Switch Rating

[Lc85]

Our client asked that all switches be rated 8A@220VAC and 8A@24VDC., Our suppliers are struggling to meet the DC rating. the closest they can find is 10A@250VAC and 5A@30VDC. Am i right in thinking that this rating would be more than suitable?

Thanks

 

[VEBill]

It really depends on what the switches are being used for. For example, if they were being used to switch 7.5A then 5A switches wouldn't be suitable.

 

[VEBill]

My example, ...with DC.

 

[Skogsgurra]

It also depends on the load. If purely resistive, it could probably work even at 8 A. But if inductive without free-wheeling diode, it won't work at all.

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[Lc85]

For this case it is temperature, level and pressure switches on a lube oil tank. Also it is for interposing relays from an instrument panel that give signals such as speed low and speed low low. Thats why I think the rating is quite high, has anybody came across this before?

Thanks

 

[ScottyUK]

If the switches are used with electrical equipment such as an MCC, rather than just instrument equipment, then it may be because of the size of the control fuse or control breaker within the equipment rather than the current demanded by the (e.g.) contactor coil. 6A is a fairly common size of control fuse for an MCC.

 

[dV8r]

I suggest that you use what works best for your load and take exception to their specs.
Make a note that not other devices may be operated through your interposing relays and/or that the end user must supply their own interposing relays for additional loads.

Letting an end user tell an OEM what must be used to operate their system is ridiculous and unwise.

 

[jraef]

The flip side of the coin in dV8r's point is that whomever wrote that spec may have had a SPECIFIC device they wanted you to use. So the spec being written that way may have been done with the knowledge that nobody else had it, therefore it was an indirect way of writing a spec that is exclusive, without appearing to be so. Sometimes you just have to find the person who wrote the spec and ask them what they had in mind. Many times when I have done that, they seem unaware that they had done anything odd and just allow you to supply whatever is an industry standard.

However from a purely engineering standpoint if you are NOT using 24VDC, I don't see why that rating would matter to be quite honest. But if you are, and the LOAD on the switch might require it, then you are going to have to look harder.

"Will work for (the memory of) salami"