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

[Mike Sullivan]

Hi Dan, 

I think the waveform problem Ray describes can most likely be resolved by installing a filter capacitor at the AC input terminals of the heat pumps. A small film cap (1 or 2 uF?) will function with the resistance and inductance of the branch circuit wiring to create a low-pass filter that will soften up those sharp edges of the 60 Hz waveform and provide a much cleaner zero crossing.

There's a huge difference between installing a small cap for filtering purposes and installing a large capacitor (or capacitor bank) to try and correct a lagging power factor. Might be worth a check-in with Outback tech support to get their blessing with this approach, but it should be a cheap and effective fix.

Cheers,

Mike Sullivan
Solar Design
Crestone, CO


> From: Ray Walters <ray at solarray.com>
> To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
> Subject: Re: [RE-wrenches] Mitsubishi Mini Split fighting with Outback
>    VFX Off Grid
> Message-ID: <54469693.9070706 at solarray.com>
> Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"
> 
> 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.
> 
> R.Ray Walters
> CTO, Solarray, Inc
> Nabcep Certified PV Installer,
> Licensed Master Electrician
> Solar Design Engineer
> 303 505-8760
> 
>> On 10/21/2014 8:54 AM, dan at foxfire-energy.com wrote:
>> Anyone else had issues with Mitsubishi Mini Split heat pumps fighting 
>> with Outback VFX off grid inverters? Everything is brand new. Outback 
>> VFX7248, three separate heat pumps. The heat pumps shut down reporting 
>> multiple / confusing input commands. The heat pump guys want to blame 
>> the power system. I'm thinking bad Sushi. Thanks db
>> 
>> 
>> Dan Brown
>> Foxfire Energy Corp.
>> Renewable Energy Systems
>> (802)-483-2564
>> www.Foxfire-Energy.com <http://www.Foxfire-Energy.com>
>> NABCEP #092907-44
>>