Microswitch question

stuhaynes

stuhaynes

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In view of all the problems I've had with my water pump pressure switch I've decided to fit an in line one. The one I've got is a Whale W7207. To deal with 24 volts @ 6amps I've ordered a SPDT button microswitch,22A 150degC from RS to replace the weedy thing that is in the switch.

Can anyone who knows more about micro switches than I do suggest whether the new micro switch is going to be man enough?

I should point out that the 'new' in line switch is one that I found on board. It's been used and the micro switch was corroded :o
 
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A device rated at 22A (continuous presumably) carrying 6A...... I may be missing something but it would seem to be well within its capabilities.
 
Its rated at 22 amps at 250 volts AC

I cannot see a rating at 24 volts DC

switch ratings are usually much lower on DC .

At least at the price you can afford to keep a spare
 
VicS said:
Its rated at 22 amps at 250 volts AC

I cannot see a rating at 24 volts DC

switch ratings are usually much lower on DC .

At least at the price you can afford to keep a spare
Click to expand...

Thanks VicS, Its the mention of 250 volts AC that made me ask the question. As I understand it the contacts on DC switches are meatier than AC. In saying that, the original micro switch is also marked 250AC.
 
Inductive loads are what destroy switch contacts. I would hook it up to a battery with bare-end wires and see if they spark upon connection. If so, it might be a good idea to use a low-rated microswitch in conjunction with a heavy duty relay instead, to switch the pump. You can usually find suitable relays under the bonnet of scrapped cars.
 
elton said:
Inductive loads are what destroy switch contacts. I would hook it up to a battery with bare-end wires and see if they spark upon connection. If so, it might be a good idea to use a low-rated microswitch in conjunction with a heavy duty relay instead, to switch the pump. You can usually find suitable relays under the bonnet of scrapped cars.
Click to expand...

We're 24volts. I do like the idea of a relay though. Any idea where simple new relays can be bought?

Came back to edit after finding this at RS. Suitable?

PCB Relay SPDT, 20A 24Vdc
 
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If you can't find a heavy Uswitch to physically fit in the holder, get a relay, there are plenty of open contact 24V ones around, which means you can clean the contacts if neccessary.
 
Its the switching arc which can restrict the DC capacity rather than the continuous current heat load.

Different switch designs cope better or worse with DC. Switching speed, contact design and material etc. influence capacity.

It would be surprising if any 22amp AC switch won't comfortably carry 6amps DC.
 
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