Engine Block Heaters and GFCI Receptacles

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L

Loss Control Consultant

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I am a loss control / safety guy that works with several municipalities. I am curoius about the proper method to power a block heater from a receptacle protected by a ground fault circuit interrupter. The electrician tied the ground connection in the block heater to the heater frame and then opened the female end of an extension cord and disconnected the ground. He then plugged the extension cord into the GFCI receptacle and block heater. This may allow the circuit breaker to trip under a short circuit, but it may prevent the GFCI from tripping under a high resistance fault, which is what a GFCI is designed to do. Also, altering the extension cord to function other than as designed by the manufacturer may be exposing municipality to a citation and liability claim, specifically if that cord is mistakenly used in some other application.

To recap, if a block heater is properly installed and the ground fault circuit interrupter receptacle is of the correct amperage and properly installed, the system should work without having nuisance tripping. If there is nuisance tripping that is indicating a problem that should be resolved and not bypassed. Am I correct?
 
L

lpelectric

Senior Member
If they're dedicated to engine block heaters and not intended for general purpose use by personnel, why would they need GFCI protection? :smile:
Pretend I hooked them up without GFCI protection...cite me. :smile: (why do I think I'm about to learn something here?) :grin:
 
J

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
Loss Control Consultant said:
To recap, if a block heater is properly installed and the ground fault circuit interrupter receptacle is of the correct amperage and properly installed, the system should work without having nuisance tripping. If there is nuisance tripping that is indicating a problem that should be resolved and not bypassed. Am I correct?
Click to expand...

Yes you are.
 
iaov

iaov

Senior Member
Location
Rhinelander WI
Engine Block Heaters

Engine Block Heaters

Welcome to the forum. You are correct. A good electrician does not alter extension cords. We usualy end up having to repair cords that some knat brain has removed the ground from. Make em fix it!!:smile:
 
iwire

iwire

Moderator
Staff member
Location
Massachusetts
lpelectric said:
If they're dedicated to engine block heaters and not intended for general purpose use by personnel, why would they need GFCI protection? :smile:
Click to expand...

Under the 2005 NEC if they are

1) Located at other than a dwelling location

2) Are outside

3) Are accessible to the public

4) Are single phase 15 or 20 amp 125 volt receptacles, either single or duplex, straight blade or twist lock...

210.8(B)(4) requires GFCI protection.
 
L

lpelectric

Senior Member
iwire said:
Under the 2005 NEC if they are

1) Located at other than a dwelling location

2) Are outside

3) Are accessible to the public

4) Are single phase 15 or 20 amp 125 volt receptacles, either single or duplex, straight blade or twist lock...

210.8(B)(4) requires GFCI protection.
Click to expand...

Okay. Take this scenario, for example. 120 volt single twist-lock 20 ampere receptacle located outside at a school bus garage which is not accessible to the public. I think we agree that 210.8(B)(1),(2),(3) &(5) don't apply, so do we agree that (4) does not apply if there's no public access? :confused: :smile:
 
iwire

iwire

Moderator
Staff member
Location
Massachusetts
lpelectric said:
Okay. Take this scenario, for example. 120 volt single twist-lock 20 ampere receptacle located outside at a school bus garage which is not accessible to the public.
Click to expand...

Forget about twist locks, the rules apply equally to straight blade or twist locks. :smile:

Under the 2005 the 'public' access question would be key.

Under the 2008 it won't make a difference, the public access part has been removed.

In it's place is an exception for 'industrial establishments' which IMO would not apply to a school bus parking lot.
 
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