Puppeteer

Author Topic: Transfer switch rant  (Read 52169 times)

mobile_bob

  • Administrator
  • Hero Member
  • *****
  • Posts: 2940
    • View Profile
Re: Transfer switch rant
« Reply #90 on: November 10, 2006, 07:28:52 AM »
buickandadeere:

"AS for a reversing starter as a transfer switch. The stinker is you will have to feed each contactor from the bottom and take power to your main house/building/service panel off the top of the contactors."


why would i have to feed from the bottom?

and how do i feed from the bottom of a type 3 allen bradley when the feed and output terminals are all out the top?

even the conventional contactors can be configured and fed from the top and output'd from the bottom, it is a simple matter of reconfiguring the wiring, is it not?
if not why not? basically you have on each two contact's with a bar that connects the two, so i see no reason that one could not connect either way, i dont see how the contactor can tell which way is which?

as for the neutral being switched  or not, why couldnt i just use 2 of the 3 poles, or in other words leave the center unswitched if so required

anyone else:

i might also mention my application perhaps it makes a difference

i am planning off grid, so the two feed sources are
1. from an inverter
2 from a generator

inverter feed one contactor, the generator the other contactor
if the generator comes online, it switches the reversing contactors so the inverter is off line and the generator is online,
when the generator goes offline the inverter switches the contactor backonline , further...

all the power apparatus will be seperate from the house panel, so the house panel has only one feed comeing into it, and as far as the house is concerned
it has no idea where the power is coming from, so

i should bond everything in the power house to ground, and bond the house panel to ground

also where i am building there is no inspector or overseeing authority to inspect anything,

so basically the way i see it is, if i follow national code in the house, then i am safe with my house no matter if the house is inspected or not, and
the power house being a seperate system if wired to code should be safe no matter if inspected or not.

basically i have two seperate systems that if inspected are the same as and should be viewed as two different systems, correct?

bob g
otherpower.com, microcogen.info, practicalmachinist.com
(useful forums), utterpower.com for all sorts of diy info

t19

  • Hero Member
  • *****
  • Posts: 1437
  • Tanks and Lister... Heavy Metal
    • View Profile
Re: Transfer switch rant
« Reply #91 on: November 10, 2006, 02:09:39 PM »
Would you please tell my wife  " Buickanddeere was right"

I could win a Nobel prize in the morning, and by the afternoon my wife would have found fault in the way I parked the car, or the flavor of ice cream I brought home, or etc etc.

And as a married man you expect to be treated differently to the rest of us ??? LOL  :D :D
There is plenty of room for all of Gods creatures... right next to the mashed potatoes...

buickanddeere

  • Hero Member
  • *****
  • Posts: 807
    • View Profile
Re: Transfer switch rant
« Reply #92 on: November 11, 2006, 03:34:28 AM »
  I was thinking today that contactors are different than breakers. The Electrical Code in any country requires the stationary contact of the breaker to be Supply side.And the moving contact side of the breaker to be load side.
  The reversing contactors would be closer to code and conventional wiring practices. If the entire reversing starter was mounted upside down.
    Then the supply from the generator and the supply from the invertor would each connect to their contactors "Top" terminals. The house would be supplied from the bottom/common "load" terminals.
 For those runing three phase you will have to "uncross" two of three phases on one of the conactors. We don't want to reverse motor loads when swapping from invertor to generator.   
  If your invertor has the neutral bonded to ground. Then the generator is required to have it's neutral bonded to earth as well. Both the invertor and generator will require their own three pole disconnect to open their neutral to isolate them from each other and the service panel.
 And again, we can't run the ground and neutral in paralell. The neutral to ground bond takes place in one location only, not two or more.
     Single phase power doesn't have phase 1 and phase 2, it's a single phase. Written as L1 and L2.
    Three phase power has three different sine waves, not one.
    To obtain fire insurance around here. An off grid solar, wind turbine, generator or  powered from "what ever" structure. Has to be wired as per the electrical code as if connected to the utility grid.   

mobile_bob

  • Administrator
  • Hero Member
  • *****
  • Posts: 2940
    • View Profile
Re: Transfer switch rant
« Reply #93 on: November 11, 2006, 04:03:49 AM »
all of the 3 phase reversing contactors i have seen , either top and down posts or the all top posts are configured with large jumpers external to the contactor

this allows the contactor to remain in the upright position, one would not want to turn one upside down as the weight of the solenoid could keep contacts locked


usually the reversing contactor has the input feeds ran to one contactor, and then jumpered to the second contactor (with 2 legs swapped). and the output terminals of each contactor is jumpered together and connected to the load.

all one has to do is remove the upper jumpers and feed each contactor from the two sources, and then use whatever controll is appropriate to switch the contactors between the two power sources.

seems pretty clean and elegant to me

bob g
otherpower.com, microcogen.info, practicalmachinist.com
(useful forums), utterpower.com for all sorts of diy info

mobile_bob

  • Administrator
  • Hero Member
  • *****
  • Posts: 2940
    • View Profile
Re: Transfer switch rant
« Reply #94 on: November 11, 2006, 04:07:01 AM »
also in the allen bradley contactors as well as everyother one i have seen all contacts are stationary, and are commuted by a moving bar that is actuated by the solenoid
so that should satisfy the requirement that the feed side be stationary and not moving.

bobg
otherpower.com, microcogen.info, practicalmachinist.com
(useful forums), utterpower.com for all sorts of diy info

buickanddeere

  • Hero Member
  • *****
  • Posts: 807
    • View Profile
Re: Transfer switch rant
« Reply #95 on: November 11, 2006, 12:05:41 PM »
  The contacters I usually work with and think off move the contact bar horizontal.

  D*mm, sorry what was I thinking :-[ :-[ :-[? Too late at night and thinking three phase and swapping phases to change rotation or something? On your application all the jumpers between the top/input of the contactors get tossed. And two sepaate supplies used. 
  Yes you can/should feed each contactor to it's top contacts. Then both contactor's bottom/output/load contacts are tied together as "load". Then the house will be supplied from the bottom terminals, just like the motor would have been. 
   Are you going to keep the over load heaters for equipment thermal protection? And what are you planning to use for short circuit protection?
 
   About all to worry about is grounding, neutrals and labelling the box " Danger more than one high voltage supply".
  To operate the contactor's coils.Chatter due to voltage drop while starting heavy loads can be eliminated if. The coils are 120V and powered off thier own UPS. Or if the coils are DC and have thier own supply that won't dip  voltages when system draw is high.

bitsnpieces1

  • Full Member
  • ***
  • Posts: 247
    • View Profile
Re: Transfer switch rant
« Reply #96 on: November 12, 2006, 06:22:55 PM »
  Another possible source would be a "low voltage start" contactor.  At the place I used to work we had several older 75Hp 3ph motors that needed to be started on a reduced voltage then switched to lne volts once up to near running speed.  The incoming voltage went through a included transformer to get the reduced voltage.  When you turned the HOA switch on, the contactor pulled in the lo-volt contacts for a determined period of time and then would disconnect them and pull in the full volt contacts. 
  You could wire the gen/line wires to the lo-volt/hi-volt terminals, then deactivate the timer and use a manual switchover.  It would also give you a center off(disconnect) position since both of the connect positions are solenoid operated .  lose power = immediate dropout of ALL contacts.  Gives you a failsafe situation.  These might be obtainable fairly cheaply with the switchover from lo-volt start to VFDs. 
Lister Petter AC1, Listeroid 12/1, Briggs & Stratton ZZ, various US Mil. surplus engines. Crosley (American) 4cyl marine engine(26hp).

SCOTT

  • Full Member
  • ***
  • Posts: 209
    • View Profile
Re: Transfer switch rant
« Reply #97 on: December 04, 2006, 04:33:55 PM »
I  just spoke to a tech rep at Reliance controls (http://www.reliancecontrols.com/)  I explained to the rep that I have a 10kw generator that will be set up 230v and I wanted to have the ability to select either utility or generator to run my house. 

The questions I have are:
  1.The required wiring of the head
  2 The wiring of the transfer switch.

1.  As I understand the documents on the ST head:
I connect the jumper bar to U5 and U6 for 230v output   
I am unsure about the following: the U3 and U4 connected will then make the neutral leg. 
If the above is in fact the case, I can run an appropriate gage wire from the gen head to the transfer switch.  The 3 wires would be the two leads on the back of the dog house plus a new lead from the U3 and U4.  The two on the back would be the 115v legs and the new 3rd lead would be the neutral.  The gen head and engine/frame is grounded to a copper rod driven into the soil.

2.   When I asked the rep at Reliance if the neutral needed to be switched he said no, it could be connected directly to my neutral bar in my existing service panel. I have done a fair amount of googling for transfer switches, and the vast majority are 2  pole vs. 3 pole.  Is there anyone who knows for SURE if what the Reliance rep said is accurate?  I do intend to have a local electrician do the transfer switch lnstall, but I want to get as much of the grunt work done as possible, digging trench, pulling cable mounting box etc.  He suggested the following switch.

              http://www.electricgeneratorsdirect.com/catalog/product_info.php?manufacturers_id=19&products_id=523&osCsid=a46bb40479d


Regarding grounding, I have the engine and gen head grounded at their location, about 80’ from the main service panel.  I would make sense to me that the house would use the existing grounding in the service panel, vs. running a ground from the gen head to the transfer switch.  If you want the shortest path to ground, it makes sense to use what is already in the main service panel.  If the above is true I can run something like 6/3  vs having to run 6/4  80’ at about $2.00/ ft

I welcome corrections and suggestions. 
net metering with a 6/1 in Connecticut
12/1
6/1

rmchambers

  • Hero Member
  • *****
  • Posts: 505
    • View Profile
Re: Transfer switch rant
« Reply #98 on: December 04, 2006, 05:35:19 PM »
Is the ST Genhead bonded to ground on the genset?  I don't believe it is, if it isn't then you wouldn't need to switch the neutral.  If the insulation ever failed on the gen-head then you could have two connected disparate grounds and that's not good.

If you switch the neutral as well then you need never worry about it since you can never have both neutrals connected at the same time.

The genset must be grounded for your own protection and that of the device but you don't ever want to be in the position of the house ground somehow competing with the genset ground rod.

Search around the site, there's a huge discussion on grounds and neutral switching.


Robert