Post by thread:[EE] Creepage distances for PCB relay connections

Good day to all. I am having an argument with another person here at work regarding creepage distances between the coil and armature of a JS1 relay (through-hole). This is in a HVAC application, where the coil is controlled from a 24 Vac signal (thermostat or whatever) and the contacts are controlling a fan motor at 120 Vac. I have been using some pretty stringent distances as relayed to me from a European standards agency: Functional Insulation is required between live & neutral. Basic insulation is required between live or neutral & protective earth (gnd). Isolation equivalent to double or reinforced insulation is required between Extra Low Voltage circuits and any line or neutral connection. Clearance / Creepage distances: Functional Insulation 2.0/3.2mm 0.079/0.126" Basic Insulation 2.0/4.0mm 0.079/0.157" Double Insulation 3.5/8.0mm 0.138/0.315" <end of copy> By the above rules, a JS1 relay is NOT suitable because the distance from the armature pin is too close to both of the coil pins. However, http://www.creepage.com says that I need only 2.0mm distance between an ELV circuit and the primary mains. In other words, Basic insulation instead of double insulation. Can someone point me towards a (some) website (s) that accurately tells me what the requirements are? Its important to note that the low voltage circuit might be touched by someone (change the battery in a smart thermostat, etc). I think that is why the requirement for double insulation - but I'm not sure. Many thanks! dwayne -- Dwayne Reid <spam_OUTdwaynerTakeThisOuTplanet.eon.net> Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax http://www.trinity-electronics.com Custom Electronics Design and Manufacturing

Can you put a slot in the pcb between the armature pin & coil pins? This could change the creepage distance into a clearance distance and make things easier. (My recollection is that 8mm creepage is needed (240VAC) but I could be wrong.) RP On 14 March 2012 12:20, Marcel Duchamp <.....marcel.duchampKILLspam@spam@sbcglobal.net> wrote: > It may be pertinent to know what jurisdiction your gear will be deployed in. > > On 3/13/2012 3:44 PM, Dwayne Reid wrote: >> Can someone point me towards a (some) website (s) that accurately >> tells me what the requirements are? >> >> > >

> Can you put a slot in the pcb between the armature pin & coil pins? > This could change the creepage distance into a clearance distance and make things > easier. > > (My recollection is that 8mm creepage is needed (240VAC) but I could be wrong.) That is the figure I recall as well, which is why opto-isolators for switch mode power supplies have weird pin configurations. A 0.3" DIP has only just enough creepage distance around the body and then you need to spread the legs wider than 0.3" on the PCB, a 0.4" DIP does better. -- Scanned by iCritical.

On Wed, Mar 14, 2012 at 6:44 AM, Dwayne Reid <dwaynerKILLspamplanet.eon.net> wrote: {Quote hidden}> Good day to all. > > I am having an argument with another person here at work regarding > creepage distances between the coil and armature of a JS1 relay > (through-hole). This is in a HVAC application, where the coil is > controlled from a 24 Vac signal (thermostat or whatever) and the > contacts are controlling a fan motor at 120 Vac. > > I have been using some pretty stringent distances as relayed to me > from a European standards agency: > > Functional Insulation is required between live & neutral. > > Basic insulation is required between live or neutral & protective earth (gnd). > > Isolation equivalent to double or reinforced insulation is required between > Extra Low Voltage circuits and any line or neutral connection. > > Clearance / Creepage distances: > > Functional Insulation 2.0/3.2mm 0.079/0.126" > Basic Insulation 2.0/4.0mm 0.079/0.157" > Double Insulation 3.5/8.0mm 0.138/0.315" > > <end of copy> What is the standard he is quoting? > By the above rules, a JS1 relay is NOT suitable because the distance > from the armature pin is too close to both of the coil pins. Also why you say JS relay is not good? It should be good since the creepage distance between the relay coil pins and the relay contact have more than 8mm distance (center to center is about 12.2mm). http://pewa.panasonic.com/assets/pcsd/catalog/js-catalog.pdf You just need to take care of the layout and not to make it below 8mm. > However, http://www.creepage.com says that I need only 2.0mm distance > between an ELV circuit and the primary mains. In other words, Basic > insulation instead of double insulation. Take note the website is using IEC60950 which is meant for IT equipment. Are you sure your device falls under the scope? The creepage distance will depend on the standard applicable. > Can someone point me towards a (some) website (s) that accurately > tells me what the requirements are? The various websites may be some source for reference. But you may still need to get the standard applicable or talk to someone who knows the standard. > Its important to note that the low voltage circuit might be touched > by someone (change the battery in a smart thermostat, etc). I think > that is why the requirement for double insulation - but I'm not sure. Yes that is one good explanation why reinforce/double insulation is required. -- Xiaofan

At 06:48 AM 3/14/2012, Xiaofan Chen wrote: >Also why you say JS relay is not good? It should be good >since the creepage distance between the relay coil pins and >the relay contact have more than 8mm distance (center to >center is about 12.2mm). >http://pewa.panasonic.com/assets/pcsd/catalog/js-catalog.pdf The fixed contacts have lots of room but the armature pin is located between the two coil pins. Using 75 mil pads on all pins (0.075") results in a clearance distance of about 4.2mm - far less than the 8mm figure. dwayne -- Dwayne Reid <.....dwaynerKILLspam.....planet.eon.net> Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax http://www.trinity-electronics.com Custom Electronics Design and Manufacturing

On Thu, Mar 15, 2012 at 4:00 AM, Dwayne Reid <EraseMEdwaynerspam_OUTTakeThisOuTplanet.eon.net> wrote: > At 06:48 AM 3/14/2012, Xiaofan Chen wrote: > >>Also why you say JS relay is not good? It should be good >>since the creepage distance between the relay coil pins and >>the relay contact have more than 8mm distance (center to >>center is about 12.2mm). >>http://pewa.panasonic.com/assets/pcsd/catalog/js-catalog.pdf > > The fixed contacts have lots of room but the armature pin is located > between the two coil pins. Using 75 mil pads on all pins (0.075") > results in a clearance distance of about 4.2mm - far less than the > 8mm figure. > Ah this is a strange relay since the COMMON pin is located between the two coil pins Now I see that. -- Xiaofan

At 07:58 AM 3/15/2012, Xiaofan Chen wrote: >On Thu, Mar 15, 2012 at 4:00 AM, Dwayne Reid <dwaynerspam_OUTplanet.eon.net> wrote: > > At 06:48 AM 3/14/2012, Xiaofan Chen wrote: > > > >>Also why you say JS relay is not good? It should be good > >>since the creepage distance between the relay coil pins and > >>the relay contact have more than 8mm distance (center to > >>center is about 12.2mm). > >>pewa.panasonic.com/assets/pcsd/catalog/js-catalog.pdf > > > > The fixed contacts have lots of room but the armature pin is located > > between the two coil pins. Using 75 mil pads on all pins (0.075") > > results in a clearance distance of about 4.2mm - far less than the > > 8mm figure. > > > >Ah this is a strange relay since the COMMON pin is located >between the two coil pins. Now I see that. I *really* like the JS1 relay - we were getting them for something like $0.37 or so each in 10k or 25k (don't recall which) lots a few years back. The price has gone up since then but they are still one of the least expensive, decent quality power relays that I have found. I use them and the AZ-2150 family from American Zettler by the thousands every year. The AZ-2150 family, BTW, does meet the creepage requirements. But they are about double the size of the JS1 family and about triple the price. On the other hand - I'm ALWAYS looking for better or less expensive alternatives. If anyone has a suggestion for inexpensive but good quality power relays, I'd very much like to hear it. If those relays have at least 8mm creepage distance between coil and contacts, even better <grin>. Many thanks! dwayne -- Dwayne Reid <@spam@dwaynerKILLspamplanet.eon.net> Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax http://www.trinity-electronics.com Custom Electronics Design and Manufacturing