We replaced the burnt out condensate pump on the side of the furnace connected the drain/discharge discharge hose to original relief, also cut the 110 plug off and hardwired in to the furnaces’s power, if the furnace does not have power the condensate pump does not have power either. This is a 90% furnace which means it is a condensing unit what this means is when the furnace is running the exhaust coming off of the burner and heat exchanger the gas exiting through a PVC tube that that ends outside the house, begins to cool down and that’s creating condensation, that condensation flows back towards the furnace down through the internal trap and into the pump. This unit needs a condensate pump because it is in the basement which is below ground level if the furnace was above ground then it could have a gravity discharge pipe from the furnace but as the cases it is below ground so a pump is required to get the condensate up and out of the house. We poured water into the condensate pump