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-   -   Frankenstein knife switch (https://www.askmehelpdesk.com/showthread.php?t=188202)

  • Feb 25, 2008, 03:22 PM
    diyDude
    Frankenstein knife switch
    Seems very odd to me that the old multi-blade knife switches like you used to see in the old horror movies would do the job.

    I'm quite surprised such a thing isn't made to handle the simple act of dis-engaging the grid and connecting a generator. All that's needed is a DPDT (or 3PDT if you want to switch 2 hots and neutral) switch of sufficient beef to handle the current.

    If you search for "Leveton knife switch" you will see what I'm talking about, though its only for 25Amps at 125 volts. I'm looking for a similar solution, albeit modernized and capable of handling 50 - 100 amps at 240VAC.
  • Feb 25, 2008, 03:36 PM
    Stratmando
    Manual transfer switches handle hundreds of amps. And is essentually like the Knife switches
  • Feb 25, 2008, 05:59 PM
    stanfortyman
    What Strat said.

    A manual transfer switch is just a BIG DPDT knife switch. Albeit a lot safer than an old Frankenstein switch. (I call them that also).
  • Feb 27, 2008, 11:17 AM
    diyDude
    So if that's true, why do they cost so much? I saw one post that said they sold one for "only" $150, but that still seems too expensive In my opinion.

    My guess is that they aren't that expensive to produce, but the manufacturers know the alt energy / backup power market will pay these high prices, so they take advantage.

    Thus us DIY folk look to find a less expensive way to solve the problem.
  • Feb 27, 2008, 11:30 AM
    Stratmando
    It is a safety thing, testing and approval that up's the price. Bare blade and contacts makes it dangerous. Is this for looks or economy?
    If you find a Knife switch you like, remember, It has to fall in the open position.
    Down is Off, Up is On.
  • Feb 27, 2008, 02:50 PM
    stanfortyman
    Quote:

    Originally Posted by diyDude
    So if thats true, why do they cost so much? I saw one post that said they sold one for "only" $150, but that still seems too expensive IMHO.

    My guess is that they aren't that expensive to produce, but the manufacturers know the alt energy / backup power market will pay these high prices, so they take advantage.

    Thus us DIY folk look to find a less expensive way to solve the problem.

    You can't be serious.
    $150 is NOT much for pretty much ANYTHING these days. Hell, it takes $100 to fill my gas tank at today's prices.

    What kills me is when folks will go out and drop a grand to $1500 on a BIG new fancy generator, yet will scoff at another $500 to hook it up SAFELY and correctly.

    Be thankful you do not need an automatic switch for $1200.
  • Feb 27, 2008, 03:25 PM
    Stratmando
    Generator InterLock Kit
    This is cheapest, fastest, safe way to connect, it is a Metal kit that bolts on to front of Electrical Panel that allows only the Main breaker on OR a 240 Volt breaker(Not Both).
    The Last Kit I bought from them was $150.00.
  • Mar 4, 2008, 02:05 PM
    diyDude
    I saw that solution, and it isn't a bad approach. I could easily make such a plate.

    You are probably right about the cost to manufacture being driven by testing. It usually does take a significant part of any product's budget.

    However, you might be more tolerant of folk that may not have as much $ as you.

    Prices are going up on EVERYTHING.

    As for costs, $150 for a simple metal plate? That costs virtually nothing to produce, but all the variations of panels, plus the UL etc approvals required to get such a product to the market are probably pretty high.

    But that seems too high. I don't know. I'm not too savy on marketing, standards approvals etc. I just look at the "thing" I get and ask what it might cost the average guy to build it if he could.

    Some things like silicone (i.e. computer) chips cost next to nothing but it takes huge capitol equipment and physics knowhow to create them. Definitely not something a person could do in their garage.

    But that certainly isn't true of the lockout plate on a fusebox.
  • Mar 4, 2008, 02:53 PM
    Stratmando
    Customer Paid for it, Didn't hurt me, and it was their cheapest way out.
    The 8, 10. And 12 circuit panels that give the circuits a choice of Electric company or generator is more expensive, and other option is transfer switch, Expensive Also.
    That kit is made of good stainless, and for a wide variety of panels. I can see the time consumed to Obtain panels and or drawings to fabricate for various panels.
    It is made well, and wide variety.
    It's actually 2 plates and sildes due to the slots and sholdered screws.
  • Mar 4, 2008, 05:57 PM
    stanfortyman
    Again, what Strat said.
    Those interlock kits are WAY more than a couple of metal plates and some generic screws.

    I'm all for making things yourself, but there's no way in hell even I'd consider making one of them myself. And I can make anything.

    Is your safety, and the safety of others, worth less than $150??

    Also, look around, I've never paid $150 for an interlock kit.
    Generator InterLock Kit is EXTREMELY overpriced.
    A typical interlock kit elsewhere is around$60-$80.
  • Mar 5, 2008, 07:58 AM
    Stratmando
    Stanforty, going to look for the $60-$80 ones, sounds a little more inline. Wonder if they took the work already done by interlockkit, allowing to be cheaper?
  • Mar 5, 2008, 02:13 PM
    stanfortyman
    The ones I have used were Sq D from the supply house.

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