Date: Fri, 25 Jul 2008 08:27:15 -0600
Reply-To: Paul Connelly <vanagonhummingbird@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Paul Connelly <vanagonhummingbird@GMAIL.COM>
Subject: Re: Inverter Questions
In-Reply-To: <20080725014819.GKGZ4226.eastrmmtao106.cox.net@eastrmimpo02.cox.net>
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Thanks David,
Okay, I'm getting the message - seemed like a good idea at the time...
What did you mean by "go the whole hog with a transfer switch" though?
Paul.
On Thu, Jul 24, 2008 at 7:48 PM, David Beierl <dbeierl@attglobal.net> wrote:
> At 07:12 PM 7/24/2008 -0600, Paul Connelly wrote:
>
>> I thought that 100 amps seemed excessive (it was for short circuit
>> protection not normal operation - it has 2 x 30 amp fuses on board for Short
>> circuit protection,
>>
>
> Ok, internal fusing for 60 amps...
>
> as well as overload and over temperature shutdown protection too) and the
>> wiring instructions calls for 10 awg (for cable runs of 10' or less, 8 awg
>> for longer runs - I am using about 5' in the original plan). 500 watts at 12
>> Volts running at max would draw a little over 40 amps
>>
>
> Remember inefficiency, and the potential difference between watts and
> volt-amperes. The unit is fused to carry 60 amps...
>
> the breaker box and run some fresh cables to the auxiliary battery. Maybe
>> a 40 amp breaker might be a better idea than a 100 watt fuse (also solves
>> the switch rating problem)?
>>
>
> A 40-amp *DC* switching breaker could be a good thing. Here's a 50-amp
> AC/DC unit from Blue Seas: <
> http://www.shipstore.com/SS/HTML/BLU/BLU7228.html> $16, not bad -- unless
> you need to stick it in a Blue Seas panel to make it work.
>
>
> On the feeding the external circuit with the inverter rather than plugging
>> directly to it, I don't see any major difference between doing that and say
>> plugging an extension strip to the inverter and running a couple of small
>> loads off of it.
>>
>
> Power strip is ok, as long as it doesn't have noise filtering circuits in
> it. The stepped-square-wave output has lots of high-frequency content,
> tends to burn up the filters.
>
> I'm talking like cell phone charger (.15 amps, laptop 1.5 amps, if not
>> using the laptop maybe a small DVD player, nothing major). Although, if the
>> inverter is accessible then so are the sockets - just kinda makes the stock
>> sockets obsolete ( I never hook up to shore power unless I'm drawing the
>> Dometic down at home before a trip.
>>
>
> *You* never...but what about your heirs and assigns, or your wife, or the
> person who buys it after you are senile? Or the kid playing with the 110v
> flap outside when you're running the inverter? You absolutely must not hook
> up in parallel with a working 110v input. No kidding. Really.
>
> Talking of the Dometic, that's the only potential high draw from that
>> circuit if I forget to switch it from 110 volts to DC or Propane. (Sorry
>> BTW, the 240 V thing is inured in my brain!)
>>
>> However, what the application of 110 VAC to the output of the inverter
>> might do if that switch was left on (on the inverter unit or breaker) I do
>> not know - might be worth a try first!!!
>>
>
> I can almost guarantee it would be much more exciting than you have any
> interest for. And I'll give sporting odds that it could be pretty exciting
> even if the inverter is not powered. In any case, as I said before, you
> simply must not do this, it's far too likely to be fatal to someone down the
> road. If you permanently disable the external 110 input, then the remaining
> issue is whether neutral and ground are bonded together inside the fan.
>
> Also, looking at the manual a little more, there is the phrase "Do not
>> connect to ... any AC circuit where the neutral conductor is connected to
>> ground or the -ve of the DC source".... which would mean the Dometic - which
>> is connected to the distribution circuit for the 110 VAC.
>>
>
> I don't know if the Dometic neutral is connected to ground at the fridge --
> probably not. I don't know if the house wiring neutral is bonded to ground
> -- might well be.
>
> But I strongly recommend to leave the existing shore-power setup intact,
> and keep the inverter wiring completely separate from it. Or go the whole
> hog with a transfer switch.
>
>
>
> --
> David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/
> '84 Westy "Dutiful Passage," '85 GL "Poor Relation"
>
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