Today I changed out the front (and only) air return register for the furnace on our 99' U270. It required a bit of modification of both the Oak register that we bought online and of the opening, but I believe it was worth it. I gives a larger air intake as well as a removable filter. The grill swings out for changing. Bonus feature is that it makes the whole furnace area much more accessible from the inside of the coach. It came with a relatively crude but washable filter screen, but I found a source on line of ready made filters of various grades. The area under the furnace was incredibly filthy with an accumulation of dust and dirt. I plan on getting the higher rated (as in finer filtration) after I clean the ducts. The main reason I did the swap was just because the metal grate looked tacky as I have been busy doing the rear half of the coaches' trim for the new bamboo floor. Pics attached. If anybody would like more details, just let me know and I will post more details such as a link to where we bought the register etc.
Don
Don, Be careful that you do not restrict the air flow to the furnace. Some filters are real good but can really restrict flow. At least you have a filter, my 280 furnaces are such that you can't filter the air.
Gary B
Don,
Atwood furnace manual specifically says NOT to use a filter in the return air duct. The blower apparently doesn't have enough reserve capacity to handle a filter, and heating efficiency of the furnace will be impaired. My guess is that with lower air flow than design spec, it will be hitting the high limit temp switch and cycling on and off a lot.
I had the same reaction that you did when I saw the dust build up in the furnace area, but apparently can't be helped with this furnace. Atwood suggests using a separate (freestanding) air filter.
Low air flow because of an air return restriction will (or should) cause the SAIL SWITCH to remain open so the furnace (propane valve open and igniter spark) will not come on.
I see no problem with an air filter IF PROPERLY DESIGNED AND CLEANED. The key here is to have more surface area to offset the restriction in the filter AND to keep the filter clean. I suspect the lack of cleaning by most RV'ers is the reason for the recommendation against the filter by Atwood.
Dave,
The filter part of this grill is optional and I can leave it out all together if necessary. Plus, the opening now has more than twice the square inches than it did originally. A bit of research turns up some info of the various filter ratings and when I replace the one it came with which has virtually no restriction (about all it would filter out is dust bunnies). Certainly something to be aware of though... Anyway, as I mentioned in my post, the main reason to replace the register is aesthetic. I also replaced that ven under the shower with an oak grill as well. It goes with the bamboo floor nicely!
Don
That was my supposition and why I chose the largest air return that would fit in the space below the fridge... Besides, I just think it looks better that way:). I plan to use a filter with very low restriction and check it often.
Don
Filter or not, your new grill looks great, and the local decoration department is asking engineering where you got it? (suspect one is in our future too...)
We got the grill from Signature Hardware. They have a variety of sizes and styles available. Here is a link Whittington Wooden Filter Wall Grille | Signature Hardware (http://www.signaturehardware.com/product8279) to the one we got. I cut the outer frame down by about a half inch all the way around because I felt it matched the rest of the woodwork better. In other words, I cut off two of the flutes leaving just the rounded edge of the first, which resulted in about a 5/8" flange. I secured it to the vertical stiles from the inside of the frame with two screws on each side. It was necessary to make it fit the opening fairly snug in order not to deform the frame when screwing it in. It could also have been just glued in with some liquid nails or such. I had to add a 2" x 12" x 3/4" piece of oak on either side to make the frame flush all of the way around. Using one of the smaller grills would allow you to skip a few steps by just enlarging the opening.
I hope that helps...
Edit: I just looked at Signature Hardwares page on that grill and it now appears to be a closeout item (it says 3 left!), so if your interested... I did find that similar items (of which there are not apparently many) from other sources to be quite a bit more expensive. If you don't want or care about the filter, there are more options. I wanted the grill to be hinged for access for cleaning etc. more than I wanted it for the filter...
Don
Thanks Don,
Just ordered one! Great idea!
Your'e welcome! I think you will find the build qulity on the grill to be adequate, maybe outstanding considering the price. When I think about how long it would take me to make it, a bargain!
Don