On extrusion systems with many heaters I have used devices such as these in the past.
I find them to be more useful than fuse indicators because a blown fuse isn't the only reason why a heater might not be working.
These will tell you if current is flowing or not for any the following reasons:
-burned out element
-blown fuse
-heater not plugged in, or plugged into wrong outlet (happens a lot)
-bad SSR/contactor
-etc

 

On extrusion systems with many heaters I have used devices such as these in the past.
I find them to be more useful than fuse indicators because a blown fuse isn't the only reason why a heater might not be working.
These will tell you if current is flowing or not for any the following reasons:
-burned out element
-blown fuse
-heater not plugged in, or plugged into wrong outlet (happens a lot)
-bad SSR/contactor
-etc

View attachment 284475

Oh I like that idea. Would those be on whenever current isn't flowing then? Like when it gets up to temp and the controller is only triggering the SSR once a second or so?

 

I was just thinking about those little current sensing torroid devices. because mostly hearer elements fail open. And sometimes when they fail they short to their case and pop a fuse. And an excessive number of dead-short trips will damage some breakers. And a fuse can be changed easier than a breaker can be replaced (when it fails.) Breakers do fail with enough abuse too many dead-short trips.

 

250-300W. They'll be these Watlow units: https://www.instrumart.com/products/21123/watlow-firerod-cartridge-heater

Seems it is to late after @strantor's post .
= = = = = = = =
Use these current transformers with LED, for each heating element.
US $1.50
https://www.aliexpress.us/item/3256801123506419.html?spm=a2g0o.productlist.main.3.2f28118dbDsTWx&algo_pvid=1890e445-bd98-4241-95a3-9a7e18bcf447&algo_exp_id=1890e445-bd98-4241-95a3-9a7e18bcf447-1&pdp_ext_f={"sku_id":"12000015678190958"}&pdp_npi=2@dis!USD!1.5!1.5!!!!!@21227a0f16728700830246243d06f1!12000015678190958!sea&curPageLogUid=UZzdDSlJ5DSJ

 

I was just thinking about those little current sensing torroid devices. because mostly hearer elements fail open. And sometimes when they fail they short to their case and pop a fuse. And an excessive number of dead-short trips will damage some breakers. And a fuse can be changed easier than a breaker can be replaced (when it fails.) Breakers do fail with enough abuse too many dead-short trips.

Yea these tend to fail short as they're installed and removed frequently so it's usually a short to case situation.

 

Oh I like that idea. Would those be on whenever current isn't flowing then? Like when it gets up to temp and the controller is only triggering the SSR once a second or so?

They're only on when current is flowing. So they will be off if the PID controller isn't calling for heat. Operators might initially think that "OFF=BAD" but they can be taught easily enough. Especially if you mount the indicator right next to the controller, since most controllers have their own LED which comes on when they call for heat. Put this new LED right next to the existing one, and tell them both LEDs should be on at the same time. If the LED on the controller is on or flashing then the new LED should be on or flashing right along with it, but if the new LED is off while the LED on the controller is on or flashing, that "=BAD".

EDIT: Also, if the LED on the controller is off while the new LED is on, or if the two LEDs are both flashing but not in unison, that's an easy indication that they have the wrong heater plugged into the wrong receptacle. Or an LED that is steady ON all the time can indicate a shorted SSR, and this can allow you save your heater (if you're paying attention) before it follows the SSR to the grave.

 

You are using 240 VAC and I assume split phase. Most industrial heater elements I have seen fail either fail open circuit which will not take out a fuse or fail short to ground (neutral). Personally in my designs I used the mentioned current sensors. I used these which at the time were about $10.00 USD each. I have no clue as to the quality of other units but when I retired at least two sets of 72 each had been in service over 20 years. Also as mentioned the technicians knew they would be on 100% during heat up and then pulse at set point temperature. Exactly as strantor mentions above.

Ron

 

Thanks guys, that sounds the easiest way to go. The plan is to have one indicator near each receptacle so they'll know exactly which heater failed and what fuses to check

 

If both lines are disconnected from the load there will be no return path.

Yes there is.
It's through the first indicator, through the load, and then through through the second indicator.
The indicators are across the fuse, and bypass the fuse when it is blown, which is why they turn on.

 

250-300W. They'll be these Watlow units: https://www.instrumart.com/products/21123/watlow-firerod-cartridge-heater

The smallest Watlow cartridge heater you linked to is 240 VAC single phase 720 Watts and that is a 1/8" diameter 1.5" or 2.0" length. If you pair them up (two heater in series) you can use 120 VAC heaters at 360 watts each. So if your power requirement is only 250 - 300 watts per heater I would just use 5 lines of 240 VAC using two 120 VAC heaters in series per line and those are 1/8" diameter cartridge heaters. If you want to run at 240 VAC it depends on your application for example a controller calls for heat using for example PID control and at set point turns the heaters off. Then it's a matter of heater size (power) and how long it takes to get to set point.

Ron

 

Yea these tend to fail short as they're installed and removed frequently so it's usually a short to case situation.

These things have that horrid fiberglass insulation. I mean, it's pretty much the only thing they can have, considering how hot they get, but it isn't nearly as tough as the wire insulation most people are used to.

I'm not sure how you are using them, but I come across them frequently in extrusion processes where they provide supplemental heat for things that aren't conveniently round and heated by band heaters. When I see them, they are almost always coming out of a die with weight (of the cable, plus huge boogers of hardened plastic) hanging on the wires at an extreme angle, causing damage to the wires right where they exit the ceramic filler. Plus when they clean the dies they are not at all gentle, they pull the heaters out by the wires, violently yanking back and forth. It makes me cringe.

As a result, it is not out of the ordinary to see exposed (or badly frayed, nearly exposed) live conductors right there where the wires exit the ceramic. They don't get replaced until they quit working or until they arc against something and blow a fuse. It's crazy, but I see it in multiple clients' plants. I can't believe it is so common, and I can't believe operators don't get shocked more often. It is a "hands off" thing because it's already such a hot process, but still, having such common opportunity to present an electrocution hazard, I'm surprised these aren't more often on GFCI breakers.

Since it sounds like you're building this from scratch, if what I'm describing sounds familiar, I suggest you look into GFCI breakers instead of fuses, as well as the cartridge heaters with metallic spiral armor protecting the wires.

 

Two things to consider here: It has been guessed that these are die heaters, but not verified by the TS. Second, GFCI breakers will certainly cause a lot of shutdowns. The power is switched off when the machine is cleaned and so there is no shock hazard then. During use that whole area is way too hot to touch. So impairing operation for the sake of avoiding a non-existing hazard makes no sense at all.

 

The smallest Watlow cartridge heater you linked to is 240 VAC single phase 720 Watts and that is a 1/8" diameter 1.5" or 2.0" length. If you pair them up (two heater in series) you can use 120 VAC heaters at 360 watts each. So if your power requirement is only 250 - 300 watts per heater I would just use 5 lines of 240 VAC using two 120 VAC heaters in series per line and those are 1/8" diameter cartridge heaters. If you want to run at 240 VAC it depends on your application for example a controller calls for heat using for example PID control and at set point turns the heaters off. Then it's a matter of heater size (power) and how long it takes to get to set point.

Ron

I'm pretty sure they're those but I could be wrong. the boss spec'd them in and said they'd be 250-300W depending on their location on the head. We do have other machines that use two 120V units in series or even multiple 240V units in parallel on the same plug but for this specific job he wants each heater to be individually plugged in so we can see if one fails as one failing could cause problems that are hard to detect if they were plugged in a different way.

These things have that horrid fiberglass insulation. I mean, it's pretty much the only thing they can have, considering how hot they get, but it isn't nearly as tough as the wire insulation most people are used to.

I'm not sure how you are using them, but I come across them frequently in extrusion processes where they provide supplemental heat for things that aren't conveniently round and heated by band heaters. When I see them, they are almost always coming out of a die with weight (of the cable, plus huge boogers of hardened plastic) hanging on the wires at an extreme angle, causing damage to the wires right where they exit the ceramic filler. Plus when they clean the dies they are not at all gentle, they pull the heaters out by the wires, violently yanking back and forth. It makes me cringe.

As a result, it is not out of the ordinary to see exposed (or badly frayed, nearly exposed) live conductors right there where the wires exit the ceramic. They don't get replaced until they quit working or until they arc against something and blow a fuse. It's crazy, but I see it in multiple clients' plants. I can't believe it is so common, and I can't believe operators don't get shocked more often. It is a "hands off" thing because it's already such a hot process, but still, having such common opportunity to present an electrocution hazard, I'm surprised these aren't more often on GFCI breakers.

Since it sounds like you're building this from scratch, if what I'm describing sounds familiar, I suggest you look into GFCI breakers instead of fuses, as well as the cartridge heaters with metallic spiral armor protecting the wires.

View attachment 284486


View attachment 284487

They are head heaters actually, a special head I designed for a specific product (can't get more into it than that unfortunately). The design of the head calls for 10 of those cartridges from 250-300W (not sure exactly which cartridges the boss ordered but I know they're the armored style and not the braided) depending on their location on the head. We almost always use the braided style in our normal setups as the cords are easier to manage than with the armored style. However most extrusion machines aren't torn down as frequently as ours are, we're changing jobs and tooling frequently so shorted heaters and popped fuses are a common occurrence here.

I was originally thinking breakers (and could tie in a failure indicator in parallel with them) but wasn't sure about trip currents and whatnot and possibly having to replace them. I'd assume breakers would be more common in the machines themselves but everyone we have (even the name-brand purchase dones) all use fast blow fuses rather than breakers.

Two things to consider here: It has been guessed that these are die heaters, but not verified by the TS. Second, GFCI breakers will certainly cause a lot of shutdowns. The power is switched off when the machine is cleaned and so there is no shock hazard then. During use that whole area is way too hot to touch. So impairing operation for the sake of avoiding a non-existing hazard makes no sense at all.

Yea they typically don't fail during operation (not shorts anyways). They usually fail when being handled during assembly/disassembly and then pop the fuse when the heats are turned on and the operators come to me and say "Hey the heat isn't coming up on this can you check the fuses"

 

I'm thinking the current clamp style would work best honestly. This way the light will come on whenever the heater is pulling current. That way if a fuse pops OR the heater fails the light just won't come on at all

I think these with the brackets will work great, I can mount them right next to the receptacle on the enclosure: https://www.crmagnetics.com/wire-mounted/cr45

 

The only difference between the CR45 and the CR2550 is the mounting. Something else is when using either the current carrying conductor can be looped through the donut. For example the CR45 has a turn on of 2.0 Amps AC. With a lighter load looping the current carrying conductor through the donut hole twice reduces turn on to 1.0 AAC. While you should not need to do this it's a good to know. Much like looping through any CT (Current Transformer). Choose whatever mounting design works best for you. In my case the CR2550 was the better choice but whatever works for you. If and when fuses are used consider the fuse type. Just for example if the heater elements are driven by electronic semi conductor devices like triac or SSR you want an ultra fast blow fuse rated at about 125% of max load current. A slower fuse will likely allow destruction of the triac or SCR before the fuse blows.

Best of luck with the project.

Ron

 

The only difference between the CR45 and the CR2550 is the mounting. Something else is when using either the current carrying conductor can be looped through the donut. For example the CR45 has a turn on of 2.0 Amps AC. With a lighter load looping the current carrying conductor through the donut hole twice reduces turn on to 1.0 AAC. While you should not need to do this it's a good to know. Much like looping through any CT (Current Transformer). Choose whatever mounting design works best for you. In my case the CR2550 was the better choice but whatever works for you. If and when fuses are used consider the fuse type. Just for example if the heater elements are driven by electronic semi conductor devices like triac or SSR you want an ultra fast blow fuse rated at about 125% of max load current. A slower fuse will likely allow destruction of the triac or SCR before the fuse blows.

Best of luck with the project.

Ron

I think the CR45 with the bracket will be best. I can mount them right ot the enclosure next to the receptacle and loop the wire through a few times as the amperage per heating element won't be too high.

I'll have to look inside this particular extruder to see what will be driving these, pretty sure they're all SSR's in there and they'll be fused properly.

Thanks for your help!

 

It only takes a few hours of lost production to make up for the saving in fuse costs by substituting breakers, and then not having a spare breaker or not having the electrician to change it. Some of those cute little CT current sensors have been tied to PLC inputs for automated machine watching, unfortunately I did not get any details about just how that was done.

 

It only takes a few hours of lost production to make up for the saving in fuse costs by substituting breakers, and then not having a spare breaker or not having the electrician to change it.

You already contradicted me and stated your case rather combatively in post #32. I didn't address it because you seemed to be begging for an argument that I wasn't interested in. Now out of nowhere you're bringing it up again. Are you going to keep doing that until I give you what you need to scratch that itch?

If so, here you go:

Is having to replace breakers something that's normal in your experience? Is not having spare breakers (or heaters or controllers or SSRs or anything that is used plant-wide) something that's normal in your experience? How about not having a single person on staff competent to replace a breaker? My experiences of not having the correct fuse on hand is one of the things that led me to suggest breakers. I've watched marginally skilled maintenance technicians blow several fuses in a row before they find the problem, and I've done it myself back before I knew my ass from a hole in the ground.

Bean counter buys a box of ten fuses thinking that should be more than enough, because after all, "every zone would have to blow its fuse for them to run out." Then the night shift extruder operator (Alberto "Executive Decision" Ramirez) who isn't supposed to even know how to open the control cabinet, goes through 8 of them before admitting defeat and leaving it for maintenance to fix in the morning. Then Sparky "Wet Behind The Ears" Tech comes in, checks the heater for shorts, all good, puts the last two fuses in, and turns it on not realizing that there's a 3kW heater plugged into the outlet designated for a 500W heater. He figures out why the last two fuses blew by chipping the molten plastic off the heater to reveal the laser-etched rating. He plugs it back in where it goes, but now there are no more 2.5A fuses to put in. All the 3A and 5A fuses are gone too, from similar incidents or from someone taking the entire box from the spares cabinet and absent mindedly leaving it in some other cabinet somewhere. So, "just to get the line back into production," he puts in the smallest value fuse that he can find which fits: 10A. He informs bean counter who orders 10 more, with the plan to put the correct fuses in when they arrive. That never happens.

1 year later the same operator does the same thing. Different maintenance tech does the same/similar thing. This maintenance tech notices the 3kW heater with "only" 10A fuses installed. "Well, there's your problem!" He says. "Some idiot put 10A fuses in here when a 3kW heater should have 15A fuses." So he puts in the "correct" fuses for the 3kW heater. Everything is great now! All good. Except for some reason the SSR failed shortly thereafter, probably for some unrelated reason.

Some of those cute little CT current sensors have been tied to PLC inputs for automated machine watching, unfortunately I did not get any details about just how that was done.

There are similar devices with switches instead of LEDS. They're a lot more expensive though. You could probably just cut the LED off the others and figure out empirically what kind of rectifier/voltage divider situation would satisfy a PLC input.

 

You already contradicted me and stated your case rather combatively in post #32. I didn't address it because you seemed to be begging for an argument that I wasn't interested in. Now out of nowhere you're bringing it up again. Are you going to keep doing that until I give you what you need to scratch that itch?

If so, here you go:

Is having to replace breakers something that's normal in your experience? Is not having spare breakers (or heaters or controllers or SSRs or anything that is used plant-wide) something that's normal in your experience? How about not having a single person on staff competent to replace a breaker? My experiences of not having the correct fuse on hand is one of the things that led me to suggest breakers. I've watched marginally skilled maintenance technicians blow several fuses in a row before they find the problem, and I've done it myself back before I knew my ass from a hole in the ground.

Bean counter buys a box of ten fuses thinking that should be more than enough, because after all, "every zone would have to blow its fuse for them to run out." Then the night shift extruder operator (Alberto "Executive Decision" Ramirez) who isn't supposed to even know how to open the control cabinet, goes through 8 of them before admitting defeat and leaving it for maintenance to fix in the morning. Then Sparky "Wet Behind The Ears" Tech comes in, checks the heater for shorts, all good, puts the last two fuses in, and turns it on not realizing that there's a 3kW heater plugged into the outlet designated for a 500W heater. He figures out why the last two fuses blew by chipping the molten plastic off the heater to reveal the laser-etched rating. He plugs it back in where it goes, but now there are no more 2.5A fuses to put in. All the 3A and 5A fuses are gone too, from similar incidents or from someone taking the entire box from the spares cabinet and absent mindedly leaving it in some other cabinet somewhere. So, "just to get the line back into production," he puts in the smallest value fuse that he can find which fits: 10A. He informs bean counter who orders 10 more, with the plan to put the correct fuses in when they arrive. That never happens.

1 year later the same operator does the same thing. Different maintenance tech does the same/similar thing. This maintenance tech notices the 3kW heater with "only" 10A fuses installed. "Well, there's your problem!" He says. "Some idiot put 10A fuses in here when a 3kW heater should have 15A fuses." So he puts in the "correct" fuses for the 3kW heater. Everything is great now! All good. Except for some reason the SSR failed shortly thereafter, probably for some unrelated reason.


There are similar devices with switches instead of LEDS. They're a lot more expensive though. You could probably just cut the LED off the others and figure out empirically what kind of rectifier/voltage divider situation would satisfy a PLC input.

We have another in-house designed extruder that has those units. They're tied to the PLC and the touch panel has little red "LED" lights that blink when the SSR switches on

 

We have another in-house designed extruder that has those units. They're tied to the PLC and the touch panel has little red "LED" lights that blink when the SSR switches on

That's the way to go nowadays IMO. The last brand new Davis Standard extruder I saw, still had individual PID controllers for the barrel zones. The last 2 extruders I modernized, don't have zone controllers any more. All the PID loops are in the PLC. One PID controller was more than the cost of a thermocouple input card which serves 4 zones. Doing the PID in the PLC opens doors for really dialing in the control if the application demands it. Your PID can have modifiers for extruder speed or product type other variables so that it performs proactively rather than reactively.