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Why MMOV®?

One of the most popular and proven components in AC mains surge protection has been the Metal Oxide Varistor (MOV). As with most things in life they age and this aging is accelerated in high surge areas. As these devices age the voltage at which they clamp gradually falls until eventually they fall to the level of the mains supply and overheat. They have in some circumstances even caught fire! Today's MOVs are coated in a flame retarding material but this alone does not guarantee safety. This is why

all Zymax MMOV® products are thermally fused.

A number of mains SPDs on the market feature parallel MOVs with one being smaller and lower energy than the other. When this weaker MOV eventually fails a warning is provided (usually visually) prompting the user to replace the device, even though protection (that's better than before) is still present. This adds to the component cost of the device which is passed down to the customer. With Zymax MMOV® products

FULL protection is present for the FULL life of the product.

The MMOV® product continuously monitors its protection status through its complete life cycle.

Other products on the market feature LEDs or Neon indicators which light when there is a failure. With no lamp test facility, how does one know that the indicator itself has not failed?

Zymax MMOV® products feature a single failsafe LED indicator which is continuously lit during normal operation.

As the MOVs begin to age the LED will flash indicating that a replacement device should be at hand. Full protection is still present. When the MOV nears the end of its useful life an audible alarm sounds and the LED continues to flash. At this point the protection device should be replaced. Protection is still present. If the user fails to observe the warnings and the MOV clamping voltage falls too low the thermal fuses will protect the device and an audible two tone signal emitted with the LED extinguished. At this point protection is no longer provided but power continuity is uninterrupted.

During installation a likely scenario could be that the engineer failed to strip the insulation properly from the earth wire. An MMOV® device would prevent this by providing an audible indication should there be a bad earth connection or the live and neutral wires are incorrectly connected.

MMOV® devices self check their connections and will let you know if they are incorrect!

MMOV is a registered trademark and the technology patent applied.


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