Check this fiddle JSFIddle
$(function () {
$("#mySlider").slider({
min: -30,
max: 50,
animate: true,
values: [0, 0, 0],
slide: function (event, ui) {
$(ui.handle).text(ui.value);
},
stop: function (event, ui) {
for(var i =0; i <= ui.values.length;i++)
{
if(ui.values[i] < 0)
{
$("#mySlider").slider("values", i, 0);
}
}
}
});
});