It is difficult to predict exact volume of condensate produced by a high efficiency appliance because it depends on its cycle rate (how often it’s operating), design (2 or 3 heat exchangers), size (BTU’s), etc. For example, a 60 000 BTU rated high efficiency furnace with two heat exchangers operating for 30 minutes can create approximately a quart of condensate.
I was searching for more information about condensate amount from different size high efficiency furnaces but can’t find any details.
If you are positive that water flooding the sump pump well has nothing to do with ground waters / elevated water table, and it is only a result of the condensate produced by your furnace, the thermostat settings
hasn’t been changed, ambient temperature is about the same as previous years, I don’t really know what could be responsible for the increase in condensate amount.
The condensate amount sometimes gets down because of a clogged heat exchanger but more condensate is usually related to longer operating time of the furnace.
Try to compare your November / December gas bills from the last 2-3 years; look for gas usage and an average temperature in the particular month. Maybe this will shine some light on this unusual situation.
Please let me know, just click “comment” below, and I'm sorry that I can't give an "absolute" answer.