AFCI trip on new furnace

[tortuga]

Someone please tell me how an RCD differs from a GFCI and how it's effective in detecting arc faults.

An RCD has a significantly faster response time to lower level ground faults than a class A GFCI.
A GFCI has to clear a 30mA ground fault in ~33 cycles of 60hz (560ms), and a RCD does in ~18 cycles (300ms)
A plain inverse time circuit breaker like a type BR would need something like 300% of its handle rating to flow constantly for about 1200 cycles (20 seconds), to clear the same fault.
Don answered the other part of your question :

The GFP device opens the circuit when the joule heating results in enough damage to the insulation to cause a ground fault.

The early tests were just comparing the two, the tests simply showed that a RCD or even a GFCI was just as good at tripping on arc faults as the AFCI.
Now AFCI's have been updated to supposedly be more accurate.
This was back in the 90's

only one needed per service need

-Hal

Back then in Europe I think they had split buss panels like we did (AKA consumer units) and they simply used one RCD on the sub main, I dont think they don't do that anymore.

Eaton has a nice application guide on RCD's here:
https://www.eaton.com/content/dam/e...on-rcd-application-guide-br019003en-en-us.pdf

 

[don_resqcapt19]

RCD or even a GFCI was just as good at tripping on arc faults as the AFCI.

I am still not convinced self sustaining arc faults exist at 120 volts.

 

[tortuga]

I am still not convinced self sustaining arc faults exist at 120 volts.

I think the testing agrees with you, or at least demonstrated a RCD (or GFCI) provided equivalent if not better protection from the faults they simulated. The issue being discussed at the time among the experts was a plain old residential inverse time circuit breaker like a Eaton BR would need something like 300% of its handle rating to flow constantly for about 1200 cycles (20 seconds), to clear a fault.
120V residential faults to ground can be erratic and intermittent add in voltage drop / circuit impedance seem to make it so a regular breaker would never trip on a simple ground fault, and various other issues unique to residential installs that well leave something to be desired CMP wanted a better performing breaker.
I have not read the tests, but if a 30mA GFPE (or GFCI) breaker really can provide equivalent protection seems like they should be allowed as a substitute for an AFCI. Or get the UL & major manufacturers to release a RCD (that they already make) for the US/Canada market and allow that as equivalent protection.

 

[ramsy]

You might want to read 230.95 again.

I see it, Thanks.

 

[ramsy]

if a 30mA GFPE (or GFCI) breaker really can provide equivalent protection seems like they should be allowed as a substitute for an AFCI.

Service electricians that exercise Test buttons are not likely to agree, since many GFCI breakers are found to be damaged junk.

Unshielded electronic circuit breakers are not suitable for service equipment, much less expected to operate properly in ambient extremes, behind sheet metal covers baking in the sun.

Thermal-Magnetic only breakers calibrated at 40C ambient alter trip curves in ambient extremes, rather than become subject to damage.

Or get the UL & major manufacturers to release a RCD (that they already make) for the US/Canada market

If 120v RCD exists, it may only fit din rail, and production for other equipment is not likely without a code mandate.

Why would NFPA code-panel members peddle existing RCD designs that last longer that xFCI junk?

 

[ActionDave]

Well then, the people who tout RCDs for arc fault detection and only one needed per service need to stop spreading false information. RCDs are just the European version of GFCIs. No more.

-Hal

I've been in favor of RCD or GFPE level of detection instead of AFCI, but not because they are an alternate form of AFCI. The reason is they work, they are not as prone to nuisance trips like GFCI and everyone would be safer from electrical hazards.

 

[hbiss]

I've been in favor of RCD or GFPE level of detection instead of AFCI, but not because they are an alternate form of AFCI. The reason is they work, they are not as prone to nuisance trips like GFCI and everyone would be safer from electrical hazards.

We need to stop making it sound like RCD and GFPE is another form of AFCI! The RCD and GFPE will not detect an arc fault and the AFCI is a fraud.

-Hal

 

[kwired]

An RCD has a significantly faster response time to lower level ground faults than a class A GFCI.
A GFCI has to clear a 30mA ground fault in ~33 cycles of 60hz (560ms), and a RCD does in ~18 cycles (300ms)

So same basic concept but with different performance specifications.

 

[tortuga]

Well were way off topic of course you dont need a AFCI on a furnace,

The RCD and GFPE will not detect an arc fault.

Hal like the term 'grounding' has little or nothing to do with the earth the term 'arc fault' is a abstruse poor choice of a term to classify a type of residential electrical fire common on single family dwellings (SFD) that a 15 and 20 amp 120V inverse time breaker does not prevent.

In the mid 1970's they set up the National Fire Incident Reporting System (NFIRS) to collect standardized fire data.
When Firefighters fill out paper work after a fire they use NFIRS codes like '445 Arcing, shorted electrical equipment' the term 'arc fault'
is a wide paint brush not how most industrial guys use the term.
In the 90's SFD (and residential occupancy) fires were a focus of the United States Consumer Product Safety Commission (CPSC).
The facts are hard to ignore Single family dwellings (SFD) tend to have more NM cable than other types of construction, on average there are about 9 SFD's to about every other type of structure in a given area of the U.S.
Looking at surveys of the US like the American Housing Survey (AHS) SFD's are about a 9:1 ratio with all other structures, everything from duplexes to large high rises, commercial industrial etc.
Surveys of licensed electricians show the majority of their work is not on SFD's. Surveys going back decades by magazines like EC&M show ECs get more of their total gross from commercial, industrial, utility and institutional (CII) work than from residential projects including multifamily.

So in the US we have a lot of structures that only a few electricians are working on, loaded with cheap appliances and cords.
In 1992, the United States Consumer Product Safety Commission (CPSC), engaged Underwriters Laboratories (UL) in a study to help evaluate products and technology that would help reduce these residential fires, other initiatives were also introduced like offering limited residential licenses to entice installers to get some education.
My point is these are not all 'arc faults' and arc fault is a misnomer.
TLDR yes I agree In my personal opinion little of this 'AFCI' craze has to to with a 'arc fault' but do we ignore a higher amount of electrical fires from a large stock of residential housing, with a cheap wiring method, installed by untrained persons and a trend of non-listed appliances , lighting, and extension cords and power strips?
I think another fix for that is to allow the use GFPE (or RCD breakers) .
Early generation AFCI's had a built in GFPE and that in my opinion is what was doing the effective protection.
If you look at the proposals at the time (1999) people like Sam Rosenbaum of Leviton had a competing product that was a leakage current detector basically a UL RCD Log #3356 , however some interests wanted to tip the tables in favor of a particular patented proprietary product when there were many products that can address the problem.
just my 2% Cheers

 

[don_resqcapt19]

but do we ignore a higher amount of electrical fires from a large stock of residential housing,

The same cause and origin studies that were used to support the inclusion of AFCIs in the NEC, showed that over 85% of the dwelling unit fires said to be of electrical origin, occurred in dwellings at least 20 years old. There were a lot of improvements in the wiring of dwellings in the 20 years preceding 1999.
In addition few of those fires are ever investigated by a trained fire investigator, with most being investigate by the company officer on the first due engine company. There was, in the past a lot of pressure, not to report the cause as unknown, so if there was anything electrical near the suspected point of origin, the fire cause would be listed as electrical, and one of the electrical causes on the NFIRS form would be checked.

 

[hbiss]

I agree In my personal opinion little of this 'AFCI' craze has to to with a 'arc fault' but do we ignore a higher amount of electrical fires from a large stock of residential housing, with a cheap wiring method, installed by untrained persons and a trend of cheap non-listed appliances , lighting, and extension cords / power strips?

The only part of that we, as ECs, can control is what's on our side of the receptacle. I've always been a critic of NM and plastic boxes. It's easily damaged in ways that aren't always apparent until years later. Overdriven staples, nails, rodents are several problems. If you make it cheap and easy to install, cheap and DIY labor will install it. Make them use an armored cable like MC and watch the number of hackers go down. Look what EMT has done for Chicago.

-Hal