Frequently Asked Questions
Each power source should be marked on its rating plate, Fig.1, with an IP rating which provides information about the degree to which the equipment is protected against water. Normally equipment will be IP21 or IP23. The second number describes protection against water ingress. A power source marked IP21 is protected from vertical drops of water, as for example may occur if the roof leaks. If the equipment is marked IP23, this means that the equipment is protected at up to 60° from the vertical and is thus suitable for outdoor use.
Areas of increased risk are in wet or humid conditions, confined spaces or when the welder is exposed to large areas of bare metal. For use in this type of environment, it is important to use a power source with an S mark, which means that the no-load voltage is below 48V rms AC or 113V peak DC. If the power source has a higher no-load voltage, a voltage reduction device should be used which will limit the voltage at the holder to approximately 25V.
Extracted from an article entitled 'Let's get technical - choosing an arc welding power source' by W Lucas and G Melton, published in Welding & Metal Fabrication, Vol.67, No.4, May 1999, pp.18-21. (Publishers - dmg BusinessMedia Ltd, Redhill, Surrey, UK - http://www.dmg.co.uk/dmgbm/ )