Date:         Wed, 24 Nov 2010 13:47:39 -0500
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: How not to unstick a frozen slider. - Westy circuit breaker
Comments: To: Rob <becida@COMCAST.NET>
In-Reply-To:  <vanagon%2010112413072551@GERRY.VANAGON.COM>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 10:07 AM 11/24/2010  -0800, Rob wrote:
>My small milk house heater plugged into the Westy shore power system
>only runs on 'low', 'hi' tripped the breaker. This normal?

That may depend on how old the heater is.  Modern 110 VAC US heaters
are limited to around 1300 watts IIRC.  That certainly shouldn't trip
your internal breaker.  However older ones could be rated 1650 watts
at 110 VAC which works out to 15 amps*.  If operated on 120 volts
they could draw almost 16.5 amps which might trip it after a bit.

*Because this is an almost purely resistive load (Power Factor = 1 or
close to it) the wattage is essentially equal to the
volt-amperage.  In an inductive load like a motor the volt-amperage
would considerably exceed the actual wattage; you're paying for the
watts but your breaker trips on amps, as it should.  This is the
non-marketing part of the reason why consumer-grade motors are often
rated in amps instead of watts.  The other reason is that the numbers
look bigger.

Both wattage and volt-amperage are considerations for inverters --
read the fine print in the manual.

I have a Holmes ceramic-type heater that settles down to 1300 watts @
115 VAC, but for the first minute or two it develops about 1650.  My
line voltage actually runs 118 and change, but the heater load drags
it down to 115 at the outlet.

Yours,
David