Can my vintage boiler wiring be updated to modern wiring?

@109A_5 The code in the 1930s did not call for a third green or bare copper conductor that you find in romex wires today. About 1947 or 1950 was the first mention of a dedicated ground wire in the NEC code books but I might be wrong about that. But I agree with your newer diagram if Northstate88 wants to keep the old look of the knife switch and fuse. The reason that there were fused disconnects back in the 1930s was to use several circuits off of one 30 amp leg and then drop down to two or three 20 amp circuits that could handle multiple appliances. If the new gas burner needed only 5 amps or less to operate the control transformer, it might be added to a basement 20 amp wire and then drop down to a lower gauge wire that had the 5 amp fuce in the switch box.

The average homeowner in the 1930s was a little bit more hands on with electric stuff and that was the reason for the 5 amp screw in fuse that also fit the same socket as the 30 amp screw in fuse. The homeowner was supposed to know not to put a 30 mp fuse into a 5 amp circuit . We all know how that turns out…

So I googed "Knife Switch" and looked at images that were all very much like the one on the right.

@mattmia2, can you explain how the one on the left is not a knife switch? Does the enclosure make this not work the same way as a knife switch? Does the handle need to be that piece of bakelite of rubber or some other insulating material at the end you lift to open the circuit? I thing this Square D enclosed fused disconnect uses two knife switches in the assembly. But I might be mistaken. I want to be accurate when explaining the facts.

old electrical switch gear

These are knife switches

I knew what he meant as well.

a knife switch is open, it isn't enclosed. almost any high current switch's contacts are going to be a bar of metal moving in any out of a pair of contacts, usually rotating on a shaft like in that enclosed safety switch, even high voltage transmission line switches have similar contacts. that contact arrangement in itself doesn't make it a knife switch. you could have a knife switch in an enclosure but in a knife switch you are moving the contact bar directly, usually with an insulated handle on the end of the bar, it isn't moved from outside of the enclosure with a remote handle.

square d made their business selling that switch as a safe replacement for knife switches.

a lot of old theater lighting systems were open slate boards with open knife switches to route the crosspoints to/from the dimmers and open dimmers.

Yes that is amusing.

To me a knife switch is a basic style of switch. If you enhance the application of it by putting it in an enclosure and that may also include mechanical interlocks, etc. and you call it a safety switch that is fine too.

To me the knife switch part is often a sub-assembly of a safety switch.

I have a boiler that actually boils water to make steam. All you hot water folks have something else, I just don't know what to call it. Apparently no one else does either so they call it a boiler. And if water is boiling inside that is BAD.

Deserve… I thrive on this type of stuff.

Thanks for your support Chris

and all refrigerators are Frigidaire

How dare you!!! We don't use the F word in my house.

@ChrisJ

My mistake. All refrigerators are😎 GE