CFM... Air Flow Question for 35,000 BTU Heater

[karldavidson]

I just purchased a 31' fifth wheel. It is a Crusader manufactured by Prime Time. The heater is located mid-trailer with ducts in the floor. The air coming out of the registers is virtually non-existent. There is one register in the wall, near the heater, where the air flow can be felt.

What should the CFM be for a 35,000 heater, has anyone had the same problem? Is there an accurate way to measure the CFM?

My wife and I are freezing. I'd like some input before taking it back to the dealer. I'm afraid they will say that is normal air flow. No way.


Thanks,
Karl Davidson
Huntsville, Texas

[C_Schomer]

Btuh = 1.08cfm x dt is the formula but it's not much good w/o accurate measurements and knowing the net btus of the furnace. I just took apart every inch of my heating system and taped, stapled, screwed, caulked and reclamped all of it and what an improvement. I can feel warm air several feet away now. My heated basement is actually a return air plenum - the return air passing thru the basement to get to the furnace. My typical access doors had shrunk up gaskets so cold outside air was being sucked in. An rv furnace isn't nearly big enough to heat all that! I also sealed all the plumbing/electric penetrations between the basement and under belly. Sucking OSA into the under belly is also counter productive to keeping the tanks warm. Seal everything! Craig

[todouble]

I have a 14' crusader and my heat pumps from the floor ducts. I have the same 35k btu furnace. Sounds like your supply plenum popped of the furnace or some ducts came loose and are blowing in the voids of the floor. At least your tanks won't freeze!

[ScottG]

I have that furnace in my TT and it puts out a lot of air flow.

[Old-Biscuit]

Rv furnace discharge plenum has openings where flexible duct work is connected. The flexible duct work is then run to the various registers and connected.

They can fall off at either end
The duct work can be kinked
The duct work can be mashed


CFM for a 35000 BTU furnace is typically 375

Also obstructions on return air side of furnace can reduce air flow

[MFL]

I have about same size FW, with 35,000 furnace. Mine has 3 ducts coming from the cabinets, as well as floor vents. I can feel the warm air blow out from several feet away, even from the side vents.

Are you sure your fan is running? You may have a vent disconnected, causing loss of air pressure.

Jerry

[rhagfo]

Likely a poor connection between the Furnace and the duct work!!
When I pulled mine out to check and fix the igniter, there was a large void between the floor and the duct work. I sealed it up and flow is much better now.