Electrical Engineering - Is there a difference between amps at 120v and amps at 240v?

Author

Is there a difference between amps at 120v and amps at 240v?

Roveer

2006-04-05, 7:21 pm

I'm putting together a load sheet for our public utility and I'm
collecting up all the devices that consume electricity and making a
table that shows each device. In NJ JCP&L uses what is called a load
sheet which is in my opinion wholly inadequate to develop the necessary
amps required for a property. An example is they ask what is the
largest horsepower pump that will be used. Well for our projects,
their may be a half dozen pumps, up to 15 A/C compressors etc. We do
big projects, the one I'm working on will most likely require 3000 amps
and JCP&L is not sure how to deal with this other than to say 3 phase.
Of course 3 phase is about 5 miles away, so we have to think outside
the box.

My question is this.

When listing the equipment and it's amperage (which is being provided
by the individual contractors), is an amp always an amp? What I mean
is if I have an A/C condenser rated at 24 amps and I know that device
is a 240 volt device does that have any special meaning to the public
utility? Or does it mean that if it were a 120v device it would have
been 48 amps?

My HVAC contractor has given me a list of equipment mixed 120 and 240
volt that adds up to 826 amps. Do I need to be concerned as to whether
it is 120 or 240? The electrician has installed a 1200 amp service for
the main house, but he has also installed an additional 800 amps in
seperate panels in two out buildings. We are currently fighting with
JCP&L that the 167KVA transformer is wholly insufficient. My
understanding is that a 167 gives 600-800 usable amps and that it may
be able to operate up to 1000 amps.

Our determinations are that we will need 1,200 amps for the house, 800
for the outbuildings, another 1,000 for the outside pumps, ponds,
irrigation, site lighting etc and another 800 amps for a large 24 stall
barn which will be installed. This gives a potential for 3,800 amps
total based on paper. Now I know that JCP&L does a calculation whereby
they know that full amperage draw will never happen, BUT in these large
scale residential properties (31,000 sq ft) It is possible that at
times (Parties), that most of this equipment is running. We are no
longer living in a "dont' have something plugged into every outlet
environment" It would happen that all 15 HVAC zones are running during
a large gala while the pond aeirators and fountains and pool and
jazuzzi pumps and significant lighting are all operational at one time.
JCP&L needs to understand this.

So, is an amp an amp when it comes to these calculations?

Thanks for your help. Oh, don't worry, I'm not trying to replace good
engineering practices, I'm just trying to make sure that my electrician
and power utility are taking everything into consideration. They still
make all the calls, I just need to be an enlightened GC.

Salmon Egg

2006-04-05, 9:21 pm

On 4/5/06 2:48 PM, in article
1144273702.345778.275860@i39g2000cwa.googlegroups.com, "Roveer"
<roveer@erols.com> wrote:

> I'm putting together a load sheet for our public utility and I'm
> collecting up all the devices that consume electricity and making a
> table that shows each device. In NJ JCP&L uses what is called a load
> sheet which is in my opinion wholly inadequate to develop the necessary
> amps required for a property. An example is they ask what is the
> largest horsepower pump that will be used. Well for our projects,
> their may be a half dozen pumps, up to 15 A/C compressors etc. We do
> big projects, the one I'm working on will most likely require 3000 amps
> and JCP&L is not sure how to deal with this other than to say 3 phase.
> Of course 3 phase is about 5 miles away, so we have to think outside
> the box.

They come in different colors. They are color coded like transistors. Look
at the fuses.

Bill
-- Ferme le Bush

gfretwell@aol.com

2006-04-06, 1:21 am

On 5 Apr 2006 14:48:22 -0700, "Roveer" <roveer@erols.com> wrote:

>I'm putting together a load sheet for our public utility and I'm
>collecting up all the devices that consume electricity and making a
>table that shows each device. In NJ JCP&L uses what is called a load
>sheet which is in my opinion wholly inadequate to develop the necessary
>amps required for a property. An example is they ask what is the
>largest horsepower pump that will be used. Well for our projects,
>their may be a half dozen pumps, up to 15 A/C compressors etc. We do
>big projects, the one I'm working on will most likely require 3000 amps
>and JCP&L is not sure how to deal with this other than to say 3 phase.
>Of course 3 phase is about 5 miles away, so we have to think outside
>the box.
>
>My question is this.
>
>When listing the equipment and it's amperage (which is being provided
>by the individual contractors), is an amp always an amp? What I mean
>is if I have an A/C condenser rated at 24 amps and I know that device
>is a 240 volt device does that have any special meaning to the public
>utility? Or does it mean that if it were a 120v device it would have
>been 48 amps?
>
>My HVAC contractor has given me a list of equipment mixed 120 and 240
>volt that adds up to 826 amps. Do I need to be concerned as to whether
>it is 120 or 240? The electrician has installed a 1200 amp service for
>the main house, but he has also installed an additional 800 amps in
>seperate panels in two out buildings. We are currently fighting with
>JCP&L that the 167KVA transformer is wholly insufficient. My
>understanding is that a 167 gives 600-800 usable amps and that it may
>be able to operate up to 1000 amps.
>
>Our determinations are that we will need 1,200 amps for the house, 800
>for the outbuildings, another 1,000 for the outside pumps, ponds,
>irrigation, site lighting etc and another 800 amps for a large 24 stall
>barn which will be installed. This gives a potential for 3,800 amps
>total based on paper. Now I know that JCP&L does a calculation whereby
>they know that full amperage draw will never happen, BUT in these large
>scale residential properties (31,000 sq ft) It is possible that at
>times (Parties), that most of this equipment is running. We are no
>longer living in a "dont' have something plugged into every outlet
>environment" It would happen that all 15 HVAC zones are running during
>a large gala while the pond aeirators and fountains and pool and
>jazuzzi pumps and significant lighting are all operational at one time.
> JCP&L needs to understand this.
>
>So, is an amp an amp when it comes to these calculations?
>
>Thanks for your help. Oh, don't worry, I'm not trying to replace good
>engineering practices, I'm just trying to make sure that my electrician
>and power utility are taking everything into consideration. They still
>make all the calls, I just need to be an enlightened GC.

When computing service load the 120v stuff ends up being half of it's
amps, assuming you balance the load across the 2 phases

TimPerry

2006-04-06, 1:21 am

"Roveer" <roveer@erols.com> wrote in message
news:1144273702.345778.275860@i39g2000cwa.googlegroups.com...
> I'm putting together a load sheet for our public utility and I'm
> collecting up all the devices that consume electricity and making a
> table that shows each device. In NJ JCP&L uses what is called a load
> sheet which is in my opinion wholly inadequate to develop the necessary
> amps required for a property. An example is they ask what is the
> largest horsepower pump that will be used. Well for our projects,
> their may be a half dozen pumps, up to 15 A/C compressors etc. We do
> big projects, the one I'm working on will most likely require 3000 amps
> and JCP&L is not sure how to deal with this other than to say 3 phase.
> Of course 3 phase is about 5 miles away, so we have to think outside
> the box.
>
> My question is this.
>
> When listing the equipment and it's amperage (which is being provided
> by the individual contractors), is an amp always an amp?

an amp is always an amp.... but: good practice is to divide up the 120 volt
loads between avalible circuits.

assuming you single phase circuit is exactly ballanced, add up the 240 loads
then 1/2 of all the 120 loads. (you have to facor in motor starting currents
and consider the possibility if multiple simultaneous starts as in the event
of a brief power intruption)

> What I mean
> is if I have an A/C condenser rated at 24 amps and I know that device
> is a 240 volt device does that have any special meaning to the public
> utility?

> Or does it mean that if it were a 120v device it would have
> been 48 amps?

P= e * i * (pf)

> My HVAC contractor has given me a list of equipment mixed 120 and 240
> volt that adds up to 826 amps. Do I need to be concerned as to whether
> it is 120 or 240? The electrician has installed a 1200 amp service for
> the main house,

see first reply

> but he has also installed an additional 800 amps in
> seperate panels in two out buildings.

We are currently fighting with
> JCP&L that the 167KVA transformer is wholly insufficient. My
> understanding is that a 167 gives 600-800 usable amps and that it may
> be able to operate up to 1000 amps.

you electrition/contractor should have had this completely organized before
installing the first wire.

>
> Our determinations are that we will need 1,200 amps for the house, 800
> for the outbuildings, another 1,000 for the outside pumps, ponds,
> irrigation, site lighting etc and another 800 amps for a large 24 stall
> barn which will be installed. This gives a potential for 3,800 amps
> total based on paper. Now I know that JCP&L does a calculation whereby
> they know that full amperage draw will never happen, BUT in these large
> scale residential properties (31,000 sq ft) It is possible that at
> times (Parties), that most of this equipment is running. We are no
> longer living in a "dont' have something plugged into every outlet
> environment" It would happen that all 15 HVAC zones are running during
> a large gala while the pond aeirators and fountains and pool and
> jazuzzi pumps and significant lighting are all operational at one time.
> JCP&L needs to understand this.

price out the differance between running a third wire for five miles and
sufficient generator power to run the parties. heres a hint: at todays
prices a brand name 100KW generator w/xfer switch + parts & labor costs
about $36K to $38K (USD) fuel is extra.

sound like you have the wiring completed already. converting to 3 phase
panels will be costly.

>
> So, is an amp an amp when it comes to these calculations?
>
> Thanks for your help. Oh, don't worry, I'm not trying to replace good
> engineering practices, I'm just trying to make sure that my electrician
> and power utility are taking everything into consideration. They still
> make all the calls, I just need to be an enlightened GC.
>

it sounds very much like its late in the project to worrying over this. what
does the architect say? who designed the AC? (no answer needed - i think
you are asking the wrong folks)

was this a design-build type project? (shudder)

it doesn't sound to me like you will sleep easy until you have hired an
independent architect or master electrician to review the situation.

Ben Miller

2006-04-06, 2:21 am

"Roveer" <roveer@erols.com> wrote in message
news:1144273702.345778.275860@i39g2000cwa.googlegroups.com...
> I'm putting together a load sheet for our public utility and I'm
> collecting up all the devices that consume electricity and making a
> table that shows each device. In NJ JCP&L uses what is called a load
> sheet which is in my opinion wholly inadequate to develop the necessary
> amps required for a property. An example is they ask what is the
> largest horsepower pump that will be used. Well for our projects,
> their may be a half dozen pumps, up to 15 A/C compressors etc. We do
> big projects, the one I'm working on will most likely require 3000 amps
> and JCP&L is not sure how to deal with this other than to say 3 phase.
> Of course 3 phase is about 5 miles away, so we have to think outside
> the box.
>
> My question is this.
>
> When listing the equipment and it's amperage (which is being provided
> by the individual contractors), is an amp always an amp? What I mean
> is if I have an A/C condenser rated at 24 amps and I know that device
> is a 240 volt device does that have any special meaning to the public
> utility? Or does it mean that if it were a 120v device it would have
> been 48 amps?
>
> My HVAC contractor has given me a list of equipment mixed 120 and 240
> volt that adds up to 826 amps. Do I need to be concerned as to whether
> it is 120 or 240? The electrician has installed a 1200 amp service for
> the main house, but he has also installed an additional 800 amps in
> seperate panels in two out buildings. We are currently fighting with
> JCP&L that the 167KVA transformer is wholly insufficient. My
> understanding is that a 167 gives 600-800 usable amps and that it may
> be able to operate up to 1000 amps.
>
> Our determinations are that we will need 1,200 amps for the house, 800
> for the outbuildings, another 1,000 for the outside pumps, ponds,
> irrigation, site lighting etc and another 800 amps for a large 24 stall
> barn which will be installed. This gives a potential for 3,800 amps
> total based on paper. Now I know that JCP&L does a calculation whereby
> they know that full amperage draw will never happen, BUT in these large
> scale residential properties (31,000 sq ft) It is possible that at
> times (Parties), that most of this equipment is running. We are no
> longer living in a "dont' have something plugged into every outlet
> environment" It would happen that all 15 HVAC zones are running during
> a large gala while the pond aeirators and fountains and pool and
> jazuzzi pumps and significant lighting are all operational at one time.
> JCP&L needs to understand this.
>
> So, is an amp an amp when it comes to these calculations?
>
> Thanks for your help. Oh, don't worry, I'm not trying to replace good
> engineering practices, I'm just trying to make sure that my electrician
> and power utility are taking everything into consideration. They still
> make all the calls, I just need to be an enlightened GC.
>

For a system that size: 1) If you didn't have a licensed electrical engineer
design the system, you should; and 2) I would think the utility would send
an engineer to meet with your electrical engineer and discuss all of those
things.

The utility load sheets are all very simplified. It gives them the numbers
that they need to size transformers and lines. Don't compare the transformer
rating with your installed capacity. They use rules of thimb and diversity
factors, and your service size is also based on diversity, all of which
results in a lot of "fudge factor". You would be surprised how low the amp
draw is on a typical service. As others have said, split the 120 loads
evenly, add the 240 loads, give them the motor information, and whatever
else they ask for. Be sure to indicate the continuous and non-continuous
loads. I would also mention special load conditions that you know about, as
you have stated above, especially simultaneous equipment operation, frequent
motor starting, etc.

If this sounds overwhelming, see number 1 above. A professional engineer
would be able to help you through all of this with very little trouble.

Ben Miller

--
Benjamin D. Miller, PE
B. MILLER ENGINEERING
www.bmillerengineering.com

Terry

2006-04-06, 3:21 pm

Paul Hovnanian P.E.

2006-04-08, 1:21 am

Roveer wrote:
>
> I'm putting together a load sheet for our public utility and I'm
> collecting up all the devices that consume electricity and making a
> table that shows each device. In NJ JCP&L uses what is called a load
> sheet which is in my opinion wholly inadequate to develop the necessary
> amps required for a property. An example is they ask what is the
> largest horsepower pump that will be used. Well for our projects,
> their may be a half dozen pumps, up to 15 A/C compressors etc. We do
> big projects, the one I'm working on will most likely require 3000 amps
> and JCP&L is not sure how to deal with this other than to say 3 phase.
> Of course 3 phase is about 5 miles away, so we have to think outside
> the box.

A 3000 Amp motor? That's either a typo, or this is a project for which
some serious engineering expertise is required. Expertise well beyond
the 'is there a difference between 120V and 240V' point.

--
Paul Hovnanian mailto:Paul@Hovnanian.com
------------------------------------------------------------------
"A doctor can bury his mistakes but an architect can only
advise his client to plant vines." -- Frank Lloyd Wright

Ben Miller

2006-04-08, 1:21 am

"Paul Hovnanian P.E." <Paul@Hovnanian.com> wrote in message
news:44373342.C6D3836A@Hovnanian.com...
> A 3000 Amp motor? That's either a typo, or this is a project for which
> some serious engineering expertise is required. Expertise well beyond
> the 'is there a difference between 120V and 240V' point.
>
He seems to have disappeared since I suggested the same thing. He probably
wants to save money. I guess he doesn't know that consultants have three
different rates...

1 Normal work, doing it right the first time - competetive
2 Emergency, gotta have it now, fixing it after it is FUBAR - premium
3 Forensic, investigating the cause of the electrical fire - expensive!

Ben Miller

--
Benjamin D. Miller, PE
B. MILLER ENGINEERING
www.bmillerengineering.com

Paul Hovnanian P.E.

2006-04-08, 1:21 pm

Ben Miller wrote:
>
> "Paul Hovnanian P.E." <Paul@Hovnanian.com> wrote in message
> news:44373342.C6D3836A@Hovnanian.com...
> He seems to have disappeared since I suggested the same thing. He probably
> wants to save money. I guess he doesn't know that consultants have three
> different rates...
>
> 1 Normal work, doing it right the first time - competetive
> 2 Emergency, gotta have it now, fixing it after it is FUBAR - premium
> 3 Forensic, investigating the cause of the electrical fire - expensive!

Do you have a rate for: 'Some unqualified person bid the job and now the
customer and/or state authorities are starting to ask questions. Like,
"Where is your license?"'

> Ben Miller
>
> --
> Benjamin D. Miller, PE
> B. MILLER ENGINEERING
> www.bmillerengineering.com

--
Paul Hovnanian mailto:Paul@Hovnanian.com
------------------------------------------------------------------
ASCII stupid question, get a stupid ANSI!

Ben Miller

2006-04-08, 4:21 pm

"Paul Hovnanian P.E." <Paul@Hovnanian.com> wrote in message
news:4437DCF5.F48577DE@Hovnanian.com...
> Do you have a rate for: 'Some unqualified person bid the job and now the
> customer and/or state authorities are starting to ask questions. Like,
> "Where is your license?"'

$50,000 x # of hoops jumped through / # of days to deadline :-)

Ben Miller
--
Benjamin D. Miller, PE
B. MILLER ENGINEERING
www.bmillerengineering.com

gfretwell@aol.com

2006-04-09, 1:21 am

On Sat, 8 Apr 2006 13:54:55 -0500, "Ben Miller"
<benmiller@worldnet.att.net> wrote:

>$50,000 x # of hoops jumped through / # of days to deadline :-)
>
>Ben Miller

Finally a decent estimating tool.

Hire this man, he is a wizard

phil-news-nospam@ipal.net

2006-04-16, 5:21 am

On Fri, 07 Apr 2006 20:51:30 -0700 Paul Hovnanian P.E. <Paul@hovnanian.com> wrote:
| Roveer wrote:
|>
|> I'm putting together a load sheet for our public utility and I'm
|> collecting up all the devices that consume electricity and making a
|> table that shows each device. In NJ JCP&L uses what is called a load
|> sheet which is in my opinion wholly inadequate to develop the necessary
|> amps required for a property. An example is they ask what is the
|> largest horsepower pump that will be used. Well for our projects,
|> their may be a half dozen pumps, up to 15 A/C compressors etc. We do
|> big projects, the one I'm working on will most likely require 3000 amps
|> and JCP&L is not sure how to deal with this other than to say 3 phase.
|> Of course 3 phase is about 5 miles away, so we have to think outside
|> the box.
|
| A 3000 Amp motor? That's either a typo, or this is a project for which
| some serious engineering expertise is required. Expertise well beyond
| the 'is there a difference between 120V and 240V' point.

Hopefully he didn't mean 3000 amps all in _one_ motor. Otherwise, that
really should be done in some higher voltage, maybe as much as 2400.
But he wouldn't qualified to mess with 2400 volts (or 3000 amps) and
neither would I.

He probably needs to be thinking in kVA and then translate to amps.

And he probably needs to get building service at 480Y/277 or 600Y/347.

--
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