I need help understanding an old fuse box

jspearsSeptember 10, 2006

I have an old fuse box that blew a fuse and I am not sure how to replace it. It has a row of 4 edison screw type fuses. The middle 2 are red and say "time delay fuse 20Amp." The outter two are clear. Abbove this row of 4 fuses are two carriages side by side. The one on the left says "Main" and the one on the right says "Range." On both carriages it says "When fully in reverse for OFF."

On the panel door it says its a murray manufacturing corporation fuse box.

I am not sure how to get into the carriages as there is no main switch. So do I just unscrew the fuses below to kill power to the carriages? Or do I need to reverse them if thats what the writing means? Since there is no main switch do I need to make sure everything in the apartment is off before I unscrew the fuses? Or should I look for another fuse box that might have the switch?

Thank you for any help or advice you can give.


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Here is a photo of the fuse box:


Here is a link that might be useful:

    Bookmark   September 10, 2006 at 3:13PM
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I'm not sure I understand what your problem is. The four screw-in fuses are for branch circuits. If only a few of your lights or receptacles don't work, it's probably because one of those fuses is open (blown). YOu can usually tell which is bad because it will have a blackened face, or (for the time delay type) the spring inside will be short rather than stretched out.

If one of these fuses has opened, it's a fairly simple matter to replace it. But first you need to turn off the main switch.

Here is the secret which shouldn't be a secret. The black bakelite blocks that are marked "When fully in reverse for OFF" are both fuse holders AND switches!

To turn off the power, seize the wire handle on the MAIN block, and pull the block straight out of the panel. Then put it back in upside down. Then you can safely change the blown branch circuit fuse. When done, pull the MAIN block out and reinsert it right side up (or the way it was before).

Now, if about half of your lights and outlets are out, and all the screw-in fuses (confusingly called "plug fuses" ;-) below seem to be OK, it could be that one of the main fuses has opened.

To check them, pull the MAIN block straight out as described above, but don't put it back in yet. Turn it over and you'll see the two main cartridge fuses. (You can see a bit of the cartridges through the holes in the blocks, in your picture.) Carefully pull the fuses out. Put the block back into the panel, upside down as above. Then take the fuses to your hardware or electrical store for testing and, if necessary, replacement.

If a main fuse fails repeatedly, it's a sign that your house's electrical service capacity is too low. In this case you'll need to hire a pro to evaluate the electrical system, and take bids on an upgrade.

    Bookmark   September 10, 2006 at 4:08PM
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You do not need to turn off the main to change a branch circuit fuse.
Unscrew the blown fuse and screw in a new fuse of the EXACT SAME TYPE.

    Bookmark   September 10, 2006 at 6:09PM
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Ron Natalie

Unscrew the blown fuse and screw in a new fuse of the EXACT SAME TYPE.

Actually, I'd think carefully about what the PROPER fuse should be. Unless you've got fusestat's, it's quite possible that someone put a larger fuse in there at some point in the intervening years. Any screw-in type fuse over 15A should be suspect :-)

    Bookmark   September 11, 2006 at 9:37AM
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I subscribe to the wisdom found at 1 Thessalonians 5:21. Once I found that a homeowner had been told that he should install the TypeS adapters and he did so. His thinking was that if 15 amps was good, 30 amps was twice as good. All his wiring was 14 gauge. I removed the 30 amp adapters with a Trico tool and installed the correct ones.

    Bookmark   September 11, 2006 at 11:27AM
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Heck my dad just busts out that plastic and adds a drop or two of solder to fix those sprung plug fusetrons links.

    Bookmark   September 11, 2006 at 12:54PM
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"Actually, I'd think carefully about what the PROPER fuse should be. "

For someone asking how to even change an edison fuse, determining the correct circuit ampacity is probably a real stretch.

    Bookmark   September 11, 2006 at 2:02PM
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I will change an Edison base fuse with the power on, but I recommend that non-electrical types open the main first. That way it's just about impossible to get hurt.

    Bookmark   September 11, 2006 at 6:39PM
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Ron Natalie

Of course, pulling and replacing the main is about as dangerous as replacing the branch circuit fuse hot.

    Bookmark   September 12, 2006 at 9:27AM
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Just out of curiousity, what is the danger in switching out an Edison base fuse with the power on?
Is it just that your finger might slip into the hole and contact the live components, or is it something else that I can't even guess at?

    Bookmark   September 12, 2006 at 1:14PM
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Both sodes of teh scrw socket in an Edison fuse are hot as soon as the fuse makes contact with them.

The design is actualy pretty good though. The base contct will not touch until the metal shell is covered pretty well.
You could work at it and touch something hot, but the biggest problem is the surprise when the fuse makes contact and instantly 'blows'.

    Bookmark   September 12, 2006 at 7:44PM
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I need one of those blocks. I have one of these old fuse boxes too, except mine is missing the "RANGE" block that goes into the right slot in that picture. It's made by Turnbull, and I can't find it anywhere.

    Bookmark   February 5, 2007 at 11:56AM
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How do you know if the blocks are upside down?
The writing appears to be same either way.

    Bookmark   February 26, 2007 at 10:53AM
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One way the contacts are made so the range or panel is "on". the other way the contacts are not made , so the range or panel is "off".

    Bookmark   February 26, 2007 at 11:14AM
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But, you can't know by just looking at the block, right?

    Bookmark   February 26, 2007 at 11:33AM
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All the ones I have are pretty clear about when they are upside down.

    Bookmark   February 26, 2007 at 8:35PM
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Some of the fuse blocks have a notch in the side that that permits reading the marking on the side of the contact base. The word "OFF" will appear in the notch when the pullout block is reversed. That word is covered when the block is in the "ON" position. For those who still have this style panel, it is vitally important that the block be pushed firmly all the way in when the panel is supplying power. A loosely installed block will soon result in a completely ruined panel.

    Bookmark   February 27, 2007 at 7:41AM
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I was just looking at the picure of the fuse box in the original posting.
By the picture, it would appear that you could not tell if the block was inserted for " on " or " off ".
What am I missing ??

    Bookmark   February 27, 2007 at 10:39AM
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Maybe this is the answer, if the block is inserted for "off", it will not go all the way in.
If insterted all the way, it would indicate it is "on".
So, if the block is all the way in, it is on.

    Bookmark   February 27, 2007 at 11:46AM
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Ron Natalie

If you don't pull the main, it's hard to get the penny in there :-)

    Bookmark   February 28, 2007 at 5:12AM
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If you pull out the blocks (they normally contain a pair of cartridge fuses) be sure to pull them fully out quickly.

This is not the time to be tentative, just pull them out.

The same goes for plugging them back in in the 'ON' positin.

Push them in quickly and firmly.

Going slowly can allow an arc to establish and damage the blades and sockets making the actual connection.

The same thing goes with screwing in Edison base fuses.
You need to look at an inserted fuse and when the new one gets near the same height finish the last turn as quickly as you can.

    Bookmark   February 8, 2013 at 4:24PM
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I have an older 100 amp fuse service in my early '60's ranch. Have asked a question or two on this forum.

I've noticed the two books on 'wiring' I've got have very little info devoted to fuses. Ninety percent is devoted to breakers even though books are ten or twenty years old.

Anyone have a recommendation on a book for fuses and boxes?
Such as why the box has both fuses and plastic square plugs with fuses inside? And should total of fuses equal the 100 amps, or be greater; and if so how much?
And some info on tracing flow to outlets, and devices needed.

    Bookmark   February 20, 2013 at 3:13PM
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Fuse panels have not been used much for over 50 years.

If you have them it is likely time to upgrade to breakers.

I used to do a changeover every Saturday for many years.

In Virginia you can do it without the POCO standing there (unload and pull the meter) and then use jumpers from the old meter base to the new meter base and shorting bars in the new base.
Plug the meter back into the old base and power is back on.

If you plan carefully power is off for about 5 minutes (or less).

After inspection the POCO returns and replaces the feed to the meter if required (and on their nickel, including weather head and drop to the meter base.).

    Bookmark   February 21, 2013 at 11:58AM
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Here are details about the Murry Fuse Box. The box has a rating...somewhere...you'll see 100amps (likely). But, when you "pull" "main" by the handle (pull it hard and fast to remove it), you'll likely see two cartegrige fuses, both 60 amp, on the other side of the handle (and what's in your hand). (For a real max of 120 amps). So, clearly they should have been 50amp (lol). They occasionally burn out....IF you pull the "range" handle, then you'll also see two cartegrige fuses...You might also have an "auxilary" fuse box, which runs along side the fuse box wired to posts in the Murry box. The range and the main, are both "240". The fuses you see are 120 circuits (or half of a 240 circuit). You should be wearing rubber gloves when you play in the fusebox. Realize this...that fuse box might be 50 years old. There are no problems...but eventually, you've got multiple house circuts running through each fuse. The last Murry box I saw like your's the water heater (240), ran off two fuses, and each of these shared other house circuits....this is called "overloaded". If I were you....I'd just replace the entire thing with a new 100 amp circuit breaker box. You might also notice that there is rust in the box...There is likely no way to really add another wire to the ground bar, without breaking the ground bar due to corrosion. This box wires neutral and green wires all to the ground bar. I would do the same with the replacement new circuit breaker box, but you also need to turn a screw to make this happen in your new box......It sounds like you should not be replacing the box yourself. If/when you opt to do this, find someone who knows what they are doing.
fyi: 1 and 3 are one side of 240, and 2 and 4 are the other side....i'd keep this the same in the new box as well.

    Bookmark   June 22, 2014 at 1:11AM
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