Ceiling fan vibrates with ac air

[jas kim]

Hi

I installed a ceiling fan in my master bed room last night. IT works fine when the ac is off and it is smooth and quiet at all speeds.

HOwever whenever the fan is on medium speed and the ac is on, there are sporadic vibration which are not severe but enough to make the metal fan power cord hit the light fixture to create a "cling" sound. Kinda distracting when trying to get some sleep.

It is weird because the ac vents only seem to affect the medium speed. I have two vents in the masterbed room but neither are point directly at the fan. They are towards the front ends of the room pointing towards the rear end of the room where as the fan is in the dead center. The master bedroom is pretty big.

Any idea on what might be causing this problem and how to solve it??

Thanks

jasguild

[Tony Hwang]

Hi, Why not close the vents for temporary and see if they interact with fan air? Tony

[Joseph Meehan]

How close is the AC/furnance unit to the fan? My guess is something is running on both the air handler at the furnance or the compressor (outside) and the fan at just about the same speed. When they get in sync, you get sympathetic vibrations.

The best bet is to change the speed of one or the other. The other solution is to provide better separation between the two.

Can you access the area above the fan? If so you could try some cross bracing in the area of the fan. Experimentation is the trick here. It is not just adding support or strength. Move them around and see if it changes.

[HVAC IsFun]

If your bedroom door is closed, then open it slightly. That should allow the air from the a/c to exit without causing overpressurization of the bedroom space which would affect the ceiling fan. If that doesnt do the trick, then, try making the ceiling fan go in the reverse direction to see if that solves it. If that doesnt work, then, close the supply registers by one-half. If that doesnt work ,then, dont use the fan during the a/c season.

Dave

[jas kim]

Thanks for all your responses.

One thing I concluded is that it is the air flow. the vents I have can just be directed down or up 90 degrees but not left or right. They were always up virtually parallel to the ceiling because the ac guy said if they are pointed down, the cool air would be wasted by bouncing off the floor and going right up into the circulation system.

To solve this problem I pointed the vents one at a time downward. POinting the left vent downwards had no effect on the problem but when I pointed the right one downwards the problem disappears.

Here is my scientific explanation. (this is coming from a lawyer) The fan is spinning counter clockwise. The vent to the left is not a problem becuase it is blowinig air consistent with the direction of the fan. However the one on the right is blowing against the direction of the fan causing the turbulance. How about that?? smile

So I guess something has to give. I guess I have to have the right vent pointed downwards and wasting air to solve this problem. It still confuses me though that it only impacts medium speed and Not High or low. Bizarre isnt it??

Feel free to add more comments.

Thanks again

jasguild

[HVAC IsFun]

'They were always up virtually parallel to the ceiling because the ac guy said if they are pointed down, the cool air would be wasted by bouncing off the floor and going right up into the circulation system.'

ME: True. you want to shoot the air upward for cooling.

'Here is my scientific explanation. (this is coming from a lawyer) The fan is spinning counter clockwise. The vent to the left is not a problem becuase it is blowinig air consistent with the direction of the fan. However the one on the right is blowing against the direction of the fan causing the turbulance. How about that?? smile'

ME: I could use someone like yourself in my hvac business. Do u come cheap ?!

'So I guess something has to give. I guess I have to have the right vent pointed downwards and wasting air to solve this problem. It still confuses me though that it only impacts medium speed and Not High or low. Bizarre isnt it?? '

ME: Just so long as you can fix the dilemna --- thats what counts. Airflow is a rather bizarre phenominon ...and if you wanted to light a fire in your bedroom, youd be able to see the air patterns that are taking place (but dont go there !)

Dave

[CBhVAC:)]

Dave...you are proving again that you are not in the trade, or have no experence with real HVAC. You can point a vent to blow in any direction you want, provided that the manual D was done correctly, and the proper CFM is being delivered to the room as governed by the manual J, room, by room, and that the return is adequate.

You just need someone that has a clue to help you out.

Umm..you dont know a thing about how to tell him to locate and repair air stagnation, do you?

[Greg O]

Damn! We have been doing it wrong! All the commercial buildings we do, we have the registers in the ceiling, blowing down. There is gonna be hell to pay straighting this mess out! Greg