Fresh air intake with booster fan

Porsche_911_s

I have an idea I'd like to run by the community...

I am thinking about installing a motorized damper and booster fan as part of my fresh air intake. The idea for a booster fan is to run when an exhaust fan is in use and the Hvac is not in use. We have a total of 5 bathroom fans, I'd like to push filtered intake air when any of those fans are in use. I know I can use a 120vac to 24vdc transformer when the fan is switched on, are there generic control boards that would consider multiple switches for one device? In other words, two fans can be in use at the same time with no negative effect on the desired damper or booster fan? I figured a booster fan would be needed given the 3700 sq ft size of the house plus filter for fresh air.

Thanks!!

Stephen

beenthere

Don't need a booster fan. The negative pressure created by the bathroom exhaust fans will be enough.

Porsche_911_s

As far as the control for the damper, what is the best way to accomplish this?

beenthere

No good way. But if you connect 120 volt coil relays to each fan, and then daisy chain the N.O. contacts and run a stat wire to the damper, you'll have what you want. Each fan will be able to open the damper by itself, with out running any other fan.

Porsche_911_s

hhhmmmm.... I was hoping to convert to 24VDC to avoid running 110 everywhere.

beenthere

The relays would be at the fans. that is why they would have 120 volt coils. Thermostat wire is used to connect them to each other, and run to the dampers and its transformer.

Porsche_911_s

It finally occurred to me that with the relays can have separate 24vac circuits energizing one 110v or 24vac circuit to operate a fan or damper.

Thank you for the information!

old_squid

You have a 3700 sq ft house with some form of fresh air intake, I'm assuming from your original post, already as part of your HVAC system.

My first question would be what is happening in the home now that has led you to installing another source of fresh air?

ddawg16

I can sort of see where the OP is going with this.

As we strive to make our homes more air tight....if you start running up to 5 bathroom vent fans at one time....if all the windows and doors are closed....those vent fans are not going to be able to pull much air if your home is really air tight....your going to need 'some' type of fresh air vent.

I don't think you need a booster fan.....a simple back flow (check valve) would work nicely.

I would run a filtered duct to an outside air source....nice big flap (it's own weight could keep it closed....with maybe a little bit of spring help) and run that to a central location. If your fans pull more air than can come in through the normal cracks....the dampner opens up to let in fresh air.

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Porsche_911_s

The home currently has no fresh air intake as it just pulls air from the cracks of the house (light and electrical sockets). My idea was to install a fresh air intake with a filter. I thought a fan might be needed to pull the air through the filter when the A/C is not running. Its a 2005 home that is fairly air tight on the external windows and doors. The air being pull into the home is via the electrical sockets. So we are basically pulling in attic air. I could seal up everything but the goal of the exhaust fans is to get rid of bad air. My goal is to just remove as much pollen or smog as possible on the air we are pulling from the outside. We live near Houston, poor air quality.

I plan on installing a 6" insulated duct to a mesh grill under my covered front foyer. I'll put a Honeywell media air cleaner filter inline, then the motorized damper. Then a Y going to both A/C unit intakes.

beenthere

The air will take the path of least resistance. So a booster fan isn't needed for the fresh air intake.

You can also set it for a min opening, that way fresh air is brought in anytime either unit runs.

HVACTECH96

Why not have a ERV system installed