AC transfer switch question

[Bigglez]

But that new guy had a good point at the end about not knowing when it would switch over and the possibility of being surprised or disappointed by the glitch.

Why not put the switch on the DC side of the inverter and let the inverter power the load 100% of the time.

Greetings Hacklesup,

You are correct, and that is how commercial UPS
systems operate (AC-DC-AC). The Op is aware
of these systems but appears to have set limitations
on what they are willing to do, and has eliminated
a commercial UPS system from the project.

Typically solar power systems are used to supplement
utility power.

i know this much.

The always on variety operate with AC-DC-AC
configuration, meaning the utility AC is converted
to DC to charge batteries, and reconverted to AC
to power the load. If the utility power is lost the
load is then powered from the battery via the
inverter without missing a beat.

i know how inverters operate, i am not new to this.

Before you put your system on-line I think you
should get your local utility to sign off on the
work.

my system will not be grid tied,,nor does my utility company offer this solution, otherwise i'd have done this already..

If it were me I'd take a close look at inverters
designed for UPS, starting with off-grid solar
vendors first.

i have looked, all the inverters i have seen only run normally on standby
(commercial power, until there is a failure, then the inverter kicks in,,as i stated, i want my system to run on inverter all the time,,then switch over to commercial power if the batterys should happen to get to low..

The OP will likely implement the AC change-over
relay solution where the relay is controlled by the
battery voltage (dropping back to utility power
when the battery is depleted).

Doesn't sound as if the OP wants to rehash the topic further.

Comments Welcome!

Peter

[haklesup]

The OP will likely implement the AC change-over
relay solution where the relay is controlled by the
battery voltage (dropping back to utility power
when the battery is depleted).

Doesn't sound as if the OP wants to rehash the topic further.

Actually I find that as a respondant, an OP dosen't always describe all the mitigating factors that led to a certain design choice. Often what seems like an ideal solution to me is not to another because I am unaware of that persons budget, skill level or physical constraints of the design.

I have dialoged with this OP and others for a while and I think he is open to debate about the solution but in the end most designs from people here are evolutionary. If he wants to start with what might be the lowest cost solution and upgrade later, thats fine.

I try to offer a solution that was asked for but if I see a better one, I will offer that too and try to explain why I think its better.

In the case of the Line to DC then charge solution (as opposed to AC switching) there are additional benefits over the few I mentioned (like longer battery life). ANother would be that in the morning, you would be able to switch back to solar immedietly after sunrise, you would not have the few hours lag time needed to charge the bank up to operating potential before you could let go of the line. So long as the load is smaller than the array can deliver, you will also have reserve on battery well into the night before line charging is needed again.

I don't see any code issues or problems from the utility. Unlike a typical solar system that needs a transfer switch to connect it to existing house circuits and disconnect the line, he is not doing that. It seems more like an appliance plugged in at the end of a normally fused branch circuit. The lighting loads he will be powering appear to be isolated from the house wiring (an assumption on my part). If howerver, DAC you are tying into existing branch circuits, you should review relevant code so you don't devalue your home in the future.

[dacflyer]

haklesup >> i plan to use the inverter all the time...and my charge controller has the ability to de activate the transfer relay, so i am not worried when it will switch over..

i been just simply wanting to know if there will be any surge or bucking of the switchover between contacts..like maybe a out of sync switchover will it be an issue or not.

my charge controller will activate or de-activate the switch automatically.
i am not worried about a blink or flicker,, just if there will be a buck or surge when switching over.
as i said earlier there is almost 1/8" gap between contacts.

[dacflyer]

additionally... sorry if i am making this sound more confusing than it is...

my solar system will be on line all the time..and i should have pleanty of battery reserve, the transfer will be dc controller by my charge controller
( pv charge controller ) i have no battery charger that plugs in.
its a 24 volt system,,

but if the batterys get low, then the commercial power will take over, untill the batterys are charged back up..

its not a matter of me being cheap here..i just simply was concerned of switch over surges or bucking what ever..
wiring will be to code etc..

ok,, your turn .....

[Bigglez]

Actually I find that as a respondant, an OP dosen't always describe all the mitigating factors that led to a certain design choice.

Greetings haklesup,
Most if not all forum posts require some detective work
before arriving at an answer.

I don't see any code issues or problems from the utility. Unlike a typical solar system that needs a transfer switch to connect it to existing house circuits and disconnect the line, he is not doing that.

That's a bad assumption. Can the OP confirm that this
project is an appliance plugged into a house wiring
outlet, and not a permanent installation?

While this is a technical forum, and the OP asked about
AC change-over relays causing load irregularities, it has
opened up to be a solar PV (Photo Voltaic) project.

The OP hasn't indicated his or her motivation, but if it's
financial ("free electricity") then this is going to be a
failure. The payback on a PV system is at least ten
years (depending upon utility rates and local sunshine),
and most if not all installation avoid storage batteries
(due to maintenance, safety hazards, and long
payback cycles).

Comments Welcome!

Peter

[Bigglez]

i been just simply wanting to know if there will be any surge or bucking of the switchover between contacts..like maybe a out of sync switchover will it be an issue or not.

Greetings DACflyer,

Yes, there will be an indeterminate disturbance on both
the load and the supply side, depending upon many factors.

If you are not concerned about "flickering lights" and will
only use this system as an appliance (and not permanently
installed) you can complete the project.

As you are dealing with equipment that can potentially be
life threatening and dangerous you might consider your
responsibilities before going forwards.

I'm not here to nag you, but your utility company will be
very interested in any energy storage device that you
could potentially connect to their service. PV solar
installations require permits, inspections, and correct
equipment safety configuration (disconnect switches
in particular) to be approved.

Not only that, but if you are a renter your landlord
might not take kindly to this project. If you are a
property owner your insurance company will be interested
in modifications that raise fire and safety concerns.

OT a bit, a cube co-work told me that when their
neighbour's home burned down the insurance company
refused to payout a penny because the fire was caused
by a home-owner installed ceiling fan done without
a building permit.

Comments Welcome!

Peter

[haklesup]

Well Dac, obviously you will briefly loose power while the relay is moving but how long that takes will depend on the relay, that would cause a dropout or brownout. A surge would be caused in this case by an arc across the relay contacts. Again the choice of relay will diminish this problem. That kind of arc should easily be clipped by a surge supressor.

WRT Bigglez comments, I've said it here many times, "going green will generally not save you any money" and I am sure the OP knows that.

As far as the insurance anicdote goes, I have no doubt it is true. It is a common but denied practice in the insuracce industry to deny certain claims based on weak reasons because statistically few of denied persons will try again. You obviously left a lot out of the 3rd hand story. Was there evidence of negligence in the fan installation or just a chess move on their part (ah ha, move unpermitted lamp to QR4 and burn the rook down checkmate, no check for you) (rhetorical, don't answer, we're not reallay discussing insurance)

Different kind of insurance but case in point
http://www.cbsnews.com/stories/2008/01/ ... 8129.shtml
"CBS News has learned that two-thirds of all applicants denied last year - nearly a million people - simply gave up after being turned down the first time"

PS, the OP, being the top poster on this board has already demonstrated an understanding of electricity and how to be safe. Its not up to us to police code, just to offer what solutions we know of. it is any posters responsibility to use any info gained on any website responsibly.

[Bigglez]

WRT Bigglez comments, I've said it here many times, "going green will generally not save you any money" and I am sure the OP knows that.

Greetings halesup,
I did not know that.

Let me clarify:

The payback on a PV system is at least ten
years (depending upon utility rates and local sunshine),
and most if not all installation avoid storage batteries
(due to maintenance, safety hazards, and long
payback cycles).

As far as the insurance anicdote goes....
Was there evidence of negligence in the fan installation or just a chess move on their part

Yes, the fire dept found that the fire started in the living
room at the newly installed fan due to poor workmanship.
The homeowner sued the insurance company and lost,
I was a little shaken by this hearsay story having
tried my hand at most building trades as a homeowner.

PS, the OP, being the top poster on this board has already demonstrated an understanding of electricity and how to be safe.

I did not know that. I have single digit posts on this forum.....

Its not up to us to police code, just to offer what solutions we know of. it is any posters responsibility to use any info gained on any website responsibly.

I did not know that either. Any other newbie advice?

Let wait to hear back from the OP, there's some open
questions about what exactly they are trying to do and
whether it's going to work as expected (or be safe).

Comments Welcome!

Peter

[dacflyer]

oh boy... was not wanting it all to get into a scwabble here..

i know i will not save as much money on a storage system as i would with a grid tie system,,but my power company here will not allow grid tie systems..

my intentions are.. the inverter will power my lights and a few dedicated outlets.. i do know wiring safety, i did work several years with a local electrical contractor etc..

i was just wanting simple advice. didn;t wanna get into insurance claims and such..

and i do own my own place here..

but as for haklesup >> you said.... Well Dac, obviously you will briefly loose power while the relay is moving but how long that takes will depend on the relay, that would cause a dropout or brownout. A surge would be caused in this case by an arc across the relay contacts. Again the choice of relay will diminish this problem. That kind of arc should easily be clipped by a surge supressor.

i was kinda thinking that as i guessed in a earlier post.. i have some R/C type arc quenchers..2 wire jobs,,but i am not sure how many i need for a DPDT relay or how to connect them, i also have MOVs too.

thanks again...

[cdenk]

Federal Law (USA) REQUIRES that you use an appropriately rated and certified transfer switch. This is to prevent killing a lineman if there is an outage on the electric service. If there is any interconnection possible between your power source, and the electric service, the safety of the line crews comes first.

I have a standby generator. The automatic transfer switch, is essentally a solenoid operated DPDT relay with "break before make". The power company requires their inspection, in addition to the local building department.

If you are planning to feed into the grid, the powere company will need to be involved, since I'm sure you will be expecting a credit on your bill. I'm not familiar with the safety aspects of that setup, but your power company needs to be involved, and probably can provide expertice. Should be a team effort.

On surges, I have a electric furnace (resistance heat) that draws 41 amps per stage, and we can switch with house including heat under power of generator back to utility under full power with no issues, generally the clocks don't even blink. I do have a whole hole surge suppressor, more for lightning strikes.

[dacflyer]

cdenk >> you said...
Federal Law (USA) REQUIRES that you use an appropriately rated and certified transfer switch. This is to prevent killing a lineman if there is an outage on the electric service. If there is any interconnection possible between your power source, and the electric service, the safety of the line crews comes first.

i know this and i stated that earlier in my post, and i said that there will be no possibility of that happening.

If you are planning to feed into the grid, the powere company will need to be involved, since I'm sure you will be expecting a credit on your bill. I'm not familiar with the safety aspects of that setup, but your power company needs to be involved, and probably can provide expertice. Should be a team effort.


aparently not all was read here... i am not planning to tie into grid here.
my power does not participate in power buy back at all here. which sux
i could be going cheaper here if that was the case...


so far as i figgure, i'll be wise to have surge protection, but also i still am concerned about bucking . i actually do not even know if it is gonna be a problem or not.

[cdenk]

Hope I didn't offend anyone, was replying as much to other replies to the thread as much as the orignal author. Seemed some were a little new at this area and was concerned with safety. . Keep pushing your electric supplier toward buy back. Only yesterday heard of a power company in the California area that is working on using plug-in electric cars (should say vehicles) that plug in at home and at work to charge batteries. There would be programming to regulate charge/discharge and your minimum allowable discharge so you could get home. The batteries would be used for load leveling say mid afternoon airconditioning, manufacturing, etc. with discharge, and would charge back up in the middle of the night. Sounded interesting, wonder how practical. Also power company would buy batteries that didn't have good recharge life, but adequate for load leveling.

[dacflyer]

cdenk >> no offence ,
the battery buy back sound like a cool deal..

my power company here says since they are a mucipality, they don;t offer to buy back any power nor let you grid tie..
but again so far as i can find out,, i'll be the only user of solar in my county.. there are some small stuff like solar powered school flashers , emergency road side phones etc. but thats it.