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relay basics

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sam288

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Is it true that a 12v relay(max switching current::7A,max switching voltage 28v dc,250v ac) can switch an appliance eg. an air conditioner with ratings 230V ac and 5A current..?
I have designed a thermostat using microcontroller and have verified the results by turning an LED on/off through a relay..
Will the same circuit work if i just replace the LED by the air conditioner..?
Also turning an ac ON means turning its compressor ON...What is its equivalent in case of heaters?
 

MikeMl

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Most Helpful Member
Th problem I see is that your relay's current limit is 7A. Even though the RUNNING current of your AC motor might be 5A, it's INRUSH starting current is likely to be 4-6 times that; i.e. 20 to 30A. You need a "motor starting contactor".

Most AC's have a motor starting contactor built-in. It is usually actuated by a 24Vac signal from the house thermostat. Can you just tap into the control side...
 

ericgibbs

Well-Known Member
Most Helpful Member
Is it true that a 12v relay(max switching current::7A,max switching voltage 28v dc,250v ac) can switch an appliance eg. an air conditioner with ratings 230V ac and 5A current..?
I have designed a thermostat using microcontroller and have verified the results by turning an LED on/off through a relay..
Will the same circuit work if i just replace the LED by the air conditioner..?
Also turning an ac ON means turning its compressor ON...What is its equivalent in case of heaters?
hi,
This pdf will tell you most things you need to about relays, handy pdf file.
 
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