I am in the USA. I would like to switch on / off my 220v Air Conditioner and my 110v attic fan with the same switch. Is there anyway of doing this? The problem being that with 2 separate switches it is possible to forget to switch on the attic fan when we put on the a/c and the a/c "cooks" in the attic.
Many thanks for any advice.
Your condensing coils are in the attic?
How about x10 switches on the same device code?
Use a relay to switch the attic fan, get a 220V relay and connect it's coil to the air conditioner circuit. You COULD do it the other way (let the relay switch the AC) but that would be MUCH more expensive since an AC is pretty large in the current department, a fan is relatively low. TTYL
Your simplest solution would be to equip the attic fan with a thermostatic switch, already often a common practice with attic fans.
Harry C.
If you can run your fan between 1 leg of the A/C's 220V & Neutral, the fan will automatically be on when the air is on.
You can buy a three pole switch from an electric supply house. Use two poles for the air conditioner and the third for your attic fan. Alternatively you could use a contactor on the attic fan circuit to control the AC or a 240 volt coil relay on the AC circuit to control the attic fan.
-- Tom H
SOME FOLLOW UP QUESTIONS !! ??
1) Thanks for all the advice so far. 2) Is it safe and USA code acceptable to take a 110v feed off one of the 220v hot wires? 3) Is it safe and USA code acceptable to put a 110v and 220v circuits on the same 3 pole switch??
Its pretty common to do so. Think about how your typical range works. The lights are 115 and the elements are 230.
I really think you should switch off both hot legs, but a lot of 220V heaters are installed with a single pole thermostatic switch.
It is common to "control" a 240v load with a single pole switch but the "disconnect" must open both legs. Two different things.
1 depends if the 220 has a neutral and a ground. If it does then maybe if not then no. 2 depends on the situation. Provide specific details and I am sure someone can help
I agree its a different thing, but I prefer (personal preference) to switch off both hot legs.
I am baffled by your response.
All branch circuits will need a ground of some sort, and I am pretty sure there are no double insulated 220V appliances, so all 220V circuits would have to include a ground wire. In your house, the 220V has a neutral whether you use it or not.
Just a thought. Why not put a relay on the low voltage (Thermostat) side of things, and leave the high voltage alone? Or use the proper relay for switching the legs on the high-voltage side, if your set on that side.
Jack
I think he's referring to the circuit. Often 220V circuits are three-wire, with no neutral. Without the neutral any 120V loads would be a no-no. With, maybe.
The most common 220V circuits in most houses would be dryers and ranges, both of which use 120V.
And both legs must have overcurrent protection.
daestrom
Ahh.. Most common, but not universal. A 240V baseboard heater for example uses two 'hot' and a ground wire, but no neutral. Can be wired up with some standard 12-2 with bare ground wire instead of 12-3 ('mark' the white wire with black tape to signify it is not a 'grounded conductor'). Electric hot-water heaters and *some* A/C units are 240V only as well.
The OP should *not* try to run a 120V circuit between one of those 'hot' and the ground wire. It would probably 'work' since the equipment grounding conductor is connected in the service panel with the neutral bus. But it would be forcing current in the equipment grounding conductor (a big no-no and against code). This defeats the purpose of the EGC and can create a shock hazard.
daestrom
Sure, and both come in 3-wire configurations (no neutral). The point is that unless a separate 120V branch is needed the neutral isn't really needed (or at least wasn't required). I believe new construction requires a 4-wire circuit though.
Jack replied: "Just a thought. Why not put a relay on the low voltage (Thermostat) side of things, and leave the high voltage alone? Or use the proper relay for switching the legs on the high-voltage side, if your set on that side."
This sounds like the safest solution of all those kindly suggested. Unfortunately I don't know what a "Relay" is. Could you enlighten me or suggest a web site where this might be explained to something of a beginner.
In any case many thanks again.
If the attic fan does not draw too much current, and there is a neutral present in your air conditioning system in the attic, you could just tap off the fan relay in the airconditioning unit and go to the attic fan. Then, when the airconditioning unit turns on, the condenser fan turns on also, and this will also turn on the attic fan so that it will be on when the airconditioner is on. Otherwise, it will not be running.
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.