MOV’s (Metal Oxide Varistor) are the round magical devices that the NTM Tech Center puts in many of our products.They are great at helping to minimize surges from induced lightning voltages, and other surges. Their use has helped to preserve the life of many electronic devices. However they are not without their limitations!
- MOV’s will wear out after a number of surges. They are damaged by the surges they absorb, and this damage is accumulative. The greater the surge the sooner they will need to be replaced. There is no easy way to determine when a MOV should be replaced. In normal tropical lightning areas, you should replace or add to your MOV’s every 4 years. If you live in a very high lightning area you should replace or add to your MOV’s every 1 -2 years. In addition if you inspect an MOV and it looks burnt or bulge it should be removed and replaced right away. The NTM Tech Center also recommends that any time you have large surge, (for example you connected your 120 volt surge suppressor to your 240 volt generator.) or any time you have lightning strike the ground near your house (1/4 mile), you should replace ALL of your MOV’s.
- When replacing a MOV, the Tech Center recommends that you solder the MOV, as this will provide the best connection. However the MOV legs should also be as short as possible to increase their effectiveness. Also be sure to replace any MOV with the correct replacement size and voltage. MOV’s come in different sizes and voltages. The larger the physical size the more energy they can absorb. The voltage rating on an MOV is not clearly listed; when the Tech Center sends you MOV’s we will list their application voltage.
- When an MOV absorbs a large surge it will get hot. If the surge is too large the MOV will explode in a beautiful display of fire, smoke and flying shrapnel. While this may be great fun as a demo for the Missionary Technology Course, it is not as much fun if it happens on your dry grass roof!!! It is for this reason that you must carefully choose the locations you place your surge suppressors, and be aware of the fire and shrapnel hazard.
The Tech Center sells replacement MOV’s pre-selected for each voltage ready to install.