Overland46
Mechanical
- Apr 22, 2025
- 1
Hello all,
First off, sorry this is a bit long for such a mim subject, but I just figured I would give you all the info I could upfront.
So as an ex HVAC contractor I am a little embarrassed to post this question, but for my own house for what sidewall registers I have, I have been mostly using the Lima 2 way registers that are of a 1/2” fin spacing design here: https://limaregister.com/products/sw/stamped-lanced-blade-register-with-multi-louver-damper
To which for that unit its fins are at a 40-degree angle.
Which to be honest, the reason for that was at least in part as since my house has a heat pump and is in the Northeast I am always looking for anyway to make it more efficient, so I guess at the time in just looking at them I felt the larger spacing or openings, and less angle would have the least restriction so would make the system work less to get the same amount of air around.
Recently though I have had a situation where I have to replace one and so was studying the design data for these as opposed to their 1/3” fin spaced, 45 degree angled units here: https://limaregister.com/products/632/stamped-ceiling-wall-register
Note on that, while on their main page it says 20 degree angle, on their spec sheets it says 45, which I think is actually correct.
So in comparing the two via their performance/engineering data sheets and at least for the 12 x 6 units I would be using and per the same face velocity & pressure lost columns, it looks to me that actually the 1/3” finned space units outperform the 1/2” finned spaced units, such as in at 500fpm face velocity & .016 pressure loss, the 1/2” unit produces 115cfm & 7.5 throw. Whereas the 1/3” finned spaced unit at the same spec produces 150cfm & 11 throw.
Interestingly by reviewing what are essentially the same spec-ed versions of the Hart & Cooley units, they produce about the same results.
So I guess what I wanted to ask first is...am I reading this right as do the 1/3” finned spaced units actually move more air?
An if so why does that happen? As I would think with the lesser fin angle and more space between them the 1/2” spaced finned units would all allow more air to pass, over the 1/3” spaced unit that has more of an angle.
But if not, does anyone know why this is?
For one thought I had was and would note I can’t seem to find any free area specs on any of these so am not even sure if the 1/3” units have less free space, but is this the typical case due to that or some other thing of a restriction they somehow are creating more static pressure and thus that is really what moves the more air?
All in all my thoughts are to possibly switch to the 1/3” units if they are going to more air for whatever reason, but if that is doing that by a restriction that is increasing my SP, my thoughts are my variable speed air handler may have to work a little harder, and also my air noise may go up a bit, so in the end it could be that I don't actually end up with a more efficient system and all with a noisier house to boot.
Thanks for any help.
First off, sorry this is a bit long for such a mim subject, but I just figured I would give you all the info I could upfront.
So as an ex HVAC contractor I am a little embarrassed to post this question, but for my own house for what sidewall registers I have, I have been mostly using the Lima 2 way registers that are of a 1/2” fin spacing design here: https://limaregister.com/products/sw/stamped-lanced-blade-register-with-multi-louver-damper
To which for that unit its fins are at a 40-degree angle.
Which to be honest, the reason for that was at least in part as since my house has a heat pump and is in the Northeast I am always looking for anyway to make it more efficient, so I guess at the time in just looking at them I felt the larger spacing or openings, and less angle would have the least restriction so would make the system work less to get the same amount of air around.
Recently though I have had a situation where I have to replace one and so was studying the design data for these as opposed to their 1/3” fin spaced, 45 degree angled units here: https://limaregister.com/products/632/stamped-ceiling-wall-register
Note on that, while on their main page it says 20 degree angle, on their spec sheets it says 45, which I think is actually correct.
So in comparing the two via their performance/engineering data sheets and at least for the 12 x 6 units I would be using and per the same face velocity & pressure lost columns, it looks to me that actually the 1/3” finned space units outperform the 1/2” finned spaced units, such as in at 500fpm face velocity & .016 pressure loss, the 1/2” unit produces 115cfm & 7.5 throw. Whereas the 1/3” finned spaced unit at the same spec produces 150cfm & 11 throw.
Interestingly by reviewing what are essentially the same spec-ed versions of the Hart & Cooley units, they produce about the same results.
So I guess what I wanted to ask first is...am I reading this right as do the 1/3” finned spaced units actually move more air?
An if so why does that happen? As I would think with the lesser fin angle and more space between them the 1/2” spaced finned units would all allow more air to pass, over the 1/3” spaced unit that has more of an angle.
But if not, does anyone know why this is?
For one thought I had was and would note I can’t seem to find any free area specs on any of these so am not even sure if the 1/3” units have less free space, but is this the typical case due to that or some other thing of a restriction they somehow are creating more static pressure and thus that is really what moves the more air?
All in all my thoughts are to possibly switch to the 1/3” units if they are going to more air for whatever reason, but if that is doing that by a restriction that is increasing my SP, my thoughts are my variable speed air handler may have to work a little harder, and also my air noise may go up a bit, so in the end it could be that I don't actually end up with a more efficient system and all with a noisier house to boot.
Thanks for any help.
