| Author | Message | ||
| John Biundo (Jbiundo) (64.175.36.81)
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The installation manual for a Coleman basement air specifies a minimum free area inside the supply duct of 48 square inches. They don't say whether this is the total area across all branches of the supply (for example if I bring a main supply up the center of the bus, and divide into front and rear branches), or that each branch should be this size. I suspect the former, but would appreciate any input from those with some experience. I've tried contacting their tech support to no avail. Thanks again for the help. John | ||
| Jayjay (65.134.221.184) Rating: N/A |
48 sq. in. is the dimension of the discharge side of the main blower. Make this larger if possible, but probably no more than 25%. This will slow and "quieten" the air flow noise. Don't put your return air grills directly over top of the unit as this becomes a path for fan noise to intrude into the coach. The above not withstanding, you will find it a very quiet unit. I used 1/2" thick, closed cell foam rubber mat (sleeping bag ground cloth-WalMart) underneath mine for vibration isolation. I've been experimenting and find that is seems to be slightly more efficient with the return air closed off. (It is designed to work without a return air) I leave a small gap open on my windows,and with filtered air flowing thru, my coach now stays much cleaner than before. I think the thermostat is a piece of junk, but due to the design parameters, I think we are stuck with them. E-mail me for more or for my phone number. Cheers...JJ | ||
| Tom Hamrick (Tomhamrick) (167.83.101.23)
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JJ, Can you be more specific about closing off the return air? Do you redirect it to draw air from the bay? If return air is closed, how do you have filtered air? Thanks for the info. Tom Hamrick Eagle 10S | ||
| John Biundo (Jbiundo) (64.175.36.81)
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Hi JJ, Your profile doesn't seem to have your e-mail address enabled (i.e., I can't send e-mail to you by clicking on your name in the header of your post). I'd like to ask you a few more questions. Can you either post your e-mail address, modify your profile, or e-mail me off-line please? Thanks, John | ||
| Jayjay (65.134.221.68)
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RV Products Literature states that the unit may be satisfactorily operated without a return air. When I did my conversion I used home floor grills in exactly the same place as GM's return air's were. I just flip the grill to open or closed `ala my house ducting. BTW my unit sits crosswise the body,in place of the original AC evaporator/heat radiator, and I had to move the batteries back in to the first bay. Snug, but everything fits. I converted it to a top discharge, and modified the old distribution manifold to accept the upward air flow and shoot is toward both sides and into the original ducting. I have a filter on both intakes of the unit. (Mines a heat pump so two filters)Any air that enters the compartment, OR the heatpump, has been filtered. Sorry about the email mixup. emjjr@outdrs.net Cheers...JJ | ||
| R.C.Bishop (128.123.88.31)
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Hey, guys, if possible, keep it in the thread..a bunch of us out here are interested in this. Thanx.  RCB | ||
| John Biundo (Jbiundo) (64.175.36.81)
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OK - I'm glad others are interested! I've got a little better picture of JJ's installation now, but I'm still not sure about the ducting size. I *think* I want to run ducting from the blower up through a wall and into the ceiling (not using the original bus ducting, which is sitting in my trash pile right now ;-) So - I think the recommendation is to oversize the main trunk from the blower (to make sure I've got my terminology straight: is the blower the same thing as the "discharge"? and the same thing as the "supply"?) up to about 25% (so, in this case, using a cross sectional area of up to say 60 square inches). But I'll have to (or want to) reduce this size going up through the wall, and then will divide the main trunk into two (or more) ducts going fore and aft from the main trunk. What size should these branch ducts be? Since ceiling space is at a premium, I'd like to keep the height dimension fairly small. So, if the cross sectional area requirement can be divided across, say, the two smaller fore and aft branch ducts, making them say 24 square inches, maybe I'd go with something like 8" wide x 3" high. Does this make sense? My other questions pertain to the ducting material. Did you use ductboard? If so, how thick is it? Where might I get instructions for forming ducts from it? Did you need to add any extra insulation? Thanks again for the info. John | ||
| Jayjay (65.134.220.141) Rating: N/A |
Hey John, the answers is "yes" to everthing down to duct material.I'm afraid you'll have to ask someone about ductboard. Where physical damage is not an issue I used 1/2" & 3/4" rigid foam building insulaton ( pink stuff from Home Depot @ $8.50 per 4'X8' sheet) Cut with a razor knife and use high quality cualk to glue it together. Tougher than you will imagine. (Build a piece and then try to bust it up- you'll be amazed!) The master craftsman Jack Conrad, did that same thing in his MCI, and made some beautiful 2" deep 6" or 8" wide flat ducts between the ribs of his ceiling. You may want to seek more competent help with this, since I'm an electrician, and seem to be staggering around with this air-flow thing. Mine works quite well, but perhaps it could be better. I'm almost afraid to mess with it now, (too lazy ?) Just remember that larger ducts mean less air velocity and volume, but lower 'noise'.BTW , thinking back I used two pieces of the foam rubber under the heatpump, and made a naugahyde "boot" between the pump and the first piece of rigid duct. Doesn't intrude on the Bach or my slumber. HTH Cheers...JJ | ||
| Jack Conrad (Jackconrad) (207.30.189.224)
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The duct dimensions are inside measurements. If the duct material is 1" thick, this adds 2" to the height and width. I did not have enough room to do this. I purchased a material call UltraDuct from Innovative Energy Systems in Lowell, Indiana. This material is approx 3/16" thick. It is made of a 1/8" layer of high density closed cell foam with a layer of heavy aluminum foil bonded to each side. It is sold in 4'x8' sheets. You cut to size, crease, fold, and tape the joint with aluminum tape. This company manufactures most of the ducts for the major RV manufacturers in the Elkhart area. Althought the 4'x8' sheets cannot be shipped via UPS, They will cut them to a smaller size so they are UPS shippable. 4'x8' by truck is MUCH more expensive. My supply duct is 16" wide by 3" tall(48 sq. in.). The return is 18" wide by 3" deep (54 sq. in.). We recently used ours in south FL, parked in sun with outside temps in low 90's. AC maintained 78 (thermostat setting) without running nonstop. Jack | ||
| Jack Conrad (Jackconrad) (207.30.189.224)
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Forgot to add, all my supply duct is 48 sq. in. I can control output by adjusting the individual 8"x8" house type discharge grills that we used. | ||
| John Biundo (Jbiundo) (172.142.15.212)
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JJ and Jack, Thanks for the advice. Jack - so if I understand correctly, you made both the main trunk and the branches 16x3 i.d.? That will probably work OK for me, especially if I use thin-walled stuff like the UltraDuct. As I said, I'm interested in saving space, hence the question about branch duct size. But I'm also a bit concerned about airflow... if I keep all branches (say I have a fore and aft branch from a midship main trunk) the same size, I'm wondering if my airflow will be too low at the end of the branches? Anyway, just thinking out loud at this point, but interested in any more comments from those who've installed ducted basement air. Thanks again, john |