Reminder: Never connect a generator to home wiring without transfer switch

Thu Sep 2 07:33:00 UTC 2021

Here’s a nice article on the code issue, which is nationwide in the US (it’s part of the NEC). It speaks specifically about the generator requirements:

https://temperaturemaster.com/furnaces-hardwired-what-you-need-to-know/

TLDR: The NEC is against plugged-in furnaces for a good reason: they consume so much electricity that they need a dedicated circuit. When you have a plug-in furnace, you’re likely to plug it into a shared outlet with other appliances. As a result, the circuit gets overloaded, damaging the furnace and the other plugged-in electrical devices or even resulting in a fire.

So, converting a hardwired furnace into a plugged-in constitutes an NEC code violation.

The article then proceeds to show how to safely violate the NEC with a plug and socket, and how to follow the letter of the law with a transfer switch or interlock kit.

I think these are the same devices my brother Peter might be talking about. :)

 -mel

On Sep 1, 2021, at 11:20 PM, Forrest Christian (List Account) <lists at packetflux.com<mailto:lists at packetflux.com>> wrote:

Let me clarify since this thread has resurrected itself.

In the northern climates where I live, almost 100% of the heat during winter is either natural gas or propane.   It's either fan forced or hot water.

In each case,  the amount of electricity consumed by a typical furnace is well under 15 amps.  Like a few hundred watts for all but the biggest furnaces.

When the power fails during the coldest part of the year the most critical thing to keep running is the furnace.  You  can have frozen pipes and other cold related damage in a relatively short time.   The amount of time is irrelevant but think multiple hours not days.

We all have flashlights,  the fridge isn't a big issue (natural freezer outdoors, and usually free ice) and so on.    But the furnace having power is critical.

The quickest fastest way to get that furnace back on is to fire up a generator or some other suitable power source and then hook the generator up to it.

The problem is that people rarely think ahead,  so they're trying to come up with a quick solution,  and most of them don't really understand wiring.   Because,  by code,  the furnace may not be connected with a plug and socket the homeowner has no option but to open up an electrical box and try to figure out how to hook his generator up.   With the not uncommon enough result of the generator trying to power the neighborhood.

The solution is dirt cheap.  Instead of requiring a hardwired connection, move to a standard 120V 15A plug and socket connection.   Based on other requirements in the code such as for a disconnecting means near the furnace which this would replace as well,  the cost is likely to be zero.

Its not uncommon to see this done even though it is against code.  Whether it will pass inspection depends on the attitude of the inspector.

On Wed, Sep 1, 2021, 10:13 PM Peter Beckman <beckman at angryox.com<mailto:beckman at angryox.com>> wrote:
On Tue, 31 Aug 2021, Forrest Christian (List Account) wrote:

> I just wish the electrical code would permit or require certain low cost
> things which make temporary generator connections more likely to be safe.
>
> For example, code requires most furnaces to be hardwired.  But a furnace is
> one of the first things you want on a generator in an extended winter power
> outage.   If instead of hardwired, the code required plug and socket
> connections at each 120v furnace  then Joe homeowner would be more likely
> to run an extension cord from his generator to his furnace instead of
> trying to rig up his generator with a suicide cord.

  Is $40-60 low cost enough for you for safe, temporary generator connections?

     - Generator Interlock Kit: $20-25 (Safety)
     - Breaker: $5 (30amp 120v) to $20 (60amp 240v) (Dedicated Power connection)
     - Generator Power Inlet Input: $15 (indoor 120v) to $50 (outdoor 240v)

     A Generator Interlock Kit is a few pieces of metal that, once
     installed on your existing electrical panel, allows one to run
     a properly-sized circuit and breaker to an outlet that you can plug your
     120v or 240v generator inverter RV output into.

     Add a Generator Power Inlet Input (indoor or outdoor) rated at 30Amp
     240v NEMA L6-30P, for example, then plug your generator into that.

     The Generator Interlock Kit physically prevents the mains from being on
     when the generator Breaker is on. This is the safety component.

     This seems affordable ($60 plus some wire and a few minutes inside your
     electrical panel) and safe.

     Add a few bucks to have your locality inspect and certify the work.

  If this is too much, why? What would be easier while also being equally as
  safe? This is work that, with a few minutes on YouTube, could do safely,
  as long as the power is disconnected at the meter outside the home during
  installation.

  PS - I suppose you could also move all of your emergency 120v stuff to one
  side of your panel and also provide only 120V to one side of your panel.
  This would also reduce costs a bit.

  Why believe me? In 2019 I read the NEC code and learned how to install a
  60amp circuit for an electric charger. I did the work myself. I had it
  inspected and certified by the county. I did so for about $100 total for
  all parts and wire.

Beckman
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Peter Beckman                                                  Internet Guy
beckman at angryox.com<mailto:beckman at angryox.com>                                 http://www.angryox.com/
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