Subfloor Pex and old Romex

Tim Weaver

Installing subfloor 1/2" pex throughout my 1500 sq. ft. 1955 ranch home. Two loops through most bays stapled up and plans to insulate below pex to at least R13 with FBF to start. I've seen concerns here and elsewhere about "older" wiring in joist bays. I'm not sure what constitutes "older" wiring. I am unable to read the manufacturer's label on what I believe to be Romex in my home. The wire has a a dark gray/black cloth type wrap (with bare equipment ground included) and plenty of paper wrapped between conductors. I would like to know the temperature rating of wire this age (and type) and what threat the fairly high temp radiant will pose to it. The floors above have no carpet but I can not afford subfloor plates at this time. Thanks for any advice you can offer.

[Deleted User]

cloth wrapped?

that's older romex, and maybe a bit dry and brittle. older than that would be knob and tube. and while you wouldn't be subjecting it to very high temps with radiant, it will dry it even more and create a potential for problems down the road. so, if you can keep the wiring below the radiant and insulation, do so. if not, i'd suggest replacing it unless it's still in good, pliably uncracking condition. have an electrician take a peek

[Deleted User]

repeated deleted

scrook_2

Plastic jacketed...

Type NM cable ("Romex" and other brands, pre mid-1980's) were 60°C (140°F), Type NM-B cable (post mid-1980's) is 90°C (194°F), the change was made primarily for greater reliability at incandescent light fixture connections.

I'm not sure what the 1950's vintage woven jacket style "Romex" non metallic cable (or metal jacketed "BX" cable) was temperature rated for, certainly not more than 60°C though. They also generally had smaller gauge (or no) bare ground wire than the insulated conductors.

Tim Weaver

Thanks for your responses. The 140* degree rated wire would be a concern for sure. I will replace all the old Romex that would have been above the subfloor insulation. At least copper wire prices are half the price they were last time I purchased. Awesome forum....thanks again.

bob young

good move, bro