blown in insulation

[rwood]

Hi
I know you can't insulate over knob and tube wiring but how about old 2 wire romex without a ground probably from the 50s
thanks in advance rob

 

[ActionDave]

Go for it. There's nothing that says you can't and there's plenty of it out there that has already been encased in old rock wool insulation already.

 

[LarryFine]

Probably a good part of the reasons for the global 15-, 20-, and 30-amp over-current limitations for 14-, 12-, and 10-gauge copper wires, respectively, which have higher ampacities in the tables.

 

[junkhound]

10 AWG is 1 mohm per foot, at 30 A dissipates just under 1 watt per foot.
to get to 60C (old NM without the -B) thermal impedance needs to be -- math left to the student..

conclusion, no problem for under 2 ft thick insulation on all sides.

 

[mtnelect]

In my opinion ... Don't walk but run away from old wiring. It is unsafe, and the insurance companies will not insure in California.

 

[James L]

If it's a hot attic and the cable are right on top of the joists, then more insulation can be better.

Reason is, heat can only dissipate toward what's cooler.

Suppose you have a 60⁰ (C) 140⁰ (F) conductor that's running full hilt, in an uninsulated attic. If it's summer and 102⁰ outside, that attic will probably be over 150⁰

Where will that 140⁰ wire dissipate to in a sweltering attic?

But suppose you have 20 inches of insulation. Above the insulation is 150⁰ but below the insulation is 75⁰

If that cable is in the bottom third, it's more likely to be in a cooler ambient temperature. So even though the insulation is thwarting heat dissipation, it's probably still better than being open to 150+

 

[James L]

In my opinion ... Don't walk but run away from old wiring. It is unsafe, and the insurance companies will not insure.

I don't know where you get the idea that insurance companies won't insure houses with old wiring. I bought my house less than 2 years ago. Built in 1951 and wired with old cloth 2-wire. It's insured with Cincinnati Insurance.

Further, it's not necessarily unsafe. The thing I've seen over and over which seems to have taken the biggest tole on wiring was people using incandescent light bulbs with wattages higher than the fixtures were rated for, and without insulation on the back of the fixture. But I've seen that over and over again in houses from tge 30s all the way to tge 2000s

 

[ActionDave]

In my opinion ... Don't walk but run away from old wiring. It is unsafe, and the insurance companies will not insure in California.

That's quite an opinion, based on what? It could be said that newer wiring is safer, but we've had electrical wires in buildings that have been in service since the 1920's and nobody's walking into them and not walking out.

 

[mtnelect]

I don't know where you get the idea that insurance companies won't insure houses with old wiring. I bought my house less than 2 years ago. Built in 1951 and wired with old cloth 2-wire. It's insured with Cincinnati Insurance.

Further, it's not necessarily unsafe. The thing I've seen over and over which seems to have taken the biggest tole on wiring was people using incandescent light bulbs with wattages higher than the fixtures were rated for, and without insulation on the back of the fixture. But I've seen that over and over again in houses from tge 30s all the way to tge 2000s

That's why people are leaving California. We have very stringent code standards, based on energy efficiency. It's all electric, no gas appliances.
In California if you have a 60 - amp panel, you will have to up - grade to at least a 200 - amp panel.
Old wiring "Romex" wiring can't handle it.

 

[Joethemechanic]

I don't know where you get the idea that insurance companies won't insure houses with old wiring. I bought my house less than 2 years ago. Built in 1951 and wired with old cloth 2-wire. It's insured with Cincinnati Insurance.

Further, it's not necessarily unsafe. The thing I've seen over and over which seems to have taken the biggest tole on wiring was people using incandescent light bulbs with wattages higher than the fixtures were rated for, and without insulation on the back of the fixture. But I've seen that over and over again in houses from tge 30s all the way to tge 2000s

I've seen intact 100 year old circuits that I'd have no problem keeping in service. The biggest problem I see with old wiring is somebody did hackwork to it

 

[mtnelect]

My home was built in 1972, with a 125-amp main, and Romex with a ground.

 

[LarryFine]

I've seen intact 100 year old circuits that I'd have no problem keeping in service. The biggest problem I see with old wiring is somebody did hackwork to it

Agreed. I have no trouble trusting unmolested, non-overloaded knob-and-tube wiring.

 

[mtnelect]

In my consulting work, I see it all the time. A homeowner wants to upgrade their two-wire cloth covered Romex. Seems like a simple fix.
They get a few estimates, then go for it. They are still in the house, while all of this work is going on. Walls are opened up, and dust with lead based paint is exposed to the occupants.
Then the contractor discovers it is more work than they expected, and abandoned the project.

 

[mtnelect]

The demand for increased electricity continues. It will be an all-electric world for everyone, not just California. Do you have the electrical capacity to meet your future needs ?

 

[LarryFine]

In my consulting work, I see it all the time. A homeowner wants to upgrade their two-wire cloth covered Romex. Seems like a simple fix.

In such cases, I recommend leaving the existing wiring as is, and running a new circuit for the new load(s), such as an A/V or computer system, appliance, etc.

That way, the existing wiring isn't subject to the additional loading, the new loads receive a direct, well-grounded supply, and the labor savings is substantial.

 

[marmathsen]

Hi
I know you can't insulate over knob and tube wiring but how about old 2 wire romex without a ground probably from the 50s
thanks in advance rob

I don't know of any issues with insulating over old snake skin wire.

Some insurance companies in Washington won't insure homes with knob and tube, others will give a discount if it's removed.

We also have a provision that an electrician can "inspect" knob and tube and give the OK to insulate over it. To this day I've never heard of an electrician who will actually perform that service. No thanks! I don't want that liability for 100 year old wiring.

Rob G, Seattle

 

[mtnelect]

In my opinion ... These older homes are an electrical hazard. The insurance companies need to implement a program to provide the homeowners a rental while the up-grades to the electrical wiring is performed.

 

[James L]

In such cases, I recommend leaving the existing wiring as is, and running a new circuit for the new load(s), such as an A/V or computer system, appliance, etc.

That way, the existing wiring isn't subject to the additional loading, the new loads receive a direct, well-grounded supply, and the labor savings is substantial.

That's what I'm doing in my own home. Much simpler, and old wiring didn't get disturbed.

2 bedrooms had 2 receptacles, master had 3. Now there are 4 in one, 5 in another, and 6 in master. All the old ones were left as-is except swapping to 3-prong receps and dual function breakers. New adds on shiny new circuits. Same scenario for living room receps. One lighting-only circuit in attic got completely removed and replaced.

 

[curt swartz]

In my opinion ... These older homes are an electrical hazard. The insurance companies need to implement a program to provide the homeowners a rental while the up-grades to the electrical wiring is performed.

In my opinion you need to stop giving opinions and providing 100% false info.
Insurance companies frequently have issues with screw in fuse protection. Sometimes they want an electrician to evaluate Zinsco or FPE equipment. I have never had a customer state they can't get insurance because they have older NM cable.

Older NM cable only has 60C conductors which is normally only a problem with over-lamped incandescent fixtures. Older NM cable is built much more robust than the current NM-B cable.

 

[mtnelect]

In my opinion you need to stop giving opinions and providing 100% false info.
Insurance companies frequently have issues with screw in fuse protection. Sometimes they want an electrician to evaluate Zinsco or FPE equipment. I have never had a customer state they can't get insurance because they have older NM cable.

Older NM cable only has 60C conductors which is normally only a problem with over-lamped incandescent fixtures. Older NM cable is built much more robust than the current NM-B cable.

Old cloth covered wiring with rubber insulation is a safety hazard. If disturbed, the insulation will fall apart and exposed open wiring will result.