Loud (return air intake) sound....

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Old 10-21-04, 11:02 AM
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Loud (return air intake) sound....

Hello, I have a problem that just started after turning on my furnace. It was not there last year.

When the furnace starts and the blower kicks in there is a very rapid sucking sound being emitted at the "wall mounted" register screen which is below the thermosat. If I remove the screen the sound disappears and I can feel the suction. The other "wall mounted" register in the basement has been blocked off and has been this way since I moved in. No problems.

BTW...these wall registers are directly in line top to bottom and are separeted by the main floor. Are these the vents which feed the furnace with air? The other wall register is in the living room and there is a dining cabinet in front of it...(3in away from wall); and it has been this was with no problems. I located another smaller return vent on the top floor.

There are no strange sounds comming from the floor registers or through the ducting. The air blowing out is warm; standing by the furnace there are no strange sounds, no high pitch squeals or whines. The filter was removed and cleaned. The diag light flashes correctly. The rushing air sound only happens when the main blower kicks in and from the wall mounted return grills.

It is a 3 level house, with the unit in the basement which has has been working well. No issues, everything is clean inside.


What could be causing this problem?

Thanks...
 

Last edited by oceanview; 10-22-04 at 01:47 PM. Reason: clarification...
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Old 10-21-04, 12:36 PM
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untape the other return, it probably is needed toget enough return back to the unit
 
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Old 10-22-04, 12:02 PM
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I opened the other return...

and it's still the same. That room has a stand alone heater; which is why I think it may have been blocked off. It's open right now.

I can only describe it as air being pulled into the wall return very fast. Removing the wall registers panels makes the sounds disappear; so that tells me it's the speed of the air rushing over the vent slots. The vents are facing down as they should be.

From what I can find in the house, all return wall registers are clear and obstruction free. These I believe are the air IN points; correct? Maybe putting those "dust filter screens" on the wall registers may slow the air down there by reducing the whistling sound. Humm...some food for thought.

I trust the blower rpm's apply to both air OUT & IN. I saw something in the paper work I have about changing the blower speed (rpm's). If this is done I guess it takes longer for to warm up the house.

Is there anything I should be looking for on the roof that may be indirectly responsible?

Thanks for your reply hvac4u.

later...
 
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Old 10-22-04, 12:38 PM
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Dont know if this is what you have here or not . But lots of time the grills will get whats called resonates. You have to like bend all the the little bars just a little more open. Some times to tighten or loosen some of the screws that hold the gril to the wall will work.

ED
 
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Old 10-23-04, 10:19 AM
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Giant Sucking Sound???..haha...(AKA Ross Perott)

Hello: oceanview

You stated:
"wall mounted" register screen which is below the thermosat. If I remove the screen the sound disappears and I can feel the suction. The other "wall mounted" register in the basement has been blocked off and has been this way since I moved in.
To clarify terms used, the intake air return is the called a cool air return intake vent. Much larger usually than a room register. Cool air return is different than a room warm air return register. Register pertains to those which blow out the warm air into any room. Just wanted to make the point so there is no confusion in my reply.

Granted & realizing, in some areas of the country, air returns are or can used in every room. For generic purposes, intake returns to furnaces there are usually or generally only one or two.

The intake air retrun vent has filters or is likely to have them. Not all do. If those you have have filters, change them. May be cuasing air intake restrictions causing the noise.

Next point. The basement intake return vent is closed to avoid taking in cold air to the furnace if all the registers in the basement are closed because no heating is want in that area or not needed.

If no heat is being supplied into the basement, registers close or none in the basement area, leaving open the intake air vent would take in basement cold air, supply it to the heater, delute the warm air in the furnace and circulate it into the house.

Out comming warm air to the room registers, from furnace, would be slightly cooler. Thus taking longer to heat the upstairs house and not the basement. Over all reducing the efficiency of the furnace. Energy costs would be higher.

Summations:
1)
If not wanting to heat the basement, the warm air registers being closed or none there, etc. it is than best to keep the cool air return vent to the furnace closed. Which is likely the reason it was closed or blocked off in the first place, likely.

2)
To keep the system the same, not heating basement or wanted intake air return to allow basement cool air into furnace but still wanting to reduce noise in the intake vent upstairs in the house, a larger intake should be installed where the existing one is already or another one added somewhere else in the house. Doing so would reduce the noise, supply enough air to the furnace and not take return air from the basement. Noise will be gone.

I do not suggest changing fan speed, at this time. Nor suspect or likely to be anything on the roof causing the noise or has anything to do with noise with anything on the roof. Roof has the venting pipe system. Best left as is.
 
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Old 10-23-04, 05:49 PM
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Understand...

Thank you for the clarifications & comments, hvac4u & Sharp Advice.

Yes the wall mounted registers I'm refering to are the returns to the furnace and are about 9x24. The main floor has 2; upstairs 1 (being half the size), and the basement 1.

The only issue is the amount of noise created as the air is pulled through the wall grilles. If I remove the grilles and listen, the whining sould is not there. Put the grilles back and it's there. I'm going to look for other returns just in case other exist. The basement heating vents are closed; and I'll probably close off the return as that is how it was before the problem.

Hope a solution pops up; the noise makes one worry.


thanks...
 

Last edited by oceanview; 10-24-04 at 02:35 AM.
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Old 10-23-04, 05:56 PM
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You can get a better grade grills for there or tune them. Bend each bar just a little.

ED
 
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Old 10-24-04, 02:42 AM
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Ed...appreciate the humor...

but really it's a bit concerning.

Question...is the amount (vol) of air blown out equal to the amount being pulled in? It's as if the blower went into a high speed mode.

Regarding the Trane XE80...are there separate blowers for pulling and pushing? Looking at the insides I've got a big blower motor at the bottom and a smaller turbine looking one above the burners. But no whining or suealing noises are being emitted from either motors.

Thanks for the help...
 

Last edited by oceanview; 10-24-04 at 03:21 AM.
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Old 10-24-04, 09:58 AM
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Hello: Ocean View

Based on the sizes of the intake returns, they could be to small for the air volume the blower is capable of handling. Regardless of fan speed, etc. Which may indicate, all other known factors considered and in working order, intakes may need to be enlarged with replacements.

To answer your question, yes. Air volume in equals air volume out. Unless some other factors come into play, etc. But for the purposes of home heating under atandard conditions, the volumes are the same.

Primary small one is the one upstairs. If that one where to be size increased, more than likely and effectively, the intake air noise would be gone. Air intake must equal air return.

Motor noise not a contributing factor. No forced air heater I am aware of or have ever encountered for residentail home heating, has or had more than one fan blower motor. Fan speeds can be selected on some models or come with automatically controlled multiple speed fan motors. Doubt that unit has a dual fan system or an auto multiple speed fan motor. Not likely.

Increasing intake air return seems like the only long term solution. Larger sized intake air returns are available at heating parts supply retail stores. Purchase one, install it and problems resolved.

Installations do require some sheetrock or other wall finished surface material be removed to install the replacement. Each intake register uses a flange which is used to attach it to the vertical wall beems.

Larger opening cutting required. Done professionally or with much care, not much wall damage done, if any. Makes patching easier... hopefully...

About all the information I can offer, think of and or provide on the issue. Good Luck
 
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Old 10-24-04, 10:11 AM
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Not humor----- have had to rework grills to get it out of them It resonates.
Also like I said check and see if you cant get a better grill there than the cheap one they put in.

ED
 
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Old 10-24-04, 08:25 PM
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Thank you everyone....

The consensus points to the return grilles as being the issue. Add in a 4 & 7 yr old and lots of scattered toys; it's possible they may have altered the fins.

ShapAdv...yes...the return upstairs is the smallest....all others are in the 8 x 32 range as follows; 2 on main floor; 1 in basement & 1 upstairs. That's all I can find.

I will be trying the following; changing the grilles first and finally adding one of those dust/pollen filter screens.

Curious; will the dust/pollen screen impeed the air flow enough to cause blower motor problems?

Thank you all, for you comments and time; I appreciate it greatly.

later...
 

Last edited by oceanview; 10-25-04 at 08:18 AM.
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Old 10-24-04, 09:04 PM
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Yes and no. Some furnaces do work well with those types of air filters. While others do no. Much too restrictive for some. Which causes a reduced air so much so some furnaces can and or do shut off on high limit to avoid overheating firebox. Other furnaces work fine with them.

Another noted problem found is the fan may turn on again shortly after turning off intially. That fan on off cycle may happen once twice or thre or more times after initally turning off. Short cycles on and off getting shorted each cycle.

Doing so to remove residual left in heat caused by, you guessed it, restricted air flow caused by overly restrictive filter.

Positive notes.
May reduce intake noise.
They do filter better.

Time for you to begin changing out the intakes. Once done note the better results and post back the update to this thread. Be interesting to note the work involved and difference made in reduced or no noise at all....
 
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Old 10-28-04, 09:52 AM
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If your going to change filters .Get a pleated kind but dont go over a MERV 5.


ED
 
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