MacGyvering a fan solution

[Apollo Serenus]

I need some assistance picking parts for a unique computer fan-based project. Though my ancient ceiling AC was recently overhauled, improving the airflow significantly, the construction around the vents themselves is causing weaker than desired airflow. I had the thought of using computer cooling fans mounted inside the vents to push the cool air out into the rooms which will turn on when the AC starts drawing power. In the rough-diagramed photo attached is my setup. The AC unit in the blue box blows cold air into the empty ceiling space of the green box. In addition to the vent shown, there is one half that size in the bedroom above the door on the right. The red squares are the not-to-scale indicators of where I'd place the fans for that vent. There'd be two in the bedroom and I'll be cutting a vent into the kitchen on the left with two fans. So, 8 fans in total that are relatively quite fans with high output.

I have just enough knowledge to know this is possible while also recognizing I don't know the terms of the components I would need to bridge the power from the AC to the fans safely. Hence, I come to all of you to help guide me in the right direction to complete this project safely.

[jaslion]

Wouldn't the solution be to just not replace the air obsructing vents in stead of trying to force air through vents that already have poor throughput?

[Apollo Serenus]

The vents are actually quite clear. The last person to live in my unit did a shitty job of repainting, there's lots of bare grey metal which looks like dust in that photo.
I like the idea of AC fans. It completely redirects my thinking. I found 4 small fans that wouldn't be overly loud (46dB all together), pump out a cumulative 800m3/h, not too expensive. While I thought about a switch as the easiest route, if I could have them turn on with the AC, that would be optimal. Perhaps a solenoid switch. Tap the solenoid switch into the AC to activate when the AC turns on, this solenoid closes the circuit to the fans which are hooked up to a separate circuit breaker. Anyone see any obvious flaws?


 

[mad dudy]

if im reading this right you have a new ac unit install and it just blows out inside the ceiling without any kind of duct work to the vents?

if that the case you should get your money back or have them fix that.

2 hours ago, Caroline said:

 

 

 

dont do that use wire nuts. you might burnt the house if you do that with high voltage lines.

 

[LogicalDrm]

-> Moved to Off Topic

 

This is not computer stuff or even related.

[Beerzerker]

One thing that comes to mind would be to check for any air leaks along the ductwork of the system.
If you have any that's where you're losing airflow potential due to loss of air pressure from the fan that "Drives" the air to and through the vents. Also be sure if you have any airflow dampers in the system they are working correctly too, if those are not working you'll have too much in one area and not enough in another.
Your setup should be really simple, not much more than an airbox with a fan (Air handler) going right to the ductwork to the vents more or less. 

Just be sure all the duct work is in good shape and sealed up, I'll also warn against leaving any metal parts of it exposed to atmosphere causing it to attract condensation during the summer months which will drip off and come down onto the floor below, could also drip and induce moisture damage to the area of the ceiling underneath. Be sure to seal and insulate those parts of it well, you'll thank yourself for it later with zero issues from that.

You can also balance the airflow in the home if for example, you have a room with a ton of airflow and another with very little by partially restricting the airflow into the room with the best airflow, that will throw more of it to the one with less airflow. Most ceiling vents can be opened or closed and that's how you'd do it, open one more and partially close another. If yours can't be opened or closed using something to restrict the airflow over the vent or right inside the vent itself will work too.

For a proper setup, here's a tip many don't think about - Here (Northern Hemisphere) the hottest room(s) are to the South, the coldest are to the North side of your home if the home/building is out in the open (No shade). Using that you can determine where the home should be warmest and coldest typically, depending on the season. The absolute warmest room(s) year round will tend to be any rooms to the SW and the coolest will tend to be to the NE - That's typical but not an absolute, based again on any shade the home/building may have around it.

I used to do maintenance in a distribution center (Warehouse/DC with 3 floors of office areas in it) and doing some of the HVAC work in it was just part of the job I once had.

[Quackers101]

always insulate wires, never have wires showing, if used in open space and not in protected casing.

not really recommending wirenuts if doing things fast, but I guess they can be used.

you do have other conections, but maybe for smaller wires.

 

3 different types of connectors shown

 

[Beerzerker]

Nothing wrong with wire nuts.
Used them all the time and never had any problems related to them, even with outdoor equipment like AC units/Heatpumps.
The trick with using them outdoors is to bend the wire once the wirenut is in place so the closed end is pointed straight up as possible so no water can settle into it.
However we're not talking about outdoor useage here but still a good idea if you suspect they may be in an area water could appear and drip onto them anyway.

[Quackers101]

15 hours ago, Beerzerker said:

Nothing wrong with wire nuts.

The trick with using them outdoors is to bend the wire once the wirenut is in place so the closed end is pointed straight up as possible so no water can settle into it.

Maybe so, but just easier to use the other ones as like in the video it wasn't done "correctly", as I think stated in the manual for wirenuts how to create a good bite. Where a lot clamp down the cables and twist them together to make a good bite at the end. But at least this would not happen and less to care about when dealing with the other types of connectors. Although a downside it adds a little bit more resistance, not a lot, since the wires are not directly touching each other like wirenuts and some other types of connectors. Also it's all about getting the right type of bite with the wirenuts? Which might mean a couple of tries at first.

 

Also for heatshrink over connections like above comments, you would need that for twisted open cables, which you can find heat shrink with solder solutions out there with some level of water seal in them too. Likely more expensive than just shrink wrap though.

[Beerzerker]

3 hours ago, Quackers101 said:

Maybe so, but just easier to use the other ones as like in the video it wasn't done "correctly", as I think stated in the manual for wirenuts how to create a good bite.
1: Where a lot clamp down the cables and twist them together to make a good bite at the end. But at least this would not happen and less to care about when dealing with the other types of connectors.

Although a downside it adds a little bit more resistance, not a lot, since the wires are not directly touching each other like wirenuts and some other types of connectors.

2: Also it's all about getting the right type of bite with the wirenuts? Which might mean a couple of tries at first.

 

Also for heatshrink over connections like above comments, you would need that for twisted open cables, which you can find heat shrink with solder solutions out there with some level of water seal in them too. Likely more expensive than just shrink wrap though.

Points 1 and 2 are easily resolved.

When using the nuts you want to hold the tips of the exposed/stripped wire evenly with each other as they go into the nut, that helps to eliminate any issues with an uneven "Bite" with those.
There is no real need to pre-twist the wires together, in fact sometimes it can cause a poor bite making one of the wires not be gripped tight as it should be creating a loose/bad connection.
That's because for the nut to grip the wires properly it has to do that along the length of the inserted exposed wire, twisting them beforehand will tend to draw the rest of the exposed length together tightly too, making the very tips of the wires be all the nut has a grip on.
As the nut tightens it's grip it will also push the length of the wires together with it's threads because it will draw a little of the wire into itself, that in turn will create grooves in the wire for the threads to grip with.
Let the nut push it all together itself as it goes when twisting.

I normally just hold the wires together with the tips even to each other as said and place the wire nut on them, I hold the wires together firmly and twist until it's tight. I then pull on each individual wire to make sure it's got a good bite on both. If you have the wires go to the bottom easily when you insert them, the nut is too big to use.

Proper exposed/stripped length of the wire is for it to be enough to go all the way in with a little insulation going in too, just enough you can't see any exposed wire when it's twisted to hold them. A little insulation seen "Going" into the nut when viewed directly from the side is what you want.

And of course using the right size nut is important, too small and the wires will not go in all the way or it may even cause it to push one of the wires back down and out causing a poor connection when it tries to grip them, too large and it won't grip them tightly if at all.

[mad dudy]

12 minutes ago, Beerzerker said:

There is no real need to pre-twist the wires together, in fact sometimes it can cause a poor bite making one of the wires not be gripped tight as it should be creating a loose/bad connection.
That's because for the nut to grip the wires properly it has to do that along the length of the inserted exposed wire, twisting them beforehand will tend to draw the rest of the exposed length together tightly too, making the very tips of the wires be all the nut has a grip on.
As the nut tightens it's grip it will also push the length of the wires together with it's threads because it will draw a little of the wire into itself, that in turn will create grooves in the wire for the threads to grip with.
Let the nut push it all together itself as it goes when twisting.
 

wires should be twisted together, cut shorter if it's too long then nutted. in school if my teacher sometime would take the wire nut to see if we twisted them or not  then take points off if it wasn't twisted before nutted.

 

i remember someone telling when tightening the nut the rest of the wire should be twisted a few time. if the wire nut ever melts off(i've seen is happen) the wire wont just split a part and ground itself to anything.

 

other then for low voltage there's no reason to use anything but wire nuts.

i seen those lever connectors fail in ceiling lights. replace the connectors with wire nuts and it lighted right up.

[Beerzerker]

I have to disagree from working experience, they always did better by not twisting them together before insertion into the nuts but will say that's the experience I had.
Yes I done it by twisting the wires before using the nut too but eventually settled on not doing that because from doing a "Pull Test" to see how secure the wires were in the nut once done, twisting them didn't work as well as letting the wire nut do it's thing.

 

[Bitter]

What you need is called a booster fan, you can set it up to run off a relay (or contactor) triggered by the main blower or a pressure switch in the duct work. Most are made for round duct but they do make some for rectangle duct, not sure what shape your duct is.

[Beerzerker]

Yes, a booster fan is what you really need.