Pool chlorinator - what does the triac do?

[Spuckle]

I've got a dud Monarch salt water pool chlorinator - no output.

It looks like the triac on the output has failed.


The circuit layout is:


AC ==> Dimmer ctrl ==> Xformer ==> Bridge rectifier ==> Triac ==> Cell


The output triac appears to have failed open. Its an ST branded BTA40.

The triac switches the -ve lead to the cell, the gate is connected
directly to a "stud" electrode in the cell.



What's the purpose of the triac?

Seems to me if the cell has water in it the triac is "on", otherwise its
"off". I dont have the full cell assembly - is the stud at the top so it
cannot run unless the cell is completely full??

 

[Trevor Wilson]

On 11/18/2012 8:14 PM, Spuckle wrote:

I've got a dud Monarch salt water pool chlorinator - no output.

It looks like the triac on the output has failed.

**That is certainly easy enough to check. TRIACs usually fail
catastrophically.

The circuit layout is:


AC ==> Dimmer ctrl ==> Xformer ==> Bridge rectifier ==> Triac ==> Cell

**I've seen this system before. It's slightly odd, but it works.

The output triac appears to have failed open. Its an ST branded BTA40.

The triac switches the -ve lead to the cell, the gate is connected
directly to a "stud" electrode in the cell.

**Yup.

What's the purpose of the triac?

**To switch off the juice, if there is insufficient water/salt solution
running through the cell.

Seems to me if the cell has water in it the triac is "on", otherwise its
"off". I dont have the full cell assembly - is the stud at the top so it
cannot run unless the cell is completely full??

**Correct. To test, you need to supply a load to the unit, such that at
least 10 Amps flows (I used a roll of speaker cable, shorted at one end.
Connect the gate to the positive supply through a (say) 330 Ohm resistor.


--
Trevor Wilson www.rageaudio.com.au

 

[Spuckle]

On 19/11/2012 3:45 AM, Trevor Wilson wrote:

On 11/18/2012 8:14 PM, Spuckle wrote:
I've got a dud Monarch salt water pool chlorinator - no output.

It looks like the triac on the output has failed.

**That is certainly easy enough to check. TRIACs usually fail
catastrophically.



The circuit layout is:


AC ==> Dimmer ctrl ==> Xformer ==> Bridge rectifier ==> Triac ==> Cell

**I've seen this system before. It's slightly odd, but it works.



The output triac appears to have failed open. Its an ST branded BTA40.

The triac switches the -ve lead to the cell, the gate is connected
directly to a "stud" electrode in the cell.

**Yup.




What's the purpose of the triac?

**To switch off the juice, if there is insufficient water/salt solution
running through the cell.


Seems to me if the cell has water in it the triac is "on", otherwise its
"off". I dont have the full cell assembly - is the stud at the top so it
cannot run unless the cell is completely full??

**Correct. To test, you need to supply a load to the unit, such that at
least 10 Amps flows (I used a roll of speaker cable, shorted at one end.
Connect the gate to the positive supply through a (say) 330 Ohm resistor.

Thanks Trevor - great, you've confirmed my thinking. Looks like its
failed o/c.

These triacs are cheap too, ~$10 in 1 offs depending where you get them.

Cheers