Where low voltage wire from sequencer plugs into heating element gets hot and melts the wire. What causes this? I changed the wire out, but it does it again.

You have a fault that is causing excessive current rain... hire a professional to locate and repair this before you have an electrical fire. And melting the insulation means you are close to having one...

It sounds like you have a shorted element in the sequencer. Sequencers are times delay relays that work by heating a bi-metal strip which bends to make contact. This brings in one element at the time, but it can be replaced with a contactor that will handle the load, like a 100 amp contactor, which I like much better. When you have such a big contactor it will work much better than the sequencers ever will work, but I like to use a small relay to drive the contactor. Wires coming from the sequencer to element should have hi-temp connectors crimped on the wire ends or they will burn off. This is not necessary with a contactor if you put the wires under the screws instead of plugging on the wires.

Old Post, but Loose connections can Generate Heat, Verify Tight conections as well.

Get rid of the sequencer and substitute a small contactor or use high-temp terminals or both. I do not like sequencers because they are really not necessary since there is no large current inrush as it is with motors starting. A 20-30 amp contactor with a 24 volt coil would work much better and is safer because they do not hang like a sequencer, and will save you some electricity use since they come on instantly and go off the same way without a delay. You can attach the wires without using a terminal, too. It also makes a better connection that will not heat up. You just take the coil wires off the sequencer and attach to the coil terminals on the contactor and attach the high voltage to the terminals and you're done.http://i172.photobucket.com/albums/w38/qwayne1000/CONTACTOR.jpg