Hi guys, I've been busy trying to figure out the best way to tackle this thing. At this point I've decided to go with a split-system (Daikin Ururu Sarara) for heating/cooling/humidity and an HRV for fresh air (Brink Flair 300). For now I am focusing on getting the HRV right by making calculations and reading threads like this one:

http://www.johnlsayers.com/phpBB2/viewtopic.php?f=1&t=21895. They are very helpful, but I'm still a bit lost on the finer details. I hope anyone can chip in and help me out

So far this is what I've come up with:

- control room volume is 81,7 m3 x 8 circulations per hour = 653 m3/h total flow rate

- booth volume is 31,8 m3 x 8 circulations per hour = 254 m3/h total flow rate

For the HRV I only need to refresh a maximum of 35% of the total flow rate, so:

- 35% of 653 = 228 m3/h for the control room

- 35% of 254 = 89 m3/h for the booth

This means I need an HRV with a max capacity of 317 m3/h. I've found that the Brink Flair 300 is a relatively silent HRV and it delivers 300 m3/h. I guess that should be more than enough since 8 circulations per hour and 35% fresh air rate is on the high side. Please correct me if I'm wrong.

Here's a tech sheet (it's in Dutch, but most values will make sense without understanding the language):

Attachment:

Brink Flair technical sheet.png

I need a maximum air flow velocity of 1,5 m/s (300 FPM) at the registers. I read somewhere that 1 m/s (200 FPM) would be even beter, don't know if this is true? To be on the safe side I calculated the register sizes by choosing middle ground (1,25 m/s or 250 FPM):

- CR: A flow rate of 228 m3/h with a flow velocity of 1,25 m3/h results in a register with a surface area of 498,7 cm2 (diameter of 25,5 cm)

- Booth: A flow rate of 89 m3/h with a flow velocity of 1,25 m3/h results in a register with a surface area of 194,7 cm2 (diameter of 15,7 cm)

So far so good?

Speaking of registers, are these appropriate to use? They come in different sizes, are made of steel, have fixed vanes and can be mounted with screws:

Attachment:

Register.png

The open area is around 70%. In the specs sheet they only mention it can be used for air return. Could this also work for air supply or do I need something else?

Because this register has an open area of 70% I need to add this to the calculation:

- 498,7 cm2/70% = 712,4 cm2 -> using a 30x25cm would suffice

- 194,7 cm2/70% = 278,1 cm2 -> using a 20x15cm would suffice

Am I still on the right track here?

Now that I know my register sizes I should look at the ducting and silencers. The connection for the ducting on the HRV has a diameter of 16 cm (201 cm2 in surface area). This means that on the side of the HRV I have 201cm2 in surface area and on the other side I have 712,4cm2 for the control room and 278,1cm2 for the booth.

I have 2 questions about this:

1. Do you think 1 register for the control room is going the be enough or do I need 2x supply and 2x return ducts/registers? And why? I think 1 register for supply and 1 for the return air in the booth should definitely be enough, but I'm not sure about the control room. One HVAC contractor I talked to was suggesting at least 2 for example. But then how does that work with the surface area of the register? Do I just divide it by 2? So I have 2 registers of 356,2cm2 for the CR?

2. I need to split the supply and return air ducts to get to both rooms (I even need to split it 3 times if I need 2 registers in the CR). How do I make sure I get 89 m3/h to the booth and 228 m3/h to the CR? And not for example 150 to one room and 150 to the other? There's only one output on the HRV so it all comes from one duct. I don't really understand how that would work.

To create an impedance mismatch I should at least double the cross sectional area right? Preferably more. So with the numbers I calculated above, is this the right way to go?

HRV -> Decflex Sonodec* ducting (201cm2) -> silencer entry point (700cm2, factor of 3,5) -> silencer exit point (1400cm2, factor of 2) -> register (712cm2)

* (as suggested by Philip Newell in his Recording Studio Design Book)Questions:

- how long should the ducting be before I go into the silencer?

- can you do both sudden cross sectional area changes in one silencer as I did here?

- is the register directly connected to the exit of the silencer or should you add extra ducting between this?

- at the exit of the silencer the cross sectional area is 1400cm2, but the register is twice as small. Won't this create turbulence and/or noise?

Please let me know if I'm on the right track and if my calculations and deductions are correct