Hitachi EX60 Isolator Switch

[dhas]

Folks, how are we?
I have a customer who has an EX60 machine that is giving him some bother with the 24v solenoid relay battery isolator switch. I fitted lights to the machine back in September for him and he asked me to throw in the replacement switch as the existing one had failed. Since then he has replaced the switch again and now today he has rang me to say it has failed again. Any ideas on what may be the issue or has anyone had similar problems with these switches?

 

[TiltyShaun]

is it fitted on the negative side?? I have seen some fitted on the positive side that failed. Why.....beyond me!!!

 

[V8Druid]

is it fitted on the negative side?? I have seen some fitted on the positive side that failed. Why.....beyond me!!!

won't take the starter loading ... most isolators are designed to go in the -ve/earth line only

 

[T whiting]

It'll be under load when it's being switched they don't like it, it's a isolator not a switch.

I worked at a company that has a isolator for switching the power to the ramps it had been oversized and still failed every 6months

 

[jd6820]

is it fitted on the negative side?? I have seen some fitted on the positive side that failed. Why.....beyond me!!!

Should be fitted to the positive side...

Reason: The switching circuit the requires a supply to activate the isolator relay, if you cut the negative circuit it cannot be switched as by isolating the ground reference the circuit won't work. If you wire round this by supplying the switching circuit with it's own earth path then you would be likely to get current from other consumers using the same little wire to operate and could potentially burn it out.

I'm afraid I can't see the logic of negative isolation with regards to current capacity as the same amount of electrons flow from positive to negative or should I say from negative to positive if you want to be accurate. I'm thinking the issue is more likely a poor starter drawing more than the rated current of the isolator or they are cranking for long periods due to another issue such as fuel running back etc.... But feel free to correct me on this? Without seeing the machine itself and monitoring the current with a DC current clamp during starting and machine operation with all the lights and fans going it's a guessing game.

 

[V8Druid]

Should be fitted to the positive side...

Reason: The switching circuit the requires a supply to activate the isolator relay, if you cut the negative circuit it cannot be switched as by isolating the ground reference the circuit won't work. If you wire round this by supplying the switching circuit with it's own earth path then you would be likely to get current from other consumers using the same little wire to operate and could potentially burn it out.

I'm afraid I can't see the logic of negative isolation with regards to current capacity as the same amount of electrons flow from positive to negative or should I say from negative to positive if you want to be accurate. I'm thinking the issue is more likely a poor starter drawing more than the rated current of the isolator or they are cranking for long periods due to another issue such as fuel running back etc.... But feel free to correct me on this? Without seeing the machine itself and monitoring the current with a DC current clamp during starting and machine operation with all the lights and fans going it's a guessing game.

didn't realise this was an isolating relay ... thought we were talking about a straight forward quarter turn kill switch/battery isolator jobby ... would have to be in the live line as said, in order to provide a supply to the relay ... must be some relay .. bit like a starter solenoid, but designed to be latched on for long periods

as for the reason the isolators are in the neg line ... it ain't carrying / coping with the current draw, that a pos line would have to ...

 

[Steve]

Current will be equal on positive and negative leads, unless the isolator is spurred off of one or the other.

 

[Smiffy]

I presume this is the standard one fitted to all Hitachi's ?? If so does it get used every day or not
I haven't seen one fail before but equally we never use them

 

[dhas]

is it fitted on the negative side?? I have seen some fitted on the positive side that failed. Why.....beyond me!!!

I'll check into this when I get back to her. Thank you

 

[dhas]

Should be fitted to the positive side...

Reason: The switching circuit the requires a supply to activate the isolator relay, if you cut the negative circuit it cannot be switched as by isolating the ground reference the circuit won't work. If you wire round this by supplying the switching circuit with it's own earth path then you would be likely to get current from other consumers using the same little wire to operate and could potentially burn it out.

I'm afraid I can't see the logic of negative isolation with regards to current capacity as the same amount of electrons flow from positive to negative or should I say from negative to positive if you want to be accurate. I'm thinking the issue is more likely a poor starter drawing more than the rated current of the isolator or they are cranking for long periods due to another issue such as fuel running back etc.... But feel free to correct me on this? Without seeing the machine itself and monitoring the current with a DC current clamp during starting and machine operation with all the lights and fans going it's a guessing game.

Thanks so much for this. I'll check the draw on the circuit when starting and see what's happening.