I think my problem might be low natural gas pressure here's the problem My furnace works but doesn't seem to work with thermostat setting.It kicks on and off when it wants to and also my gas water heater doesn't always give enough hot water.I replaced the hot water tank and still the same problem & also I cleaned the floor furnace and replaced the thermostat.It seems unlikely that both the furnace and water tank need to be replaced the floor furnace is only 10 yrs. Old. Is it possible that low gas pressure could be my problem.

Not likely, but it is a good idea to have gas pressures checked anyway. You may look at replacing thermostat, and check temp setting on water heater. Let me know how the gas pressure test goes. I believe we are dealing with two separate problems, lets take one at a time, start by checking gas pressures, and then we can move on from there. Good luck and please let us know what you find.