any heating/cooling/duct guys?

[ddream11]

had a repair on furnace from my gas provider after he fixed part he said my ducts are lined wrong or as he said "insuffucient" the duct from the water heater because it so tall and my basement is so low runs tilting down slightly then almost straight into main duct. he said it needs to go from down to up.

from the furnace the duct goes up slightly and then slightly dip down(i probably could pull it up) and then is about parrell as the water hear into the wall or main duct(cannot remember)

how much of this is all true and he also said the ducts need to be strapped, none are strapped. he threatened to shut the furnance off immediately but then said i give u 30 days. i have had main of there tech's in plus others(all licensed) guys for tune ups, repairs etc and plus they installed the water heater as i rent it, never a word of this, plus on x-mass eve i a sensor issue, frunance fired on off repeatly so i called in told them i smelt gas guy comes says all if fine, i cleaned the sensor starts working no problem. so why wouldn't that emergency guy tell me i may have gas build up in my "insufficient" ducts then. so confused

[MightyMike]

I used to be in that Field ...When you say Ducts are you talking about air ducts that move the Heated air into your house or your vent from the furnce to the Chimmey?? which is supposed to go straight up ..It vents the CO2 to the outside ..Which should go up .There should be no downward slope to it
I would suggest you have the duct if it's the CO2 from the furnace going striaght up

The switch might be what is called a spill switch it will sense the CO2 coming back down the chimmey or Vent and turn your furnce out ..It's a saftey switch ..You might have had a back draft or something like that ..That is if it's the switch i am thinking of
I have seen Birds and stuff stuck in the chimmey that would cause something like that
They would block the Vent causing the spill switch to cut off the furnace