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Author Topic: Anyone here who's measured a Generac generator waveform?  (Read 671 times)

Brad Johnson

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Anyone here who's measured a Generac generator waveform?
« on: April 26, 2021, 12:51:53 PM »

SWMBO and I are considering a home generator.

Option A is a semi-portable unit like the Honda EB10000. Based on rough calcs, the EB10000 it would power the whole house, including a single A/C unit. Pros are it is a true inverter unit, it isn't quite so spendy as a dedicated whole-home unit, and we could haul the generator somewhere else if needed (bulky, but doable). Cons are a measly 3-5 hour run time (read: regular fueling), on-demand setup and manual switchover, and the need to store it and fuel somewhere during the "most of the time" it wouldn't be in use. 

Option B is a dedicated unit that will power the whole house, runs on natural gas, and has automatic switchover. Cons are a higher initial cost and no portability. Strong eyeball on Generac as they are a known quantity and I don't see them going away any time soon (i.e reliability, support, service, maintenance parts, etc).

My question revolves around power waveforms. I've found several waveform images for the Honda (FYI, it's gorgeous) but can't find any for the Generac. I know Generac has been around forever, but therein lies the problem. Long histories come with a tendency towards "the way we've always done it". Sure, their units have a track record for reliable power output, but what about the quality of that power? Just because you can churn out steady-state 120v 60Hz power doesn't automatically mean the waveform isn't equipment-killing crap. They don't mention anything about inverter tech, nor do they publish any type of measured or graphed examples. I don't see anything in their documentation that talks about output quality other than a few frilly marketing blurbs. I want to see something objective, preferably an o-scope image of the waveform.

No matter which way we go, mission-critical items like our computers will be on a UPS for both backup power and power conditioning reasons. It's the other stuff that concerns me... HVAC controls, microcontrollers in appliances, expensive home theater equipment, etc.. Those quickly add up to serious coin and I'd like to mitigate the risk as much as possible.

Brad
« Last Edit: April 26, 2021, 02:23:36 PM by Brad Johnson »
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K Frame

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Re: Anyone here who's measured a Generac generator waveform?
« Reply #1 on: April 26, 2021, 01:19:45 PM »

Can't answer your question, but I can tell you that friends of mine bought a house about 3 years ago that has a Generac whole house unit (32Kw, I believe).

It's kicked in several times after storms. Longest they've been on it has been about a day, I believe.

They have the full bevy of modern appliances -- computers, refrigerators, TVs, a couple of freezers, etc., and everything has survived.
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RocketMan

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Re: Anyone here who's measured a Generac generator waveform?
« Reply #2 on: April 26, 2021, 01:46:08 PM »

Just a guess, but I would think the Generac units provide a standard sinusoidal waveform.  It is a generator (alternator actually) and they typically produce sine wave outputs.  The 60Hz output is maintained by the genset's governor.  That may be a mechanical or electronic governor depending on the sophistication of the unit.
Modern appliances prefer sine waves, though many will tolerate square waves well enough.
To get a sawtooth or square wave output would require running the output of the generator through an inverter of some sort, and it doesn't really make sense to me that Generac would do that.
You might shoot them an email asking them about the waveform from their whole house units.
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Re: Anyone here who's measured a Generac generator waveform?
« Reply #3 on: April 26, 2021, 01:52:46 PM »

Just a guess, but I would think the Generac units provide a standard sinusoidal waveform.  It is a generator (alternator actually) and they typically produce sine wave outputs.  The 60Hz output is maintained by the genset's governor.  That may be a mechanical or electronic governor depending on the sophistication of the unit.

Agreed.

Also, by and large, most "sensitive electronics" immediately rectify the incoming AC as the first stage of a switched mode power supply.  They don't care about waveform.

Electromagnetic devices like motors and transformers may be somewhat more annoyed about modified square waves like those produced by cheap inverters.

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Re: Anyone here who's measured a Generac generator waveform?
« Reply #4 on: April 26, 2021, 04:00:54 PM »

My friend the appliance guy says that smaller generators seem to kill appliances. The bigger ones don't bog down when appliances like freezers kick in. High school physics was a few years ago, but I'm thinking, when the generator gets a heavy load, the voltage drops and the amps go up.... or something like that, and the sensitive stuff gets burned up.

I have that 32k generator, and it's nice to be able to run multiple buildings, freezers, pool pump, a/c, etc., during an outage. The downside is that it is a gas sucking beast. I have a 500 propane tank which will likely work for about 1 week but kill me on cost!
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dogmush

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Re: Anyone here who's measured a Generac generator waveform?
« Reply #5 on: April 26, 2021, 05:01:11 PM »

In general when you bog down the engine by adding load, the frequency dips badly.  The voltage tends to be pretty steady inside the range of the AVR, until the regulator trips and opens the circuit. I suppose the really small (like 5kw and under) portable sets may have a shittier voltage regulator, but most of the gens I play with will pop the circuit open if voltage deviates more than 7ish% from nominal.

Brad Johnson

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Re: Anyone here who's measured a Generac generator waveform?
« Reply #6 on: April 26, 2021, 06:04:54 PM »

I have that 32k generator, and it's nice to be able to run multiple buildings, freezers, pool pump, a/c, etc., during an outage. The downside is that it is a gas sucking beast. I have a 500 propane tank which will likely work for about 1 week but kill me on cost!

We have two AC units, both 2 ton, but little else that's power hungry save the clothes dryer and oven. According to Generac's estimator, the 22Kw unit is sufficient to provide us full home power with plenty to spare. If we decide to go the installed-generator route, we'd go the natural gas option. Service here is both super reliable and ridiculously cheap. It also gives us the option of quickly converting to tanked-in propane if all else fails.

This will be in the context of intermittent service interruptions, not constant power. Unfortunately, with our provider's switch to ERCOT, we presume our historically reliable service will become much less so in the future.

The whole-home genset is likely a pipe dream anyway, as I'm coming up with somewhere in the neighborhood of $9-10k for a turn-key setup. What will probably happen is a 6-8Kw portable which will be enough to run the freezer, fridge, a smattering of small appliances, and maybe some entertainment/comms gear on extension cords. I might get fancy and install a dedicated connector for the service panel where I can manually kill the service breaker and switch over to the genset for powering specific circuits. No AC in the dead of summer would suck, but we would have food storage and most of our electronic conveniences. I'd probably include the air handler circuit, too. Losing power during a bitter cold spell entails a lot more negatives than just being sweaty and losing a few things in the freezer. Our heat is gas fueled so all that's needed keep warmth flowing is having power to the furnace cabinet. If we went this route, storing 50+ gallons of fuel would be a pain, and topping off the fuel tank every 4-6 hours would suck, but we would have several days of uninterrupted heat and power. Many more if we rationed a bit. I figure it would run us $3-4k if we went all-in with the panel upgrades.

Brad
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Brad Johnson

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Re: Anyone here who's measured a Generac generator waveform?
« Reply #7 on: April 29, 2021, 10:12:09 AM »

Thinking more on this...

Is there any reason I can't simply backfeed the panel through a circuit breaker? By that I mean installing a 14-50 plug somewhere outside that I could plug the generator into, and connecting it to the panel via a simple 50A breaker. If the power fails, I plug the genset into that plug. It would require manually configuring the breakers, sure, but that's as easy as labeling the breakers as "Hey dummy, only these breakers when on gen power!". Simply trip the main panel cutoff, fire up the generator, and re-enable only the breakers feeding designated circuits. It would also allow the use of pretty much any decent genset with 240V capability.

If it would work, this setup would be super easy to install, essentially a breaker, plug, weather tight mounting box, and a few feet of wire. I'm fairly up to speed on basic wiring but this is beyond my experience and ability to confidently infer. I don't want to presume anything when it comes to wrangling angry pixies.

If this type setup would work, I suppose I could use the existing dryer plug to do the same thing. Only problem is I'd have to string a power cable through the back door, meaning compromised security, though I suppose I could piggy-back off that plug to an external connection seeing as how the dryer plug is on an exterior wall. Only issue there is the dryer is a 30A circuit and not a 50A. That creeps me out a little just from not having a big chunk of current headroom, though I suppose if I'm only running absolute essentials like freezer, fridge, a few LED lights, a microwave, and maybe the air handler for winter heat (nat gas fuel, not resistive), then I'm way under any danger threshold.

*Edit to add* After doing some digging, looks like Square D actually makes an interlock setup just for this purpose. Installs directly in the breaker panel and includes a simple mechanism which effectively blocks the backfeed breaker until the main breaker is in the off position. https://www.youtube.com/watch?v=6RG9nfFE7Zw I'll have to check and see what brand our panel is.

Brad
« Last Edit: April 29, 2021, 10:36:59 AM by Brad Johnson »
It's all about the pancakes, people.
"And he thought cops wouldn't chase... a STOLEN DONUT TRUCK???? That would be like Willie Nelson ignoring a pickup full of weed."
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Jim147

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Re: Anyone here who's measured a Generac generator waveform?
« Reply #8 on: April 29, 2021, 10:47:42 AM »

Around here the most likely time for power outage is an ice storm so people around here with portable gen sets move the dryer, run the cable threw the vent and can run fridge, freezer and gas furnace.
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Brad Johnson

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Re: Anyone here who's measured a Generac generator waveform?
« Reply #9 on: April 29, 2021, 10:52:50 AM »

Around here the most likely time for power outage is an ice storm so people around here with portable gen sets move the dryer, run the cable threw the vent and can run fridge, freezer and gas furnace.

Damn, that's a brilliant idea. Saves having to keep the door open.

Brad
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charby

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Re: Anyone here who's measured a Generac generator waveform?
« Reply #10 on: April 29, 2021, 10:52:59 AM »

We have two AC units, both 2 ton, but little else that's power hungry save the clothes dryer and oven. According to Generac's estimator, the 22Kw unit is sufficient to provide us full home power with plenty to spare. If we decide to go the installed-generator route, we'd go the natural gas option. Service here is both super reliable and ridiculously cheap. It also gives us the option of quickly converting to tanked-in propane if all else fails.

This will be in the context of intermittent service interruptions, not constant power. Unfortunately, with our provider's switch to ERCOT, we presume our historically reliable service will become much less so in the future.

The whole-home genset is likely a pipe dream anyway, as I'm coming up with somewhere in the neighborhood of $9-10k for a turn-key setup. What will probably happen is a 6-8Kw portable which will be enough to run the freezer, fridge, a smattering of small appliances, and maybe some entertainment/comms gear on extension cords. I might get fancy and install a dedicated connector for the service panel where I can manually kill the service breaker and switch over to the genset for powering specific circuits. No AC in the dead of summer would suck, but we would have food storage and most of our electronic conveniences. I'd probably include the air handler circuit, too. Losing power during a bitter cold spell entails a lot more negatives than just being sweaty and losing a few things in the freezer. Our heat is gas fueled so all that's needed keep warmth flowing is having power to the furnace cabinet. If we went this route, storing 50+ gallons of fuel would be a pain, and topping off the fuel tank every 4-6 hours would suck, but we would have several days of uninterrupted heat and power. Many more if we rationed a bit. I figure it would run us $3-4k if we went all-in with the panel upgrades.

Brad

Didn't you have a bunch of cash from the sales of both of your houses? Don't dick around by going the cheaper route, just buy the whole house Generac. You'll probably save money in the long run.
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K Frame

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Re: Anyone here who's measured a Generac generator waveform?
« Reply #11 on: April 29, 2021, 10:58:09 AM »

"Is there any reason I can't simply backfeed the panel through a circuit breaker? "

You can, but I believe that it's illegal in a lot of jurisdictions.

Guy I know did just that kind of set up, only he would run double male-end extension cords from the generator to a particular outlet circuit

He would throw the breaker on that particular circuit so that it wouldn't back feed the the service.

Only problem with that was when he discovered that... when he threw the breaker to isolate the circuit... it didn't isolate the circuit. He had a Federal Pacific panel with Stablok breakers and over half of the breakers in the panel had failed. And when Stabloks fail, they invariably fail on and won't trip under any circumstances.
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Brad Johnson

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Re: Anyone here who's measured a Generac generator waveform?
« Reply #12 on: April 29, 2021, 11:20:46 AM »

Didn't you have a bunch of cash from the sales of both of your houses? Don't dick around by going the cheaper route, just buy the whole house Generac. You'll probably save money in the long run.

I have the Vanguard account I created with the sale of a house. Pulling that money out would incur a significant tax penalty, not to mention reducing the performing asset by that amount (which, at current returns, would be a brick-dumb move).

I would love the convenience and reliability of the Generac but $10k is a hard pill to swallow for an occasional-need item, especially if I can easily and simply accommodate the need for less than half that amount. For the $5k-$6k difference, I can figure out a place to put the genset and safely store fuel.

Brad
It's all about the pancakes, people.
"And he thought cops wouldn't chase... a STOLEN DONUT TRUCK???? That would be like Willie Nelson ignoring a pickup full of weed."
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charby

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Re: Anyone here who's measured a Generac generator waveform?
« Reply #13 on: April 29, 2021, 11:24:35 AM »

I have the Vanguard account I created with the sale of a house. To pull that money out would incur a significant tax penalty, not to mention reducing the performing asset by that amount (which, at current returns, would be a brick-dumb move).

I would love the convenience and reliability of the Generac but $10k is a hard pill to swallow for an occasional-need item, especially if I can easily and simply accommodate the need for less than half that amount. For the $5k-$6k difference, I can figure out a place to put the genset and safely store fuel.

Brad

Portable generator also doesn't start itself if the power goes out if you are away from home.
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Brad Johnson

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Re: Anyone here who's measured a Generac generator waveform?
« Reply #14 on: April 29, 2021, 11:27:06 AM »

Portable generator also doesn't start itself if the power goes out if you are away from home.

That's one of the variables we're considering before making any decision.

Unfortunately we just got our tax returns and Uncle Sam came knocking hard this year. With the way the ranch returns worked out, our tax bill is a good bit higher than expected. It's punched a huge hole in our cash reserves and kinda torpedoed our whole-house genset plans.

Brad
« Last Edit: April 29, 2021, 11:40:16 AM by Brad Johnson »
It's all about the pancakes, people.
"And he thought cops wouldn't chase... a STOLEN DONUT TRUCK???? That would be like Willie Nelson ignoring a pickup full of weed."
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dogmush

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Re: Anyone here who's measured a Generac generator waveform?
« Reply #15 on: April 29, 2021, 11:41:39 AM »

You can backfeed through a 50A 220 plug (Stove and Dryer are the common choices, Welder works too) but as you mentioned you have to be careful about what you leave on, and as Hawk mentioned it's illegal without an interlock.

If you can swing the interlock, that's really the way to go for safety.  In FL at least that requires hiring and electrician to attach 6 wires, pulling a permit, and having the power company bless it, which is why I haven't gotten around to it yet.

Whole house auto switching is very nice, but is very pricey.  Even with hurricanes I only lose power long enough to want a Genset once or twice a year, and the delta between the portable and fixed gensets is to much for me to stomach for a use case that rare.  YMMV.

Brad Johnson

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Re: Anyone here who's measured a Generac generator waveform?
« Reply #16 on: April 29, 2021, 12:23:36 PM »

You can backfeed through a 50A 220 plug (Stove and Dryer are the common choices, Welder works too) but as you mentioned you have to be careful about what you leave on, and as Hawk mentioned it's illegal without an interlock.

If you can swing the interlock, that's really the way to go for safety.  In FL at least that requires hiring and electrician to attach 6 wires, pulling a permit, and having the power company bless it, which is why I haven't gotten around to it yet.

Whole house auto switching is very nice, but is very pricey.  Even with hurricanes I only lose power long enough to want a Genset once or twice a year, and the delta between the portable and fixed gensets is to much for me to stomach for a use case that rare.  YMMV.

Hard-eyeballing the interlock setup. It's cheap, it works, and it keeps us in good graces with both the power company and local code enforcement. If I'm going to install a dedicated breaker, the couple bucks and extra few minutes to install an interlock plate are a no-brainer.

We may go ahead and piggyback the genset port install onto electrical work we're having done in a couple weeks. Even if we plan to eventually get a whole-house unit, going ahead with the port install as part of an already-planned project would be simple, cost-effective, and give us near-term options until we can pop for the more comprehensive setup.

*Edit to add* Kinda eyeballing this. https://www.generac.com/all-products/generators/portable-generators/gp-series/gp15000e
If I've calculated correctly, we would be at roughly 8500w constant draw for pretty much everything in the house (one A/C unit, not both). Add 5000w for the A/C starting draw and a genset rated for 15Kw constant and 22.5Kw start seems more than enough, plus plenty of headroom if I miscalculated. The GP15000 also has a 14-50 plug, not a common item on portables, or so it seems. Combined with the 16 gallon tank and reasonable price, it's a darned attractive solution. I figured about a grand in parts and labor for panel install, so less than $5k total and we still have a generator we can haul around for other needs. Fuel storage would still be a headache but I could come up with something.

Brad
« Last Edit: April 29, 2021, 05:03:50 PM by Brad Johnson »
It's all about the pancakes, people.
"And he thought cops wouldn't chase... a STOLEN DONUT TRUCK???? That would be like Willie Nelson ignoring a pickup full of weed."
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Brad Johnson

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Re: Anyone here who's measured a Generac generator waveform?
« Reply #17 on: May 07, 2021, 04:28:33 PM »

Steering away from shopping purely by wattage and brand reputation. Dropped my self-imposed requirement of being able to run at least one AC unit and backed off to a few necessities, some basic comforts, and keeping heat flowing for winter possibilities. Revising focus to only inverter units and finding that higher-wattage inverters are a different set of issues. Seems as the inverter genset market is primarily built around portability and sound levels. There are lots of models in the 2000-3000 watt range, but offerings in the 7000w-plus range are much more limited. Cream of the crop is Honda's eu7000i, a fantastic unit with plenty of power, typical Honda reliability, and amazingly precise power output characteristics. Unfortunately its premium quality is matched by a similarly premium price ($4600 street). There are some store-brand units which I don't trust one bit, at least in terms of longevity and reliability.

Then there is Champion. I see the name everywhere but have zero experience with the brand. Anyone here who's dealt with their products? They have an inverter genset that's comparable in power to the Honda, but the HUGE difference in price ($1200 street) makes me leery. I have an inherent distrust of "similar" products which cost 75% less than the benchmark product.

Brad
It's all about the pancakes, people.
"And he thought cops wouldn't chase... a STOLEN DONUT TRUCK???? That would be like Willie Nelson ignoring a pickup full of weed."
-HankB

BobR

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Re: Anyone here who's measured a Generac generator waveform?
« Reply #18 on: May 07, 2021, 05:08:05 PM »

Just a random thought, Onan seems to have the RV genset market wrapped up but being in an area where there is a lot of RV snowbirds I see Onan 4k and 5.5K generators for sale on a regular basis. Maybe something you could look into. It should'nt be that hard to adapt for residential use.

bob

Brad Johnson

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Re: Anyone here who's measured a Generac generator waveform?
« Reply #19 on: May 07, 2021, 05:21:05 PM »

Just a random thought, Onan seems to have the RV genset market wrapped up but being in an area where there is a lot of RV snowbirds I see Onan 4k and 5.5K generators for sale on a regular basis. Maybe something you could look into. It should'nt be that hard to adapt for residential use.

bob

Onan (Cummins) was on the list, but ended up a non-contender because they don't have a 240v-capable inverter genset. That's one of my criteria. 240V makes it easier to set up at the panel. One double-pole breaker and the whole panel gets power. This setup also gets us future-proofed for 50a service. If we do the 240v 30a setup with oversized wire, jumping to 50a is a simple input plug and breaker swap.

Brad
« Last Edit: May 07, 2021, 05:34:58 PM by Brad Johnson »
It's all about the pancakes, people.
"And he thought cops wouldn't chase... a STOLEN DONUT TRUCK???? That would be like Willie Nelson ignoring a pickup full of weed."
-HankB

Hawkmoon

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Re: Anyone here who's measured a Generac generator waveform?
« Reply #20 on: May 07, 2021, 07:41:36 PM »

I did emergency power for years by backfeeding through a 30-amp welder outlet in my main garage. That generator was an old Coleman with a 3-conductor plug. It finally died and I replaced it with a new one, slightly more output, from Harbor Freight. The new one has a 4-conductor, twist-lock receptacle so I bought the matching cable and replaced the welder outlet with a recessed, male receptacle made for the purpose. And it was only then that I realized the inherent danger of doing a backfeed through a normal receptacle:

With a backfeed to any normal receptacle, the plug is male and the prongs are exposed. If you plug in the generator end first and start the generator, you now have a cord with exposed, hot prongs. Not really a good idea. If nothing else, get a proper receptacle and be safe. And, to keep the NEC people happy, look into an interlock for your breaker panel. Have you determined who made the panel? Do you have any unused spaces?

Brad Johnson

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Re: Anyone here who's measured a Generac generator waveform?
« Reply #21 on: May 07, 2021, 09:22:30 PM »

Panel is CH (Cutler-Hammer, now Eaton). 200 amp with a vertical-throw master breaker. Breakers will be reconfigured so that the genset feed is the 1/3 slots (top left). Has to be that way for interlock function. Feed box will be a proper box with male receptacle. GE and Westinghouse both have 30 amp UL-listed inlet boxes. There are a bunch of cheapo ETL-listed boxes, but no. I want UL and a name I at least recognize. We have an exterior closet that's ostensibly for yard tools but will also make a handy protected area to mount the inlet box out of the weather and away from most critters. It's also less than ten feet from the main panel with nice, open attic space above for install access. Guesstimating $200-$225 in parts plus install. Electrician will be by next week to quote the project addition.

Brad
« Last Edit: May 07, 2021, 10:48:01 PM by Brad Johnson »
It's all about the pancakes, people.
"And he thought cops wouldn't chase... a STOLEN DONUT TRUCK???? That would be like Willie Nelson ignoring a pickup full of weed."
-HankB

Hawkmoon

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Re: Anyone here who's measured a Generac generator waveform?
« Reply #22 on: May 07, 2021, 10:12:41 PM »

Sounds like a plan.

Brad Johnson

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Re: Anyone here who's measured a Generac generator waveform?
« Reply #23 on: May 10, 2021, 12:42:17 PM »

After doing a bunch of self-education, mostly about plug types and available cabling configurations, I've been able to plan a setup that's actually a bit better in terms physical connection, and a lot better in terms of future-proofing.

I had intended to go with a 30a inlet box and breaker, but wire with 6ga so that the circuit could be converted to 50a if needed. Since 30a and 50a boxes aren't much different in price, I've decided to go with a 50a box and breaker. Wire will be significantly more expensive, but it's a one-shot deal and makes the setup 50a capable right from the start. No "down the road" conversion costs if we ever pop for a 50a genset. Box is a GE T050N. It's not your typical "square box with a hole in the front" type connecter. It's a downward-angled receptacle with a box that has plenty of space for wiring (saw lots of grumbles about limited wiring space in the typical square inlet boxes). It's a skosh thicker than most boxes, but that's the net thickness even when in use. No connector and cable jutting straight out of it when plugged in. The configuration also takes strain off the cable and the box can be closed while in use to provide a bit of extra protection. Iron Box makes a cable just for this application (IBX-6112-25). It's already set up as L14-30P to CS6364 (typical genset 30a/240v connector to typical 50a inlet box connector). No adapter required.

In addition to simplifying generator hookup, the revised configuration gives ridiculous amounts of headroom for 30a service and more solidly future-proofs the overall setup. Should we ever take the dive, all that's required for a 50a genset upgrade will be a new cable. Also, if I ever need high-juice power at the back of the house, the GE box's standard opening means I can easily convert it from power inlet to power outlet by simply changing the insert. Not sure I'd ever need it, but nice to know I can.

Brad
It's all about the pancakes, people.
"And he thought cops wouldn't chase... a STOLEN DONUT TRUCK???? That would be like Willie Nelson ignoring a pickup full of weed."
-HankB

JTHunter

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Re: Anyone here who's measured a Generac generator waveform?
« Reply #24 on: May 10, 2021, 05:56:04 PM »

Brad -
If you can find a reasonably priced DIESEL generator that fits your needs, this might be better.  With diesel, you won't use the fuel as quickly nor will you risk it going "bad" the way ethanol-enhanced gasoline does so frequently.  You might even be able to mount a 55 gallon drum on a framework to feed the generator directly rather than the tank on the unit.
“I have little patience with people who take the Bill of Rights for granted.  The Bill of Rights, contained in the first ten amendments to the Constitution, is every American’s guarantee of freedom.” - - President Harry S. Truman, “Years of Trial and Hope”
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