Sorry, typo, above I meant to say radiator heaters are "safe and silent."

Thanks ky114. I appreciate your response to my problem. I have one of those electric radiators already, but only use it in my sun room because there are no heat ducts out there and it works fine there. However, even if I solve the problem during the winter, I still will have the noise during the air conditioning season to contend with. As costly as it may be, I still sort of lean toward moving it outside. If I build an insulated shed on the side of my home to house the furnace and A coil and ran the ducts under the home with as much insulation as possible, it might possibly work. (I would only need to run it about 10 feet under the house to tie in with the existing ductwork. You are right, it would be costly, but maybe I can do some of the work myself if I can get some help from an HVAC engineer in my area. No matter what the cost, it would make my wife happy. lol

Yes, if you use the existing furnace and do some of the work yourself, it would not have to be that costly. I was thinking of the cost of an entirely new furnace. Before starting on this project, it might be worth a few bucks to have a good, local HVAC company take a look at the system to see if there is anything else that could be done. For example, increasing the size of ductwork can reduce noise. Also, I'm wondering if the return air vent could be moved, since you are probably picking up most of your noise through that. (I'm guessing that the return air vent is on the wall behind the TV, and that's probably the only return air vent you have -- is that right?) If you could move that, you could then seal up the wall separating the living room from the furnace, cutting the noise. You would then use ductwork to relocate the return air vent to a different location, or possibly install two, which would make the system work better and also make it quieter.

Yup, the only return air vent is actually in the louvered door on the front of the closet that the furnace is in. Being a manufactured home, the heat ducts are inside the "belly" of the home and are covered with insulation. I have to assume that replacing them on a home this big would be quite a job, and possibly one that nobody around here would want. Changing the way that the return air gets to the furnace might be the answer or at least part of the answer. I am going to take your advice and try to find an HVAC person experienced in manufactured homes and have him take a look at the system. If I find an answer I will be the most popular guy around here. I will post my solution if I find one. Thanks again.

If the noise is as bad as you claim, it makes me wonder if it's a vibration of the cabinet rather than the fan making the noise. If you can open the door while it's running (probably have to hold the door switch in) try pressing on different areas of any metal in the furnace to see if the noise changes. If it does then it's just a matter of finding something metal to wedge in an area that helps cut down on the vibration. Normally the loosest part is the metal door itself.

I have encounted this problem with Miller HVAC units before as well as some Gibson and Tempstars.

The HVAC cabinet usually vibrates due to the fan motor. Possible solutions are,

1. Does the unit "suck" the closet door closed when it kicks on. Like if you open it about two inches does it suck it shut? IF so, enlarge the return air vent. This will make a unit louder than it needs to be because it is restricting air flow making the unit work harder.

2. Acid clean the coils (spray foam available at most bigger home improvement stores. Also, pull the squirrel cage and clean the dirt off of it. There will be some built up on it possibly throwing the cage off balance. This will lession air noise due to cleaning off dirt that got past your filter that could be obstructing air flow.

3. Replace the rubber gromments holding the motor to the cage if they are dried out. Oil the motor with regular
SAE-30 car oil. About 15 drops per oil hole. (there normally is a metal or plastic plug on each side of the motor on the edge of the casing. A dry motor will make more noise, waste electricity and eventually burn up.

I am always amazed at how many motors get burned up due to not being oiled on a regular basis.. Only need oiled one to two times a year.

4. Re-Tighten the squirrel cage to cabinet mounting screws. They loosen with vibration and eventually start to hum real loud.

If all else fails, and it is completely driving you insane, consider having a secondary return duct ran. It is simple if your unit is a downdraft split unit, It involves putting in a floor mounted return filter grill ( which means cutting a hole in the floor, running a flex duct back to the air handler closet..) Not too hard nor too expensive if you do it yourself. Expect to pay a HVAC tech about $250-$300 or more to do this. Some may be cheaper, but very unlikely.

If you are lucky, the rear side of the closet may face another room.. If so, relocate the return air to that side and close off the vent in the other side. Just cut a hole in the wall carefully, install a return filter grill like you will find at the hardware store and then go close off the other side. Having secondary filtration always helps in the long run.

James