Date: Mon, 26 Apr 1999 19:38:55 -0400
Reply-To: Bulley <gmbulley@BULLEY-HEWLETT.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Bulley <gmbulley@BULLEY-HEWLETT.COM>
Subject: Re: why pre-heat, explained was: Refrigerator Problems
Roy-
I dunno. I'm sure a thermodynamic guy could help us on that, but I'm not
sure we have one on the list. My fridge lights up without pre-heating,
winter or summer, by simply pushing in the gas button, pumping the air pump
a few times, igniting, then puffing a bit more air for about half a minute.
If yours is tough to start, it may be time for an overhaul?
G. Matthew Bulley
Bulley-Hewlett & Associates
www.bulley-hewlett.com
Cary, NC USA
888.468.4880 tollfree
-----Original Message-----
From: Roy O. [SMTP:keepsake@PANGEA.CA]
Sent: Monday, April 26, 1999 3:26 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: why pre-heat, explained was: Refrigerator Problems
Mr. Bulley,
What you say makes sense to me (almost). Please further expand on your
hypothesis and explain why my fridge (and probably many others') is
difficult to
start when the interior of the van is in excess of 40 degrees Celsius, as
is can
be when parked in the sun during the summer. Everything in the van, incl
uding
the exhaust tube, ambient air, etc. is very warm (might I say hot?) then.
Roy O.
'87 Westfalia
(till death us do part)
----- Original Message -----
From: Bulley <gmbulley@BULLEY-HEWLETT.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Monday, April 26, 1999 11:23 AM
Subject: why pre-heat, explained was: Refrigerator Problems
| The reason that "pre-heating" the refrigerator on 120 or 12v helps get
the
| propane cycle working is pretty simple. The stainless-steel exhaust tube
| for the refrigerator warms up...
|
| Okay, now you are going, "Huh?"
|
| Some will tell you that you run the electric to "pre-heat the ammonia",
or
| some other mystical part or fluid inside the refrigerator. Poppycock.
|
| The propane burner assembly doesn't care what temperature the ammonia is.
| All it cares about is getting the right mixture of propane and air, and
| being able to exhaust its waste products efficiently to the outside the
| van. That's all that flame wants out of life. When the exhaust pipe is
| cool, it can't exhaust very well, and it chokes.
|
| Think about the density of air for a moment. Hot air rises, right? Of
| course it does.
|
| The exhaust from the propane cycle has a long distance to travel, and
very
| little "motivating it"; only the difference in its density to get it
there.
| The meager exhaust from the tiny little propane flame that you light in
| the bottom of your fridge has a run of about two and a half feet of
| corrugated stainless steel exhaust before it makes its way to the
outside.
|
| When that stainless steel tube is cool, the warm exhaust quickly cools,
| thus becoming denser, and it loses velocity. Soon the flame smothers
itself
| in exhaust. Complicating matters when the pipe is cool, moisture present
| in the exhaust may condense in the cool pipe, and run down into the
burner
| area, extinguishing the flame.
|
| By running the refrigerator either on 12 volts or 120 volts, the entire
| rear area of the refrigerator warms up, thus warming the stainless steel
| exhaust pipe, making the propane cycle much more likely to work from the
| get go.
|
| Instead of running it on electric, I find that by gently pumping the air
| pump, after the flame is lit one can effectively drive the warm exhaust
up
| the cool exhaust pipe, thus eliminating the need for pre-heating the
| refrigerator.
|
| The first few times that you try this, (pumping air into be burning
chamber
| after the flame is let), you may want a try it late in the evening when
you
| can watch the flame through the flame window. At least on ours, the
| additional air will not blow out the flame, however you can tell when the
| flame is beginning to smother, and pump in additional air that point or
| re-light while the burner is still hot.
|
| Party on,
|
| G. Matthew Bulley
| Bulley-Hewlett & Associates
| www.bulley-hewlett.com
| Cary, NC USA
| 888.468.4880 tollfree
|
|
| -----Original Message-----
| From: Bob Stratton [SMTP:rslist@SDII.COM]
| Sent: Monday, April 26, 1999 10:39 AM
| To: vanagon@GERRY.VANAGON.COM
| Subject: Re: Refrigerator Problems
|
| At 08:39 AM 1999-04-25 -0700, Mike Finkbiner wrote:
| >
| >It cools on 110v and 12v, I can see a nice fat spark through the sight
| >glass, but there has never been any flame. I pulled the outer vent
| >cap off and vacuumed it out to clean up any spiders, etc. (After all,
| >who knows what could have moved in while it was in North Carolina)
| >After that I blew compressed air into the drain plug on the front to
| >see if that would clear out blockages.
|
| If you've already tried this, then ignore me, but if it seems to run on
12V
| and 110V and the problem is that it just won't light, you can try this
| technique.
|
| The guys (J&R VW) I bought my Syncro from told me this, and it works like
a
| charm.
|
| Run your refrigerator for about 45minutes on 12V. Driving or stopped,
| doesn't seem to matter, though I'd probably avoid parking on big hills,
| since it really needs a level surface to get going well.
|
| After about 45 mins on 12V, try to start it with propane. Mine usually
| lights up within 3 tries if I ran it on battery first. I have no idea why
| this should work, as I can't see the 12V heating element being hot enough
| to cause ignition, but it does help.
|
|
| --Bob, KE4GDC
| 89 Westy Syncro GL
|
| 
