duct booster fan?

[Snipe Hunter]

I have 1 bedroom on the 2nd floor on its own duct, cold in the winter, warm in the summer. The air handler is in the basement. All other bedrooms are fed from a main riser and duct in a bulkhead on the 1st floor. Those rooms are fine. The room in question is fed from its own riser from the basement in a wall cavity between the un-conditioned garage and family room. I believe the temperature in the garage is part of the problem. I can't really control that. The flow through it's register is somewhat lower than the other bedrooms. But there is flow. No return in the bedroom but it doesn't make much difference with the door open.

If I install a booster fan in the accessible duct in the basement or a powered fan register in the bedroom, will it help or just move the wrong temperature air faster? I've also thought about bumping out the garage wall where the duct riser is and insulate it.

A. Powered floor register, 130 cm $50
B. Quiet 6" duct booster, 350 cm $110 plus duct adapters to make square to round connections $?? 20 bucks? I'd probable need to tap into some power too, another $20. I have wire and receptacles, probably no box.
C. Bump out the wall to insulate the riser duct $100? And my time. I have mud and tape. Then see what happens?
D. ??

What say the braintrust?

[daddo]

I'd have to really see it to know which route is best, but anything you can do to help the air maintain temperature on a long run is important.

I would use the duct booster. A vent booster of only 130 cfm probably isn't going to help much.

120v supply and a low 24 voltage relay to turn the fan on anytime the furnace/air handler blower is being called for.

[blackhat]

I would take a small box fan and cardboard and duct tape a transition to the register.  Let it run a few days and see if it makes a difference.  If it helps, buy a booster, if its worse, the duct riser is the problem.

[TDKPE]

If the wall is 2x4 or 2x6" constructed, with a flat duct inside of it, I'd bet the 'outside' face has next to no insulation on it.  I'd probably start with bumping it out, cutting the drywall out where the duct is, and putting some real insulation around that duct, then drywall per the fire code.  As long as a bumped-out chase won't interfere with anything.  Maybe run a conduit in there in case you need electric or communication cable in the future.  Maybe even install another 20A receptacle in the chase if it would be useful.  Passive (insulation) is cheap to build and costs nothing once it's done.

I added two duct boosters to MBR ducts in my house, down in the basement.  I only use them for A/C, but they do help.  I have a pair of switches on the ceiling of the basement to disconnect them.  The blowers are loud enough to hear when the furnace blower comes on, but not so loud as to be annoying.  Air flow is roughly double or more when they're running.

The house should have been built with at least two separate systems, or perhaps zones, but it wasn't, and it would be very costly to modify after the fact.  So duct boosters were the best I could do for that room and the MBath, with three outside walls, lots of windows, plus the attic above with 2 ft of insulation on the ceiling.

[Snipe Hunter]

Thanks all. Did some more looking. The garage wall at the duct is 44 degrees. Most registers are between 73 and 74 degrees. This register is 70/71 degrees. Enough to feel the difference. I used an infrared thermometer.

Used a piece of paper over the registers to detect flow. Definitely much lower flow at this register. I can hear air moving through the rest. Can barley hear this one.

Interesting looking at duct booster reviews... apparently pot growers buy a lot of them. For 20 bucks I can buy a simple fan only in a sheet metal housing. Complaints are loud and short lifespan. For 110 bucks I can buy a variable speed with a thermostat. Plastic housing, very quiet and great reviews. Don't really need a T-Stat. It would be nice if I could connect it to the blower contactor/circuit in the air handler about 15 ft away. Is that possible? Any problem with 2 fans starting at the same time? Would also bump out the wall in the garage to add insulation.

[Roly]

Thanks all. Did some more looking. The garage wall at the duct is 44 degrees. Most registers are between 73 and 74 degrees. This register is 70/71 degrees. Enough to feel the difference. I used an infrared thermometer.

Used a piece of paper over the registers to detect flow. Definitely much lower flow at this register. I can hear air moving through the rest. Can barley hear this one.

Interesting looking at duct booster reviews... apparently pot growers buy a lot of them.  For 20 bucks I can buy a simple fan only in a sheet metal housing. Complaints are loud and short lifespan.  For 110 bucks I can buy a variable speed with a thermostat. Plastic housing, very quiet and great reviews.  Don't really need a T-Stat. It would be nice if I could connect it to the blower contactor/circuit in the air handler about 15 ft away. Is that possible? Any problem with 2 fans starting at the same time? Would also bump out the wall in the garage to add insulation.

Most of the duct booster fans are low wattage which will not have any effect on adding to the fan contactor .    I would suggest doing as Blackhat said, temporally put a fan on top of the register to see what difference it makes.   I would think you will have a major slug of cold air come in the room all at once when the blower starts in the winter.   The insulation will help but their will still be a slug of cold air, just not as much.   Remember the cold air will settle to the low point in the ducts when blower is not running and must be pushed out before the heat comes. Roly

[TDKPE]

It would be nice if I could connect it to the blower contactor/circuit in the air handler about 15 ft away. Is that possible? Any problem with 2 fans starting at the same time? Would also bump out the wall in the garage to add insulation.

That's what I did - connected to the blower relay.  It's single-speed, 3/4 hp, and the two tiny shaded pole motors barely register current. 

Starting current on a shaded pole motor, by the way, is barely more than running current.  Like the typical table or box fan, with very weak starting torque (resulting in very slow starts), and nearly constant current draw across the entire speed range, including stalled, which is what every motor rotor is when first started.

[blackhat]

Depends on what you have for an air handler or furnace. Shoot me a model number and I’ll check it out.

[Snipe Hunter]

Blackhat,

It's a very old Ruud heat pump.
Ser# M0199 04704 (1999 )
MOD# UBHB-24J14SFDA

We're planning on a small addition and will replace it then. Hope it lasts that long

[blackhat]

Googlefoo fail.  I couldn't find an online wiring diagram.  Most importantly, is the airhandler 120 or 240 volt?  If its 240, there shouldn't be a neutral and the booster would need powered from another source.  Secondly, how many speeds does the blower fan operate on?  Different speeds for heating and cooling?  I could set up a wiring diagram for you if I had those answers.