I have a question. I have wondered about taking two of the breaker/fuse boxes with the levers on the outside as opposed to having a breaker inside the box. Mounting one right side up and the other upside down then connecting the levers by welding a rod to each. That one when one is opened the other would be closed. The problem that jumped to my mind was the fact that there could be a small amount of time when they both COULD be connected because the throw on one box might be a little longer than the other. But this would be a fraction of a second and could be gotten around by making sure your genny and the line breaker both are thrown before switching.
If you have space for installing two large disconnects, it is easier and cheaper to install one proper transfer switch than two disconnects in an odd configuration.
And that "making sure that your genny and the line breaker both are thrown before switching" is exactly what the interlocks that I mentioned, are supposed to prevent without fail. If interlocks are in place, it is impossible to do wrong.
My problem is that it is very difficult to place a transfer switch properly due to location of service entrance vs. electrical panel vs. the ceiling of the basement.
I have plenty of space and I have several of these old switch/fuse/breaker boxes laying around which is why I was thinking of trying this.
Done correctly my correctly would be fool proof. You'd just have to make sure that each switch has enough throw. Being a 'better over save than sorry' type I'd still toss the main breaker in the box before moving the switch.
Run into a lot of problems like that with older houses.
This style of transfer panel (available from 2 or 3 manufacturers) may fix that.
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You don't have to mess with your service entrance conductors, and you can come out the side or bottom of your electrical box.
I like mine for three reasons:
1) Since it transfers on a "per circuit" basis, I can exercise the generator on part of my house while leaving other circuits undisturbed, still connected to the grid. and;
2) I can unplug my main generator at any time and substitute a portable generator, or even an inverter by simply plugging it into my transfer panel. This feature has come in very handy twice when my (trusty, reliable, faithful?) old Onan has died halfway through a week-long power outage. Also it gives me the option of substituting my very frugal EU2000 during times of light load. When you have a several-day-long outage, the cost of fuel becomes a major consideration.
3) The built-in metering is very handy and eliminates guesswork about your generator's load.
OK, it isn't cheap. You can't have everything! Thanks to a tip I received right here on this group, I bought mine off a clearance table at Home Depot at an obscene discount.
I went through that discussion too many times and I do not want to restart it. My house is big, has way too many circuits, which use minimal current but which are necessary, for these sorts of panels.
I need to power sump pump, furnace, two fridges, freezer, computer, it is an absolute must. All 115v and all on different circuits. Then I have a dozen circuits for lights. Not all have to work but some are needed. All use minimal current due to use of compact fluorescent and regular fluorescent lighting. At most I expect 300-500 watts total.
Connecting the "must have" lines to this little transfer panel, would leave me totally in the dark and without any comfort. I am not sure if the 20 amp circuits are two pole for 220v connections or can be rewired. In any case, not enough circuits. I have no interest in those Emergen panels, though it would be different if I lived in a smaller house -- I admit their utility for smaller homes.
I went through this issue a little bit too much. I hope that I have not tired anyone, and apologize if I did. I am going to install the interlocks securely. That will, practically, solve the backfeeding issue to my satisfaction. I "might one day" install a whole house transfer switch, which is quite difficult due to location of service panel and service entrance (not enough space).
I do not care too much about obscure scenarios such as "what happens if I die". If I die, no one is going to maintain and use this generator. And if I do not die and move to another house, I will take it and the interlocks with me.
_I_ wasn't. Backfed wires are a hazard to everyone. Linesmen are just one.
Even trained linesmen get tired, make mistakes, or just get zapped by something unforeseen.
You have an ice storm that takes out power for weeks. The crews are dead tired. There's wire draped over _everything_, buried under snow and ice. Linesmen are hanging out the side of helicopters 200' up at
-40F and strong winds (not to mention the windchill factor from the helicopter itself!) trying to repair HT lines. The army is out dragging out power poles and the remains of high tension towers, rescuing people from frozen homes, stuck cars, and houses filled full of CO. Everybody is just trying to survive and get the job done as quickly as possible.[+]
How do you think they'd feel about idiots backfeeding?
Then is not the time to set booby traps. It's just stupid. Do it right.
There's a special place in hell reserved for those who endanger emergency crews or steal emergency equipment during an emergency.
[+] Great ice storm of 1998. I helped out in that. Inspecting/doing generator hookup in homes and emergency depots. You better believe we were careful making it _impossible_ for backfeed to occur.
Has everybody missed the point that fitting proper interlocks is _precisely_ what Iggy is proposing to do? OK he's not buying a nice idiot homeowner retail kit from home-generators_R_us. He is engineering a solution that is at least as foolproof and effective. Good luck to him!
It doesn't appear to have enough poles to be effective - it doesn't switch both sides of the panel. Secondly, it's probably not approved for the purpose of switching residential feeds, and there may well be a reason why it wouldn't be.
To do it right is to do it within the NEC (or CEC) with devices UL or CSA-approved for the purpose, or be able to find an electrical engineer who is willing to sign off on it.
No point missed. He isn't engineering anything. He is trying to cobble stuff together to avoid the use of a proven, approved for the purpose and readily available DPDT transfer switch.
You design, test and submit for approval alternative devices when a suitable device is not manufactured.
It's not a switch, it's an interlock. To be interfaced with the switch to prevent it closing unless the interlock bar is retracted. It thus becomes physically impossible to have both switches closed at once, since the switch must be opened in order to be able to extract the key and the key must be in the interlock in order to close the switch. Since there is only one key available, only one switch can be closed at a time... even if they are a mile apart.
Iggy's solution is far safer than the silly panels with switches linked together. Specifically, it is fail safe.
A double pole double throw switch is _not_ a safe design for a transfer switch an inductive load that causes arcing on the opening contacts can result in connecting both sources together or one source onto a fault. A panel that has pairs of switches tied together can connect both sources to the load if one switch or the link fails, with no opportunity to verify that the disconnect occurred before the connect occurred. Neither protect against trying to synchronise the source network a long way out of phase with the load network
Iggy's solution requires that one source is isolated well before the other source can be connected.
Oh, and I have, in my role as an electrical engineer, in the last year had to refuse to connect UL and CE marked equipment supplied by a major (Blue) manufacturer because it was unsafe as assembled. When the installation "engineer" claimed that similar equipment had been installed all over the country, I had to state that it's use would be illegal in each of those installations. I'm not that bothered about safety except where the lack of it endangers people, then I get quite particular.
It's only safe as long as someone follows the rules and there is only one key. You could just as easily leave out the key and just keep the rule, "Thou shalt switch OFF the one before you switch ON the other", which is nothing at all like a proper transfer switch.
Seems to me that having a transfer switch feed a subpanel with only certain circuits on it is far too limiting. And one of those panels where individual circuits can be flipped one way or the other is a neat idea but again it's limiting. I think it's preferrable just to have a big switch that cuts the whole house over so *everything* is live. Obviously that doesn't mean you have the power to run everything at once but how much easier not to have to run extension cords because only certain outlets are hot. And of course the matter of hard wired fixtures and devices. Sure, you'd have your furnace powered but what about the lights in the bathroom? Energize the whole house and just take care on what's on at the same time.
"You take your choice and you pay your money." Every solution has both advantages and disadvantages. As Iggy pointed out, sometimes a proper whole house transfer switch can be virtually impossible without major (read expensive) renovations.
Also, if you have any chance of a protracted outage in your area, avoid the urge to install a large generator! You can't believe how much gas even a modest genny can burn in a week or three. Our stationary generator is only 4 KW. We have to live without central air, and do without our electric range, but otherwise life in our home is just about normal. We have a window unit in our bedroom to provide us with a cool refuge.
It depends, if you have a big switch and don't have generator capacity to support your total load someone still needs to manage loads. If you are the "expert" you need to consider how other occupants will manage things if you aren't there.
My buddy lives in a rural area with frequent power outages. He bought a genset with an small automatic transfer switch. We selected all of the critical loads such as the heating system, well pump, sewage pump, refrigeration and basic lighting and ran them into a smaller panel which is fed by the transfer switch. The advantage of this is that his family doesn't have to scramble when the generator stalls because loads are managed properly and they really don't have to do anything since all of the essential needs are covered.
No one needs to know the "secret method" to make it work.
And a good side benefit is that since no intervention is required the system will startup on its own. So say they are away the house isn't going to be frozen in the winter or have a refrigerator of rotten food in the summer.
I'm coming in late on this, didn't see the original post but from reading the replies I'm infering Iggy wants to use a couple of keyed lock mechanical doohickies to prevent his genny breaker & mains disconnect from both being "on" at the same time.
This is, everyplace I've ever been, perfectly legal as long as theres only one key & it can only be withdrawn from the lock when the doohicky has the breaker in the "off" position. I've had a number of systems like this in sites where the feeds were physically seperated.
Now, that isn't to say I don't prefer a single changeover switch type of deal, 'cause I very much do, but the keyed switchs are perfectly acceptable if properly designed.
This has been discussed before somewheres on usenet, I remember posting on it.
Yes, a "Kirk Key®" interlock is legal - but ONLY where access is restricted to trained and responsible personnel like at power plants and industrial buildings. People who know what will happen if they screw up, and that they'll be held fully to account for it.
It is too easy to deliberately bypass that type of mechanical interlock and cause a backfeed, as easy as unbolting the front panel of the switchboard that the interlocks are secured to and operating the circuit breakers out of sequence. Takes only seconds.
And there are too many fools who are ready and willing to do it out of total and deliberate ignorance of the consequences.
For residential and light commercial/industrial applications where the transfer equipment is not secured and can and will be operated by untrained personnel, it HAS TO BE type accepted for that use. That calls for a pre-packaged automatic or manual transfer switch of some sort that has failsafes against backfeeds, and eliminates any "Kirk Key®" type systems from consideration.
Unless you want to be up for multiple counts of Murder 2 for backfeeding the utility service and killing a few workers on the line gang, out trying to restore power after the storm...
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