Relay and Contactor based GENSET BACKFEED PREVENTER?

[SQLit]

http://www.green-trust.org/wiki/index.php?title=Automatic_Transfer_Switch

What I am describing is a manual switch. The user would have to
perform the following steps manually:

1) Turn off the main breaker.
2) Turn on the mechanical switch for DC input circuit to the relay,
which becomes possible only if the main breaker is off.
3) Turn on the generator (could be done at any other time in this
sequence)
4) Press the START button on the start/stop switch.

At any time, if the interlocked mechanical switch is turned off, the
contactor would open and electrical power would no longer be supplied
to the house from the generator. The interlocked switch must be in the
off position for the main breaker to be turned on.

I caught your concept of a "manual transfer device".

Where I live there MUST be mechanical interlocks. That means if either
breaker is forced into the other position BOTH breakers change state at the
same time. I am talking about internal switching from one device to
another. Steps 1&2 would have to happen with one operation.

The utilities used to have a requirement for "visible blade disconnection" I
got into a situation where no one made a 4000 amp visible blade disconnect.
So they changed the spec to mechanical interlock.
I will bet that your contactors are not 'service rated'. Do you know the
fault current your generator is capable of? How about the serving utility?
10000 amps is pretty common I have seen places where special circuit
breakers were needed because the fault current was over 10k.

Call the local jurisdictional authorities and talk to them. I do not know of
a utility that would allow what you describe. I am familiar with the
utilities in 4 western states.



--------snipped----------------

 

[Ignoramus25850]

I caught your concept of a "manual transfer device".

Where I live there MUST be mechanical interlocks. That means if either
breaker is forced into the other position BOTH breakers change state at the
same time.

That would be the case for what I was planning (now, I think, I will
just buy an interlock kit).

I am talking about internal switching from one device to
another. Steps 1&2 would have to happen with one operation.

I believe that the concept of an interlock simply prevents both from
being on at the same time. I do not think that it should be impossible
to have both devices off at the same time. That situation (both
sources off) corresponds to the OFF position on the mechanical
transfer switch.

The utilities used to have a requirement for "visible blade disconnection" I
got into a situation where no one made a 4000 amp visible blade disconnect.
So they changed the spec to mechanical interlock.
I will bet that your contactors are not 'service rated'. Do you know the
fault current your generator is capable of? How about the serving utility?
10000 amps is pretty common I have seen places where special circuit
breakers were needed because the fault current was over 10k.

You can see a sample contactor at

http://yabe.algebra.com/~ichudov/misc/ebay/Furnas75AContactor/dscf0036.jpg

Call the local jurisdictional authorities and talk to them. I do not know of
a utility that would allow what you describe. I am familiar with the
utilities in 4 western states.

Thanks... I think that I will just buy an interlock kit.

i

 

[John Grabowski]

As of now, my favorite plan is as follows.

1. Install a premade interlock kit rather than dick around with
relays. Mostly for legal reasons.

2. Also have a mag starter style switch in the line from generator to
the power panel, to help prevent arcing in the circuit breaker that is
used to feed the panel.

i

I'm not sure what your concern for arcing in the circuit breaker is about.
Circuit breakers are made to be turned on and off under load. You could
always install wiring and a circuit breaker bigger than the rated capacity
of your generator.

John G.

 

[ATP*]

I have been playing with using relays of various kinds, as well as
contactors. I already built 2 phase converters, and a remote switch,
for instance. I have a few 90A and 75A contactors and solid state
relays and mag starter buttons and whatnot.

Here's what I have been thinking about. I have a 7 kW Onan DJE
generator that I have for emergencies. I want it to power my entire
house in emergencies (I know that I cannot run AC and some other
devices while under generator power).

Not a DIY job. Get a UL listed transfer switch, have a licensed electrician
install it and get it inspected.

 

[[email protected]]

Contactors can and will fail closed! Not a good idea for a transfer switch!
I could not count the number of failed closed contactors I have replaced in
the last six years!!
Greg

I suppose you COULD use a DPDT contactor - but then why not just use
the old standby knife switch. The contactor needs power to activate
it.

And if the contactor sticks in the line position you can't use the
genset. If it sticks in the genset position, you cannot connect to the
grid. - so you are back to manually operating it anyway. Back to the
knife switch.

 

[Steve Spence]

riggghhttt. anyone with a bit of sense can install a transfer switch.

Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html

 

[ATP*]

riggghhttt. anyone with a bit of sense can install a transfer switch.

Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html

I've seen plenty of simpler electrical jobs screwed up or just poorly
executed by people with more than a bit of sense. In any case, it has to be
listed and inspected per the local utility regulations.

 

[Steve Spence]

maybe in your community, but not in mine. I wired my whole house, panels
and entrance. The power company only dropped to the meter on the pole.
that was the end of it. I did the rest.

Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html

 

[Eric R Snow]

maybe in your community, but not in mine. I wired my whole house, panels
and entrance. The power company only dropped to the meter on the pole.
that was the end of it. I did the rest.

Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html

In Washington state you are allowed to wire your own house. It then
must pass inspection. After that you must live in it for five years
before you can sell it. This is done to prevent bad wiring done by
people who are building spec homes. Not that everybody who builds a
spec home is going to do a bad job. Just that some people will skimp
and not use qualified people to do the wiring.
ERS

 

[Vaughn]

On Wed, 07 Sep 2005 18:51:51 -0400, Steve Spence
In Washington state you are allowed to wire your own house. It then
must pass inspection. After that you must live in it for five years
before you can sell it.

Strange! Here a homeowner can pull a permit to do most anything. Then the
job must pass inspection just like anything else and you are done with the
process.

Vaughn

 

[Christopher Tidy]

In Washington state you are allowed to wire your own house. It then
must pass inspection. After that you must live in it for five years
before you can sell it.

That seems like a pretty harsh regulation. Here I believe you can
legally wire your own house, but you're supposed to have it inspected
afterwards, and certainly before you sell it. But we also have a stupid
new law which means that only qualified electricians can buy consumer
units. Most people with time and good practical skills, but little
money, aren't going to pay an electrician to wire their workshop.
They'll find a consumer unit from a friend, or a demolition site, or a
dumpster. It just drives work underground. Another sad example of
European over-regulation!

Chris

 

[Ignoramus11916]

That seems like a pretty harsh regulation. Here I believe you can
legally wire your own house, but you're supposed to have it inspected
afterwards, and certainly before you sell it. But we also have a stupid
new law which means that only qualified electricians can buy consumer
units. Most people with time and good practical skills, but little
money, aren't going to pay an electrician to wire their workshop.
They'll find a consumer unit from a friend, or a demolition site, or a
dumpster. It just drives work underground. Another sad example of
European over-regulation!

Christopher, what do you mean by a consumer unit?

i

 

[Bob Vaughan]

Christopher, what do you mean by a consumer unit?

Lets see how my grasp of european terms is..


consumer unit = Breaker panel (made of plastic, with DIN rails)

RCD = GFI (or something very similar)

T+E = Twin+Earth = Romex

ring main = circuit fed from both ends (from the same breaker)

 

[Michelle P]

If your house is insured it will be void if you install the device. The
insurance companies frown on anything that is not UL approved.
Michelle

Ignoramus25850 wrote:

 

[Vaughn]

If your house is insured it will be void if you install the device. The
insurance companies frown on anything that is not UL approved.

Could you give us a reference please? What other things might I do that
will void my home insurance? Can you give us a specific case where someone lost
their home and then had the insurance company refuse to pay because a non-UL
device was installed somewhere in the house?

Thanks
Vaughn

 

[Steve Spence]

Incorrect. If the loss was due to the non-compliant device, then you may
have a problem collecting. If the loss was due to something else, the
insurance company must cough up.


Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html

 

[Duane Bozarth]

Eric R Snow wrote:
....

In Washington state you are allowed to wire your own house. It then
must pass inspection.

So far, so good...

...After that you must live in it for five years
before you can sell it. ...

How could they possibly enforce that?

 

[Eric R Snow]

Eric R Snow wrote:
...

So far, so good...


How could they possibly enforce that?

Beats me. When I wired my shop I learned all sorts of regulations. But
hardly any reasons. In WA the inspection is done by Labor &
Industries. They come out when they come out. And do hold up projects.
My father-in-law is a licensed electrician. I flew him up to WA to
help with the wiring to make sure it all done to code. He told me that
in Santa Clara county in CA the inspectors have 24 hours to show up
and do the inspection. If they don't then the wiring can be covered
and is considered to be up to code. BTW, just because a house is wired
by a "professional" and has passed inspection it doesn't mean that the
wiring will be done correctly. My last house had all the wiring in the
garage and laundry room backwards. So all the white wires were hot and
the black wires neutral. The problem was in a junction box where
someone had connected the wires in reverse. This box had undisturbed
mud and paint on it from the original drywall. So the wiring had not
been changed by any previous owners.
ERS

 

[[email protected]]

Could you give us a reference please? What other things might I do that
will void my home insurance? Can you give us a specific case where someone lost
their home and then had the insurance company refuse to pay because a non-UL
device was installed somewhere in the house?

Thanks
Vaughn

Well, insurance companies are getting EXTREMELY adverse to risk. Many
will not insure a building with aluminum wiring unless it has ALL
DEVICES either replaced with COALR devices or every connection
pigtailed to copper with a certified device - and an inspection to
prove it. Any Knob and tube left in the house and they won't touch it.
A wood stove that is not certified? No insurance. Not installed to
code? No insurance. Many other conditions as well. I'm not an
insurance agent, nor do I play one on TV, but I AM the IT guy for a
pretty big brokerage.

Coverage HAS been denied. One of the stickiest players in Canada is
ING - and they own half the business.

 

[[email protected]]

Incorrect. If the loss was due to the non-compliant device, then you may
have a problem collecting. If the loss was due to something else, the
insurance company must cough up.

If the non compliant device CONTRIBUTED to the loss, you lose. Does
not need to be the root cause. They MAY decide to be benevolent and
assign proportional blame and pay a small part of the damage - UNLESS
you have signed anything stating nothing has been modified from code.