Back Up Power for Refrigerator/Freezer

[trader4]

Maybe new ones suddenly got quiet, but I doubt it. I wound up getting a 12KW Generac unit that was about 5 years old from a neighbor because it quit during an outage and the service company told him it wasn't worth fixing. It looked almost like new, so I thought I'd see if maybe I could fix it and use it. It started up and ran, so I heard what it sounded like. And it sure wasn't like any idling car, except maybe one with a broken muffler. More like a loud garden tractor, which kind of makes sense, since it's a similar ~25hp engine.

Here's a youtube of one if you don't believe me:

Make sure you listen until about 25 secs in, when it actually starts. Before that there is something in the background that does sound more like a car.

Let me know what you think after you watch the video.

I've also been

One big difference there you're talking about an engine that's an order of magnitude smaller than one in a whole house type. The quietest ones are the inverter type, where they sythensize the AC waveform. That decouples the frequency from the engine speed. At low loads, the engine can run at lower RPMS instead of full speed.

[Unquestionably Confused]

Yeah, you're correct. I didn't give that enough thought. Sometimes Occam's razor ain't all that sharp

Still, consider just leaving it be and properly matching the backup generator to the task(s) at hand. It (the defrost) should not add that much load to the system.

[Stormin Mormon]

So, your loud generator some how disproves the other poster who said he had a quiet one? What's the point you're trying to make?

. Christopher A. Young Learn about Jesus

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[trader4]

He said his 17KW Generac is quiet. You said:

"Glad to know Generac are fairly quiet."

I've seen and heard a few of the Generac whole house generators. I worked on the one I received for free and had it running. It sounded like the one in the youtube video I provided. None of them sounded even close to an idling car. Maybe new ones are quieter but I still doubt they are as quiet as an idling car. But the point is your assumption that Generac are fairly quiet is wrong, unless you think the one in that video is quiet. What's there is typical of what the one's I have heard sounded like.

[Mark Lloyd]

[snip]

There was a storm here that caused a 5-day power outage (thees fell on power line). According to the noise, a lot of people were running generators all night. The weather was OK (no need for heat/AC). I know of one man on the block who has sleep apnea (needs to run breathing machine).

BTW, I considered sleeping outside one night (no excessive light), but it was too noisy.

[The Daring Dufas]

I installed a number of different Generac systems back in the 1990's and the water cooled units had a critical grade muffler on top and those units were very quiet. The air cooled 8kw gensets with the B&S Vanguard V-twin engines were louder but made no more noise than a typical air conditioner condensing unit. The last Generac genset I installed was within the last 10 years and it had the big Generac manufactured air cooled V-twin and it was extremely quiet for an air cooled generator. ^_^

TDD

[trader4]

Did they sound like the one in the youtube video?

That is what the one's I've heard sound like.

[makolber]

some people need to keep the sump pump going, especially after a storm.

Mark

[(PeteCresswell)]

Per [e-mail]:

I can think of an alternative possibility: neighbors driven half crazy by the racket from an el-cheapo gennie. Maybe not *all* that probable, but I suspect I've been close to pissing in one guy's gas tank more than once.

[(PeteCresswell)]

Per [e-mail]:

Wouldn't it be largely a function of the type of muffler used?

Or do some air-cooled engines make noise above and beyond exhaust noise?

[(PeteCresswell)]

Per [e-mail]:

I liked the suggestion about being sure to eat all the ice cream before it melted. Even so we have little gennie, I'm going to try to sell that one to the wife next time around..... -)

[Stormin Mormon]

I wasn't all that impressed with the guy around the corner from me, and his 24/7 generator. But who knows, might need Cpap.

. Christopher A. Young Learn about Jesus

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[The Daring Dufas]

The 10kw liquid cooled Generac gensets I installed back in the 90's were my favorite because the engine ran at 1,800rpm which made for a very quiet unit that was not overstressed. The service problem that affected all the Generac gensets back then was a horrible oil pressure switch which seemed to fail on all of them. I even looked at getting a replacement switch meant for an old model Ford truck engine. The loudest gensets by far are the 3,600rpm screamers. A 10-20kw air cooled genset can be very loud depending on the sound insulation of the housing. My favorite air cooled gensets were the Onan 15kw 4cyl air cooled gensets which I installed in a number of grocery stores. I wish I had one for the house. The darn things are actually fairly quiet even though being air cooled. ^_^

TDD

[The Daring Dufas]

That one is loud because it's a 14kw air cooled and to get that power level from the big V-twin it must run a 3,600rpm. I'll bet an 8kw unit running the same air cooled engine at 1,800rpm would be very quiet. ^_^

TDD

[The Daring Dufas]

The side by side fridge we have here at the house uses halogen lamp tubes as defrost heaters and a fellow looking in the freezer during the defrost cycle freaked when he thought the fridge was on fire. ^_^

TDD

[trader4]

No question most of the noise is from the exhaust. How much quieter you could make it with a better muffler, IDK. The muffler on the Generac I worked on was fairly large, not like you'd find on a garden tractor. I would say it was about 18" x 10", by 5". I don't know the dynamics of muffler design, ie if you made it 30% bigger, how much difference it would make. But then you also have the problem of bigger muffler, now you need bigger cabinet, etc. These things sell for $2500, so cost is a factor.

One thing that lowers the noise is using an 1800 RPM engine instead of 3600. The low cost generators run at 3600. The more expensive, liquid cooled, etc run at 1800. For smaller portable, the quietest are the inverter type, where the AC is synthesized, allowing the engine speed to be decoupled from the freq. So, with no or little load the engine can be near idle, quieter and using less fuel. But last time I looked it was like $4000 for one that was 4KW or so. A lot compared to the China specials.

And there is other noise from any engine besides just the exhaust.

[trader4]

Those are the ones I'm talking about. They are what you typically find for residential use, no? Because people aren't going to pay for the 1800 RPM water cooled, that probably cost 3 - 4X and also come in higher output than most houses would need.

[N8N]

I understand what you're saying and agree with you, but it is very common f or engineers, or at least spec-writers, to specify double conversion and/or true sine wave UPSes for those uses, when it is a "mission critical" appli cation. Nothing succeeds like massive overkill, I guess.

I actually have one of those units running my home theater and cable modem/ wireless router, I believe I've related that before, although there's actua lly a reason for that - the APC line-interactive UPS that I had there befor e made the TV (Samsung 46" LCD) hum/buzz alarmingly. And I got it used and cheap. I did replace the cooling fan with an "ultra quiet" PC fan and ins tall a thermostatic fan control to quiet it down though.

[The Daring Dufas]

I installed a number of 10kw liquid cooled Generac gensets in homes that were the 4cyl 1,800 rpm units. The 10kw gensets had a Turkish Fiat 4 cylinder liquid cooled engine and I seem to recall a 12 or 15kw unit that had a Nissan 4cyl liquid cooled engine. All were installed in homes and I even installed a 40kw Kohler genset in a home. My late friend GB built a doghouse which matched the house to camouflage the big Kohler. I remember the Kohler having a Ford liquid cooled engine. I could swear I saw an Onan that had a Slant Six in it. o_O

TDD

[The Daring Dufas]

********************Trim Da Phat********************

About 30 minutes ago I put a new pair of 12 volt AGM batteries in an APC Smart UPS 1000 that I may use on a surveillance camera job and it was a scrap pile rescue that had absolutely nothing wrong with it except that it needed a new pair of batteries. I get UPS units all the time that are in the same shape needing only batteries and I'll never understand why people throw the darn things in the trash. I sell the old batteries to a recycler and have a good as new UPS to sell for a cost less than $35.00 in new batteries. I may get $250.00 for this one. ^_^

TDD