Effect of lower humidity on indoor Electrical Equipments
Effect of lower humidity on indoor Electrical Equipments
(OP)
What is the effect of lower humidity (i.e; say much lower than 50% relative humidity)on the performance of indoor Electrical Equipments like switchgears, panels UPS etc.
As I understand, for the electrical equipments humidity variation by a wide range is considered to be more risky, as it would result in condensation. However, having relatively lower humidity should be a favourable scenario.
Any view?
As I understand, for the electrical equipments humidity variation by a wide range is considered to be more risky, as it would result in condensation. However, having relatively lower humidity should be a favourable scenario.
Any view?






RE: Effect of lower humidity on indoor Electrical Equipments
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington
RE: Effect of lower humidity on indoor Electrical Equipments
Thank you very much. Quite convincing reply.
RE: Effect of lower humidity on indoor Electrical Equipments
In the IEC world, for "Low-voltage switchgear and controlgear assemblies" was previously covered by IEC Standard 60439-., now replaced by new IEC 61439-.
The IEC 61439-1 defines the general requirements for all the following product sections in the 61439-. series.
In the IEC 60439-1
a) Clause 6 [Service conditions]; where sub-clause 6.1 [Normal service conditions] states "ASSEMBLIES conforming to this standards are intended for use under the following service conditions" with Note "If components, for example relays, electronic equipment, are used which are not designed for these conditions, appropriate steps should be taken..."
b) Sub-clause 6.1.2.1 [Atmospheric conditions for indoor installations] "The air is clean and its relative humidity (RH*)does not exceed 50 % at a maximum temperature of +40 degree C. Higher relative humidities may be permitted at a lower temperatures, for example 90 % at +20 degree C. Care should be taken of moderate condensation which may occasionally occur due to variation in temperature"
c) Sub-clause 6.1.2.2 [ Atmospheric condition for outdoor installations]....
There is no guideline on the effect with (RH*)much lower than 50 %.
In general, (RH*)is not a major issue in LV systems and components voltage, current, making/breaking capacity ratings and clearance/creepage distance requirements.
The Standard does not stipulate the (RH*) value for insulation/impulse tests(for voltage rating),temperature-rise test(for current rating), voltage+current+power-factor(for making/breaking capacity tests)and separation distance (for creepage and clearance distance requirements).
Likewise, test laboratories do not adjust, record or report on the (RH*) value during the above tests/measurements.
RE: Effect of lower humidity on indoor Electrical Equipments
RE: Effect of lower humidity on indoor Electrical Equipments
RE: Effect of lower humidity on indoor Electrical Equipments
If you're selling to my area, you better make sure your equipment will withstand 'on the order of' 5% RH.
RE: Effect of lower humidity on indoor Electrical Equipments
There was a week or so back in 2011 where the RH in Las Vegas dropped below 5% several times, hitting the record low for the US at 1%. There were a LOT of electronic board failures that week.
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington
RE: Effect of lower humidity on indoor Electrical Equipments
If I read the charts right the SVP at 40C is more than 10 times higher than that at 0C. So 50% RH at 0C would have less water vapor concentration than 5% RH at 40C.
I am presuming that it is the absolute concentration of water vapor in air that controls its electrical conductivity and its ability to bleed off charges that would determine the risk of harmful static electric discharges.
RE: Effect of lower humidity on indoor Electrical Equipments