I have done a few of these now and I have never run one to the main panel. It is a bond. The bonding conductor(#6) goes from the end of the yellow pipe to the black pipe or the manifold. Some places may require the black pipe to be grounded but most do not. It is not to be used as a grounding electrode conductor. This way if the service gets hit the gas is still OK. The bond is to keep currant off the yellow pipe if the gas line were hit or the appliance were to be hit or short. Either way whether you ground the gas line or not the bond must be run from the gas pipe to the appliance parallel to the yellow pipe. I come accross this incorect installation quite often as of late.
