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Home > Archive > Alternative Power sources > October 2005 > 100A vs 200A transfer switch, Generac 15kW natural gas
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100A vs 200A transfer switch, Generac 15kW natural gas
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| wcwood@gmail.com 2005-10-17, 9:21 pm |
| I've lurked on this group for a while now, but can't seem to figure
this out. I was looking at (what seemed like) a good deal for a
Guardian 15kW (13kW NG) generator by Generac. By my calculations, that
is 108 to 125 amps at 120V. The generator can support even higher
wattages in surges.
But it comes bundled with a 100A transfer switch. My house (and
essentially all around here) are 200A at the meter. Can anyone explain
the logic behind this? Am I interpreting this incorrectly, or can the
generator supply more current than the bundled transfer switch can
handle?
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| RF Dude 2005-10-17, 10:21 pm |
| It is 15 kW divided by 240V.
Unless you introduce a sub panel so as to not exceed your generator output
(put essential loads on a 100A fused sub panel), you will want a 200A
transfer switch. This way it goes in line with your 200A service. Your
whole house will transfer to the generator. You can't use a 100A xfer
switch on 200A rated service.
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| Vaughn 2005-10-17, 10:21 pm |
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<wcwood@gmail.com> wrote in message
news:1129593047.431189.135170@g43g2000cwa.googlegroups.com...
> I've lurked on this group for a while now, but can't seem to figure
> this out. I was looking at (what seemed like) a good deal for a
> Guardian 15kW (13kW NG) generator by Generac. By my calculations, that
> is 108 to 125 amps at 120V.
It is probably not rated to supply full power to one side. 15KW at 220
volts comes out to 68 amps.
>The generator can support even higher
> wattages in surges.
Just for fun, figure out what it will cost you to run that thing at 50%
power for 30 days.
>
> But it comes bundled with a 100A transfer switch. My house (and
> essentially all around here) are 200A at the meter. Can anyone explain
> the logic behind this?
No. It will likely not be allowed by your electrical inspector. That
said, what size is your main breaker?
> Am I interpreting this incorrectly, or can the
> generator supply more current than the bundled transfer switch can
> handle?
The generator can supply 68 amps per side, but the problem is that your
utility can supply 200 and you will probably have to supply a transfer switch
sized for that, unless you are going to power a sub-panel.
Vaughn
>
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| Steve Spence 2005-10-17, 11:21 pm |
| wcwood@gmail.com wrote:
> I've lurked on this group for a while now, but can't seem to figure
> this out. I was looking at (what seemed like) a good deal for a
> Guardian 15kW (13kW NG) generator by Generac. By my calculations, that
> is 108 to 125 amps at 120V. The generator can support even higher
> wattages in surges.
>
> But it comes bundled with a 100A transfer switch. My house (and
> essentially all around here) are 200A at the meter. Can anyone explain
> the logic behind this? Am I interpreting this incorrectly, or can the
> generator supply more current than the bundled transfer switch can
> handle?
>
15kw / 220vac = 68 amps. so you have 2 legs of 120vac at 60amps each or
thereabouts. Your transfer switch is probably good for 100 amps / leg.
--
Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html
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| SQLit 2005-10-17, 11:21 pm |
|
"Vaughn" <vaughnsimonHATESSPAM@att.fake.net> wrote in message
news:5vX4f.451447$5N3.363142@bgtnsc05-news.ops.worldnet.att.net...
>
> <wcwood@gmail.com> wrote in message
> news:1129593047.431189.135170@g43g2000cwa.googlegroups.com...
>
> It is probably not rated to supply full power to one side. 15KW at
220
> volts comes out to 68 amps.
>
>
> Just for fun, figure out what it will cost you to run that thing at
50%
> power for 30 days.
>
> No. It will likely not be allowed by your electrical inspector.
That
> said, what size is your main breaker?
The electrical inspector will only care if the new equipment is not
installed properly. Main breaker is irrelevant. The generac package was
designed to be installed nation wide with only a few local code
considerations.
Most folks understand when they install a 15kw genny that they are NOT going
to operate like normal. Some loads will have to be used one at a time. The
electrical service considers that you WILL OPERATE EVERYTHING AT ONCE.
These gennys are not rated for PRIME power. Do not even think about running
it for long periods of time at 100%. Unless of course your looking for a
failure at the worst possible time.
Good rule is figure your load first and then divide the gen capacity by 80%
keep that as your max load. Check the fuel consumption values, they can be
daunting.
Check with some one knowlegable/local on NG before ya buy. There can be some
issues with NG and cold weather.
>
> The generator can supply 68 amps per side, but the problem is that
your
> utility can supply 200 and you will probably have to supply a transfer
switch
> sized for that, unless you are going to power a sub-panel.
>
> Vaughn
>
>
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| Vaughn 2005-10-18, 8:21 am |
|
"SQLit" <sqlit@qwest.net> wrote in message
news:uRY4f.101$Gb6.19251@news.uswest.net...
>
> That
>
> The electrical inspector will only care if the new equipment is not
> installed properly. Main breaker is irrelevant. The generac package was
> designed to be installed nation wide with only a few local code
> considerations.
>
The potential problem is the size of the service conductors for the house
and the size of the main breaker. The electrical inspector is unlikely to allow
a 100-amp component in a 200-amp circuit. That said, differing areas vary
widely in what you can get away with, and I learned a long time ago to stop
predicting the behavior of building officials.
I CAN predict, however, that the inspector will not be impressed with the
argument that the generator package was designed for nationwide use and
therefore local code does not apply.
Vaughn
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| On Tue, 18 Oct 2005 10:19:27 GMT, "Vaughn" <vaughnsimonHATESSPAM@att.fake.net>
wrote:
>
>"SQLit" <sqlit@qwest.net> wrote in message
>news:uRY4f.101$Gb6.19251@news.uswest.net...
> The potential problem is the size of the service conductors for the house
>and the size of the main breaker. The electrical inspector is unlikely to allow
>a 100-amp component in a 200-amp circuit. That said, differing areas vary
>widely in what you can get away with, and I learned a long time ago to stop
>predicting the behavior of building officials.
>
> I CAN predict, however, that the inspector will not be impressed with the
>argument that the generator package was designed for nationwide use and
>therefore local code does not apply.
>
>Vaughn
>
>
Hi Vaughn,
These aren't "whole house" switches that install between the
meter and the main panel.
All the Generac auto-tranfer switches I've seen sold lately
are designed to be sub-panels attached to whatever sized main
panel you have via a 60-100 breaker.
Important loads are then connected to the sub-panel, hopefully
staying under the limit of both the feed breaker and the genset
capacity.
If you see one for sale on eBay, be aware that people are cut/pasting
stuff from the Generac home page. The transfer switches have no
smarts, don't autostart anything, or exercise your genset weekly.
That capability is supplied by their gensets themselves.
But they Are UL approved, and have room for a dozen or so standard
(Murray or Homeline?) breakers. And a heavy 240V powered
break-before-make solenoid switch. Nice sub-panels.
They'll switch if the main power is off, and genset power comes up.
And return to mains (if available), when genset goes off.
Steve (beertender/zeromedic)
ps. I have a fair copy of Onan major service manual 927-500 for
CCK spec A thru K if you need. 60 pages.
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| Vaughn 2005-10-18, 9:21 pm |
|
"zero" <zeromedic@go.com> wrote in message
news:4354ea98.138228037@news.verizon.net...
> All the Generac auto-tranfer switches I've seen sold lately
> are designed to be sub-panels attached to whatever sized main
> panel you have via a 60-100 breaker.
So that's the deal. Thanks for solving the mystery.
> ps. I have a fair copy of Onan major service manual 927-500 for
> CCK spec A thru K if you need. 60 pages.
Let's make a deal! I hope I never need it, but I would hate to need it and
not have it.
Vaughn
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| On Tue, 18 Oct 2005 23:58:29 GMT, "Vaughn" <vaughnsimonHATESSPAM@att.fake.net>
wrote:
>
>"zero" <zeromedic@go.com> wrote in message
>news:4354ea98.138228037@news.verizon.net...
>
> So that's the deal. Thanks for solving the mystery.
>
>
> Let's make a deal! I hope I never need it, but I would hate to need it and
>not have it.
>
>Vaughn
>
You've got mail. From me but via a Yahoo account.
Steve
| |
| Bruce in Alaska 2005-10-19, 4:21 pm |
| In article
<F_f5f.457577$5N3.214753@bgtnsc05-news.ops.worldnet.att.net>,
"Vaughn" <vaughnsimonHATESSPAM@att.fake.net> wrote:
> "zero" <zeromedic@go.com> wrote in message
> news:4354ea98.138228037@news.verizon.net...
>
> So that's the deal. Thanks for solving the mystery.
>
>
> Let's make a deal! I hope I never need it, but I would hate to need it
> and
> not have it.
>
> Vaughn
>
>
>
If you have that manual as a PDF file, I would appreciate a copy.
Bruce in alaska
--
add a <2> before @
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