[Shop-talk] Power-vented water heater kicks out.

[pethier at comcast.net]

----- Original Message -----
> From: "Arvid Jedlicka" <arvidj at visi.com>
> To: pethier at comcast.net
> Cc: "shop talk" <shop-talk at autox.team.net>
> Sent: Friday, September 13, 2013 10:13:58 PM
> Subject: Re: [Shop-talk] Power-vented water heater kicks out.
> Phil,
>
> Doesn't that imply that it runs better when the gas is going the wrong
> way in the vent? By that I mean that if you suck enough air out of the
> house that air comes in the vent ... or at least does not go out as
> fast as it should ... then the pressure in the vent is low enough to
> keep it on.
>
> Or maybe I do not understand what is going on.
>
> Arvid

You do understand what is going on, and it does not make sense.

Pulling a (fantastically-slight) vacuum on the "flame" side of the fan is
supposed to indicate to the sensor that the fan is running. B If the fan
fails, there is no vacuum, the sensor thinks the fan has failed or a bird is
stuck in the pipe and we are all going to die of CO poisoning. B So the
micro-switch on the diaphragm opens and the control system shuts off the power
to the fan circuit and kills the gas flame.

Even though I measured the vacuum at 7/8 inches, which is supposed to be
enough to keep things humming, the old switch was open.

You can't just jumper over the switch. B The control system is too smart for
that. B If the thermostat calls for flame, the control system checks the
diaphragm switch first. B If the switch is closed, the control refuses to
start the flame and flashes a code that tells you the switch is shorted out.
B 
It seemed to work better when the house was closed up and there was an exhaust
fan on.  Counterintuitive, huh?

OK, so with the spec the tech guy gave me on the phone, the switch was bad.
Trouble is, they sent the whole thing.  Sigh.

My wife just drew a bath, and the silly thing was just working WITH THE
WINDOWS OPEN, so I'm going down to see how it's doing.


=====

I'm back.

It's heating, and showing the "heartbeat" (their word) code for normal
heating.  I hope this means that diaphram was stiff from being new and is OK
now.  Knocking furiously on wood.



Phil Ethier West Side Saint Paul Minnesota USA
1973 Triumph Stag LE22439UBW "uncle jack", Sapphire Blue
2004 Suburban 8.1, Sport Red, the only automatic of the bunch
2005 Lotus Elise, Bordeaux Red Pearl
2007 Saturn Ion 3 2.4, Berry Red
pethier at comcast.net
http://www.flickr.com/photos/pethier
http://www.flickr.com/groups/triumphtransamerica
http://www.mnautox.com
http://www.mntriumphs.org