QO-1, Fuse Blocks/Breakers

[jmellc]

Went with a friend the other day to check out some damage and saw a QO panel with both breakers & fuse blocks in it. SP fuse block is a QO breaker housing with slot for a small cartridge fuse. Never saw this before, but I assume Square D had been making this panel a while and these fuse blocks, then designed the QO breaker to fit the same panel? My friend had never seen it either, never heard of it. Panel also had several DP tandem fuse blocks and a SP tandem fuse block. Had 1 std QO 120 breaker in same panel.

How cool is that? Designed that in some cases a breaker could replace the fuse block. Anyone else ever seen these?

 

[jim dungar]

They are called QF. They used class G fuses. They were pullout devices with built in blown fuse indication.
By 1975 they had 'disappeared' from the Square D Digest.

 

[jmellc]

These were installed about the early 1960's, best we could figure. Outstanding thinking, to follow through with breakers designed for the same fit.

Never know what you will find. I started doing this work in 1976 and never saw it before.

 

[jim dungar]

These were installed about the early 1960's, best we could figure. Outstanding thinking, to follow through with breakers designed for the same fit.

Never know what you will find. I started doing this work in 1976 and never saw it before.

The line of QO family (breakers and panels) was introduced in the mid 50's. The QF fusible device was not introduced until around 1964.

 

[jmellc]

The line of QO family (breakers and panels) was introduced in the mid 50's. The QF fusible device was not introduced until around 1964.

Thanks, I had that backward. I thought the fuse block came before the breaker.