@lesmar96 would you be willing to share a schematic? I think a Varistor or R/C suppressor will help, will it 100% fix the issue, I am not sure.
RC network design
- Thread starter lesmar96
- Start date
@lesmar96 would you be willing to share a schematic? I think a Varistor or R/C suppressor will help, will it 100% fix the issue, I am not sure.
Steve Bailey
Lifetime Supporting Member + Moderator
Start with the model of the 30 Amp contactor you're using. Go to the catalog pages, look under the accessories and select the appropriate surge suppressor for whichever coil you have.
The contact rating for your model loop controller is 5 Amps resistive, but you are switching an inductive load. I suspect the inrush current is what is killing the contacts.
Also, once every 18 seconds is a bit on the high side of normal for a contact output. If the system is running 24/7 you're cycling on and off 4800 times per day. If the contact is rated for 1 million cycles under ideal conditions, that's less than one year.
You might be better served by a controller with solid state (no moving parts) output, with proper surge suppression. Or a solid state contactor with an analog front end and use a loop controller with 4 - 20 mA output.
The contact rating for your model loop controller is 5 Amps resistive, but you are switching an inductive load. I suspect the inrush current is what is killing the contacts.
Also, once every 18 seconds is a bit on the high side of normal for a contact output. If the system is running 24/7 you're cycling on and off 4800 times per day. If the contact is rated for 1 million cycles under ideal conditions, that's less than one year.
You might be better served by a controller with solid state (no moving parts) output, with proper surge suppression. Or a solid state contactor with an analog front end and use a loop controller with 4 - 20 mA output.
All of the above. In the meantime, an intermediate interposing relay between the controller and the contactor coil might save the controller contact. I wouldn't recommend an interposing relay as a long-term solution. You really need to consider the solid state solution as Steve has said.
GaryS
Member
Solid state relays don't need RC Networks or other suppression the input it typically less then 20ma ( Opto Isolated) and the outputs are designed to switch at line frequency with the Zero Crossing option they turn on and off at Zero current when the sign wave of the line is at zero. they are used all the time in heating applications.
you can get solid state relays with either zero crossing and phase control. the zero crossing produce less noise on the line. if they are rated right you will probably never replace one I have seen them run for many years problems free.
I recommend you check with the manufactures of the relay
you can get solid state relays with either zero crossing and phase control. the zero crossing produce less noise on the line. if they are rated right you will probably never replace one I have seen them run for many years problems free.
I recommend you check with the manufactures of the relay
You could check out electrocube for RC networks..
I normally use RC networks for AC and diodes for DC when needed. Although the 1/2 watt resistor in network sizing works for most, make sure you watch with the frequent on off cycles of the contactors. The more cycles/minute will dictate that larger wattage.
Side note. It's not the coil energizing that causes the need for suppression it's the collapsing of the magnetic field of the coil which causes this spike.
Hope you get it figured out!
I normally use RC networks for AC and diodes for DC when needed. Although the 1/2 watt resistor in network sizing works for most, make sure you watch with the frequent on off cycles of the contactors. The more cycles/minute will dictate that larger wattage.
Side note. It's not the coil energizing that causes the need for suppression it's the collapsing of the magnetic field of the coil which causes this spike.
Hope you get it figured out!
Relay - Contactor is wrong for your application.
Change controller to 16B-23. Keep the contactor in place for the alarm circuit. Size SSR to 3.5x the current of the heater. If it's a 120V heater and 1000 Watts, that would be about 8 Amps. For that, use a 30 Amp SSR hockey puck style. Here is a 75 Amp SSR from Automation Direct.
Wire output 1 to the SSR. Output 2 to the contactor. Configure output 2 for overtemp alarm. Latching. If SSR ever goes shorted, the contactor will protect you from overtemp.
75 Amp is the highest you can go with most hockey puck style SSR's. I think Crydom makes a 90 Amp. If you need to go higher, you need something called a Phase Angle Controller. Uses SCR's, and varies output like a lamp dimmer. With that, you would use 16B-53 or 16B-63 voltage. I would go 16B-53 and set for 4-20 mA output.
Change controller to 16B-23. Keep the contactor in place for the alarm circuit. Size SSR to 3.5x the current of the heater. If it's a 120V heater and 1000 Watts, that would be about 8 Amps. For that, use a 30 Amp SSR hockey puck style. Here is a 75 Amp SSR from Automation Direct.
Wire output 1 to the SSR. Output 2 to the contactor. Configure output 2 for overtemp alarm. Latching. If SSR ever goes shorted, the contactor will protect you from overtemp.
75 Amp is the highest you can go with most hockey puck style SSR's. I think Crydom makes a 90 Amp. If you need to go higher, you need something called a Phase Angle Controller. Uses SCR's, and varies output like a lamp dimmer. With that, you would use 16B-53 or 16B-63 voltage. I would go 16B-53 and set for 4-20 mA output.
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