John Samuel
New member
Installed a CV1800 last weekend. It is the Australian model, so it runs off 240V with a VSD driving the 3kW (5HP) three phase motor. I am not using filters and the plan was always to vent to the outside.
When I turned it on with the VSD set to 60Hz, the noise was terrible; about 97dB; but there was no ducting on either the intake or exhaust sides.
I just fitted a length of 200mm insulated HVAC ducting to the exhaust, and dropped it out of a high window.
The sound reduction is good. Here are the results before and after the exhaust duct was fitted.
At 50 Hz ... without duct ... 86dB ... with duct ... 70-76dB.
At 60 Hz ... without duct ... 97 dB ...with duct ... 72-78dB.
The range for the "with duct" reading is because it is clear some of the noise is directional. Moving laterally creates this range of values at a constant distance to the blower of 3M. As we might expect, the louder readings are towards the back of the "L" shaped shop which is closed off and smaller; the lower readings occur when I stand towards the bigger, more open area of the shop between the cyclone and the garage door. My principal work area is near that door, so the fan can blow over me and out through the big opening.
In any event, I now have the noise down to 72-78dB running at 60Hz. Given that a reduction of 10dB about halves the noise this is a great start! At 60 Hz I now have about one quarter of the noise that used to be present before the exhaust duct was fitted. At 50Hz it has halved. Clearly the frequency/harmonic/power/pressure produced by the higher speed is different to that produced at lower speeds, and the HVAC duct does a better job of suppressing the noise frequency/harmonic/power/pressure produced at the higher speed. With the duct on, the two noise levels are quite close.
Put my ear to the wall. Sure enough, a very low rumbling is now detected. However, when I step inside the house to the ensuite (house and shop are the same brick veneer building) and close the hollow core door the noise drops to 45dB 1.5M behind that door. The next room is our bedroom, and the noise there drops to 40dB with the door open and to 25dB with it closed.
The very good news is that the neighbours should not be bothered by this at all. Standing beside the fence near the neighbour's house produces about 40db. At the back of the house where the exhaust duct exits the reading is less than 40dB. It varies a bit depending on where I stand, but stays under 40dB. It looks like I'll not need a baffle. Bill Pentz did say that most of the noise came from the exhaust and that he had been told by an associate that 8-10 feet of insulated HVAC duct would make a big difference ... and it did. So much so that I am considering wrapping some more insulation around the 1M or so of the existing duct that is inside the shop. The duct only has a fairly thin layer of polyester (I think R1). Might also put a wrap around the blower before I enclose it.
When I turned it on with the VSD set to 60Hz, the noise was terrible; about 97dB; but there was no ducting on either the intake or exhaust sides.
I just fitted a length of 200mm insulated HVAC ducting to the exhaust, and dropped it out of a high window.
The sound reduction is good. Here are the results before and after the exhaust duct was fitted.
At 50 Hz ... without duct ... 86dB ... with duct ... 70-76dB.
At 60 Hz ... without duct ... 97 dB ...with duct ... 72-78dB.
The range for the "with duct" reading is because it is clear some of the noise is directional. Moving laterally creates this range of values at a constant distance to the blower of 3M. As we might expect, the louder readings are towards the back of the "L" shaped shop which is closed off and smaller; the lower readings occur when I stand towards the bigger, more open area of the shop between the cyclone and the garage door. My principal work area is near that door, so the fan can blow over me and out through the big opening.
In any event, I now have the noise down to 72-78dB running at 60Hz. Given that a reduction of 10dB about halves the noise this is a great start! At 60 Hz I now have about one quarter of the noise that used to be present before the exhaust duct was fitted. At 50Hz it has halved. Clearly the frequency/harmonic/power/pressure produced by the higher speed is different to that produced at lower speeds, and the HVAC duct does a better job of suppressing the noise frequency/harmonic/power/pressure produced at the higher speed. With the duct on, the two noise levels are quite close.
Put my ear to the wall. Sure enough, a very low rumbling is now detected. However, when I step inside the house to the ensuite (house and shop are the same brick veneer building) and close the hollow core door the noise drops to 45dB 1.5M behind that door. The next room is our bedroom, and the noise there drops to 40dB with the door open and to 25dB with it closed.
The very good news is that the neighbours should not be bothered by this at all. Standing beside the fence near the neighbour's house produces about 40db. At the back of the house where the exhaust duct exits the reading is less than 40dB. It varies a bit depending on where I stand, but stays under 40dB. It looks like I'll not need a baffle. Bill Pentz did say that most of the noise came from the exhaust and that he had been told by an associate that 8-10 feet of insulated HVAC duct would make a big difference ... and it did. So much so that I am considering wrapping some more insulation around the 1M or so of the existing duct that is inside the shop. The duct only has a fairly thin layer of polyester (I think R1). Might also put a wrap around the blower before I enclose it.
