Shut off the gas valve feeding the heater until a qualfied service person diagnoses and repairs the problem. The valve should be just outside the heater, turn the handle 90 degrees until it is perpendicular to the pipe.
The heater core may be plugged or bad. You can either flush the heater core and the 2 lines running thru the firewall to the heater core or you can replace the heater core.
Yes, a hotwater heater may be placed outside anywhere in the state of Florida. It should be under cover such as a garage or shed.
A reverse cycle A/C must mean a heat pump. Every heat pump has a C.O.P. or coefficient of performance. They are rated at 17 and 47 degrees outside. A new heat pump should be around 3.3 at 47 degrees and 2.1 at 17 degrees. This means even at 17 degrees outside, it will produce 2.1 btu per kilowatt to 1 btu per kilowatt of an electric strip heater. And 3.3 to 1 at 47 degrees. Depending on where you live though, the electric heater may be needed to supplement the capacity of the heat pump.
Most comfortable is 85 degrees F.
You should only use them outside with good ventilation.
60 degrees C
you may have your switch on your heater control set to recirculate the inside air. it should be set for outside air recirculation
How long it takes a car heater to warm up depends on the temperature outside. In cold weather the heater can take several minutes to warm up.
For safety, it should be kept below 120 degrees F.
the heater fan resister,it is or should be on inside or on outside heater box.
3kw heater heating a 10 foot pool may take 4 to 8 hours for heating it up to 20 to 25 Degrees Celsius. This also depends on the outside temperature.