Date:         Fri, 08 Sep 1995 21:31:37 -0600
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         Dieter Dworkin Muller <dworkin@village.org>
Subject:      empirical data on heating a bus


Here are some observations I made while driving home just now.  The
Gerbil is a '66 camper, with no pop-top.  The side windows are hinged
at the top, and stay closed mostly through gravity (the casement-style
opening mechanisms are partly stripped from overtightening).  The
stock heating system is permanently and fully on, to assist in engine
cooling (i.e., the heater box flaps are tied in the open position).
The implication of the window situation is that this is most
definitely *not* an air-tight bus.

- with all windows closed and the fresh air vent between driver and
  passenger open, there is no detectable airflow out of the heater
  vent.  The metal around the vent is at the ambient temperature.
- if the fresh air vent is closed, a small amount of air flows out of
  the heater vent.  It's enough to start warming the metal, but not
  the windshield.
- if the driver side sliding window is opened to the first notch, a
  large amount of air starts coming out of the heater vent.
- opening the fresh air vent in addition to the side window cuts the
  heated air volume by about half.

I ended up driving most of the way home with the fresh air vent
closed, and the driver side window open to the first notch.  Most of
the windshield got warm to the touch (except for the corner diagonally
opposite the heater vent).  The ambient temperature in the front seat
area was noticeably higher than just behind the bench area (i.e., if I
put my arm over the back of the seat, the air felt cooler).  The air
flowing through the driver side window was definitely warmer than the
outside ambient air, as measured by holding my hand up to the opening,
and then outside the opening.  Driving wind probably had something to
do with it, but it definitely felt like some warm air was escaping,
rather than cold air coming in.

As a conclusion, I'd say that opening one of the rear side windows
would be the best bet, as that would allow warm to enter the cab, and
not be exhausted until it had circulated throughout the passenger
compartment.

I hope this is useful data for someone....

	Dworkin