[RE-wrenches] mechanical vs. electronic kwh meter

Jeff Clearwater jeffc at villagepower.com
Fri Aug 12 20:43:27 PDT 2011


There are really 3 kinds of meters in terms of running backwards and 
billing.

1  True mechanical - these run and read forwards and backwards and are 
not only safe to run backwards but they will inherently bill that way 
too as there is not way for the utility to know whether they ran forward 
or backwards.

2.  Mechanical disk with magnetic sensor spot and pick-up.  These look 
mechanical from the outside - spinning disk - turning numbers - but 
they've been retrofitted with a magneitc spot and a pick up that counts 
everytime it goes by.  These will run the wheell backwards but the 
pickup doesn't know which way it's going  and just counts magnetic 
passes as revolutions no matter which way the disk is spinning - hence 
you get billed forward even if it runs backward.

3. True electronic - which totally depend on software to read the 
signals in terms of billing.

On the mechanical meters you can see whether it has the magnetic sensor 
inside or not.

Hope that helps.

Jeff



Dana wrote:
> Another issue is with our local mechanical meters is no
> matter which way they run they are adding KWHR so to leave
> it running you are costing your customer $ not saving them
> $. We test to see that is does back feed for 5 minutes and
> then turn it off till the net meter is installed.
>
> Dana Orzel
> Great Solar Works, Inc
> E -dana at solarwork.com
> V - 970.626.5253
> F - 970.626.4140
> C - 970.209.4076
> web -www.solarwork.com
>
> "Responsible Technologies for Responsible People since 1988"
> Do not ever believe anything, but seriously trust through
> action.
>
> -----Original Message-----
> From:re-wrenches-bounces at lists.re-wrenches.org
> [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf
> Of Dave Click
> Sent: Friday, August 12, 2011 9:15 AM
> To: RE-wrenches
> Subject: Re: [RE-wrenches] mechanical vs. electronic kwh
> meter
>
> I just asked a guy I know in utility metering, and he
> confirms that
> there's no basis for the utility's concern. Their claim that
> backfeeding
> is a safety hazard could be an attempt to dissuade some
> non-PV folks
> from flipping their meters to steal power. Or that could be
> their
> justification to charge the customer for the new electronic
> meter (some
> utilities do this, apparently).
>
> As an anti-theft precaution, some mechanical meters don't
> actually spin
> backwards- so whether you're importing or exporting a 1kW,
> after an hour
> your counter has ticked up by one. So just because it's a
> mechanical
> meter doesn't mean that you should necessary leave it
> running until the
> utility installs that bidirectional electronic meter.
>
> On 2011/8/12 9:45, Kirk Herander wrote:
>> Hello,
>>
>> I am now in a debate with the metering dept. of a local
> utility. They
>> don't want a PV system to be energized and tested until a
> bidirectional
>> electronic meter is installed. They insist that an old
> plain Jane
>> mechanical meter can be damaged and is a safety concern if
> power is
>> pushed through it (its running backwards) to the grid. I
> have never
>> heard of, witnessed, or been told this by any utility or
> AHJ inspector
>> until now. Have any of you ever?
>>
>> I don't know the reason for their paranoia. I assume that
> many utility
>> districts don't to this day install bidirectional
> electronic meters. And
>> rely on the original mechanical meter to count backwards
> reliably and
>> safely.
>>
>> Kirk Herander
>>
>> VT Solar, LLC
>>
>> dba Vermont Solar Engineering
>>
>> NABCEP^TM Certified installer Charter Member
>>
>> NYSERDA-eligible Installer
>>
>> VT RE Incentive Program Partner
>>
>>
>>
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