Device to run bathroom fan based on the duration the lights were on [closed]


Tom Schmidt


Revised 2/18/2011

When we built our home knew humidity control would be an issue because it is so tightly constructed. Home has two bathrooms with an exhaust fan in each one. Upstairs bathroom has a skylight, first floor has operable window.

During design phase did not put a lot of effort into thinking about bathroom exhaust fan control. Each bathroom has two switches one for light and one for fan. Over the years have experimented with different types of control. This paper discusses the pros and cons of each method.

Note: For simplicity ground wiring is not shown. Per National Electrical Code (NEC) all devices/fixtures need to be grounded.

First implementation simply had two single pole (SPST) switches by each bathroom door, one for lighting other for fan. Worked for years but had to remember to turn fan on/off. Turning fan off immediately after taking a shower does not...

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Bathroom Fans

Bathroom fans are an important part of your home's ventilation system. They remove odours from your house, which improves indoor air quality. They also remove moisture, which decreases the level of humidity in your house. High humidity can damage building materials and can cause mold growth. Mold may affect your family's health.

The minimum size for a bathroom with a window is 50cfm, or a bathroom with no window is 60cfm. this gives us a target of 8 complete air changes each hour

The two most common types of bathroom fans are impeller bladed fans and squirrel cage blower fans. Squirrel cage fans and generally move more air, and are generally quieter than impeller fans. Noise determines whether people use a fan. Many people won’t use a noisy fan. Select the quietest fan in the size you need. The best fans have sound ratings of 0.5 sones or less, noisier units typically can run up to 6 sones.

A low-resistance (smooth) exhaust ducting is...

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I'm posting this as an example of how the Program Logic Timer Switch (PLTS) twin timing intervals can be useful.

I have long been aggravated by the way my en-suite bathroom fan operates. As installed by the builder, the fan triggers whenever the bathroom light is switched on. After the light is turned off, the fan keeps running for a period set by its internal timer. The minimum setting is about three minutes - long enough to be annoying when the bathroom is used during the night. There is an isolator switch that disables the fan but, if I turn it off, I forget to turn it on again so then when I use the shower the bathroom gets all steamed-up. Even when the fan runs I have to leave the light switched on for at least 30 minutes after I use the shower to clear the room of water vapour. Then I discover I left it running all day. It's just a pain!

In a previous house I triggered the bathroom fan whenever the shower pump ran. The current house uses a pressurized water...

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Adding this board (translated) to your bathroom fan will turn it into a smart device. It’s designed to automatically shut off the fan after it’s had some time to clear humidity from the room. It replaces the wall switch which normally controls these fans by converting the fan connection to always be connected to mains. The board draws constant power to keep the ATtiny13 running via a half-wave rectification circuit. A single LED that rises from the center of the PCB lights up to signal that the fan is in operation, but it is also used as a light sensor, similar to the LED communications hack from a couple of days ago. When the lights go on in the bathroom the microcontroller will turn on the exhaust fan via a Triac. It will remain on until the light level in the bathroom drops.

There’s an interesting timing algorithm that delays the fan startup, and varies the amount of time it will stay on in the dark depending on how long the bathroom lights were on. This way, a...

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Well this is a good idea,

Итак, это хорошая идея -

He wouldn't do it if it wasn't,

Он бы этого не сделал, не будь это так.

He wouldn't do it if it wasn't one.

Он бы этого не сделал, не будь это так.

Well my friend fancies you,

Итак, ты нравишься моему другу.

Oh what a way to begin it all,

О, что за начало.

You said it's always exciting words to hear

Ты сказала, это всегда здорово – такое слышать.

And we woke up together not quite realizing how,

И мы проснулись с тобой, даже не понимая как,

Awkwardly stretching and yawning,

Чудовищно потягиваясь и зевая –

It's always hard in the morning,

По утрам всегда трудно.

And I suppose that's the price you pay,

И я думаю, это цена, которую ты платишь,

Oh it isn't what it was,

О, это было совсем не то!

She's thinking he looks different today,

Она думает, что сегодня он выглядит...

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Is it better to install a bathroom vent fan in the shower or the middle of the bathroom? -Steve

As long as the wiring for your bathroom vent fans is attached to a Ground Fault Circuit Interrupter (GFCI) and the fan is rated for a shower area, the best place to locate your vent fan is on the ceiling in or near the shower where it will do the most good. Vent fans that include a heater, however, should not be installed over a shower.

Another consideration is that the fan should be located away from the intake air source, such as a door or window (if the window will be open). If the window and door will be closed, make sure there is a 5/8” or greater gap under the door to allow fresh air into the room.

Other vent fan installation tips include:

Make sure the vent fan moves enough cubic feet per minute (CFM) of air for the size of your bathroom. Exhaust the air from the vent fan to the outside of the house, not in the attic. Use smooth ductwork and limit the...
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When renovating any bathroom, you need to recognize the high levels of moisture and account for it by installing a good ventilation system. With constant showering and bathing, vapour builds up in the bathroom. Over time, this can cause severe damage to the grout and tiles and to the cabinet finishes and wall paint. While bathroom ventilation improves air quality, it also keeps the space from being a breeding ground for mold and bacteria, making a fan in your bathroom an indispensable addition. What factors should you keep in mind in order to ensure optimal ventilation inside your bathroom?

The fan's strength

The amount of power with which your bathroom fan operates is arguably the most important factor to consider. A fan’s strength, or its ability to move air, is rated in cubic feet per minute (CFM). It is recommended that you aim for a minimum performance of 50 CFM when a heat recovery ventilation system is not installed.

The Home Ventilating Institute...

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Test the lowest area of the building that is used on a regular basis. EXCEPTION: Citizens of Pennsylvania are required to test the lowest LIVABLE area of the building. This is especially important if only one test is being conducted, or if this is a follow-up test to confirm the need to mitigate for radon. Place it where it will not be disturbed. The preferred method is to hang the sampler centrally in the room. Use one sampler for every 2000 square feet of floor space being tested. It should be within the normal breathing zone (2 to 6 feet from the floor). The sampler may be hung from an interior non-masonry wall as long as the opening is not blocked (at least 4 inches clearance) and it is facing toward an open area of the room. String may be useful to hang the kit from the ceiling or light fixture. DO NOT place it in a draft. Keep it 3 feet or more from doorways, hallways, windows, exterior walls, and heating or air-conditioning vents. Do not place it in the same room with any...

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With ever increasing locations that need GFCI protection, knowing how to select, install, and test these devices is crucial.

Today's ground fault circuit interrupter (GFCI) is the result of a convergence of technology with need. In the late 1960s, over 600 people were electrocuted in the United States using consumer products every year. By 1988, that number had been reduced to fewer than 290 (according to the Consumer Product Safety Commission). Other safety improvements, such as battery powered tools and double insulation, also have played an important role. Nonetheless, the importance of GFCI protection is clear.

A constant over the years has been the need for installers to understand how GFCIs function in order to provide the customer with the best possible installation and to properly test to assure correct installation. The more installers "think like a GFCI," the better the GFCI installation and the fewer the call-backs.

To get a better understanding,...

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Radon: Truth vs. myth

Radon – A Brief Discussion

Caoimhнn P. Connell
Forensic Industrial Hygienist

Prelude A large portion of the general population is under the misconception that the frequently published risks associated with radon are well accepted scientific facts. In reality, the vast majority of well designed studies do not support policy or positions that exposures to indoor radon pose a significant threat to health, and indeed, the majority of those studies indicate that, at concentrations typically seen in homes, as the level of radon increases, the risk of lung cancer goes down, not up. The following section is a brief discussion of how radon occurs and the science-based risks associated with radon exposure.

In a separate discussion, we have also reviewed some of the commonly cited literature and you can read those reviews by clicking, here. At the end of this discussion, there are links to a two-hour lecture on radon in four...

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