I have a bathroom wall switch that only turns on the exhaust fan located in the ceiling. I would like to change this ceiling exhaust fan to a combination fan/light unit, to be operated by the same wall switch. I have read that if I install a fan/light combination unit that turns both on at the same time. I could hook up to the same wiring without having to run extra wiring. Can I do it this way?

2nd question: If I wanted to install a fan and light combination unit, where I have a switch for the fan and a switch for the light. Would I have to run extra wiring? They make switches that have both toggles on the same wall switch so you can have a separate toggle for the fan and one for the light. This way I could just turn on the fan and/or the light by itself.

What you propose would cause all thre fixtures to come on/off at the same time. The question you need to research is the amperage draw of all 3 fixture and the amp rating of your switch and existing wirng. Many homes run 14-2 wire to the ceiling fixture and use a 15 amp breaker. This may be inadequate for a heater, fan and light. Tell us the amperage for the units and what gauge wire goes in/out of the switch box.

Since it is a light and fan combo, you can use existing wires like ballenger says and is OK, If in conduit, you may be able to push or pull an extra wire in, use the stacked switch and your done.
If it is a 4X4 box with single gang mudring, you can carefully cut just enough to allow removal of single gang and the installation of 2 gang mudring, to allow 2 separate switches, maybe a dimmer?

Dah, I don't know where I got that 3rd fixture. I thought incorrectly that Wayne was also thinking light/fan/heater combo. The heater alone can draw 15 amps but just a light/fan should be fine on existing 14-2.

I have a bathroom wall switch that only turns on the exhaust fan located in the ceiling. I would like to change this ceiling exhaust fan to a combination fan/light unit, to be operated by the same wall switch. I have read that if I install a fan/light combination unit that turns both on at the same time. I could hook up to the same wiring without having to run extra wiring. Can I do it this way?

2nd question: If I wanted to install a fan and light combination unit, where I have a switch for the fan and a switch for the light. Would I have to run extra wiring? They make switches that have both toggles on the same wall switch so you can have a separate toggle for the fan and one for the light. This way I could just turn on the fan and/or the light by itself.
No matter what you do, Use Panasonic brand no matter what you do. They make the best and quietest fans you will ever find. My 150 CFM (to example) is quieter than the builders cheap 50CFM fart fan. They are not sold in those DIY junk hardware stores, and you may have to search, but its worth it. Replaced all mine with Panasonic. Love 'em.

What waynejc should be asking himself is "Can I get the the proper wire down the wall to the switch so I can have it myway". Bet he can.

Nutone/Broan also make Super Quiet Fans, QXTEN series .3 Sones(Very Quiet) It is the quietes I have heard, will have to compare with the Panasonic. With these, you don't need a switch for the fan, they are very quiet, Nutone/Broan also make one that is humidity sensing for Automatic Operation.

I have a bathroom wall switch that only turns on the exhaust fan located in the ceiling. I would like to change this ceiling exhaust fan to a combination fan/light unit, to be operated by the same wall switch. I have read that if I install a fan/light combination unit that turns both on at the same time. I could hook up to the same wiring without having to run extra wiring. Can I do it this way?

2nd question: If I wanted to install a fan and light combination unit, where I have a switch for the fan and a switch for the light. Would I have to run extra wiring? They make switches that have both toggles on the same wall switch so you can have a separate toggle for the fan and one for the light. This way I could just turn on the fan and/or the light by itself.
To:ballengerb1, Stratmadno, BGH and hkstroud. Really appreciate your comments. I now know what to do because of your answers. THANKS, Wayne

Don't forget, we canb probably help you pull another wire from the unit to the switch. Tell us is you have cable or are in conduit. Good luck Wayne

*Fishing* a wire down the inside wall of 99% of any home is easy. In the attic, just look for the top header 2x4, that is the wall. Drill a 1/2 inch hole, and drop down a small chain with the wire connected to it,, at the box, use a coat hanger to fish around inside the wall to catch the small chain,, pull it through the knock out in the box, and there is your feed, or switch leg for fan or what ever. Did the above for many years remodeling and rewiring elect heating in homes, works easy and painless. As far as the wire, a 14/2 will easily handle 1850 watts, but also consider, what else is on the circuit.

You do not want to use 14-2 for a 1850watt load. You will need to run a 12-2 which can safely be on a 20amp circuit.

The "easily handle 1850 watts" is incorrect. The NEC requires circuits to be rated at 80%, which is approximately 1440 watts. Yes the 14/2 wiring is rated higher, but code restrictions allow 80%, not 100% of the capacity.
Either way waynejc, it's unlikely you will have a problem with what you are intending to do.

Good luck.

Wire is not sized by how many watts is can handle, it is sized by amperage and the two are are only proportional to each other if the voltage is the same for both. Also, 1850 watts is fine on a 15 amp circuit, if it's 240V. Which is possibly why the guy that does electric heat made that error. Watts is a useless number for sizing wire unless you know the voltage.