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Two Mini Splits in one control room
Old 1 week ago
  #1
Two Mini Splits in one control room

Two Mini Splits in one control room

The control room I am planning for a ground-up build is rather large – 20 x 23 x 12.5. And, sometimes I will use that room as a classroom with 15 students in the room. The MEP engineer says I need 1.5 tons of AC.

The Daikin Emura mini split has very low noise for the .75 ton model and the 1 ton model. But a bit loud for the 1.5 ton model.

Do you see any reason why I can’t use two quiet air handler units in the room? Please view this video with specs that I sent to the MEP today. https://youtu.be/-KBVdApwBPA
Old 1 week ago
  #2
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Kyle P. Gushue's Avatar
Multi splits are what allow multiple blowers in to connect to a single outdoor unit. Daiken makes outdoor units up to 48,000 btu.

https://www.acwholesalers.com/Daikin...JU/p26516.html

Its possible to buy the emura blower seperately, if thats the one you want, and just get watever outdoor unit you like seperately as well.

https://www.acwholesalers.com/Daikin...US/p99737.html

A ceiling cassette might be a good option if you need reinforcement. This one is 29db. Placed 12ft high it will be more like 23db at head height, assuming daiken tested the sound at 1m away.

https://www.acwholesalers.com/Daikin...JU/p82376.html

According to energy.gov a room your sqft requires a 12,000 btu unit. You could possibly squeeze by with a 10k btu unit since your room is only 10sqft larger than than 450, the max for 10k btu

https://www.energystar.gov/products/...ditioning_room

Remember your in an air sealed super insulated structure, which has a lot less thermal loss than a typical room. The guidlines are for typical rooms.

Last edited by Kyle P. Gushue; 1 week ago at 08:31 PM..
Old 1 week ago
  #3
Thank you Kyle. You are always helpful.

I downloaded the PDF Engineering Data for the Cassette. For a 12,000 BTU, the noise level at the lowest setting is 29 dB(A). It has two fan speeds.

The wall mount 12,000 BTU unit is 20 dB(A) at the lowest setting. And it has 5 fan speeds...

Don't know why the wall mount would be quieter...

But I need 1.5 tons. (18,000 BTU). Because sometimes I will have the room with 15-18 students.

Marius
Old 1 week ago
  #4
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Kyle P. Gushue's Avatar
Quote:
Originally Posted by MariusPerron View Post
Thank you Kyle. You are always helpful.

I downloaded the PDF Engineering Data for the Cassette. For a 12,000 BTU, the noise level at the lowest setting is 29 dB(A). It has two fan speeds.

The wall mount 12,000 BTU unit is 20 dB(A) at the lowest setting. And it has 5 fan speeds...

Don't know why the wall mount would be quieter...

But I need 1.5 tons. (18,000 BTU). Because sometimes I will have the room with 15-18 students.

Marius
My thinking was use the ceiling cassette and wall unit. Just use the ceiling cassette as supplementary / additionsl cool air when you have students, and quietness is a bit less critical. I like it because its high up and out of the way, and could offer better distribution.

Or use an 18k btu unit which is around 30db lowest setting. If mounted at the rear of the room, up high, it would be roughly 9-12db less at the listening position, assuming they measured at 3ft away. Sound reduces 6db each time you double the distance in a free feild.

You could just do 2x 9k btu. Im not sure 2x 20db units would be quieter than a single 30db unit, but you do have the option of one at a time.

Have you confirmed that the calculation doesn't change because its an air sealed super insulated room? I know in the winter the gear racks can keep a control room warm.

As an aside, my cousin put a daiken multi split wall unit in his CR at home, and it was very quiet even in a 12x14 space.

Best of luck.
Old 1 week ago
  #5
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The LG Multi-F is 19dB in the lowest mode with less than 1 ton IDU's and is multizone, double check the specs, but at least the 1 ton lsn120hsv5 Idu's i have are 19dB(a) on the lowest of the 5 fan speeds. Also the wifi function is pretty handy.

I run two of them in the big room for the same reason (2 ton unit only has 3 speeds, with the lowest being ~26dB.

The distribution boxes for multi-zone splits are noisy though- you don't want them in the room at all, run two linesets to the hall or something if you do use multi-zone.
Old 1 week ago
  #6
Quote:
Originally Posted by Kyle P. Gushue View Post
Have you confirmed that the calculation doesn't change because its an air sealed super insulated room? I know in the winter the gear racks can keep a control room warm.
Kyle -

I sure appreciate your input. You make some very good points - especially the cassette up high in the room...

My MEP engineer does the calculations. He has to put his seal on it... I will remind him that it is a "air sealed super insulated room".

You wrote: "in the winter the gear racks can keep a control room warm."
I am in south Texas and I am more concern with keeping the room cool.
Old 1 week ago
  #7
Quote:
Originally Posted by RyanC View Post
The LG Multi-F is 19dB in the lowest mode with less than 1 ton IDU's and is multizone, double check the specs, but at least the 1 ton lsn120hsv5 Idu's i have are 19dB(a) on the lowest of the 5 fan speeds. Also the wifi function is pretty handy.

I run two of them in the big room for the same reason (2 ton unit only has 3 speeds, with the lowest being ~26dB.

The distribution boxes for multi-zone splits are noisy though- you don't want them in the room at all, run two linesets to the hall or something if you do use multi-zone.

Ryan,

Nice to hear from you. It took me a while to figure out what "IDU" was... Indoor Unit !

My MEP recommended the LG products. From the LG site, I downloaded two different PDF with the Engineering specs for your LG LSN120HSV5. I am confused because the specs give differing info depending on where you look. (see attached screenshots).

I can't attach the PDFs - they are too large. The name of the two files are:

EM_MultiF_IDU.pdf
and
EM_SZ_HighEfficiencyWallMount_HSV5.pdf

Marius
Attached Thumbnails
Two Mini Splits in one control room-lsn120hsv5-noise-specs.jpg   Two Mini Splits in one control room-lsn120hsv5-noise-specs-3.jpg   Two Mini Splits in one control room-lsn120hsv5-noise-specs-2.jpg  
Old 1 week ago
  #8
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Quote:
Originally Posted by MariusPerron View Post
Ryan,

Nice to hear from you. It took me a while to figure out what "IDU" was... Indoor Unit !

My MEP recommended the LG products. From the LG site, I downloaded two different PDF with the Engineering specs for your LG LSN120HSV5. I am confused because the specs give differing info depending on where you look. (see attached screenshots).

I can't attach the PDFs - they are too large. The name of the two files are:

EM_MultiF_IDU.pdf
and
EM_SZ_HighEfficiencyWallMount_HSV5.pdf

Marius
There are actually 5 fan speeds, they are all pretty quiet...to the point where it's difficult to get a reading from the SPL meters that I have. I think they aren't really doing specs here for all of the fan speeds.

In any case, the actual hardware SPL meters that I have don't go below 30dB. The one on my phone will go down to 27, but it stays at 27 with IDU either on or off. I think it's probably just hitting the limit on noise from the phone mic there...

But they are really quiet. I can only tell if it's on because of the air. Have not had any issues with the system being on and being able to pick it up in a mic either. In the highest fan speeds I still can't hear it. I though I was hearing it the otherday, but the noise I heard was a mac book pro's fan that my client had.
Old 1 week ago
  #9
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avare's Avatar
 

With the numbers you have given, assuming EBU tech 3276 design criteria, the RT will be around 0.3 s and the Dc around 1.2 m. That is about the measuring distance in the items you posted.. Those values will be about what you will hear throughout the room.

Last edited by avare; 1 week ago at 06:59 PM.. Reason: Corrected TR to RT
Old 1 week ago
  #10
Quote:
Originally Posted by avare View Post
The TR will be around 0.3 s and the Dc around 1.2 m. That is about the measuring distance in the items you posted.. Those values will be about what you will hear throughout the room.
AVARE ! Can you explain this please?
Old 1 week ago
  #11
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avare's Avatar
 

Quote:
Originally Posted by MariusPerron View Post
AVARE ! Can you explain this please?
1. I miss spelt RT (reverb time).

2. EBU tech 3276 has an equation for calculating RT based on room time.

3. Dc (critical Distance from a source in room where the direect sound from the source wheree the dirct sound is the same level as the diffuse field, where the no longer decays.

4. In your room this is approximately 4.4 feet.

5. The diagrams a 4.6 foot distance between the mic and unit being tested.
Old 1 week ago
  #12
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Kyle P. Gushue's Avatar
Quote:
Originally Posted by avare View Post
1. I miss spelt RT (reverb time).

2. EBU tech 3276 has an equation for calculating RT based on room time.

3. Dc (critical Distance from a source in room where the direect sound from the source wheree the dirct sound is the same level as the diffuse field, where the no longer decays.

4. In your room this is approximately 4.4 feet.

5. The diagrams a 4.6 foot distance between the mic and unit being tested.
So to clarify, the sound won't decay any further than the measured level at 4.4 feet?

Example: blower unit on rear wall, and DB meter front wall 23ft away. The sound will measure the same at 23ft as 4.4ft?

Just want to make sure my thinking was incorrect in my previous post, using decay of a free feild.

Also, if two units are 20db each when running solo, how many db do they create when running simultaneously? An audio calculator app says 23db, just want to make sure that's applicable in this case.

Last edited by Kyle P. Gushue; 1 week ago at 10:28 PM..
Old 1 week ago
  #13
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Kyle P. Gushue's Avatar
Quote:
Originally Posted by MariusPerron View Post
Kyle -

I sure appreciate your input. You make some very good points - especially the cassette up high in the room...

My MEP engineer does the calculations. He has to put his seal on it... I will remind him that it is a "air sealed super insulated room".

You wrote: "in the winter the gear racks can keep a control room warm."
I am in south Texas and I am more concern with keeping the room cool.
Gotcha, i just picture how much harder a fridge would have to work if the seal wasn't airtight. Ive actually had to run ac in the winter before.
Old 1 week ago
  #14
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avare's Avatar
 

Quote:
Originally Posted by Kyle P. Gushue View Post
So to clarify, the sound won't decay any further than the measured level at 4.4 feet?

Example: blower unit on rear wall, and DB meter front wall 23ft away. The sound will measure the same at 23ft as 4.4ft?

Just want to make sure my thinking was incorrect in my previous post, using decay of a free feild.

Also, if two units are 20db each when running solo, how many db do they create when running simultaneously? An audio calculator app says 23db, just want to make sure that's applicable in this case.
Correct in both.
Old 1 week ago
  #15
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Kyle P. Gushue's Avatar
Quote:
Originally Posted by avare View Post
Correct in both.
thanks.
Old 1 week ago
  #16
Quote:
Originally Posted by avare View Post
EBU tech 3276 has an equation for calculating RT based on room time.

.
Avare - Thank you for the clarification.

What is "room time"? Do you mean Room Size?
Old 1 week ago
  #17
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avare's Avatar
 

Quote:
Originally Posted by MariusPerron View Post
Avare - Thank you for the clarification.

What is "room time"? Do you mean Room Size?
You are welcome

I misspelt it, it is the time it takes for a sound to decay 60 dB. In the beginning it was for concert halls which have diffuse fields. As we use it itmeans "the time to reduce 60 dB. To maintain the usual confusion it is called "reverb time" "RT' and "RT60' It is like "phase" for "polarity" on consoles. People in the know it but many do not.
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