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Mike G.
Mike G., Master Electrician
Category: Electrical
Satisfied Customers: 7488
Experience:  Proven Professional 48 years Experience
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First I should say I am in Europe so we are dealing with

Customer Question

First I should say I am in Europe so we are dealing with 230V 50/60 Hz. The colors of the wires are different also, but line is line,
neutral is neutral, and ground is ground everywhere.
I have three vent fans:
Bathroom vent fan.
Stove hood fan.
Booster fan.
The fan in the bathroom and is switched on with the light. The stove hood fan is in the hood of course. The booster fan is installed in-
line in the vent duct. All three fans have to be connected to a single line power source.
All three fans are connected to the same vent duct by a tee that has a single exhaust into an old chimney (this building is 500 years
old). The booster fan is past the tee (as the air flows, there are two backdraft valves in the tee).
What I need is for the bathroom fan and the in-line booster fan to turn on when you turn on the bathroom fan - but not turn on the stove
What I also need is when you turn on the stove fan it will also turn on the booster fan - but not turn on the bathroom fan.
If someone uses the bathroom while the stove fan and booster fan are running will the double line voltage into the booster fan damage it?
Thanks for any help you can give.
Submitted: 1 year ago.
Category: Electrical
Expert:  Mike G. replied 1 year ago.

Hi, I'm Mike G and I'll be assisting you. One way to achieve the desired results would be to install a double pole switch at each fan having one side control the interior fans and the other for the booster fan. When either was on, the booster would also be on. Having both going to the booster would not produce a feedback.

Customer: replied 1 year ago.
Hi Mike,Thanks for your response.I'm certainly no expert, but your idea is what I was thinking - 2 double pole switches. I'd already bought the switches.I checked the switch in the bathroom and it is single pole. I assume in the junction box laying on the ceiling of the bathroom (I can see it through an access hole I cut) that all three recessed ceiling lights, the two lights above the sink, and the original in-line fan are all connected there and run to the bathroom switch so that when you turn on the switch the lights and the old fan would turn on. There is a third unconnected wire in the bathroom wall switch box. It is brown which means power here, not neutral. I'm going to pull down this junction box tomorrow (Saturday) through one of the recessed light holes and take a look.Also, the bathroom is very small so I will disconnect two of the three recessed ceiling lights. I keep burned out bulbs in those two lights now. Why the original designers thought they needed so much light in this 6x7 ft. bathroom is a mystery.The stove hood fan has a four position switch. It can be off, or on at one of three speeds, so 0,1,2,3. There is also a light switch in the hood.Can I connect the new double pole switch line going to the booster fan to the 1 position on the fan switch?, or should I connect the line to the booster fan past the hood switch and directly to the line that runs into the hood fan?One other concern is the size of the internal fan switch wiring in the hood, it's 16 gauge. From there to the new double pole switch (permanently on) then on to the booster fan it would be 12 gauge for 8-9 feet.I can figure most of this out. My big concern is clarification that if the booster fan receives power from both the stove hood and the bathroom fan at the same time it will not burn out. If I understand you correctly this won't happen and is not a problem?Thank you Mike. If you can help me more I will certainly pay much more than justanswer is asking.BTW - I'm an American living in Czech Republic. The 230V standard and wire color difference here is taking a bit of study.Thanks,
Expert:  Mike G. replied 1 year ago.

Hey Doug,

If all 3 fans are on the same circuit there won't be an issue with feeding from either or both of the double pole switches. You'll need a switched wire from each location to the booster, being on the same circuit the neutral is already there. The existing feed to the booster is what you need to check as to its proxcimity to the switches.

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