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Old 09-16-2007, 06:06 PM   #1
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Automatic Transfer Switch


I recently purchased a house with a 150 amp service. There is an existing manual transfer switch that I have been using with my portable generator. (Power has been out six times in 4 months.) I just purchased a 16 kw standby unit with a 16 circuit ats. My main panel is just about full and it seems that the house was spilt up into many circuits. (House is 4 bdrm, 2 1/2 bath, well and AC. Heat and cook with propane.)

I have (12) 15amp circuits, (9) 20 amp circuits, (1) 30 amp circuit, (1) 2p 20 amp for the well pump, (1) 2p 40 amp for the AC and a (1) 2p 40 amp feeding a sub panel in the garage. No permit is required but I need to have an NYS underwriter sign off.

Here are my questions.

1) Is it advisable to power two 15 amp circuits in the main panel from one 15 amp breaker in the ats?

2) In NYS, since I have to have an underwriter come out, will I be required to change out bedroom breakers to arc faults in both panels?

3) What are your thoughts on piggy-back breakers in the main panel?

4) Can I use an existing grounding rod (used for the mail panel) for the generator?

Thanks

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Old 09-16-2007, 06:19 PM   #2
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Automatic Transfer Switch


In my opinion (IMO), it would be good if you could provide more info from the nameplate on the generator. If possible state the value of 'regulation' - it is usually a percentage.

Also, generators must be sized (if very poorly regulated) to account for any 'starting' currents. This means that anything that uses electric motors (refrigerators, air conditioning & the like) will generally use 4 to 8 times their 'run' current when starting. A poorly regulated generator will not cope with this, if it is not capable of delivering this kind of current. It may stall or be damaged under such conditions.

It's great that you have provided circuit breaker details but it's more important that you provide the details of the devices & their current/power ratings that are connected to these circuits.

I'm sorry if this seems difficult but this is the correct way to ensure that a generator is sized correctly for the load.

I have designed many ATS units on large switchboards. It is critical that they are connected appropriately to the supply authoritys' power & that the ATS functions in a way that is not detrimental to the generator or the supply.

Again, sorry if this sounds complicated but start with providing the types & sizes of loads you have on each circuit.

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Old 09-16-2007, 06:26 PM   #3
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Automatic Transfer Switch


You need to be sure that your panel is rated to be backfed and also that it is rated for piggyback breakers. I would not switch out to afci breakers because they are grandfathered in plus they are not part of your scope of work.
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Old 09-16-2007, 07:01 PM   #4
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Automatic Transfer Switch


First our friend in Thailand obviously has expertise in what your doing so I would give particular attention to his advice.
I'll answer the questions based on my level of experience with ats switches.
One thing that would be nice is if you could give us the model number and maker of your generator and ats.

Quote:
1) Is it advisable to power two 15 amp circuits in the main panel from one 15 amp breaker in the ats?
I suppose you could but I doubt if you would be compliant doing so and it opens a pretty big bag of worms as to loads and manufacturer requirements. If the maker of the ats says you can then go for it if not in their literature don't do it. Maybe call their tech support and see what they say.

Quote:
2) In NYS, since I have to have an underwriter come out, will I be required to change out bedroom breakers to arc faults in both panels?
I wouldn't think so since you are not touching the bedrooms.

Quote:
3) What are your thoughts on piggy-back breakers in the main panel?
They are fine if the panel excepts them.

Quote:
4) Can I use an existing grounding rod (used for the mail panel) for the generator?
Depends on the transfer switch. If it switches the the neutral of the utility then you have a seperately derived source at the generator and you would drive a ground rod and attach to the frame with a bonding jumper.

If it does not switch the neutral of the utility then it is not seperately derived and you use the grounding electrode of the main service.

Check the ats literature to see if it switches the neutral.

Here are some diagrams that may help. We can explain if you need that.

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Old 09-16-2007, 07:01 PM   #5
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Quote:
Originally Posted by guyam View Post
I recently purchased a house with a 150 amp service. There is an existing manual transfer switch that I have been using with my portable generator. (Power has been out six times in 4 months.) I just purchased a 16 kw standby unit with a 16 circuit ats. My main panel is just about full and it seems that the house was spilt up into many circuits. (House is 4 bdrm, 2 1/2 bath, well and AC. Heat and cook with propane.)

I have (12) 15amp circuits, (9) 20 amp circuits, (1) 30 amp circuit, (1) 2p 20 amp for the well pump, (1) 2p 40 amp for the AC and a (1) 2p 40 amp feeding a sub panel in the garage. No permit is required but I need to have an NYS underwriter sign off.

Here are my questions.

1) Is it advisable to power two 15 amp circuits in the main panel from one 15 amp breaker in the ats?

2) In NYS, since I have to have an underwriter come out, will I be required to change out bedroom breakers to arc faults in both panels?

3) What are your thoughts on piggy-back breakers in the main panel?

4) Can I use an existing grounding rod (used for the mail panel) for the generator?

Thanks
Actually, come to think of it, I may have overstepped the mark a tad.

My original comment was based on;

1] your new generator is not similarly sized to your portable generator,
2] your existing MTS (Manual Transfer Switch) in some way provides for 'load shedding'.

But in answer to your questions based upon the information provided;

1] no, not without knowing the loads on these circuits,
2] don't know...unless fault current details are provided,
3] piggy-back? Don't know...the Stubbs can answer this.
4] depends on the generator but generally, no.
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Last edited by elkangorito; 09-16-2007 at 07:07 PM.
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Old 09-16-2007, 07:08 PM   #6
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Automatic Transfer Switch


Kangaroo

Piggy back is just a circuit breaker that has two breakers in one mold that is single pole. Lets you increase circuits if your panel is full of full size breakers. For instance if my panel has 1 inch breakers I can remove it and add a piggy back or also called tandem breaker to gain an extra circuit off that one pole of the bus stab.

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Old 09-16-2007, 07:12 PM   #7
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Quote:
Originally Posted by Stubbie View Post
Kangaroo

Piggy back is just a circuit breaker that has two breakers in one mold that is single pole. Lets you increase circuits if your panel is full of full size breakers. For instance if my panel has 1 inch breakers I can remove it and add a piggy back or also called tandem breaker to gain an extra circuit off that one pole of the bus stab.

Stubbie
Thanks mate. I'm familiar with the term 'Tandem' breaker. Thanks for the clarification...wasn't sure about 'piggy-back' though.

EDIT: BTW, Good diags. Auxiliary power generation is generally a simple thing in OZ, with the exception of allowing for harmonics & non-sinusoidal power factor.
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Last edited by elkangorito; 09-16-2007 at 07:16 PM.
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Old 09-16-2007, 07:19 PM   #8
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No problem, just have to get used to our slang for electrical devices... even I have to scratch my head sometimes. To add I already have a pretty good idea of your level of expertise based on your posts I suspect I'll be asking you for clarification on something before long.

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Old 09-16-2007, 07:27 PM   #9
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Quote:
Originally Posted by Stubbie View Post
No problem, just have to get used to our slang for electrical devices... even I have to scratch my head sometimes. To add I already have a pretty good idea of your level of expertise based on your posts I suspect I'll be asking you for clarification on something before long.

Stubbie
I dunno about that! I have restricted my comments on this forum to the stuff that I'm familiar with, which means I'll generally keep out of NEC code related stuff (unless it is of a purely universally technical nature).

I find it is a good thing to exercise my brain in regards to electrical & quite often I can learn many new things on these forums.

But anyway mate (aussie slang), thanks for the vote of confidence. I'd love to get back into engineering here in Thailand but the government does not easily allow foreigners to occupy the jobs that they think Thai people can do. Strange considering the place is short on quality skilled people.

Anyway, I'm 'off topic', so please excuse me.
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Old 09-16-2007, 08:02 PM   #10
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Automatic Transfer Switch


Thanks very much for all the replies...

The generator liturature states, "Automatic voltage regulation - Regulates the output voltage to 2% prevents damaging voltage spikes."

Some of the following is over my head but I included everyting in case elk is bored.

GENERATOR Model 05243
Rated Maximum Continuous Power Capacity (LP) 16,000 Watts
Rated Voltage 120/240
Rated Maximum Continuous Load Current
120 Volts 133.3 LP/125 NG
240 Volts 66.6 LP/62.5 NG
Main Line Circuit Breaker 65 Amp
Phase 1
Number of Rotor Poles 2
Rated AC Frequency 60Hz
Power Factor 1

ENGINE Model 05243
Type of Engine GENERAC OHVI V-TWIN
Number of Cylinders 2
Rated Horsepower 30 @ 3,600 rpm
Displacement 992cc
Cylinder Block Aluminum w/Cast Iron Sleeve
Valve Arrangement Overhead Valve
Ignition System Solid-state w/Magneto
Governor System Electronic
Compression Ratio 9.5:1
Starter 12Vdc
Standby Operating RPM 3,600
Exercise RPM 2400
Fuel Consumption
Liquid Propane ft3/hr (gal/hr)
1/2 Load 59 (1.59)
Full Load 92 (2.51)

CONTROLS
Mode Switch
-Auto Automatic Start on Utility failure
7 day exerciser
-Off Stops unit. Power is removed
Control and charger still operate
-Manual/Test (start) Start with starter control, unit stays on. If utility fails, transfer to load takes place.
Engine Start Sequence Cyclic cranking: 7 sec. on, 7 rest (90 sec. maximum duration)
2.5 Amp Timed Trickle Battery Charger
Automatic Voltage Regulator w/Overvoltage Protection
Automatic Low Oil Pressure Shutdown
Overspeed Shutdown 72Hz
High Temperature Shutdown
Overcrank Protection
Safety Fuse Standard
Rating definitions - Standby: Applicable for supplying emergency power for the duration of the utility power outage. No overload capability is available for this rating. (All ratings in accordance with BS5514, ISO3046 and DIN6271). Maximum wattage and current are subject to and limited by such factors as fuel Btu content, ambient temperature, altitude, engine power and condition, etc. Maximum power decreases about 3.5 percent for each 1,000 feet above sea level; and also will decrease about 1 percent for each 12 C (10 F) above 15.5 C (60F).
Required fuel pressure to generator fuel inlet at all load ranges - 5 to 7 inches of water column for natural gas, 10 to 12 inches of water column for LP gas

TRANSFER SWITCH & EMERGENCY LOAD CENTER Model: 05243
No. of Poles 2
Current Rating (amps) 100
Voltage Rating (VAC) 250
Utility Voltage Monitor (fixed)
-Pick-up 70%
-Dropout 60%
Return to Utility approx. 13 sec.
Exerciser weekly for 12 minutes
UL Listed
Total of Pre-wired Circuits 16
No. 15A 120V 5
No. 20A 120V 5
No. 20A 240V 1
No. 40A 240V 1
No. 50A 240V 1
Circuit Breaker Protected
Available RMS Symmetrical
Fault Current @ 250 Volts 10,000

I have a standard rural residence. Nothing fancy. Well pump currenty protected by a 2p 20 amp breaker. AC unit sized for a 2700 sq ft home currently protected by a 2p 40 amp breaker. That is the big stuff that will be protected aside from standards like a fridge, tv and lights.

I think I worded my question wrong regarding the grounding rod. I have a rod in the ground for my main panel. Can I ground my generator directly to that rod?

Thanks for everyone's help.
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Old 09-16-2007, 08:51 PM   #11
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Quote:
Originally Posted by guyam View Post
I recently purchased a house with a 150 amp service. There is an existing manual transfer switch that I have been using with my portable generator. (Power has been out six times in 4 months.) I just purchased a 16 kw standby unit with a 16 circuit ats. My main panel is just about full and it seems that the house was spilt up into many circuits. (House is 4 bdrm, 2 1/2 bath, well and AC. Heat and cook with propane.)

I have (12) 15amp circuits, (9) 20 amp circuits, (1) 30 amp circuit, (1) 2p 20 amp for the well pump, (1) 2p 40 amp for the AC and a (1) 2p 40 amp feeding a sub panel in the garage. No permit is required but I need to have an NYS underwriter sign off.

Here are my questions.

1) Is it advisable to power two 15 amp circuits in the main panel from one 15 amp breaker in the ats?

2) In NYS, since I have to have an underwriter come out, will I be required to change out bedroom breakers to arc faults in both panels?

3) What are your thoughts on piggy-back breakers in the main panel?

4) Can I use an existing grounding rod (used for the mail panel) for the generator?

Thanks
Ok. Now we have the specs for the generator, I'll assume it will be fueled with LP & therefore give you a slightly higher power output.

In the meantime, you have mentioned that you have;

"(1) 2p 20 amp for the well pump, (1) 2p 40 amp for the AC".

It would be very beneficial to know the electrical details of each of these appliances because if I go by the circuit breaker sizes alone, the simultaneous starting current of both of these devices (assuming a minimum of 4 times the 'run' current) exceed that of the output of the generator.

EDIT: If applicable, please provide the Power Factor details of your well pump & your a/c. It may be indicated on the rating plates as 'P.F.' or Cos phi.
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Last edited by elkangorito; 09-16-2007 at 09:09 PM. Reason: Additional question.
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Old 09-16-2007, 09:05 PM   #12
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Quote:
I think I worded my question wrong regarding the grounding rod. I have a rod in the ground for my main panel. Can I ground my generator directly to that rod?
Well I can't find your transfer switch online, however a 2 pole transfer switch as your literature mentions will not switch the neutral and you will stay solidly connected to the utility neutral. You do not need to run the generator frame to any earth electrodes nor do you drive one for the generator. Your generator will be connected to the ground rod for the main panel via the connection in the transfer switch with the generator feed and service neutral which is bonded to the ground rod. Your wiring schematic will show this. Ground fault protection will be there from the equipment ground ran with the 4 wire feed of the generator to the ats and then to the neutral bar of the main service panel in your home. You can see this in the diagram posted for non-separately derived generator. Just follow the wire (neutral) that starts at the generator at the center of the Wye and you will see why you don't need to run a connection from the frame.... it would be redundant. Of course it is always a good idea to get local qualified assistance in putting your system in...

Hope this helps

Stubbie

Last edited by Stubbie; 09-16-2007 at 09:18 PM.
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Old 09-16-2007, 09:07 PM   #13
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With regard to some of your original questions:
You will not need tandems in the main panel because you will be freeing up space when you move the circuits over to the transfer panel.
Typically these panels are basically sub-panels and need to be fed by a feeder. A usual size is 50-100 amps.
Unless you will be adding new circuits you will wind up freeing up as many spaces in the main panel as there are spaces in the transfer panel.
To save space in the new panel you can certainly combine two circuits into one. This only makes sense if the two circuit are very lightly used, meaning they do not have much on them.

NY State does NOT require the use of AFCIs at all, even in new construction, so don't worry about them.

As Roo said, be careful running that big A/C off the genset. You may have starting issues. Especially if other things are running at the same time.
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Last edited by Speedy Petey; 09-16-2007 at 09:09 PM. Reason: Added info
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Old 09-17-2007, 11:55 AM   #14
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Attached is a generator selection guide (with the help of some web info) I put together some time ago for foreigners in Thailand. Please note that voltage & current references do not generally relate to the US system but will give an idea of what is required.

Also, I note from your generator specifications that it has a prospective fault current of 10 000 (ten thousand) Amps & the 'pick up' voltage is 70% of the supply voltage (as detected at the ATS). I would like to discuss these issues after your have provided the data for your air cond. & well pump.
Attached Files
File Type: zip PortableGenerators.zip (15.2 KB, 37 views)
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Last edited by elkangorito; 09-17-2007 at 12:00 PM.
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Old 09-17-2007, 01:42 PM   #15
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I am not a pro electrician, just a long-time DIYer, so these guys lost me way back. LOL
However, here is an alternative called a Connection Hub, available directly from our power company (Dominion NC Power for this part of northeastern NC and formerly called Virginia Electric Power Company or VEPCO). Check with your power company to see if they have anything like this available.
http://www.dom.com/products/generators/hub.jsp
Maybe your power company offers something similar. It costs less than an ats, and is much easier and faster to install.
Basically, the Connection Hub is installed on the meter base, and does not require a new panel of any type (AND it's portable). You simply use your existing panel.
I went with one of these in lieu of a transfer switch set-up. When I had it done, it cost me $975 including the cord vs a $1,250 quote for a limited transfer switch setup at the time, but I see from the link that it has gone up to $1,095 now plus the cost of the power cord between the meter and the generator. It operates portable or automatic generators up to 12,000 watts on 100-200 amp panels.
I have only a portable 5500 watt generator, so I can only operate all of my 120v circuits without any 240v circuits on. If the power goes out for any length of time, I simply turn off all of the 240v breakers and run all of the 120v circuits off my portable generator. If I need hot water in a prolonged outage, I shutoff all 120v breakers, and just turn on the 240v water heater breaker for an hour or so. Basically, I can run everything but the central electric heatpump system, one way or another.
When the utility line power is restored, the Hub automatically switches over to line power and cuts off the power for 30 seconds to let you know to turn off your generator.
Works for me!
Mike


Last edited by Mike Swearingen; 09-18-2007 at 02:52 AM.
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