Problems with point of use TVSS and AFCI circuits

Status
Not open for further replies.

hurk27

Senior Member
I have been holding back on this after the first few problems showed up but now we been having many call backs when a home owner places there computer in bedrooms or install a surge protector on the TV.
So far it's been the N-G or H-G protection in these that have been causing the problems and I have duplicated this problem in my own house to make sure it is a real problem.

Here's what I found so far that is causing nuisance tripping of the AFCI's

When the home owner uses a vacuum cleaner or a hair dryer and switch's it off a spike is produced this spike hit's the MOV in the surge protector and cause a current spike on the H-G MOV this cause's an imbalance between the hot and neutral in the AFCI and the resultant nuisance tripping of it. The only way I have to prove this is because one home owner said the problem went away when he used a grounding adapter on the surge protector unit. :eek: This kind of set me back for a home owner to know this? then I found out he is a electrical engineer up in Chicago. He also agree's that this is not the answer to the problem as we all must be able to use TVSS system on bedroom circuits.

Has anyone else had this problem?
As with AFCI going to be Incorporated into more and more of the house circuits in the future I hope there is a solution. One would be that manufactures to quit using H-G and N-G MOV's and just protect between the hot and neutral but is that the best answer?
 

dereckbc

Moderator
Staff member
Location
Plano, TX
Re: Problems with point of use TVSS and AFCI circuits

Wayne that is interesting. You are probable in a Catch-22 situation. Because most Class-A (Point-Of-Use) TVSS devices contain common mode (L-G, & N-G) SPD's on the AC circuitry. However IMO for a residence common modes are not needed. The reason I say this is because most lightning events are on the primary side of the transformer, which appear on the secondary side in the normal mode (L-L, & L-N). You also have the N-G bond at the service entrance which nullifies the N-G event.

A common mode event occurs from sources inside the facility or a direct lightning strike (rare). In the event of a direct strike, no device is going to protect you. Other common mode sevices are your Telco and CATV, which SPD's are useful in common and normal modes.

So what is a person to do. Well for starts; install a service entrance TVSS, and then try to find point-of-use devices with only L-N SPD's (good luck), or do without them. Ultimate solution: Service entrance TVSS and isolation transformer.
 

hurk27

Senior Member
Re: Problems with point of use TVSS and AFCI circuits

The problem I found is that three of the home owners stated that they will replace the AFCI breaker with a standard one before they allow their equipment to go without surge protection.
If this will be the results then maybe UL or some other agency should be notified of this problem? And maybe we can get just L-N devices more available so they don't remove a much more valuable safety device.
 

hurk27

Senior Member
Re: Problems with point of use TVSS and AFCI circuits

Dereck I agree with what you said but this:
A common mode event occurs from sources inside the facility
How is this possible? as most motors and coils that causes these events will only produce them L-N which is picked up at the AFCI because of the N-G connection at the service. this in turn will cause the L-G SPD to create the path back to the service to the neutral which is why the AFCI trips. I have tried to find any surge protectors that I can point a home owner to that only has L-N SPD's but I haven't found any, and even Tripp-Lite tells me you have to have the L-G and N-G SPD's to protect for lightning or they will not back there product. I think that this thinking needs to be revised don't you?
 

dereckbc

Moderator
Staff member
Location
Plano, TX
Re: Problems with point of use TVSS and AFCI circuits

Originally posted by hurk27:
Dereck I agree with what you said but this:
A common mode event occurs from sources inside the facility
How is this possible? I think that this thinking needs to be revised don't you?
It is induced into nearby neutral and grounding conductors with respect to local grounds. The inductance in the branch circuit conductors is high enough with respect to high frequencies, that the N-G bond via GEC/GES is irrelevant.

I really cannot speak to AFCI breakers, since all my experience deals with industrial. I know what they are suppose to do, but not how they work. Maybe some type of time delay to ignore surge occurrence could be added.
 

hurk27

Senior Member
Re: Problems with point of use TVSS and AFCI circuits

Thank's dereck

I wasn't thinking about inductance. But I guess it could.
Do you know anyone that manufacturs a surge suppressor that only uses L-N SPDs ?
 
Re: Problems with point of use TVSS and AFCI circuits

Members requesting TVSS SPD's that use normal mode(L-N) only...these are available from Transtector, a member of the Smith Companies (Polyphaser et al) and ZeroSurge. These SPD's come in all forms from class-C to class A, and include the power strip types. All are available with non-degrading avalanching silicone diode protection. These should not trip the fault-current interrupts. I use them successfully in a radio station where common-mode (L-G or N-G) SPD's are prohibited.

See http://www.transtector.com
and
http://www.zerosurge.com/HTML/mode2.html

Regards, Jack
 
Status
Not open for further replies.
Top