UL HI-POT Testing

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larryjoma

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Location
Illinois
Hello,

Is hi-pot testing a requirement for a control panel to be UL certified? I thought only CSA had the hi-pot requirement but I cant find anything that states different.

Larry
 

Jraef

Moderator, OTD
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You would not hi-pot anything under 5KV cable I don't believe. Certainly nothing below 2KV.

Huh. Done all the time on 480V Switchboards, MCCs and Panelboards etc. The rule is, DC V for Hi Pot = 2X AC V + 1000V. So for a 480V MCC, we would Hi Pot them at 2200VDC (because technically, they are rated for 600V).

There is nothing in UL508a for doing Hi Pot testing of control panels etc., because when building one, you are REQUIRED to use components that have ALREADY been listed. In the COMPONENT listing, or if, like in an MCC or Switchboard where there are more POWER CARRYING components to make the assembly, you have to do that. But there is no equivalent to UL 508a for Switchboards and MCCs, only manufacturers can do that.

And UL is technically not saying you MUST do a Hi Pot test, it says your equipment must show a DIELECTRIC WITHSTAND rating, but the most common way to prove that is with a Hi Pot test.
 

larryjoma

Member
Location
Illinois
Huh. Done all the time on 480V Switchboards, MCCs and Panelboards etc. The rule is, DC V for Hi Pot = 2X AC V + 1000V. So for a 480V MCC, we would Hi Pot them at 2200VDC (because technically, they are rated for 600V).

There is nothing in UL508a for doing Hi Pot testing of control panels etc., because when building one, you are REQUIRED to use components that have ALREADY been listed. In the COMPONENT listing, or if, like in an MCC or Switchboard where there are more POWER CARRYING components to make the assembly, you have to do that. But there is no equivalent to UL 508a for Switchboards and MCCs, only manufacturers can do that.

And UL is technically not saying you MUST do a Hi Pot test, it says your equipment must show a DIELECTRIC WITHSTAND rating, but the most common way to prove that is with a Hi Pot test.

So when I build a control panel with all UL certified parts using 508A rules, I don't technically have to do the hi-pot test?
 

Jraef

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Electrical Engineer
So when I build a control panel with all UL certified parts using 508A rules, I don't technically have to do the hi-pot test?
Correct. Thee is nothing in UL508a that requires additional dielectric withstand ratings, just that the components you use are already UL listed, which would have included that if necessary. but that's why uu can't just 'roll your own" busbar systems under UL 508a. Then it becomes a Switchboard, MCC or panelboard, where different UL rules apply.

Where are you getting this from?
The formula? Don't remember, probably ANSI? IEEE?

Follow-up:
More likely in UL845 (MCCs) which is what I used to build. I don't have that standard with me here, but here is similar wording from UL 73.
UL Standard 73 - Motor Operated Appliances
“An appliance shall withstand for 1 minute without breakdown
the application of a 60-hertz essentially sinusoidal
potential between live parts and dead metal parts with the
appliance at the maximum operative temperature reached in
normal use. The test potential for the primary circuit shall
be:
A. One-thousand volts for an appliance employing
a motor rate 1/2 horsepower (373 W output) or
less or 250 volts or less.
B. One-thousand volts plus twice the rated voltage
for (1) an appliance employing a motor rated
more than 1/2 horsepower or more than 250
volts, or (2) an appliance applied directly to persons
- see item C.”
C. Twenty-five hundred volts for an appliance that
is applied in a wet or moist condition directly to
persons.”

For CABLES, you don't usually do Hi Pot testing for LV, just MV and above, but it's different for EQUIPMENT, which is what the OP asked.
 
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petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
UL508a has never required any kind of insulation testing.

It is required by CE rules though for all industrial control panels. See EN 60204-1 18.2. You also have to do a 10A ground bond test.
 
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