My coach doesn't put out an impressive amount of heat through the chassis system -- the under-dash radiator seems smallish, and the 40' hose/pipe run (with not-very-large hose) from the engine has some heat loss as well. It only seems adequate down to about 30-40 degrees ambient temperature while going over the road.
When the A/H system is activated, the number of radiators actively supplying heat can overcome the heat-loss through the coach body. The heat is transferred from the engine cooling system (with some efficiency losses) but with 180 degree water passing through the heat-transfer coils of the A/H, it is usually adequate to supply interior heat without the burner running.Â
You can ensure that the burner doesn't come on by switching off the "hydronic heat" switch on the dashboard. (This may be the key piece of information you need.) This switch doesn't seem to stop the pumps from operating.
However, even if the burner is operating in very cold conditions, it really doesn't use all that much fuel. It's rated at about 1/4 gallon per hour of operation -- but the burner actually may only operate 20 or 30 minutes of every hour, so that's less than a pint per hour. (When parked, I've had the A/H on for days... and I couldn't tell, from the MPG figures I track, that any significant amount of fuel had been used. The generator is -much- more noticeable.
If the over-the-road heat isn't sufficient (in really cold conditions), then start your generator and run some of the electric heat, too. That will use extra diesel for sure, but the alternative of freezing to death is better avoided.
Be sure you've checked the seals and caulking around vents, etc. in your coach. You might also be losing heat through the AC units (they're far from perfectly sealed). You may be able to cover the AC openings with foam, somehow. (I haven't done this-- at least not yet.) It's not so much the amount of heat coming in being inadequate, but the amount of heat being lost. If you travel in cold weather frequently, you may want to figure out how to better seal or insulate the vents and windows. (Some newer RVs have dual pane glass -- but that's a pretty expensive upgrade.)
I note, too, that my basement compartment door weather stripping was quite worn. (I noticed an intrusion of exhaust soot past the adjacent compartment door when I was having a problem with my generator.) I replaced the weather seal on all the compartment doors. Keeping the cold air out (as much as possible) benefits keeping the coach interior warm. The many holes between the interior and the basement _should_ be well sealed, but even so, heat is lost through the floor to the colder basement below.
Note: I've driven in temperatures as low as 17 degrees, as recently as last December in Colorado, NM, and AZ.
Since I only have a '95 and haven't driven/ridden in an earlier 'bird with the Primus, I can't say if it's more or less efficient.
Pete Masterson
'95 Blue Bird Wanderlodge WBDA 42
El Sobrante CA
"aeonix1@mac.com"
On Feb 19, 2008, at 8:25 AM, martingregg598 wrote:
Do 95-97 wanderlodges with A/H stay warmer while driving down the roadÂ
with the ambient temp below 25 deg. than 93 or 94's with Primis. Do theÂ
93-94's run engine coolant throughout the hydronic house system? In myÂ
95 BMC 37 I have to run the A/H (consuming $ 3.00 plus a gallon diesel)Â
and the dash heat to keep it in the 60's when it's 20 deg or less and IÂ
am driving down the highway.Â
Marty Gregg
95 BMC 37
Kennewick WA.