[RE-wrenches] Mitsubishi Mini Split fighting with Outback VFX Off Grid

[Ray Walters]

Just because its worked in the past for me doesn't always make it a good 
idea.  I appreciate having an actual inverter expert on our list to 
caution us before we create a potential problem. One nice thing is that 
we've never needed to "fix" an Exeltech sine wave output.

R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760

On 10/22/2014 7:16 AM, Exeltech wrote:
>> We used to use capacitors, but Dan from Exeltech just poo pooed that fix
>> in another recent thread, so I don't have any other tricks up my sleeve.
>
> No poo.  Just a cautionary comment.  Capacitors connected across the output of an inverter can .. in some circumstances .. cause the voltage control loop to go crazy, resulting in unstable and unpredictable output voltage.  Just how much capacitance would cause trouble depends on the inverter design, so I don't have a specific value in mind.  And no .. it may not affect all inverters .. or may affect them differently  Think of it as a "do it at your own risk" fix.  If it works with one inverter, it may not work with another model and/or brand.
>
>
> Dan
>
>
> --------------------------------------------
> On Tue, 10/21/14, Ray Walters <ray at solarray.com> wrote:
>
>   Subject: Re: [RE-wrenches] Mitsubishi Mini Split fighting with Outback VFX Off Grid
>   To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
>   Date: Tuesday, October 21, 2014, 12:23 PM
>
> The Outback is not a perfect Sinewave.  It still has tiny steps in the wave, and when electronics have a problem, its usually with the wave form as it crosses zero voltage .  Instead of being instantaneous, it has a few milliseconds of time the wave is at the zero crossing, which can drive some electronics nuts.  I don't understand the issue beyond that, but apparently the electronics use the zero crossing for timers and synchronizing, and they're looking for an instant "click", not a smear.
>
> Do the heat pumps work with the generator?  Even though generators can have more harmonic distortion, they do usually have a clean zero crossing.
>
> If this is the case, I'm afraid I don't have a cure.  We used to use capacitors, but Dan from Exeltech just poo pooed that fix in another recent thread, so I don't have any other tricks up my sleeve.
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