Created Date: September 12,2013

Created by: Do-more PE

The manual calls for 0.1A max per output and 0.5mA for each input. I plan to fuse each output with one 0.1A fast blow fuse, and the input commons with a fuse (5ma\point x 4 points = 20ma, 0.02mA which are hard to find. Is this fusing scheme correct? Should I bother fusing the inputs? I don't have any planned at the minute, but may add some level switches and pushbuttons in the future.

Fuse the individual points. No need to fuse the commons if each point is fused properly. Fusing inputs is all well and good, but if you wire them as sinking you shouldn't need to worry about frying one.

There is no diode module for the 781 series relay. Should I worry about putting a diode or MOV on these? I will be driving 1.6FLA pumps by switching the hot side of 120VAC.

Send the SZ-Z31 back as it is designed for 48VDC circuits and get some common 1n1004 diodes to use as suppression. Wire them in reverse polarity (+ to - and - to +) across the coil so they don't pop your output points by shorting them out. See the manual for proper orientation.

Created Date: September 12,2013

Created by: Tinker

There is no diode module for the 781 series relay. Should I worry about putting a diode or MOV on these?

Yes you should, I tend to use the 782 relays even if I only need one pole because there are diode/MOV modules AD-BSMD-250 or AD-BSMM-24 that plug into the socket. But you can use an ordinary wire lead diode (or if you have a lot of extra money there is a Zip-Link transorb assembly with 8 transorbs and nice terminal strips)

Another significant probem is your SC-E3G-24VDC contactors, those have a 12W coil (1/2A @ 24VDC) much too much for your C0-01DD1-D.

I'd consider using a a couple more 78x relays (I'd probably use 782 as mentioned above) to switch the contactors.

I'm curious what you are switching with the contactors, since you have a couple of small pumps, I'm guessing this is some sort of heating application? and you may be switching heaters (a resistive load), on the other hand, if you are switching a large inductive load you may want to keep the SZ-Z31, putting a simple diode across a contactor coil slows the opening and can increase contact erosion with large inductive load. (but on small realys a diode is not usualy a problem)

Also, if you do use an interposing relay to drive the contacors, the 240V relay contacts won't be bothered at all by the 48V rating of the SZ-Z31

Created Date: September 17,2013

Created by: muhteeus

Yes you should, I tend to use the 782 relays even if I only need one pole because there are diode/MOV modules AD-BSMD-250 or AD-BSMM-24 that plug into the socket. But you can use an ordinary wire lead diode (or if you have a lot of extra money there is a Zip-Link transorb assembly with 8 transorbs and nice terminal strips)

Another significant probem is your SC-E3G-24VDC contactors, those have a 12W coil (1/2A @ 24VDC) much too much for your C0-01DD1-D.

I'd consider using a a couple more 78x relays (I'd probably use 782 as mentioned above) to switch the contactors.

I'm curious what you are switching with the contactors, since you have a couple of small pumps, I'm guessing this is some sort of heating application? and you may be switching heaters (a resistive load), on the other hand, if you are switching a large inductive load you may want to keep the SZ-Z31, putting a simple diode across a contactor coil slows the opening and can increase contact erosion with large inductive load. (but on small realys a diode is not usualy a problem)

Also, if you do use an interposing relay to drive the contacors, the 240V relay contacts won't be bothered at all by the 48V rating of the SZ-Z31

I am switching supply voltage from heater SSR A to heater SSR B to ensure only one element can run at a time.

Would you suggest wiring my output to a 78x series relay and having that coil switch supply to the SC-E3G coil? I must have read 12W and just forgot about it. :(

Created Date: September 18,2013

Created by: Tinker

I am switching supply voltage from heater SSR A to heater SSR B to ensure only one element can run at a time.

Since you are switching resistive loads, and especialy if you can arrange to switch the SC-E3G only when the SSRs are off, then you could use the chaper simple diode across the SC-E3G coil as ADApp asist suggested, but since you already bought the SZ-Z31s I'd use tham rather than send them back.

Would you suggest wiring my output to a 78x series relay and having that coil switch supply to the SC-E3G coil? I must have read 12W and just forgot about it. :( Yes, I would.

Created Date: September 18,2013

Created by: muhteeus

Since you are switching resistive loads, and especialy if you can arrange to switch the SC-E3G only when the SSRs are off, then you could use the chaper simple diode across the SC-E3G coil as ADApp asist suggested, but since you already bought the SZ-Z31s I'd use tham rather than send them back.

Yes, I would.

The SSRs will be PID controlled, and the PID will only be put into auto (or allowed to have a manual output) if an element is selected. So this should be the best solution. I have not purchased the SZ-Z31s yet, just laying out a BOM for this project.

I will pick up some 1n1004 diodes, seems easy enough. Thanks again for the help Tinker and ADApp Assist! I appreciate it!

Created Date: September 20,2013

Created by: muhteeus

Fuse the individual points. No need to fuse the commons if each point is fused properly. Fusing inputs is all well and good, but if you wire them as sinking you shouldn't need to worry about frying one.

Send the SZ-Z31 back as it is designed for 48VDC circuits and get some common 1n1004 diodes to use as suppression. Wire them in reverse polarity (+ to - and - to +) across the coil so they don't pop your output points by shorting them out. See the manual for proper orientation.

Not to sound like an idiot, but I can't seem to find a 1n1004 diode on mouser, newark, or google. What are the specifics of a 1n1004?

Created Date: September 12,2013

Created by: muhteeus

Hello all,

I am working on a personal project and have a question about fusing... hoping I am right.

I am using a C0-01DD1-D to turn on 2 SC-E3G-24VDC contactors and 2 781-1C-24D cube relays. I have the specified SZ-Z31 diode module for surge supression on the two contactors.

My questions are:

The manual calls for 0.1A max per output and 0.5mA for each input. I plan to fuse each output with one 0.1A fast blow fuse, and the input commons with a fuse (5ma\point x 4 points = 20ma, 0.02mA which are hard to find. Is this fusing scheme correct? Should I bother fusing the inputs? I don't have any planned at the minute, but may add some level switches and pushbuttons in the future.

There is no diode module for the 781 series relay. Should I worry about putting a diode or MOV on these? I will be driving 1.6FLA pumps by switching the hot side of 120VAC.

I just don't want to burn out I/O on my new $200 investment.