Why Is My Mobile Home Furnace So Loud?


Mobile home furnaces are inherently loud because of the close proximity and openness of the furnace to the living area. Most mobile home cold air returns are virtually non existent. Not enough return air ducting is the main problem with mobile home furnace noise.

This photo shows the furnace without the door and the panel or piece of 1/4 inch plywood that is placed over the furnace compartment to force all the return air through the filter.

You can fix a loud mobile home furnace with a larger filter relocated above the furnace and a door over the furnace cavity. The door is very simple. Buy a sheet of nice looking quarter inch plywood and cut it slightly larger than the furnace cavity.

I’ve done some research and have been in a lot of mobile homes. These mobile home heating systems are almost all noisy enough to effect your TV volume.

When is a mobile home furnace too loud? When you have to turn the volume up when the furnace cycles on and turn the volume down when the noisy thing goes off. Or maybe you just want to quiet things down.

Above is a mobile home furnace with doors and filters grill removed. Even with the furnace doors on there is nothing to block the noise from the furnace.

Cut the plywood to completely cover the furnace opening and fasten it to cover the opening. Keep in mind that it should make a good seal to keep dust and pet hair from seeping in through the cracks.

These filter grilles are available on Amazon. I could only find them to fit a one inch thick filter. You can make up the problem of having one of those flimsy one inch filters by purchasing a thicker filter made to fit into the one inch frame.

Both Honeywell and Practical Pleat make an excellent filter to give you somewhere around a years worth of filtering.

By installing a filter grill just above the furnace taking advantage of the void above the furnace together with the cover over the front of the furnace will create a chamber that will help reduce the noise.

Keep the filters as large as possible to allow for the best air flow and longer service.

Sometimes it’s easy to get the return grill even further away from the furnace for even quieter operation. Remember it has to seal completely clear around the door. This includes the bottom of the door. This door is easy to remove with sheet rock screws. If your are a craftsman, build a nicer door.

If the seal is not good, it won’t take long and you will notice the dust collecting around the door. Use a thin bead of white or clear caulk and paint the door to match the surrounding wall.

These filter grills come in sizes that will hold a 2 inch thick or more pleated filter. Common sizes that work best are 20 X 20 or 20 X 25. Keeping the size common makes it easier to find replacement filters.

Let me show you how to do this and about how much it should cost.

Remember that any work you do to change the air flow or alter the duct system should be checked by a qualified technician to insure no damage to your heating and cooling system will occur.

From the factory, mobile homes, come with the poorest air filter system. In fact, most all furnaces come with a little slot to slide in a little one inch filter relative to the depth and width of the furnace. It’s just never good enough.

Furnace manufactures place those filter slots in their equipment because installers take the cheap way out by not adding sufficient filtering. This includes mobile home manufactures.

Most of the time when you remove these filters they lose a certain amount of dirt down onto the fan that then gets blown into the duct work. After several filter changes that little bit of dirt makes for some very dirty duct work.

And some filters are crammed into the furnace door. Another poor solution for home air filtering.

Using this better filter system keeps the dirt in the filter and then in the garbage where it belongs plus improving the air quality and the noise.

And, no, you don’t have to buy a new furnace. You can make even an old relic sound so much quieter. It may even be a great little DYI project.

You’ll be much happier when you that can leave the TV volume at one level.

My last customer that I did this for took the job and ran with it. Did an excellent job. And he left me a great review on Google.

Specifically this applies to electric furnaces, with or without cooling units or heat pumps, and in only certain types of furnace closets.

The furnace closet should be for just the furnace with no other appliances, but can be done if the electric water heater is in the same space.

If your furnace cavity contains a washer and dryer then the project gets a little more difficult, but it can be done. Once you understand the principle of encasing the furnace you can figure a way to get it done.

If your mobile home has a fossil fuel burning unit, which means natural gas, propane or oil, certain issues with combustion air enter in and it could be hazardous to use this method of making your mobile home furnace quieter. Consult a professional before enclosing.

Fossil fuel furnace that have a two pipe or concentric venting system will qualify for this solution. You can google the model number of your furnace to determine the type of venting.

A two pipe is generally vented in PVC pipe. One is outside air into the combustion chamber and the other is venting the products of combustion.

For your safety I’d consult someone familiar with combustion venting to see if my new filter method applies.

Along with the inherent noise in these furnace installations you should first determine if the noise is something other than normal fan and air movement through the system.

Two types of blower systems exist. The direct drive blower has a blower wheel mounded directly on the motor shaft and the motor is mounted on the side of the blower housing.

The belt drive blower motor is mounted on top of the blower and the blower belt connects the drive pulley to the driven pulley mounted on a shaft with two bearings holding the blower wheel.

A fan wheel rubbing on the fan housing will cause quite a racket. If your fan motor has a bad bearing it sometimes comes with some vibration and a noise.

Another very obvious source of noise and rubbing noise could be the fan motor bracket. Again, easily checked by turning off the breakers and carefully reaching in the opposite side of the motor and wiggling the motor shaft. Using a flashlight at the same time looking at the motor and visually looking a the bracket.

Use caution reaching in to tight places. Not long ago I reached into a blower motor to check to see how hot it was and slowly removed my hand. Without even so much as a ounce of pain I had cut open my hand to the tune of 9 stitches. There is some sharp edges inside these units.

Many home owners ask what a furnace blower bearing replacement costs. Even if you could find a motor repair shop that would repair fractional horse power motors the cost would be very close to that of a new motor.

Then consider after you pay for the new bearings you still have winding’s and wiring of an old motor that could short and burn.

Changing the fan to a lower speed is possible. Much more so with just an electric furnace. A heat pump requires so much air through the indoor coil and should be on high speed. Not enough air flow could be detrimental to the compressor.

Most fan motors have 3 or 4 speeds. An electric furnace without a heat pump attached can run on the lowest speed. A good service technician can determine this for you. It’s well worth a service call to make sure if you have any doubts.

Another noise created by these poor duct systems is the vent that is closest to the furnace.

It’s not advisable to block air flow in heat pump applications. But one vent, especially that one vent right near the furnace has never created an issue in my experience.

The air from these vents located next to the furnace does very little to influence the room temperature because it short cycles right back into the return.

Pull the vent out and cut a piece of cardboard to fit the bottom and tape it on. The better seal you make the more noise reduction you will notice.

Conclusion

It’s a shame that the mobile home industry won’t add simple ideas to create less noise pollution and better filtering. It’s a tightly budgeted segment of housing and does provide an inexpensive way to own a home, but I can’t help but think some ideas could be offered as options.

The filters available for the slot in a the furnaces that come in any home are totally insufficient. They only lead to more maintenance or more repairs without maintenance.

If your asking yourself how to replace a mobile home filter, consider replacing the type of filter and the location to help reduce the noise and increase the filtering capability of the forced air system.

Chad Peterson

Chad Peterson is near 40 year veteran of the HVAC industry. "I like to explain heating and air conditioning problems in a way the average home owner can understand. "

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