Noisy central ventilation system


  #1  
Old 01-27-16, 02:40 AM
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Noisy central ventilation system

Hi,

We have moved into an old apartment from 1885. A central ventilation system was installed in the bathroom and the kitchen in all the apartments before we moved in.

The whole system is connected to an engine on the roof (metal pipe with a mushroom shaped engine on the top).

1) The level of the system can be set from 1 to 10. It is currently set to 5.

If I turn the level of the system all the way down to 1, the noise level in the bathroom and the kitchen is still 50-52 decibel (when the measurement tool is held next to the ventilation hole in the bathroom/the turned off exhaust in the kitchen).

If I turn the system off, the noise level goes down to wonderful 35 decibel in both the bathroom and the kitchen.

Any idea what could be wrong when the system create so much noise even if turned all the way down to 1?

2) The engine on the roof is placed 3-4 meters from out balcony

When the engine is running, the noise level on the balcony is 52-54 decibel. If I turn of the engine, the noise level goes down to around 46 decibel (we live in the middle of the city).

Can something be done to the engine so we can start using our balcony?

3) If I turn off the engine on the roof, the noise level in the bathroom and kitchen is still the same as if the engine is turned on (50-52 decibel).

It is only if I turn of the system that the noise level goes down to 35 decibel in the bathroom and the kitchen.

Any idea why the noise level doesn't go down when I turn of the engine?

Thanks a lot for your help.

// Mads
 
  #2  
Old 01-27-16, 02:59 AM
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Welcome to the forums! What type "engine" are you talking about? It would help us, also, if you were to complete your profile. We need to know where you are located, as it is obviously not in North America. This is primarily a North American site, and most advice here deals with domestic problems. We may be able to help, but we need more information.
 
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Old 01-27-16, 03:16 AM
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Thanks a lot for the reply.

We are in Denmark, Europe (no local ventilation forum here... - that's why I posted here).

Attached are some photos of the engine + pipe to the engine and control panel (engine and system):

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Old 01-27-16, 03:23 AM
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OK. We consider "engines" to be internal combustion type, while you are talking about an electric motor. With the noise it seems to be making, it sounds as if it could be either a bearing in the motor going bad, or a mount within the roof mounted frame broken. Is there any way you can check the mounts safely? With a constant din of noise regardless of speed, I would favor a motor replacement should your investigation determine the bearings are causing the problem.
 
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Old 01-27-16, 03:34 AM
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Good plan. I'll go and check.

But let's say the electric engine or the mount is broken. Then why doesn't the noise level go down when I turn of the engine?

Can there be another engine or is there something else I need to consider?

Thanks,
Mads
 
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Old 01-27-16, 03:58 AM
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It could be that no matter what speed the motor is turning, if the mount is broken, every revolution will cause an imbalance and either a thumping or squeaking noise. Now, as far as turning the motor "off", I haven't a clue, unless you really aren't turning the power off, or the switch is bad. Can you remove the power completely from your fuse/breaker panel? Does the noise stop, then?
 
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Old 01-27-16, 04:02 AM
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I can hear that the engine stops when I turn it off (in the attic).

When I go down in our apartment, I can still hear and measure the usual noise levels (except on the balcony where it matters a lot that the engine is turned off).
 
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Old 01-27-16, 04:12 AM
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With two switches, is it possible you have more than one motor? Maybe a booster fan in the ductwork. Can you trace the wiring to see where it leads from the switches?
 
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Old 01-27-16, 04:38 AM
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A booster fan could definitely be a possibility, but I can't trace the cables (they goes into the walls/ceilings in the attic).

But I found out that the pipe in my photos from the attic doesn't go to the electric engine. It goes to one of the pipes higher up on the roof.

The pipe (?) to the electric engine is build inside what looks like an old chimney channel.

I'll try to see if someone has schematics for the system or something like that (the building is quite small and there is no official maintenance guy, guess that's part of getting an extremely cheap apartment

Thanks a lot for your help so far! Makes me feel there is hope for finding a solution.
 
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Old 01-27-16, 06:11 AM
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I don't see any idolators in the pictures. A canvas connector would be a start.
 
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Old 01-27-16, 06:29 AM
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Nice idea with the canvas connector (didn't know about such a thing before, should they be installed in the attic or in our apartment?)

What is "idolators"?
 
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Old 01-27-16, 07:02 AM
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It sounds like there is a lot of detailed information about the whole systen missing.
We are unsure how the whole sysrem works.

I will take a guess and say there is one "fan unit" on the roof that serves multiple apartments.
I wiill further guess that there is a damper that when you set the fan to position " 1", the damper closes.
Is this how yours works?

Another possibility is that there is one fan per apartment and your control slows down the fan.
Is this how yours works?

We need many detailed pictures and an explananation of the workings of the whole system.

I will say that the style of fan (mushroom) you show can be very noisy if whoever paid for this system tried to save money.
 
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Old 01-27-16, 11:16 AM
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Thanks - and I totally agree, a lot of info is missing (we just moved in, trying to find the information myself here, but it's a bit difficult with no official maintenance person etc.)

If there is a damper that closes when set to position 1, I would think the noise level in the apartment would decrease. But it doesn't. It stays the same no matter what position I set.

As far as I can see there is no separate fan for each apartment + there is only one control panel in the attic (the building has 5 floors with a total of 16 apartments).
 
 

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