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Onan 7.5DKDFL - A good fit for me?


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  #51  
Old 01-09-2018, 02:24:05 PM
DieselBound DieselBound is offline
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Default Re: Onan 7.5DKDFL - A good fit for me?

Yeah, when the plug is connected the neutral is connected via the main panel.

I probably should have measured Hz, but I was distracted by the low voltage. I didn't want to keep running with low voltage so I stopped everything.

Plug is due in another week, but won't be able to get around to trying it for another couple weeks. Meanwhile rain and high winds are expected in the next couple of days, wouldn't you know it! (circumstances have kept me from being proactive)
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  #52  
Old 01-09-2018, 03:35:34 PM
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Default Re: Onan 7.5DKDFL - A good fit for me?

When you do get to measuring voltage again be sure to measure it at the input to the gen internal breaker if it seems off. Many a time a poor connection somewhere has caused a lot of needless work to be done when all that was necessary was to tighten up a connection. Also check your volt meter against your house power to make sure that the volt meter is OK. Cheers Dan
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Old 01-09-2018, 05:17:42 PM
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Default Re: Onan 7.5DKDFL - A good fit for me?

Quote:
Originally Posted by DieselBound View Post

Plug is due in another week, but won't be able to get around to trying it for another couple weeks. Meanwhile rain and high winds are expected in the next couple of days, wouldn't you know it! (circumstances have kept me from being proactive)
Situations such as this a Big Block or maybe a Dual Quad from Nutty's Grill is recommended. A 4 Banger at the very least!
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  #54  
Old 01-09-2018, 10:15:27 PM
DieselBound DieselBound is offline
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Default Re: Onan 7.5DKDFL - A good fit for me?

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Originally Posted by BigBlockChev View Post
When you do get to measuring voltage again be sure to measure it at the input to the gen internal breaker if it seems off. Many a time a poor connection somewhere has caused a lot of needless work to be done when all that was necessary was to tighten up a connection. Also check your volt meter against your house power to make sure that the volt meter is OK. Cheers Dan
Thanks for that tip. Post breaker I've got the plug, the connection for the receptacle and then the connection at the house's main breaker panel. Electrician did the wiring for the receptacle and the main breaker panel, so am hoping that that's good.

I've got a Fluke DMM, so good there.
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Old 01-10-2018, 10:39:06 AM
armandh armandh is offline
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Default Re: Onan 7.5DKDFL - A good fit for me?

please keep in mind that local codes may differ but the national code allows
a means to prevent inadvertent cross connection [interlocking breakers]
for connection of a portable generator [ie plugs in] so....
keep it "looking" some what portable [not in a shed it cannot be removed from]

permanent stand by generators require a transfer system.
much more expensive.

but since your electrical work was done by an electrician [as far as it went]
doing the rest safely falls to you
be sure you understand how you are wiring things.
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Old 01-10-2018, 01:54:22 PM
len k len k is offline
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Default Re: Onan 7.5DKDFL - A good fit for me?

THD in brushless gens......... Different types of brushless gens. Apples and oranges.

-- Onan types with electronic voltage regs
-- cheapie capacitor regulated types from big box stores --- these can have high TDH and spikes at the top of voltage sinewave.

------------------------------------

But a switching power supply should happily eat any scrappy power, it rectifies it all to DC first, then uses it. Computers use switchers as power supply, computer UPS were frequently square wave output

In transformers and motors the higher frequency harmonics that THD has end up as waste heat. So they run a bit hotter. But I haven't heard of any failing from that.

The voltage level of the harmonics is lower than the fundamental 60 hz, so the 60 hz voltage dominates and clocks and motors run at their 60hz speed

Last edited by len k; 01-10-2018 at 02:06:01 PM.
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Old 01-10-2018, 02:55:24 PM
Wayne 440 Wayne 440 is offline
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Default Re: Onan 7.5DKDFL - A good fit for me?

DISCLAIMER - the following is based on my experience, yours may vary.

I have "a few" years of experience around engine generator sets, from 500W to 1MW. I cannot think of any residential sized instance where the THD of the supplied power from a generator set created a problem. Most of the issues I found were frequency related, and confined to one brand of UPS device that apparently requires 60.000000Hz input or it goes nuts. The solution was a trashcan to receive those UPS devices, and replacing same with a better product.

In the absence of a UPS device, my experience has been that so-called "sensitive" devices such as computers, TV sets etc. will run from just about anything that happens to come out of a generator set as long as it is even close to 120V, 60Hz. If it is AC, and will light a 100W incandescent bulb without (very much) visible flicker, I don't hesitate to plug in and use it.
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Old 01-10-2018, 03:07:12 PM
DieselBound DieselBound is offline
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Default Re: Onan 7.5DKDFL - A good fit for me?

Quote:
Originally Posted by armandh View Post
please keep in mind that local codes may differ but the national code allows
a means to prevent inadvertent cross connection [interlocking breakers]
for connection of a portable generator [ie plugs in] so....
keep it "looking" some what portable [not in a shed it cannot be removed from]

permanent stand by generators require a transfer system.
much more expensive.

but since your electrical work was done by an electrician [as far as it went]
doing the rest safely falls to you
be sure you understand how you are wiring things.
I did extensive research. I'm using a interlock kit: UL listed and acknowledged/accepted by my local utility company.

The professional electrician wasn't aware of the need to break the neutral bond at the generator I explained it to him and he's now "aware." I am 99.999% confident that things are, messed up plug aside, wired correctly.

Wayne, yeah, my limited understanding is that frequency seem to be the biggest thing. Last I'd checked this generator held frequency very well. One of my UPSes was really perturbed with the low voltage; not surprised; when I get the current issue resolved I'll see if it then is OK (if not I'll contemplate whether I want to swap it out- it's nearly 7 years old).
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Old 01-10-2018, 03:22:35 PM
len k len k is offline
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Default Re: Onan 7.5DKDFL - A good fit for me?

I only bumped into knowing about THD when I called manufacture and asked what their gen was specd at . Think he said 15- 20 % THD. ....WOW That's HIGH !!!!!! Mostly a peaked sinewave with additional spikes on the peak. It was a capacitor regulated gen. Porter maybe??

Those THD numbers are on par with a APC computer UPS I have that outputs modifed square waves

This was NOT a quality gen, was a cheapie one. Onan gens are in vastly superior catagory of quality.

Quote:
Originally Posted by DieselBound View Post
The professional electrician wasn't aware of the need to break the neutral bond at the generator
Reminds me of electricians that used to cut the green wire off cables when wiring up a breaker box and branch wiring......
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Old 01-11-2018, 08:30:32 AM
armandh armandh is offline
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Default Re: Onan 7.5DKDFL - A good fit for me?

UPS[es] and generators

some UPS are overly sensitive to power HZ fluctuation, as I understand it,
they use a shift in the zero crossing interval to indicate loss of grid power.

for my basement servers I went to an "always on" double conversion UPS.

this type converts grid power to DC and back to sign wave AC for the load.
the batteries [on mine] feed a DC/DC up voltage converter.
the two DC supplies are then paralleled. [no switch over]

lt is a lightly loaded 1KW commercial unit bought "refurbished" over 7 years ago,
and on its second set of batteries, still going just fine. [knock wood]
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Last edited by armandh; 01-11-2018 at 04:58:43 PM.
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