Extract Fan Options

[EnOm]

Hi,
I have a house that has 10 toilets/wash rooms that is to be serviced by a central exhaust fan. I want to discuss some of the options that I have regarding this.

1- Intermittent Exhaust #1:
Use a constant speed fan that is turned ON/OFF whenever a switch is flipped in any toilet or washroom. In my opinion this is not advisable because firstly it will waste energy as air will be exhausted from all the 10 exhaust points even though only one needs to be exhausted. Secondly the wear will be quite high on the fan motor from being cycled ON/OFF so often.

2- Continuous Exhaust:
Use a continuous constant speed exhaust fan that exhausts air at a rate lower than that of the fan above. With this arises the need for a small FAHU to bring in air to replace the air that is leaving the building.

3- Intermittent Exhaust #2:
Use a fan c/w an electronic speed controller that increases the fan speed to match that of the required exhaust. As in the fan is off when all the exhaust switches are OFF, if a switch is activated the fan will exhaust air at the rate set for that switch, if another switch comes ON the fan speed is increased...etc. This eliminates the need for the FAHU while also reducing the strain on the fan.

All input is greatly appreciated. Thank you.

Regards

 

[trashcanman]

Why complicate the problem? All of the above will be tough to test and balance and controls costly.
Just use 1 fan/toilet with a timer to shut it off after 5 minutes.

 

[cdxx139]

I am going to have to agree.

Its only 10 toilet rooms, assuming one fixture per room, its not a lot of air. And code allows lower exhaust rates if continuous, making the central fan even smaller, reducing your energy savings even more, but trying to shut off spaces (with the cost of controls you are trying to add). I would have to think the payback in energy savings would be a long time. Plus, a light exhaust in the wash rooms, at all occupied hours, keeps the space "fresher"

If cost was no object? You place a small fan in each wash room activated by occupancy sensor. Add a central exhaust fan and run it on static pressure.

knowledge is power

 

[tys90]

Look into a small ERV with continuous exhaust.

 

[EnergyProfessional]

for code you need to ensure exhaust in the bathroom that is occupied. So you would need a damper there to open up when the light is on (assuming these are interior without daylight) or turned on by occupant. this seems complex since you want to control fanspeed. Even with a Building automation system i would have to think about that...

Regarding continuous exhaust, I would not do that unless you have an ERV for balanced flow. Exhaust is not ventilation. Yes, as much air as you exhaust comes in somewhere. But where? through the basement with Radon, through moldy walls with high VOC material? You will need some dedicated make-up air. The easiest would be a gravity damper to duct air into the furnace.