24V power sup­ply

The Shed - - My shed -

In a di­rect elec­tri­cal cur­rent (DC) the cur­rent trav­els in just one di­rec­tion, from pos­i­tive to neg­a­tive. Just to make things more in­ter­est­ing the elec­trons that make up the cur­rent ac­tu­ally travel from neg­a­tive to pos­i­tive. In al­ter­nat­ing cur­rent (AC) the elec­trons shut­tle for­ward and back, per­haps 50 times per sec­ond.

There are some ad­van­tages to a 24V DC elec­tric­ity sup­ply.

The com­mon be­lief is that more than 50V is needed to pro­duce a suf­fi­ciently large cur­rent in the hu­man body to cause elec­tro­cu­tion, so 24V should be safe; es­pe­cially when com­pared with the 230V AC that is the usual house­hold sup­ply in New Zealand and Aus­tralia.

If elec­tric­ity is pro­duced by so­lar pan­els or wind gen­er­a­tors it will prob­a­bly be 24V. An­other ad­van­tage is that de­vices that run on 24V DC, such as lap­top com­put­ers, don’t need a trans­former and rec­ti­fier be­tween them and the 24V power sup­ply. It is said that a 24V sup­ply doesn’t need to be in­stalled by a reg­is­tered elec­tri­cian, how­ever this is of­ten not the case. There are dis­ad­van­tages to a 24V DC sup­ply.

It may not be as safe as it seems. Over­seas there have been some fa­tal­i­ties caused by low-volt­age elec­tric­ity sup­plies. Ac­cord­ing to the elec­tri­cal reg­u­la­tions, in most sit­u­a­tions, for in­stance when con­nect­ing to so­lar pan­els, a reg­is­tered trades­per­son is needed. Arc­ing causes more prob­lems for DC than it does for AC. ‘Arc­ing’ is when the elec­trons travel short dis­tances through the air in­stead of stay­ing in the wire — as seen in a petrol en­gine’s spark plugs. The greater the volt­age, the greater dis­tance the arc­ing can cross. Arc­ing is es­pe­cially dan­ger­ous in a build­ing’s wiring, as it causes heat that can re­sult in a fire. The usual cause of the arc­ing is a loose con­nec­tion or a small break in the wiring that the elec­trons can jump across. Spe­cial fuses are also needed in a 24V cir­cuit. Volt­age drop over longish wires is more of a prob­lem at low volt­ages than at higher ones.

If you are in­stalling a 24V DC elec­tric­ity sup­ply, pro­fes­sional ad­vice is ab­so­lutely es­sen­tial. You are mak­ing a big mis­take if your sole rea­son for want­ing a 24V sys­tem is avoid­ing the use of a reg­is­tered elec­tri­cian.

For more on cre­at­ing a DC power sup­ply see this ar­ti­cle on The Shed web­site: the-shed.nz/home/2019/7/8/ acdc-con­vert­ing-sim­ply.

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