Sunday, August 30, 2015

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What is Role of PTC Relay and How a Compressor PTC Relay works

In my last post i talk about the compressor overload and in this post you will learn about PTC Relay which we use mostly for every refrigerator compressor starting. PTC means positive temperature coefficient thermistor however we can called starting relay or compressor starting relay in simple words.


How a Refrigerator PTC Relay Working and Function

In the refrigerator compressor we use the split phase single phase induction motor  and this motor have internal two types of winding which we called running and starting winding or auxiliary winding. We know that a single phase motor did not start with a starting capacitor or a staring current.
In simple words the refrigerator ptc relay gave a current to start winding and when the motor stat up the ptc compressor relay remove the start winding from the circuit.
So the above is a simple and short explanation of refrigerator relay and it's working, So lets know the working method of a PTC.

refrigerator ptc relay
Compressor starting relays


As i written above that ptc mean positive temperature coefficient thermistor which means that a relay with working relation with temperature. Basically a ptc thermistor is a resistor whose resistance increase with increase of temperature.



So let's explain it step by step
We know that compressor motor or fridge compressor have split phase induction motor which have two types of winding, the main winding which we called him RUN Winding  and the auxiliary winding which we called START Winding. A fridge compressor required a starting current to start normally and for this we connect the starting relay.
Compressor three terminals called START, RUN and COMMON. Common means the point where the start and run is connected.

Also read
What is working of capacitor in single phase motor
What's Overload and How a overload protector works
Internal structure of induction motor winding connection

How to identify refrigerator compressor terminals

We connect overload protector to compressor common terminal and ptc relay to the run and start terminal. In ptc relay the supply goes direct to the run winding but between supply and start winding a thermistor is connected in series and when we switch on the refrigerator the current start flowing through the thermistor to auxiliary and compressor start up, this current flow heat thermistor and due to temperature the resistance of thermistor high and thermistor remove the start winding from supply.
E.g Example : If you start you fridge and then you switch off and then start it, you will notes that the compressor is not start again because of heat thermistor or relay. And when you switch off again and try after 5 to 10 minutes you will find the fridge compressor start normally.

In many cases we connect a staring and running capacitor to the ptc relay which help very much in staring compressor. With starting capacitor we connect ptc relay thermistor in series which make remove of start capacitor form the circuit. In many ptc compressor relay have a connection point for run capacitor and we connect the run capacitor in parallel with relay which help in better staring and running compressor.

Message :

I hope you learn some thing form this post about the ptc compressor staring relay and it's working, however i will guide you about all types of ptc relays and it's wiring methods with complete diagrams.


10 comments:

  1. I have a frigidaire chest freezer that sat in a few inches of water for a day. it continued to work for a week, then stopped. I've tested the compressor and the temperature control. I believe the problem is the ptc relay. The manufacture says the part is not replaceable. Can I substitute a different start device, along with a run capacitor to accomplish what's needed?

    ReplyDelete
    Replies
    1. Dear can you send me the images of the compressor and relay, and one thing more test the compressor terminals and find out the star run and common. and when you find out then connect a relay regarding the terminals, my mean that replace a relay which M point match with your compressor run terminal and S point match starting terminal.
      In some compressor the overload protector is instill internally and in some the overload is connect with PTC rely. if your old relay have an overload protector then connect a overload between the common terminal and supply wire. and if overload is not instill with old relay then connect the other wire to the common terminal.
      Before you starting doing this , switch off the supply wire and May ALLAH Safe you and best of luck.
      However if you send some images then i will try my best to help you. And you can also connect a starting or running capacitor with relay but if the relay have points for capacitor or the relay is capacitor type relay. The below post will help you.

      http://www.electricalonline4u.com/2015/07/compressor-terminals-identifying.html

      http://www.electricalonline4u.com/2015/08/overload-protector.html

      Delete
  2. I am using two compressors.I want to connect a capacitor to one refrigerator compressor? I'm trying to make two compressors run on Infinity Loop please make a diagram I appreciate it very much thanks!

    ReplyDelete
  3. I am using two compressors.I want to connect a capacitor to one refrigerator compressor? I'm trying to make two compressors run on Infinity Loop please make a diagram I appreciate it very much thanks!

    ReplyDelete
    Replies
    1. Dear soon i will design a diagram about this. So stay tune with us.

      Delete
  4. i have a frigidare chest freezer that wont run just clicks after its on for 1 min or so ordered new start relay and overload need a diagram of where the wires should be think someone else has messed with them

    ReplyDelete
  5. i have a frigidare chest freezer that wont run just clicks after its on for 1 min or so ordered new start relay and overload need a diagram of where the wires should be think someone else has messed with them

    ReplyDelete
    Replies
    1. Dear if yo want to instill the a new relay frigidare chest freezer compressor then first identify the compressor terminals that which one is star,run and common then when you find out that. Connect your overload protector to common terminal. And relay point which for (M) point running connect to run terminal.
      This will be best for you to seen us some images of your compressor and relay and overload using my email id. One thing more That IN SHA ALLAH Soon i will write about this........

      Delete