Possible to slow the blower speed in a Fujitsu ducted inverter?

[mrclunk]

Hi Chaps,
We've just changed out our old AC system to a new Fujitsu Ducted systems ARY30EL(B) indoor (inverter?) and a AOY30EM condenser. (single phase)
( cooling only system)
I can't actually find anything on the fujitsu site about this model, perhaps its an older model. The current similar model seem to be ARYA30.

We're a recording studio so noise is a big issue for us...
Unfortunatly the indoor unit is very noisy and probably a bit large for the job it needs to do..
A lot of the noise is air flow or duct noise but a big factor is also the blower motors.
We'd like if possible to slow down the fan speed a little more, i'm aware that we can't slow it down too much or it'll ice up.
Majority of the time the unit is just acting as a fan sucking in cooler fresh air from outside and hot air is being extracted out of the rooms.

My question is can we reprogram the fan speeds or do we need to come up with an electronic solution?
Looking at the pcb it seems to have 3 relays switching for the different speed settings thru a Triac to i assume an induction motor?
Also is the speed of the indoor fan linked to the speed of the external unit?
Apoligies for the silly questions but we're not ac experts... but do have a fair understanding of electronics.
I'm going to call fujistsu and see if they let me have the service manual, schematic hopefully there's a software solution.
many thanks
paul

[paul_h]

You can't slow down a 240V AC motor with software, it's constructed/hard wired to run 3 fixed speeds.
You need to come up with a mechanical/air flow solution.

Bigger ducts (supply and return), more outlets, right angled plenums for diffusers, bigger diffusers, and return air right angle plenums.

Also are you sure that you have a damper system installed to allow outside fresh air?
The default is no fresh air at all, you're just recycling air.
Commercial premises require a fix percentage of outside air (nothing big, sometimes 15%-20%) so still the majority recycled air.
Unless you dropped a a lot of money of a fresh air damper and return air damper, extra air filters etc, you aren't getting any (or much) outside air at all.
edit:
I don't think there's a triac as it's not a variable speed motor, I think that's a solid state relay to switch the fan on and off, with three relays to switch in the motors 3 windings to change the three speeds.

[mrclunk]

Thanks Paul,
Ah ok you may well be right about the relays switching in different motor windings, i won't know until i get hold of the schematic. Maybe i could stick a step down transformer or variac on one of the windings if this is the case.

We've two 200mm's sucking in outside air through an air filter box and a 150mm for re-circulated air. (the recirculated air part isnt fitted yet, this will have a damper on it.)
There's 3 x 200mm outs, on flexible insulated ducting, thu silencers to the rooms.
Actually the units designed to have 4 x 200mm in and 4 x 200mm outputs so i think alot of the noise is because of the air being squeezed thru too small a space...
Basically the units far to big for whats needed. We've another fujitsu cassette type in the other studio and its wisper quiet on the low speed mode, on this big unit there's not that much difference between the speed settings.

We might try some of this ridged glasswool lined ducting, its suppose to absorb a fair bit of sound.

[RSTC]

Did you not tell the designer it was a sound studio?

I would suggest you first change the ducting to 4x200 mm sonic lined ducts and fit plenum boxes to the rear of the grills eg Halton, system air or Flakt Woods (there are several UK manufacturers also). Also make sure the indoor unit is fitted with anti-vibration mountings.

[paul_h]

Thanks Paul,
Ah ok you may well be right about the relays switching in different motor windings, i won't know until i get hold of the schematic. Maybe i could stick a step down transformer or variac on one of the windings if this is the case.

We've two 200mm's sucking in outside air through an air filter box and a 150mm for re-circulated air. (the recirculated air part isnt fitted yet, this will have a damper on it.)
There's 3 x 200mm outs, on flexible insulated ducting, thu silencers to the rooms.
Actually the units designed to have 4 x 200mm in and 4 x 200mm outputs so i think alot of the noise is because of the air being squeezed thru too small a space...
Basically the units far to big for whats needed. We've another fujitsu cassette type in the other studio and its wisper quiet on the low speed mode, on this big unit there's not that much difference between the speed settings.

We might try some of this ridged glasswool lined ducting, its suppose to absorb a fair bit of sound.

Well you size the unit for the heat load, then design the ducting to make it work with that size unit.
Are you saying the unit is too big for the heat load? Or saying it flows too noisy even though it's the right size a/c for the heat load?
Even if you slow down the airflow through electronic/electrical means, that will just make the a/c too big for it's airflow (cut out on low temp faults in cooling , cut out on high temp fault in heating). The a/c is matched to itself, change something and it will not like it. Not to mention you have it set up to allow air changes (outside air) a slow fan won't be efficient flowing outside air, you'll need to run cooling recirc more often because the slow fan can't ventilate enough.
It would be better if you designed the ducting to work with the unit and have high airflow that's not noisy IMHO. that would make the fresh outside air system work better. I've never heard a loud small fujitsu ducted system myself, they are designed to run 3 outlets pretty quietly.

[chemi-cool]

Yes you can mess up the speed by using a simple elactronic dimmer, if you connect the "0" through it.
I would not suggest you to do it though.

Noise from ac unit means air velocity too high, larger ducts with acustic insulation and larger defusers will reduce the air speed.
Did you installed registers at the end of each duct?

[mrclunk]

Thanks chaps,
the more i read it seems we're restricting the air flow too much. Slowing down the blower does't seem the correct solution at all.
Also when changing duct sizing we're introducing more noise by not using tapered size adapters etc.
paul_h
yes the unit is to big for the heat load, our original thought was to have an oversized unit but run it at slower settings for quieter operation but that was perhaps silly..

chemi_cool
What are registers? and no we probably havent got any...

RSTC

Did you not tell the designer it was a sound studio?

We've designed/installed it ourselves so it's all bit Heath Robinson.... but we're learning!
The units on rubber isolation mounts and decoupled from the building stucture.

We're going to rework some of the ducting, maybe build some larger silencers for critical rooms. Can someone recomend a supplier for acoustic sheet duct lining please?
One of the biggest problems in all this is what parts are called and where to buy them.
thanks again
paul

[chemi-cool]

I have uploaded a picture.

[mrclunk]

Ok yeah we've got those. But they introduce there own wind noise when you close them a touch. Best to have a big open hole sound wise.

[Brian_UK]

Have a read of this document from Trox regarding duct sound attenuators, it may give you some guidance.

http://www.troxuk.co.uk/uk/service/d..._1_1_ds_dk.pdf

[dannycool]

Try these guys
http://www.allawayacoustics.co.uk/attenuators.htm
Give them your duct sizes, air volumes and what sound levels you are working to and they will come up with a solution.
Your probably talking about £60-70 an attenuator

Hope this helps.

P.S I have no connection with this company at all! But have found them very helpful in the past

[Nesey]

Unfortunatly the indoor unit is very noisy

It is unlikely that noise is the fan. Most likely the vibration transmitted from the indoor unit to the wall and it resonates. I'm between the wall and stuck a piece of the block mats - perfect dampens vibrations.

[Nesey]

Most often, vibration is transmitted from external unit through the ***** line. That is necessary to isolate the external unit.

[gozoboy]

We had the same problem with daikin units in a conference/ wedding hall. During conferences the units were too noisy as the ducts are very short and there is no space for attenuators. So after asking around we were told to change the indoor fan capacitor with another capacitor half the original. I was very pessimistic that it would work, but units have been running for nearly 2 years now without any problem.

[back2space]

Thanks chaps,
yes the unit is to big for the heat load, our original thought was to have an oversized unit but run it at slower settings for quieter operation but that was perhaps silly..

I have my units oversized at home so that I wouldnt need to run in high fan speed (plus theres the extra capacity there if need be) the thing to bear in mind here is that at low fan speeds your unit is outputting less cooling anyway so the cooling out put probably fits the heat load of the room anyway. System cooling/heating capacities mentioned on the sales literature are based on high fan speed operation at lower fan speeds this will be less.

I think as others have said this comes down to duct design and the diffusers. Perhaps also line the walls and ceiling void area (assuming it is a false ceiling) with the rubber mats you can get for sound proofing. Have silencers on the connections to the diffusers and maybe have more diffusers.

[chilliwilly]

Hi Chaps,
We've just changed out our old AC system to a new Fujitsu Ducted systems ARY30EL(B) indoor (inverter?) and a AOY30EM condenser. (single phase)
( cooling only system)
I can't actually find anything on the fujitsu site about this model, perhaps its an older model. The current similar model seem to be ARYA30.

We're a recording studio so noise is a big issue for us...
Unfortunatly the indoor unit is very noisy and probably a bit large for the job it needs to do..
A lot of the noise is air flow or duct noise but a big factor is also the blower motors.
We'd like if possible to slow down the fan speed a little more, i'm aware that we can't slow it down too much or it'll ice up.
Majority of the time the unit is just acting as a fan sucking in cooler fresh air from outside and hot air is being extracted out of the rooms.

My question is can we reprogram the fan speeds or do we need to come up with an electronic solution?
Looking at the pcb it seems to have 3 relays switching for the different speed settings thru a Triac to i assume an induction motor?
Also is the speed of the indoor fan linked to the speed of the external unit?
Apoligies for the silly questions but we're not ac experts... but do have a fair understanding of electronics.
I'm going to call fujistsu and see if they let me have the service manual, schematic hopefully there's a software solution.
many thanks
paul

Check that the ducting is balanced out correctly, one or more of the damping registers may be closed down too much. You may be able to install some kind of bypass that short cycles the air flow so the pressure of the delivered air speed is cut down, this could reduce the need to install a bigger ducting as it does sound like the air flow capacity is greater than the ducting can handle. Better still get back in touch with your installer and tell them your not happy with the choice of unit you have been supplied with. On the other hand I'm not familiar with a unit like one of these that takes in fresh cool air from the outside then extracts the warm air? One of them DIY type similiar to a window unit with the condensor and evaporator in the same unit with an external air intake and exhaust springs to mind. If so its the wrong choice for the application.