Would the idea be to set the 10K pots so that the dump loads come in at e.g. 14V and 15V and the 100K (500K) pots to turn the dump loads off at X and Y volts?
The setting of the 100 k pots is the feedback and it determines the gap between on voltage and off voltage. Set it in a mid range position. Set the 10 k so that the load comes on at about 14.5 volts. Set both the same more or less. One will come on first but they are both at 14.5 volts or thereabouts. As the volts fall, the relays should turn off at about 13.5 volts. If this is not the case then you can do some fine tuning with the 100k pot and then possibly adjust the 10 k again. 4.