2 safety switch questions

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Old 12-19-17, 06:13 PM
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2 safety switch questions

In the first picture, I have an old Dominion electric switch with what looks like brown resin in one of the connectors under the fuse. What could that be?

In the second, safety switch has 6 metal contact points. Top two are line. The middle are load. What are the bottom two below the fuses for?
 
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Last edited by qwertyjjj; 12-19-17 at 07:05 PM.
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Old 12-19-17, 07:49 PM
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The terminals in the fuse panel are line and load.
 
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Old 12-19-17, 09:41 PM
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Originally Posted by pcboss View Post
The terminals in the fuse panel are line and load.
The bottom two are not indicated. There are 6. You mean there are 4 load connections?
 
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Old 12-19-17, 10:00 PM
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You only connect to line and load. The two in the middle are connecting screws.

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Old 12-19-17, 10:21 PM
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The 2 middle screws have load written next to them! That's the confusing thing. They have holes to put a wire inside.
 
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Old 12-20-17, 09:51 AM
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Any ideas on the brown resin under the fuses? Doesn't seem like rust
 
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Old 12-20-17, 12:19 PM
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Says line at the top and then the v2 nearest screws have load on them?!
 
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Old 12-20-17, 03:10 PM
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The same parts are used to make un-fused and fused switches. The center terminals are used for wiring when there is no fuse present. Some rare installations may use them as "feed-through" lugs to a different (separately fused or protected) circuit that is required to be powered off at the same time as the load/circuit through the fuses in this switch.

The "resin" is just that. I've seen this appearance on fuse-holders that have overheated from having too large a fuse installed. At first I thought this was a new switch but I see the fuse-holder shell has been chewed up some with pliers or something.
 
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Old 12-20-17, 04:00 PM
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The switch with resin is probably 30+ years old. The other switch is new.
Still not sure why they print load on the line terminals (zoom in) bit I've connected the source there now.
Worth cleaning up the resin or leave as is?
 
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Old 12-21-17, 04:20 PM
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The breaker is 25a - do I need a 25a fuse on left and right in the box? Or do you divide it in two? 12.5a on each
Do I even need fuses? Could just make it an on off switch protected by the breaker.
 
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Old 12-21-17, 04:23 PM
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Size the fuses to the load. Depending on just what the load is, you may want to use time-lag (slow-blow) fuses.
 
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Old 12-21-17, 04:28 PM
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2x25A?
What's the purpose of slow blow? Wouldn't that just mean the breaker would trip first?
Do I even need fuses?
 
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Old 12-21-17, 04:53 PM
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The breaker is 25a - do I need a 25a fuse on left and right in the box? Or do you divide it in two? 12.5a on each
25A fuse. Not 12.5A. Current comes out from one wire and comes back to another. Therefore, same amount of current flows on both fuses on 240V circuit.
This value really depends on what the load requires. If the load requires smaller fuse, you should use smaller fuse.

Do I even need fuses? Could just make it an on off switch protected by the breaker.
If your load requires 25A protection, then yes. You don't need fuses. However, since you already have fused disconnect switch why not? Do not modify the switch to bypass fuses. You have to buy non fused switch/disconnect if you choose not to use fuses.

What's the purpose of slow blow? Wouldn't that just mean the breaker would trip first?
Many inductive loads such as a compressor or a large motor have a large starting current and this current will often go over the rating of the fuse or breaker. With fast blow fuse, the fuse will blow right away. Slow blow fuse will allow short time of overload. Most breakers are HACR type and they are also slow trip and allows a brief overloads.
 
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Old 12-21-17, 04:57 PM
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Without knowing the supply voltage and the current load PLUS the type of load I have no idea what to recommend. You may, or may not, need fuses.

I'll ask again, what is the load? Give me ALL the details as I am not a mind reader nor do I have a crystal ball. Don't be surprised if I take a couple of hours to respond.
 
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Old 12-21-17, 05:03 PM
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Sorry I missed the load question - water heater 19.85 A
We are allowed to run them on 25a breakers and 12/2 wire in Canada since it's constant load, it doesn't exceed the 20a wire rating and the breaker is sized to 125%
 
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Old 12-21-17, 05:09 PM
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20 ampere should hold but you can use 25 ampere.
 
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Old 12-21-17, 06:45 PM
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So, the middle screws are definitely the load screws. I did a video to show it with and without fuses.
I still cannot get any voltage to the bottom screws?! What are these?
My finger is not as close to the live as it looks in the video due to perspective.
https://youtu.be/YFJWuBszK2s
 
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Old 12-21-17, 06:52 PM
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That bottom terminal does not appear to be connected to anything. My guess is that is a splice point for neutral for 120/240V circuit.
 
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Old 12-21-17, 07:38 PM
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What fuse is best? Time delay or quick?
Is a 20 fuse allowed on 25 breaker? I have 20a fuses in there right now
 
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Old 12-22-17, 06:14 AM
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What fuse is best? Time delay or quick?
Either is fine for a water heater. Standard duty, time delay is fine.

Is a 20 fuse allowed on 25 breaker? I have 20a fuses in there right now
Yes, but the 20 amp fuse will blow before the 25 amp breaker will trip. At 19.85 A I would recommend 25 amp fuses.
 
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Old 12-22-17, 08:59 AM
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If this switch is being used simply as a local disconnect, and it reads to me as if this is the case, it really does not need to have fuses and therefore you could install 30 ampere fuses to preclude their blowing.

However, it has been my experience that when an inspector sees a fused switch, even when a non-fused switch is acceptable in the installation, they want to see the proper sized fuses used in the switch.
 
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