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Decisions: 2021 Household Projects

As we come to the end of the year, I’m looking back across a range of substantial household projects. We rather famously lost power for a few days back in February 2021 during an unusually cold snap. This lead to some additional thinking about household projects, including the new air conditioner. Specifically, how best to adapt our home to operation without utility power? After all, the Great Texas Freeze of 2021 was not the first time we lost power for days. We were without power for several weeks after Hurricane Ike in 2008.

Generac Standby Generator Beauty Shot copy

The most common approach that we see around the neighborhood is the installation of a standby generator. These are permanently installed systems that startup and take over when utility power fails. Generac, Kohler and Cummins are the most common brands. They typically run on natural gas and I’ve seen systems from 14 kW to 32 kW hereabouts.

Standby Generator vs Air Conditioner

Given the position of our home on the lot, and the location of the gas meter and breaker panel, it’s not really practical for us to install a standby generator. It would be prohibitively expensive given the required location of the generator. We’d need to run buried pipe for natural gas, and conduit for electrical cable, a considerable distance. The cost of the installation is much more than the generator itself. The entire project cost is as much as a new air conditioner, for a benefit that that would only occasionally be realized.

In contrast, a new air conditioner improves our daily quality-of-life. The choice was clear. We had the new air conditioner installed. The plan is that we continue to rely upon a portable generator on an as-needed basis.

Phase 1: New Breaker Panel & Interlock

In April we upgraded the vintage 60 Amp electrical service to a new 200 Amp breaker panel. This was long overdue. The larger breaker panel allowed us the space to add a direct connection for the generator.

A simple, mechanical interlock ensures that the main breaker must be off before we can physically turn on the connection to the generator. With the whole house connected to the generator, we don’t need to run an array of extension cords. That’s both safer and more convenient.

Phase 2: Instrumentation

Knowing that we’d be running from a modest, portable generator, I set out to learn something about our power requirements. There’s no way a portable generator could run everything. I needed to get a sense of our pattern of usage.

Shelly 3EM

I installed a Shelly 3 EM current monitoring device (above left.) This lets me track the overall power drawn by the house. It has a web-based portal (above right), but it also integrated with our Home Assistant.

Just as I did this the Home Assistant team released an update with extensions designed to accommodate home with solar panels and battery storage. It can track power drawn from and/or fed back to the utility.

While I’ve not conducted a detailed study, I’ve seen enough that I’m confident the generator will run what we truly need. It won’t run all the appliances (AC, washer, gas dryer, dishwasher, microwave & coffee maker) at the same time, but that’s not truly necessary.

Phase 3: Air Conditioning

The air conditioner is the major appliance in the house. What follows reflects some of the research I did in choosing the variable speed air conditioner described previously.

When a traditional, single stage AC unit turns on it draws a huge surge of what’s called “in-rush current.” This is required to get the compressor, fan and blower initially moving.

The in-rush current is brief, but huge. I measured over 36 Amps on our old single-stage AC unit. Once running it settled back to just 11 Amps. This also explains why an AC unit with continuous draw of just 22 Amps needs to be connected to a 50 Amp (!) breaker, using wire sized appropriate for a 30 Amp load. When connected to a 30 Amp breaker the compressor starting would occasionally trip the breaker.

This in-rush current has consequences. If you are considering potentially operating on a standby generator, it tells you what the largest peak load might be. In the case of an installed standby generator, it figures in calculating how large a system you must install.

Modifications: Soft Start

This huge in-rush surge can be addressed by installing a “soft start kit.” This is an electronic circuit that will intelligently manage the start-up process to reduce the in-rush current by as much as 70%. These were originally designed to allow RVs to run their air conditioners from a smallish (3-5 kW) portable generators they typically carry. In the case of larger RVs, they may have two AC units that can be run from a single generator.

RV air conditioners typically run on 120 VAC power. In contrast, a typical household AC unit requires 240 VAC. Happily, there seem to be a couple of companies that also make soft start kits for household use.

MicroAir Soft Start Kit

The MicroAir EasyStart (pictured above) seems to be the most common. They have a model that will allow up to a 5T household AC (240 VAC) unit to be run from a portable generator. It costs around $375. I found a great video showing someone installing and testing such a kit. Also, another here and here. Sadly, household AC contractors don’t seem to have much exposure to these sorts of things.

Variable Speed Air Conditioning

Variable speed AC units simply don’t have this massive in-rush current, so they don’t need a soft start kit. In essence, soft start is built into their normal operation. The measured startup draw of our new VS AC unit is around 13 Amps. That’s easily within the range that a mid-sized, portable generator can handle.

Phase 4: Invertor Generator

Actually, to be precise, the new AC unit can be run from a portable invertor generator. An invertor is required where a sensitive load requires clean, steady power. The experience of February 2021 taught us that the digitally controlled blower in our furnace requires an invertor. Also, the UPSs that run our network core require invertor power.

If, like us, you’re planning on running on a large portable generator, you need to be careful to get one large enough to do the job. This may not be solely expressed in how much power it can deliver in Watts. It may also involve the type of connection it supports.

Predator-6500

A generator rated for 7,200 Watts or more may have a NEMA 14-30 connector capable of delivering 30A @ 240VAC. This is commonly used to provide power to an RV. Note that the model pictured above is only rated for 6,500 Watts peak. While it has the 240 V 30 Amp connector, it can only deliver 25 Amps. This is clearly labelled near the connector.

Duromax XP15000EH

A generator rated for 12,000 Watts or more (Duromax XP15000EH pictured above) may have a NEMA 14-50 connector capable of delivering 50A @ 240VAC. This is commonly used to connect an electric dryer or some EV car chargers.

Our brand new Predator 9500 (pictured below) is rated for 9,500 Watts surge, and 7,600 Watts continuous load. It’s single biggest connection is 30A @ 240 VAC via a NEMA 14-30 twist-lock. (30A x 240 VAC = 7,200 Watts.)

Predator 9500 Beauty Shot

I believe this is currently the largest, affordable invertor generator available. I’m comfortable that it will run everything we need in the house from the 240 VAC 30 Amp circuit. A separate 120 VAC 15 Amp circuit remains available to power the network core in the garage/office. In reality, that’s a very light load. Barely 100 watts.

Want More Power?

In the past, when inverters were in the 2-4 kW range, “parallel kits” were offered. This allowed a pair of smaller inverters to be run in tandem, doubling output power. In some cases, they allow a pair of generators that each deliver 120 VAC to provide 240 VAC. This can be desirable for residential standby applications.

Harbor Freight Parallel Kit

Thus far, the Harbor Freight has not offered such a kit for this largest model. It would seem less necessary, given the considerable output of a single unit. Even so, Jason Wallace, an enterprising YouTuber, has created his own to run his entire home from a pair of 9500s. The combination delivers 15.2 kW of clean, continuous, which is comparable to some installed standby generators.

Now we wait

I’m old enough to remember George Peppard playing Colonel Hannibal Smith in The A-Team. He often quipped, “I love it when a plan comes together.” That’s how I feel as we wind down 2021. After our various projects, large and small, with the recent acquisition of the Predator generator, our plan is complete. We’re as-ready-as-we-can-be to take on whatever the combination of weather, ERCOT, the Texas PUC and Governor Greg Abbott can mismanage. Whatever happens, the lights, heat and/or cooling will remain on.

P.S. – Genny, the Predator 8750 generator that served us so well in Feb 2020, is being re-homed. She will serve another family in the years to come.

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