electrical people: what kind of plug is this?

[drkshdw]

Gutting a house that was (supposedly) built in the late 20's to early 30's. Tearing out a wall today and came across this plug and switch buried in the wall. I've never seen either before but it's wired into a knob and tube system. Anyone know what kind of plug and switch this is? And when it would've been used?

And as a side note, this wasn't a planned gut but I'm sure glad it turned into one! The whole knob and tube wiring is still wired to the fuse box and live but all the outlets and light sockets were shoved into the walls and ceilings when the house was remodeled in the 50's. And buried in wadded up newspapers they used as 'insulation'. This was a disaster waiting to happen but it's being taken care of now...

[WolfeMacleod]

T-slot duplex socket.

US combination duplex socket


The parallel and tandem socket accepts normal parallel NEMA 1‐15 plugs and also tandem NEMA 2‐15 plugs. Both pairs of sockets are fed internally by the same supply.

A more recent and fairly common version of this type is the T-slot socket, in which the locations of the tandem and the parallel slots were combined to create T-shaped slots. This version also accepts normal parallel NEMA 1‐15 plugs and also tandem NEMA 2‐15 plugs. Incidentally, a NEMA 5‐20, NEMA 6-15, or NEMA 6‐20 plug with a missing earth pin would fit this socket. This receptacle type has been unavailable in retail shops since the 1960s but still available from the manufacturer Leviton (model 5000-I) for replacement only and not for new installations.

Harvey Hubbell had patented the parallel blade plug in 1913, and patented a polarized version in 1916. He also patented the T-slot single outlet in 1915, and a duplex T-slot outlet in 1916 both meant to take his older 1904 tandem and newer parallel plug design. (Single: US Pat. 1146938; Duplex: US Pat. 1210176). Prior to the 1930s, when Hubbell's parallel blade plug received its official rating of 125v (and became the United States' general service electrical plug standard), all of his electrical connectors were used interchangeably on either 120v or 240v. The two blade tandem configuration plug received its official rating of 250v in the 1950s but has been "banned" from use since the 1960s because of its lack of a ground or neutral.

Note: See the NEMA 1-15 ungrounded (Type A) section of this page for the parallel blade patent reference numbers.

[oldE]

Originally Posted by drkshdw

Gutting a house that was (supposedly) built in the late 20's to early 30's. Tearing out a wall today and came across this plug and switch buried in the wall. I've never seen either before but it's wired into a knob and tube system. Anyone know what kind of plug and switch this is? And when it would've been used?

And as a side note, this wasn't a planned gut but I'm sure glad it turned into one! The whole knob and tube wiring is still wired to the fuse box and live but all the outlets and light sockets were shoved into the walls and ceilings when the house was remodeled in the 50's. And buried in wadded up newspapers they used as 'insulation'. This was a disaster waiting to happen but it's being taken care of now...

Just old 110 v. The house I grew up in had similar plugs (but no exposed wiring, as it wasn't wired until the '50s.

Best
Les

[rwest]

Appears that it can supply both 240 or 120 volts in the same outlet

https://www.plugsocketmuseum.nl/NorthAm2.html

Must feel good that you discovered that fire hazard on your schedule rather than a hot surprise!

[drkshdw]

Thanks for the info guys. I've never seen this tandem style before. Obviously seen it on 220 but not on both prongs on the outlet. Learn something new every day. Also weird that this is the only outlet like this (all the others are standard outlets for parallel plugs) and also the only one with this switch on it. Glad to get it taken outta the wall and put into the 'stuff we found in the walls' box (that is so far 3 boxes instead of just 1).