Quieting a loud ceiling air return.

woobagooba

Hello all. I recently replaced a failed AC unit with a cold climate heat pump. Old AC had the filter co-located with the air handler and was relatively quiet at the central ceiling return. New unit, with the filter now colocated at the return grill, is substantially louder. The return is hard ducted with no opportunity for flex. Do I have any options to get the noise down? The system is whisper quiet when the return filter is removed. Seems most of the noise is from air trying to get around the edges of the filter? Seal the filter edges? Different filter tech? Cheers

mattmia2

Move the filter to the air handler?

ChrisJ

What size is the return filter?

What size is this system?

A properly sized filter shouldn't be that restrictive when clean.

pecmsg

The new unit IS moving more air. Have the installing contractor check the static pressure. TESP and find out is it the supply, return, filter face area or a combination of all. 

HVACNUT

Is it a new or existing return grill? 
Is the return box and filter frame square? (Not square shape, 90° angles).
Is there a MERV rating on the filter? Pleated? Even a MERV 8 will be restrictive in a one inch filter. Any room at the air handler for a 4 or 5 inch filter cabinet? 

EBEBRATT-Ed

Sounds like the filter is too small and too restrictive. The velocity at the filter must be kept low or the dirt and dust will pass through.

Your ac guy should have known this. Install a proper sized filter rack at the ahu

woobagooba

AHU is a Bosch BVA-36WN1-M20 installed in a very tight spot over a laundry room in an apartment building (drop ceiling underneath the AHU, next floor structure just above).

IIRC the AHU was longer than the prior AC AHU which made filter box placement at AHU very difficult, also difficult for filter changes. So now the filter is at the return ceiling grill. I should have taken a photo of the filter, but I estimate it is 20x20x1" with unknown MERV rating. Maybe try a filter like this instead? ... https://www.supplyhouse.com/Honeywell-Home-FC40R1003-20-x-20-Return-Grill-Media-Air-Filter

clammy

What type of return grill ? Most decent hvac contractors will use a wide bar style return filter grill of course there about more then double the price of a prison license plate stamped return filter grill but usually always quieter then a stamp faced el cheap grill . Being your units a heat pump have you realized that most heat pump a/h are rated at 450 cfm per ton not 400 . Possibly your contractors has not checked and set fan speed via dip stitches . Also have a ducted return does not help but it could be either replaced w a proper size hard duct or re done using 18 flex say for a 3 ton unit . What size is your existing return grill .I was taught ions ago for a quite return size your return grill for a min of 1 sq ft per ton ,it’s always worked for myself and just about every job I’ve done throughout my career I ve never had a complaint about either return noise or supply whistling . This kinda happens when the person doing the job cares which usually is a rarity being most gave up caring when the customers wanted a bar again price in which case it’s a change out quick and simple . I think the days of installers really caring is in the sunset just about every body cares about one thing get the money lol . With all the apps and tech it’s amazing guys still get it wrong basically it’s all about money in the pocket and great acting and performances .
Peace and good luck clammy

HVACNUT

Can it be framed out larger than 20 x 20? That's pretty tight for a 3 ton drive. Is it 20 x 20 in hard duct back to the air handler? 
What's the depth of the ceiling return box? Post a lot of pics and measurements. A deep 20 x 30 or 24 x 30 would be better.
Is the air handler very close to the return grill? Approximately how long is the return duct between the grill and air handler?

woobagooba

Meeting with the installer tomorrow. I did find these pics of the return filter. I'm going to guess y'all think it and the filter grill assembly are inadequate for the return...




Perhaps something like this filter will be a better alternative to quiet down the return ...

https://www.supplyhouse.com/Honeywell-Home-FC40R1185-18-x-18-Return-Grill-Media-Air-Filter?utm_source=google_ad&utm_medium=Shopping_ntm&utm_campaign=Shopping_NTM_New_users&gclid=Cj0KCQjw_5unBhCMARIsACZyzS2rNaLxc9xxa8xFmnZQhvOmF8WW_PcRoOj7mD3OJd6IzlPtH98-6dwaAmspEALw_wcB
.

woobagooba

Problem solved. Installation of the Honeywell FC40R1185 media filter has the return noise down to an acceptable level. Thanks for all your advice.

HVACNUT

That's basically a 20x20x1 glued to an 18x18x2 I guess. Prevents whistling around the edges.

Teemok

Egg crate grill that thing. I see so many 4 ton systems running with way less than 3 tons of air movement. Variable speed helps prevent call backs and early component death but you just can't move the BTU's if you don't move the air. People are paying for modern HiPo V8 and are getting 70's V6 performance. The equipment needs to closely match the whole duct system. Rant over.

ChrisJ

Teemok said:

Egg crate grill that thing. I see so many 4 ton systems running with way less than 3 tons of air movement. Variable speed helps prevent call backs and early component death but you just can't move the BTU's if you don't move the air. People are paying for modern HiPo V8 and are getting 70's V6 performance. The equipment needs to closely match the whole duct system. Rant over.

You mean paying for turbo 4 cyl and getting late 1970s V8 performance....

Teemok

I suppose that works as well. I meant like paying for 412HP 26mpg mustang gt and getting pacer v6 performance.

tim smith

? is now, do you have enough airflow to support the tonnage. That filter is going to reduce your airflow some. Need to verify.