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I need to clarify a question that I have.
Can a 20kw generator back a entire house panel that is 200amps 240volt. The generator has a 100 main breaker. I know the load of the house is 66 amps one leg second leg 53 amps.
I wanna know if the install is nec complaint. Regardless of load!!
 

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I need to clarify a question that I have.
Can a 20kw generator back a entire house panel that is 200amps 240volt. The generator has a 100 main breaker. I know the load of the house is 66 amps one leg second leg 53 amps.
I wanna know if the install is nec complaint. Regardless of load!!
What do you mean regardless of the load. If the generator is rated 100 amps and the panel has a max load of 66 amps then it should be okay.
 

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Dennis Alwon said:
What do you mean regardless of the load. If the generator is rated 100 amps and the panel has a max load of 66 amps then it should be okay.
Rumor is that there was an issue from ecmag or some other mag, that stated you can only back up a 200 amp house with and equal generator cable of handling 200 amps. Anyone here of this
 

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Rumor is that there was an issue from ecmag or some other mag, that stated you can only back up a 200 amp house with and equal generator cable of handling 200 amps. Anyone here of this
If that was true (it is not), few generators would get installed. Owners like the ability to select different loads at different times.
 
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Rumor is that there was an issue from ecmag or some other mag, that stated you can only back up a 200 amp house with and equal generator cable of handling 200 amps. Anyone here of this
I believe you cannot have a generator that is 100 amps feeding loads totalling more than 100 amps with an automatic transfer switch unless there is a system that will shed the loads.
 
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We install 20KW generators on homes ranging 1500 to 3500 sq ft with no problem, depending on the set up. Using automatic transfer switches, with load shedding capacity. It's all about load management. New transfer switches dump loads to stay on line. Basically, it is what are you asking the generator to handle. If generators had to handle the entire load of a building or home, then they would never be practical.
 

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Discussion Starter #8
tufts46argled said:
We install 20KW generators on homes ranging 1500 to 3500 sq ft with no problem, depending on the set up. Using automatic transfer switches, with load shedding capacity. It's all about load management. New transfer switches dump loads to stay on line. Basically, it is what are you asking the generator to handle. If generators had to handle the entire load of a building or home, then they would never be practical.
Let me rephrase the question. Is it code complaint to backup an entire house panel for a " residential application. " That has a 200 amp 120/240 service with a automatic transfer switch that is capable of shedding loads referred to as " load management. " as anyone done this type of installation and have AHJ pass the installation?
 

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Let me rephrase the question. Is it code complaint to backup an entire house panel for a " residential application. " That has a 200 amp 120/240 service with a automatic transfer switch that is capable of shedding loads referred to as " load management. " as anyone done this type of installation and have AHJ pass the installation?
Never hurts to call your AHJ to verify, but as long as the T-switch is service rated @ 200amps and you utilize the load shedding controls, I don't see why it wouldn't be compliant.
 

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Another thing you may need to consider is if the existing panel is a 3-wire service.

I believe that once you install the t-switch, it becomes a feeder, and the main panel a sub panel. 4-wire will be required.
 

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Let me rephrase the question. Is it code complaint to backup an entire house panel for a " residential application. " That has a 200 amp 120/240 service with a automatic transfer switch that is capable of shedding loads referred to as " load management. " as anyone done this type of installation and have AHJ pass the installation?
Let me just say, we have never had an issue with an AHJ and we work in multiple districts.
 

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Another thing you may need to consider is if the existing panel is a 3-wire service.

I believe that once you install the t-switch, it becomes a feeder, and the main panel a sub panel. 4-wire will be required.
We wire the ATS and the panel down stream from the ATS 4-wire.
 

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I need to clarify a question that I have.
Can a 20kw generator back a entire house panel that is 200amps 240volt. The generator has a 100 main breaker. I know the load of the house is 66 amps one leg second leg 53 amps.
I wanna know if the install is nec complaint. Regardless of load!!
yes, i did it year before last.
presuming this is a standard house generator:
if the gen.. is nat. gas its only 18kw, lp its 20kw (usually)
also, if you read into the gen manual a bit, its not supposed to be continuously loaded over a certain amount (i think its 50%).
if you look the 100a breaker is only fed with #6 or #8.

i would tell them if they have to serve that load continuously during an outage, the gen needs to be bigger, just to cover your arse when they kill it lol
 

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This was added to the 2008 NEC


702.5 Capacity and Rating.

(A) Available Short-Circuit Current.
Optional standby
system equipment shall be suitable for the maximum available
short-circuit current at its terminals.

(B) System Capacity. The calculations of load on the
standby source shall be made in accordance with Article
220 or by another approved method.

(1) Manual Transfer Equipment. Where manual transfer
equipment is used, an optional standby system shall have
adequate capacity and rating for the supply of all equipment
intended to be operated at one time. The user of the
optional standby system shall be permitted to select the
load connected to the system.

(2) Automatic Transfer Equipment. Where automatic
transfer equipment is used, an optional standby system
shall comply with (2)(a) or (2)(b).

(a) Full Load. The standby source shall be capable of
supplying the full load that is transferred by the automatic
transfer equipment.

(b) Load Management. Where a system is employed
that will automatically manage the connected load, the
standby source shall have a capacity sufficient to supply the
maximum load that will be connected by the load management
system.
 

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Our jurisdiction required us to do a full load calculation on the dwelling and size the generator according to the final calculations.
Most people here ended up with a 40kw. Way over kill due to the fact that the typical 2000 sf house really can only draw 60amps with everything running.
20kw seems to be practical for the average full electric house.
Maybe the load shed equipment is the way to go. I have only installed one of those and it was a Briggs and Stratton that the owner supplied.

Did I just jack this thread??
 

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(b) Load Management. Where a system is employed
that will automatically manage the connected load, the
standby source shall have a capacity sufficient to supply the
maximum load that will be connected by the load management
system.

What are we talking about here with "automatic load management"?

A PLC with inputs that turns contactors on/off? or.... ?
 

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What are we talking about here with "automatic load management"?

A PLC with inputs that turns contactors on/off? or.... ?
That's a little over the top but it could be done. A more common way is to have the desired loads on a seperate panel fed from the ATS.

There are also smart panels that basically performs the same function in a single load center.

Roger
 

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What are we talking about here with "automatic load management"?

A PLC with inputs that turns contactors on/off? or.... ?
In my opinion anything you can up with.

It might be as simple as using auxiliary contacts on the ATS to break the air conditioning control circuit(s).

I am guessing that for most homes it would be more economical to set a separate panel for the standby loads instead of getting too elaborate with PLCs or other controls.

(Looks like Roger beat me to it while I was typing) :)
 

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That's a little over the top
I once used a PLC to control an regular overhead door ...... OK I had spare time, I had the PLC and I was trying to learn programing ......... god help the people that had to figure it out after I was gone.
 

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If I had a generator tied to my electrical system, I would want to be able to heat water, dry clothes, run my A/C, turn on my heater, or cook, but I'd hate to pay extra to be able to do them all at once as I'm capable of manual load control. Putting selective loads on a separate panel would not allow this.
 
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