I don't have ice damming but do have a lot of ice and snow on the roof should I install a ice melting cables?
No. Best case scenario you just waste the money that it would take to install them, worst case scenario you create a problem that didn't exist before.
Ice dams are typically created by sharp surface temperature gradients on roofs, usually caused by inadequate insulation in the attic. Heated air escapes through the attic and warms the roof deck, melting the bottom of the snow accumulated there. The water runs down the surface of the roof until it gets to an area that isn't being heated from below (typically the eaves), where it freezes again and creates a dam.
If you don't have an ice damming issue and start melting snow off of the eaves, the surface temperature gradient will be at the top of the ice melting cable. Gravity will be on your side in this case, but there is still a risk that you'll get ice forming above the ice melting cable.
Finally, having snow accumulate on the roof is only a problem if there is too much weight. Outside of that, you want to have snow on your roof because it provides some additional insulating value and an excellent wind barrier. As an interesting side note, you can see this incorporated into traditional building designs in different parts of the world. Areas with heavy snow falls tended to have steeper roofs, but they get less steep as the snow fall drops off largely in order to balance the amount of snow that stays on the roof.
If you are worried about ice dams forming, one very effective (and cheap) thing you can do is use a snow roof rake to remove snow from the bottom ~3 feet of the roof. That is where melted snow is likely to build up and refreeze into a dam, so by keeping that area clear you greatly reduce the chances of an ice dam forming.
(If the rake handle is long enough you may be able to remove the snow from most of the roof, but that's probably not necessary unless you have a history of water leaking or you are concerned about the structural integrity of the roof.)
I second the opinion on using a snow roof rake. As long as it reaches the area above the gutters. You want to leave some snow on, but you don't want icicles to form. I have the cables (from a previous owner of my house who left them) and after observing the roof through my first winter in the house, I concluded that they provide no significant benefit that you can't implement just by raking off the snow from the roof after the weather system is finished. To confirm my opinion, I drove around the neighborhood and observed others doing the same thing.
The cables are really just a lazy option.