[Trooper2]

Looking to install Inline duct fan (boosters) to some of my HVAC duct work to improve circulation to master bedroom. We have a two story house, The plenum is in the attic, the Master is downstairs and furthest run from unit and gets the least amount of flow despite two 10" ducts and a 12" x 12" return. I have tried restricting flow to other rooms with little improvement.

I want to try installing two 10" inline 120 VAC duct booster fans. I am looking at some that have a power cord. There are some temp switches available to provide on/off control but they seem "cheesy". I would rather the fans to just turn on when the AC's fan is turned on.

Can I wire an outlet that is powered by the same output to the AC fan? This seems to be the easiest idea, just plug in the booster fans to an outlet that is powered when the main unit comes on and turns off when cycled down.

Is there any risk to the central air unit, in the event that on of the duct fans fails or goes to ground? If so, Would a GFCI proved enough protection?

Should I consider a relay of some sort to isolate the fans from the main unit?

This is a Lennox unit about 10 yrs old. I have had to have the control circuit board replaced following a lightning strike.

Open to any suggestions.

Houston, TX area.

 

[beenthere]

May end up stealing air from other supply runs.

Before installing duct boosters. Remove your air filter and run your A/c. Does that room get more air when you do that. If so, you need more return air for your system.

 

[roughneck]

It is my personal opinion that boosters increase noise, cost the customer money, increase energy use, cause issues with other rooms on the duct system and may not help the rooms in question at all. I've never put one in nor do I recommend them.
Look into balancing the duct system out. Or finding the reason why those rooms are not properly balanced.

 

[supers05]

They are used sometimes here because of the multiple floors. They help, but like roughneck said, they also have issues. When placed about near the foot of the upstairs riser, they provide the little extra static pressure needed to get air upstairs without stealing too much from other runs. (they are only compensating for the lift in this role) This is only for cooling, since in heating, the hot air should be rising quite nicely.

They are no longer as popular as the higher static ecms do a great job in getting air to the top floors. Try been's test first.

Cheers!

 

[Trooper2]

May end up stealing air from other supply runs.

Before installing duct boosters. Remove your air filter and run your A/c. Does that room get more air when you do that. If so, you need more return air for your system.

The 12" x 12" return in the master is probably questionable, filter is never as dirty as 30" x 20" main. It could be undersized but unfortunately is something that cannot be change due to the way it is routed from attic -thru 2nd floor to the 1st floor.

The routing of the ducts /and return air are most likely the main issue. I imagine they are restricted by angles or support (or both).

The system does not have dampeners at the plenum, have thought about pinching off some of the other ducts with rope or some kind of strapping material.

I could try just one booster duct fan instead of two, I really don't think it will rob much flow....

 

[Trooper2]

It is my personal opinion that boosters increase noise, cost the customer money, increase energy use, cause issues with other rooms on the duct system and may not help the rooms in question at all. I've never put one in nor do I recommend them.
Look into balancing the duct system out. Or finding the reason why those rooms are not properly balanced.

The fan motors I am looking at are around 1 amp, not too concerned with power especially if they make us more comfortable. Not sure how noisy they could be in attic of two story; they are advertised as "whisper"........

There are no dampeners at the plenum. I could try restricting the "soft" ducts to some of the other rooms; with rope or strapping material.