Ahhhh! OK, I get it.I was comparing plan C and D - a single 14kw system to 3 x 4kw systems - both indoor ducted systems with an external condenser and an indoor unit (or 3 indoor units) which sit in a mini machine room. I have already given up on plan A, the one with the mini splits, as it doesn’t make any sense. So comparing plan C and D …
So you are comparing having a single large AHU in an external utility room, outside of the isolation shell for the studio, against having three smaller AHU's in the same utility room. In both cases, the air flow would be suitably ducted to and from the relative rooms.
The issue I see here is the "suitably ducted" thing: With a single AHU you only need one silencer box on the wall penetration into the isolated area: you can split the flow downstream, after that one single silencer. With three AHU's you'd need three separate silencer boxes, and three wall penetrations. that's three times as much expense, and three times as much potential failure points.
And that's just the supply side of things: you'd also need three additional silencer boxes on the three return ducts, and another three penetrations. That's a lot of silencer boxes! And a lot of wall penetrations! Six of each, instead of just two of each... Silencers are also very bog anyway: trying to fit in six of those beasts is going to be an issue...
Three times the cost in silencer boxes, three times as many wall penetrations, three times the work... Among others.There may be some drawbacks of plan D compared to plan B but I don’t know what they are?
It sounds like you should be thinking of hiring a studio designer to do the HVAC design for you. Not an HVAC designer: a studio designer. Here's a link to a sad case of a studio that let an HVAC designer do the job,. and look how they ended up... http://www.johnlsayers.com/phpBB2/viewt ... =2&t=20571I want to be certain but it is difficult as I am not capable of making those calculations. I tried to understand all the the HVAC nitty gritty for some months but realise it is beyond me. I am just a musician!
Does he have studio experience? I'm wondering...That is why I got a pro HVAC guy to calculate the requirements for the rooms and their occupancy. He has never seen homemade baffles like mine
Then he's not the right guy t be doing your HVAC design for a studio! Sorry. He might be a great guy, and he might be really good at typical HVAC installations, but studios are very different.As far as sound isolation goes he doesn’t know anything
Sadly, that happens way too frequently with studios. It's a but more complex than many people realize, and especially people who should know better, such as HVAC installers.To be honest it is not going well.
That's not the static pressure that they produce: that's the maximum static pressure they can handle. Static pressure is basically like resistance to airflow. All of the duct-work, dampers, registers, silencers, and everything else in the path of air flow combines to create a certain amount of resistance to the movement of air. The fans in the AHU have to be able to overcome that, in order to move the air.Static pressure for the 3 x FDUM40VF units I am considering is 100PA.
So if your static pressure is 200 Pa, and the static pressure capability of the AHU is only 100 Pa, then you have a problem: the fans will be running up against too much resistance. The air won't move correctly, the fans blades will not be working within their design specifications, the fan motors will overspeed, the whole thing will be noisy and inefficient, and it won't work. The AHU will be overloaded, and its life will be short and noisy. It's like using a car to pull a truck up a hill.
On the other hand, if your AHU can handle 100 Pa and the static pressure of your system is only 50 pa, then that's great. No problem. It's like using a truck to pull a car up the hill.
So you have to make sure that the static pressure of your system is low enough that the AHU can deal with it. 100 Pa static pressure is only medium. Depending on what static pressure your system has, you might need a unit that can handle a higher static pressure.
Are you sure that's enough for your place? What is the total room volume, in cubic meters? Multiply that by six, to get the number of room changes per hour that you need. Dived that by 60 to get the number of cubic meters per minute that you need.Max air flow is 10 m3/min
I suppose that is the maximum distance between the AHU and the compressor? That's not really important for figuring the airflow, but it is important for locating the equipment: the AHU cannot be more than 30m away from the compressor, and that includes all the ups and downs, curves, bumps and deviations.maximum length communication is 30m.
200mm diameter duct = 310 cm2 cross sectional area, which is 0.03 m2. 10m3 per minute flowing through an area of 0.03 m2 is 333 m/min = 5.6 m/s. That is way, way too high. It needs to be no higher than 1.5 m/s, and preferably around 0.5m/s. If the air flow is any faster than that, it is very noisy.From this, knowing the duct size is 200mm, I calculate (quite possibly wrongly!) that the duct velocity will be at maximum 12.5 m/s,
Right, but you need to calculate what the correct rate is! As I mentioned above: room volume x 6 = room changes per hour. Divide that by 60 to get the airflow rate you need.although I suspect I will not be using the system at full power very often so it should be a lot less than this most of the time.
It seems like they have not been calculated correctly....!The units have already been calculated as being right for the rooms based on the ventilation/cooling/heating requirements
You cannot have speeds of nearly 6 m/s at the registers! That's about 20 km/hr! Try riding your bike at 20 km/hr, and listen to the wind noise as the air moves past your ears.... that's the noise that will be coming out of your registers....So no, the calculations have not been done correctly for a studio. 6 m/s might be fine for an office, but not for a studio... Perhaps the heating /cooling capacity has been calculated, but clearly the air flow has not been.
Assuming that 10 m3/min is the correct flow rate for your room, you will need to increase the cross-sectional area of the registers by a factor of about 4, in order to get the flow velocity slow enough for a studio. However, that's a big assumption! 10 m3/min might be too much for your room, or it might not be enough. Do the math, and you'll know for sure.how (or if) I should adjust the design of the baffles based on these figures?
- Stuart -
