Furnace

[Socal-Paul]

Our furnace operates normally but after a period of time starts to sound like a prop airplane taking off. The air flow doesn't appear to change it just sounds terrible. I opened the access, the furnace itself seems securely fastened but did notice some wiring laying on top of it and there were areas where it felt like the furnace sides might vibrate against itself. Took some duct tape in two spots just to bring the areas tighter together and secured the wiring which change the noise to a deeper base.

It's obvious that I'm going to need to investigate further when we get home and that duct tape isn't the solution but I'm wondering if anyone has run across this problem. I've been doing this for a lot of years and never heard of anything like this. Not looking forward to doing the crawl thing through the pass through, to make matters worse looking at the screws outside holding the furnace in place and it looks like they are all stripped. Suggestions as to cause and fix? Thank You

 

[RoadJunkie]

It sure sounds like something is rubbing on the blower wheel (fan). I think you're on the right track.

 

[George]

I had 12vdc wiring tucked into the squirrel cage. Check on the left side of the furnace from outside the coach.

 

[Socal-Paul]

Today a serious start to find the source of my Suburban SF-35 VHQ furnace noise. I removed the side walls in the pass through and discovered the furnace has the minimum 4 ducts as required by the installation instructions. Problem is one of the ducts is shoved into the under belly space which has no air return which according to the instructions is not acceptable and won't count against the minimum 4 ducts. The new problem is going to find a way to add another 4" into the living area.

Our 23ML has single vents in the bath and bedroom while the main living area also has one at the far end (20' from the furnace) which is weak so I would love to add one in this space close to the furnace. Might be easier to put in a SF-30VHQ which requires minimum of 3 ducts.

While out recently I noticed the pass through was very warm (more so than the living space) plus appeared to be pressurized when the door was opened. I'm thinking that the back pressure may have caused the blower to vibrate causing the noise.

I also noticed that the furnace is mounted to plywood but the rear of the plywood is not secured to the floor which allows it to bounce over every bump.

As always ideas and comments appreciated!