Parallel Kits for the Predator 9500 (or similar) Inverters
Our strategy for whole house backup power involves a portable inverter generator connected to the house using an inlet and mechanical interlock. As is my habit, I did quite a bit of research to arrive at this strategy. Now that we have a couple of years experience with its use, I am happy to share that knowledge with those who are following down the same line of thought.
One of the most common questions I see in various online space involves how to deliver more power by connecting a pair of inverters in parallel. On the surface, it’s a simple question, but as ever, there’s some detail to the answer.
For the sake of this discussion I’m going to consider the Predator 9500, AIVolt AT20-2100001E, Duromax XP9000iH, Pulsar 9500, and Genmax GM9000iE. These five popular models are all made in the same Chinese factory. They vary only slightly from one to the next. They all have a built-in facility for parallel operation.
Synchronization
With an invertor, the powerhead creates AC power. That’s converted to DC. Then the inverter electronically creates pristine, sine wave power for delivery to the load. This process is very similar to how a high-quality, dual-conversion UPS works. This is why inverters are ideal for sensitive loads.
One happy feature of these inverters is that the circuitry creating the sine wave power can be locked to an external reference. Inverters that have parallel connections built-in automatically synchronize their output to another inverter connected in parallel. When so connected, the pair functions as a single, more powerful invertor.
This synchronization capability is not found in the traditional, low-cost generators commonly available to homeowners. It’s only available in much larger and more costly generators used for commercial and industrial applications.
Why Parallel Operation
Portable inverters were first popular in RVs, where they could be used to provide power while off-grid. They’d run small loads; lights, a fridge, TV, laptop, etc. The largest load would typically be an air conditioner. At this scale, 120V is all that was required. So, small inverters (under 4kW) only output 120V power.
There are some pretty big, fancy RVs out there. Some with two, independent air conditioners. So, sometimes more than one inverter would be required to run the whole ship. Manufacturers responded, offering “parallel kits” allowing a pair of 4 kW inverters to deliver a combined 8 kW to run all the amenities in a large RV.
These parallel kits have both 30A and 50A connectors, but still deliver 120V power. As shown above, they are clearly marked as 120V power only.
Household Backup Power
Providing backup power for an entire home, such as ours, requires 240V power. This is where the new generation of 9+ kW inverters really shine. They can be set to deliver 120V or 240V power. Our Predator 9500 can deliver 32A @ 240VAC. That’s enough to run our entire home, including the 48k BTU central air conditioner.
Ours is a modest sized home. Someone with a much larger home might want to use two such inverters in parallel. To do that requires a parallel kit that supports 240V operation.
Isn’t it curious how much these two devices from DuroMax look alike? It’s a little confusing. They both have 30A connector and 50A connectors. But they address different situations.
Harbor Freight does not offer a 240V parallel kit for the Predator 9500. I think some companies see 9kW as being adequate for most situations where people would seek to use a portable invertor. The logic being that anyone who needs more power would opt for an installed backup generator, like those sold by Cummins or Generac.
DuroMax does offer such a parallel kit. The DuroMax parallel kit (pictured above) can be used to connect two Predator 9500s together. YouTuber and Houston resident Gavin has demonstrated this. Note that this parallel kit is clearly marked as supporting 240V connections.
You can even mix one Predator 9500 and a Duromax XP9000iH, Genmax GM9000iE or Pulsar 9500. Gavin demonstrated this as well. This video very is very good at pointing out that some models have dedicated neutral wire in the parallel connection, while others rely on the ground being bonded to neutral.
AIVolt offer the very same 120v and 240V parallel kits. Just in a different color scheme.
Genmax Parallel Cable
It’s worth noting that the Genmax GM9000iE is a little bit special. Since it has both 30A and 50A 240V connectors built-in, the Genmax parallel connection is just a cable. The load is connected to the 50A plug on one of the inverters.
Genmax is Special
Genmax make quite a collection of inverters in the 4kW range. Consistent with this size class, these are 120V models. To enhance their utility they offer a unique “series-parallel kit.”
This harness includes extra connectors the inverters use to coordinate synchronization. Rather that simply match phase, the series-parallel kit allows you to force the invertors to operate anti-phase. Thus, a pair 120v 4 kW inverters can be used to deliver 240V power.
I believe that this arrangement is unique. But, I’m not sure exactly how useful. It might be interesting for a company that would normally have a number of small inverters readily at hand. Perhaps a campground or a company that rents RVs.
However, I further believe that for most people who need 240V power, a larger inverter (7+ kW) that natively delivers 240v is likely a better solution.
Summary
There you have it. An overview of why and how to connect a pair of inverters in parallel to address situations that require more power than one can deliver. It’s a bit of a niche application. The main thing to know is that there are different parallel kits for 120V and 240V situations.