Inverter based heat pumps - success stories ?

Discussion about OutBack Inverters in Off Grid Applications

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My RE system: Failed Founder of Sangha Energy - the first off grid utility company and B-Corp. Off gridders are worse than utility customers when it comes to paying for services, so we shut it down. Plus, how do you shut them off when they don't pay - it's an issue for scaling the off grid tech.

Inverter based heat pumps - success stories ?

Post by » Tue Aug 18, 2015 11:28 am

Can anyone share their success or failures running inverter based heat pumps off grid with Outback inverters?

So far my experience has been:
1. America-Aire unit at 18,000 BTU failed after six months - board level and other repairs all failed, unit finally removed. Assumptions was Chinese quality so that was the issue - still lingering concern that inverters feeding inverters may be an issue.
2. Ground source Heat Pump with VFXs - sort of worked so we upgraded to a 8048 Radian - that seemed to solve the power surge on start up problem. Heat pump then started throwing error codes and required restart often. Manufacturer said local repair people should be called.
3. Now I have a customer with a Klimaire KSIN009H115 - which can pull up to 29.2 amps on start up but is also a nice small and inexpensive machine. I'll be running this off a VFX3524 or possible a VFX3648. I'm hopeful but concerned this will work ok.

Anyone especially HVAC engineers have an knowledge of odd inverter to inverter harmonics or as we have seen LEDs flashing when the generator is charging batteries - could these noise issues be degrading or impacting inverter - heat pump life?
Tod duBois - Sangha

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Re: Inverter based heat pumps - success stories ?

Post by SwDoctor » Fri Aug 04, 2017 9:04 pm

This is a reply to a fairly old post, but the info may be useful to someone since I have some relative info to offer...

My Radian system is feeding three separate inverter based air conditioners...
They are 220v, and are mini-splits. (fresh air system is a series of recovery exchangers)

They are controlled by the automation computer primarily thru IR commands to allow cranking them on high during diversion events which delays the cooling requirement after sundown as much as possible.
My A/C units are able to be completely "inhibited" by the automation system if they fail to respond/cycle properly because they are wired thru a Solid State Relay.
(this is in case of a compressor failure, or loss of IR response, whereas the unit may continue burning power and is not needed or able to be operated due to low battery.)

The SSR offers a slight bit of harmonic suppression being a resistive semiconductor. But I do monitor everything, and there are no notable harmonics to using more than one at a time. (I do own a very expensive 3phase harmonic analyzer that I tested for this very issue.)

My system is totally off grid. Thus the need of killing a failed air conditioner before the system died was useful. Same application technique was applied to each of the three refrigerator (one freezer) unit(s) except with added internal temp probes and door sensors to prevent power (and just as importantly- food) waste.

There is one great feature about the Inverter based units (at least mini splits that I have), is the startup inrush power is "non existent" since it RAMPS UP starting at a mere 120-150w and gently goes up to max (1500w nominally) if max is needed, in fact to maintain temperature (once homeostasis is achieved) they typically consume about 150w when compressor is cooling, of course more on the days when it is 30degrees hotter outside!
These A/C units are "easier" on the Radian inverter because there is zero inrush. So having three of them pose no risk even if they all started at the same time, this is simply NOT POSSIBLE with 30amps inrush per A/C unit, that would put a load of ~90amps across the system, probably tripping a breaker or tossing off the Radian.

The same is true with "inverter based" (variable speed compressor) refrigerators/freezers; there is zero inrush current.
(although non-inverter fridges -that DO have inrush- are not usually more than 800w for just a few seconds, an air condition inrush is usually much much higher...)

Out of 3 fridges that I have, one is a new "inverter based" compressor. It uses about 25% less power and has no notable harmonics, so when the others eventually fail - it is a hands down decision to go inverter (or variable speed compressor) based, there is far less danger of overloading/failure to a Radian Inverter using these type of refrigeration/air conditioning systems. Not to mention they really are more energy saving.

A technical note: There are 24,000BTU mini splits (inverter based) that operate from 48vDC. This would keep a load totally off your RADIAN. It would result in a cooler electrical system too. They are available from China at this time, and are used in telecommunications "equipment" which operate from 48v batteries typically. I went with standard for "ease of availability" but there is a huge advantage to going 48v with such a large load to keep it off the power inverter bank... (plus they are really conservative on amperage!)

Hope info helps someone.
(otherwise I just ranted for no reason)

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Re: Inverter based heat pumps - success stories ?

Post by blackswan555 » Fri Aug 04, 2017 9:27 pm

Just to add, If like many off gridders (or anyone that does a lot of pumping & wants to save a significant amount of money) you are pumping water out of a well/borehole into maybe a cistern for storage & then re-pressurising for use, It may be a good idea to looking at adding separate inverters to those systems ( VFD, Variable frequency drive is actually the correct term for them) If you have central heating type circulation pumps that run for more than a few hours (A lot run 24/7 but people do not notice) They are a "no brainer" to replace with something like ... alpha.html

My comments are based on my experience and research, They are not endorsed or checked by Outback.I am an independent British electrician living in Spain, So please take this into account when reading /acting on my post`s.

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Re: Inverter based heat pumps - success stories ?

Post by ooi21 » Sat Dec 29, 2018 7:32 am

Hello Guys,

I have to buy a heat pump for my pool. I have never heard about the Inverter based heat pumps. Can anyone tell me about its features? Should I buy this? Please help me with this.


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Re: Inverter based heat pumps - success stories ?

Post by SwDoctor » Mon Dec 31, 2018 1:03 pm

Inverter based motor controls (refrigeration compressors and other pumps typically) use a multiple phase motor and an electronic circuit to drive it like a stepper motor.
It is called inverter based because it inverts the power to a high voltage (usually held in capacitor bank) before actually "driving" the motor.
It is more efficient method of load control.
It has nothing to do with "power inverter" for solar use, if this matters to you.
The inverter based motors are excellent choice for use with solar systems because there is no "startup inrush" current that typically would overload a circuit if for example 3 fridge units cycle at the same time, instead they start up using a few watts and ramp up to whatever they need to perform the job.
Minisplit air conditioners use this technology also.

The only drawback I have found with inverter based motor control, is they sometimes emit EMF on the power line(s) and may need to install a choke or coil to dampen if you use sensitive equipment.
This is only an issue if your home automation system is "old school X10" type, most newer automation is immune to such noise. (in reality many LED drivers for lighting produce more EMF)

In summary, the technology is good.

I hope that helps.

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Re: Inverter based heat pumps - success stories ?

Post by David LeBow » Wed Jan 02, 2019 8:42 am

@ooi21: your e-mail address as registered with this forum seems to be incorrect. Topic reply notifications are being returned with this fur ball:

The email address you entered couldn't be found. Please check the recipient's email address and try to resend the message. If the problem continues, please contact your helpdesk.
David LeBow
Sr. Director, Software Engineering

Alpha Technologies Inc. / OutBack Power Technologies
3767 Alpha Way Bellingham WA 98226 USA

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