> wrote:
> If you do not understand what a 'Class 2' power source
> is, you probably should not be doing any sort of
> evaluation of safety requirements.
>
> For IT equipment, a Class 2 source is supposed to
> provide limited voltage, current, and power under both
> normal and some fault conditions. Electrical codes have
> other requirements for class 2 sources and associated
> wiring, depending on the intended end use.
>
> Also, for use in North America, there are other
> agencies, such as TUV Rhineland and CSA, that will
> provide prompt and cost-effective safety assessment and
> certification services.
>

Thank you for your comments. I'm not really trying to do "evaluation
of safety requirements," but, instead, looking for ways we can reduce
costs of the evaluation. Perhaps the use of a UL listed filtered power
inlet, UL listed open frame switching supply, and UL listed power
switch is the best we can do. I was thinking that a "pre-approved"
module that handles all line connected components would help, but
perhaps not.

Again, thanks for the comments!

Harold