Fuses versus circuit breakers

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mjc1060

Senior Member
I have a question regarding residential service panels. I have a customer who was told by thier home inspector that the existing panel board[which is fuses]must be changed to circuit breakers. The fuse panel is 100 Amps and has no overloaded circuits. Does any one know if this a problem with safety? Is there any sort of UL,NFPA or other NRTL reports that suggest circuit breakers are safer?
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
I have heard that some insurance companies will not insure homes with fuses. Typically the HI writes this up and the panel or service gets changed before the sale. What good is buying a home if no on will insure it. :)
 

jumper

Senior Member
The main problem cited is that the old fuses could be swapped too easily, put a 30 amp in if the 20 amp will not hold.

Bit of BS since after you swap the panel and the 20 amp breaker does not hold, the HO goes to a DIY big box and puts in a 30 SP breaker.
 

LEO2854

Esteemed Member
Location
Ma
The main problem cited is that the old fuses could be swapped too easily, put a 30 amp in if the 20 amp will not hold.

Bit of BS since after you swap the panel and the 20 amp breaker does not hold, the HO goes to a DIY big box and puts in a 30 SP breaker.

I have found them with 50 single poles...:blink:


I never saw a 50 amp screw in fuse have you?
 

renosteinke

Senior Member
Location
NE Arkansas
"told by thier home inspector"

It appears that the HI is only partly aware of what he is saying. Sort of like the folks who can tell you E=MC2, but also believe in perpetual motion.

For the 'skinny' on this idea that you have to replace your fuses with breakers, one needs to look to the homeowners' insurance business. That industry has a few 'conventions' that need to be recognized.

The first is that ther are different levels, or 'forms,' of homeowners' insurance. These levels go from the 'best coverage and cheapest premiums' to the 'least coverage and highest premiums' types. Key to understanding this is that no company offers ALL the forms of homeowners' insurance.

One of the big 'turning points' is the age of the house. 40 years is the dividing line; at 40 years, coverage starts getting eliminated- UNLESS the home has been updated, remodeled, etc., to something resembling current codes. With the lesser 'forms,' the insurance company is also going to be looking at the details of the house a bit more closely, as well.

It's not so much 'does the house have fuses' as a question whether the house has been maintained, repaired, and worked on by competent people.

For our trade, well, the insurance companies look for the classic issues that lead to trouble. Here are different parts of the picture:
1) Service size .... 60 amps just isn't going to cut it with most folks these days- not with the multitude of appliances and central air conditioning. Insurance companies know that such homes usually have all manner of DIY electrical nightmares so that they could add air conditioning, dryers, etc. to the house;

2) Fuses .... Apart from the over-fusing issue, there's the simple matter of there not being enough circuits;

3) Lack of a ground wire with the branch circuits;

3) absence of receptacles in the bathroom, along the kitchen counter, or GFI protection anywhere; and,

4) Lack of an outside or main disconnecting means.

The short version is that a house with fuses will be difficult to insure- and that insurance will have a higher premium and greater restrictions than you might want.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I suspect any residential electrical system that still has fuses is probably old enough that a service replacement is in order, along with a serious look at the interior wiring.
 

mjc1060

Senior Member
Thank you for the responses.

Thank you for the responses.

The wiring in the house appears to be fine. There are only five spare circuits. But the panel load does include a 30A 240V receptacle for a dryer,a 30A 250 V circuit for an A/C compressor. The problem as I see it is the Grounding Electrode Conductor. This is not current with local electrical codes[chicago],also there is no supplementary ground[in this case aground rod]. The conductor insulation is MTW and I do not know how long the insulation for the conductors is rated[such as 20 or 30 years]. This leads into another question. Does anyone know how long conductor insulation is good for? When should all the premise wiring be replaced?
 

charlie b

Moderator
Staff member
Location
Lockport, IL
Occupation
Retired Electrical Engineer
Does anyone know how long conductor insulation is good for?
I have always thought the answer to that question was 40 years. But I have no reference to back up that claim. I will say that the primary cause of insulation failure is "heating over time." A rule of thumb (for which there is a technical basis) is that if you add 10 degrees C to the temperature of a wire, and keep the wire at that temperature for its entire life, then you will reduce the life of the insulation by half. This is cumulative: every 10 degrees you add will reduce the life by another half. But on the other hand, most household wiring is never operated anywhere near its rated temperature. This will have the effect of increasing the useful lifetime.
 
The wiring in the house appears to be fine. There are only five spare circuits. But the panel load does include a 30A 240V receptacle for a dryer,a 30A 250 V circuit for an A/C compressor. The problem as I see it is the Grounding Electrode Conductor. This is not current with local electrical codes[chicago],also there is no supplementary ground[in this case aground rod]. The conductor insulation is MTW and I do not know how long the insulation for the conductors is rated[such as 20 or 30 years]. This leads into another question. Does anyone know how long conductor insulation is good for? When should all the premise wiring be replaced?

I thought that you were required to put in nonremovable and nontamperable adapters when you ran into these type of fuses/edison base NEC 2008 240.51, 240.52, 240.53 and 240.54. Also, the type S fuses are suppose to be noninterchangeable with lower ampere classification. That would put an end to over fusing in most cases.
 
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