Why use an SSR when Lee states the Pro 4 20lb pot (100v) only draws 6.36 amps?

[benellinut]

Looking for thoughts on using the PDI's with the built in 10amp relay on the Lee Pro pot and doing away with the added SSR relay, sure would be simpler, I would think? I asked Lee through their website what the max amps the Pro 4 20lb 100 volt pot would draw, below is the response for them including a link for calculation;

6.36 Amps

700watt, 110 V

http://www.rapidtables.com/calc/electric/watt-volt-amp-calculator.htm

Thanks,

Lee Precision, Inc.
4275 Highway U
Hartford, WI 53027
phone: 262-673-3075

This is the PDI I ordered which has the built in 10amp relay, the Pro pot should be here today, still waiting for the thermocouple. I did also order a 10amp SSR, just in case I need it, but if the pot draws less then 10amp do I really need to use it?

http://www.amazon.com/gp/product/B007MMOEWY

[bhn22]

I see the specs showing up to 240V, 3 amp output (Main output: RELAY: capacity 250V/3A AC, 30V/3A DC). I have a 24 amp relay running an 8 amp pot since they're only about $9.00 with a heat sink.

[dragon813gt]

Relays will fail. Would you rather replace a SSR or a PID? Just an extra ounce of precaution. A 20A relay will also last longer w/ less of a load on it. While you don't need one I have one on mine.

[benellinut]

Well I know the SSR is cheaper but the PDI only cost me $22 shipped, not a big deal. I can always solder a new relay on the board, I can see the relay inside the PDI, this is the relay
http://www.alibaba.com/product-detail/100-New-HONGFA-JZC-33F-024_1174339563.html

Rated 10 amp for 120 volts, just what the instructions reads. I worked as a auto tech for 25 years and I can count on one hand how many relays I seen fail. My 10 year old stove had relays, it was still working great but the wife wanted a shiny new one. :-) Wish I had kept it, I could have used it in the garage for baking coated bullets, ugh!

[dragon813gt]

No relay in an automobile is going to be used as much as the one for the PID. They all have an expected life cycle. The ones I use in my trade are typically around 10k cycles. An I'm replacing them weekly. You don't need one but there is a reason it's recommended.

[benellinut]

Oh I don't know about that, any idea how many times a cooling fan or AC relay kicks on and off in it's lifetime? How many times do you hear the cooling fan or AC clutch cycle while setting at a red light? I replaced one cooling fan relay in my 25 years of twisting wrenches. Anyways, I understand your point, the SSR will outlast. I guess I'll be the test case and see how long my PDI lasts. If I get two years out of it, that's less then a buck a month so I won't feel too bad about it. It's going to make for a much smaller setup, everything wires to the PDI and nothing else in the box.

[dragon813gt]

I work in the HVAC trade and those cycles are nothing. You will understand when your PID is working. It will be cycling a lot when the pot is up to temp. A few times a second is normal.

[kencha]

The PID is going to do one heck of a lot more switching than an HVAC or automotive system.

You may get a significant life span out of a mechanical relay. Heck, you may end up never needing to replace it.

On the other hand, you could end up burning through 3 per year. You're operating very close to max rated capacity on chinese goods, too. They tend to be generous in their ratings as it is.

You pays your money and you takes your chances.

[bhn22]

And unless you fly it in, your PIDs will be coming from China. It took mine almost a month to get here. I had a thermocouple act up a bit, and replacements were in China, with estimated 30 day delivery time. I bought my replacements from Auber and had them in a couple of days.

[dikman]

A couple of points, yes, relays can be very reliable, the telephone exchanges I worked on years ago basically worked on relay switching, so lots of relays, operating almost continuously and it was rare for a relay to fail - but these were bigger relays than the tiny ones used in PIDs.
I would not trust the rating of the PID relay, it's likely to be over-rated and be operating very close to its limit at the amps you're talking about. If you can find a higher rated relay and replace the one inside it would, I think, be a prudent move.
My PID had a relay output, but I replaced the relay with wire links and use an SSR as I feel it is the better option in this case.
I also keep a spare PID/SSR/temp probe, just in case of any failure (better than having to wait for the slow boat from China!!).

Having said all that, I think you should try it and then you can report to us all if it works ok ('cos I don't think anyone else has tried it yet :-)).

[benellinut]

A couple of points, yes, relays can be very reliable, the telephone exchanges I worked on years ago basically worked on relay switching, so lots of relays, operating almost continuously and it was rare for a relay to fail - but these were bigger relays than the tiny ones used in PIDs.
I would not trust the rating of the PID relay, it's likely to be over-rated and be operating very close to its limit at the amps you're talking about. If you can find a higher rated relay and replace the one inside it would, I think, be a prudent move.
My PID had a relay output, but I replaced the relay with wire links and use an SSR as I feel it is the better option in this case.
I also keep a spare PID/SSR/temp probe, just in case of any failure (better than having to wait for the slow boat from China!!).

Having said all that, I think you should try it and then you can report to us all if it works ok ('cos I don't think anyone else has tried it yet :-)).

"I replaced the relay with wire links and use an SSR" <-- Not sure what you mean, did you remove the relay from the board and solder wires to it for the SSR? If not how did you hook up the SSR to it? I'll come clean and be honest, I ordered this one by mistake but when I read the instructions saying the relay will handle 10 amps I wanted to know what amps the pot draws, that why I asked Lee. What the heck, I'll probably just run it as is and see what happens, worse case it fails and I'll buy another PDI or replace the relay inside.

My Pro pot came today, I also ordered the Lee ingot mold, some sizer's and a couple .44 mag molds. I had to laugh when I opened the box, and saw this small box for the ingot mold, I thought to myself, "that can't be the ingot mold!", well it was and that thing is tiny! Guess I'll make my own out of angle iron like I saw on youtube, I've got lots of it and I've got some other welding projects to do this weekend.

BTW, I really do appreciate everyone's feedback on this. I didn't mean to come across as argumentative, my Dad use to tell me, "you get strong headed sometimes".

DIY ingot mold video, long video but you can jump ahead and get the idea.


https://www.youtube.com/watch?v=XabJiFyPAvM

[Springfield]

I use my Magma pot almost every day and in 4 years I have already burned out 2 SSR's. Easier to change out and cheaper than a new PID unit. FWIW I have had to replace a relay in my 1992 Ranger and also one in my 2002 Chevy Silverado, so they do go out.

[OuchHot!]

I am using a PID with an internal relay and was told, authoritatively, by members here that it would fail. It probably will. But, the last three years have been trouble free. I also use it with a Pro-melt that draws quite a lot more current. I play with electronics for a hobby and have a pid running an ssr that drives an oven for making circuit boards. Cooling the ssr was mandatory as it gets pretty warm. When/if the relay in my first unit cacks, I have a ssr to replace it with but will have to rebox as there is no room for the heat sink.

[bangerjim]

Just buy the SSR.

[sawzall]

20 years as an automotive and medium duty tech and I've replaced lots of relays. Fuel pump relays being the most common. They actually arc every time they close so they do burn out. Chinese relays certainly don't last like European relays either. For the aforementioned $9, why take the chance? Think of it as a fuse for the PID. The SSR goes out instead of the PID.

[Mal Paso]

Too many cycles a minute once close to operating temp for a conventional relay to be good engineering. It takes a lot more energy to close a relay than to hold it closed and most of the wasted energy becomes heat. High cycle rates are better handled with SSRs. They generate heat only when the load is on and are rated to be on all the time so cycling isn't an issue. Most conventional relays are rated to be on all the time but with them high cycle rates increase wear and they are rated by average cycles before failure which SSRs are not. Modern SSRs also do their switching at 0 AC Volts so there's no radio noise. No Arc. Howzat

[Lars-K]

Well, most PID's can be opened. You will find the relay on the board. Most have two or three relays for current and alarms. It's easy to solder two wires on the two input pins running the relay.
So, if the relay breaks, just solder the wires and use them to run the SSR. For safety, use a multimeter and measure the current running the relay. (most is 3-5V or so)
I have this sorted out on my Omron PID's the day the relay is gone...

[OuchHot!]

Yeah, I'm not concerned about replacing the relay function with an ssr. My problem is that I didn't plan ahead. I used a box that is too small so when I go ssr on my first unit, I get to set up another box or hang the ssr and heat sink off the back. Poor planning on my part, but typical.

[benellinut]

Well, most PID's can be opened. You will find the relay on the board. Most have two or three relays for current and alarms. It's easy to solder two wires on the two input pins running the relay.
So, if the relay breaks, just solder the wires and use them to run the SSR. For safety, use a multimeter and measure the current running the relay. (most is 3-5V or so)
I have this sorted out on my Omron PID's the day the relay is gone...

That is exactly what I was thinking, I've already had my PDI apart, lift two tabs, the face plate and boards slide right out. Mine has two of those relays, identical, one is the relay output and the other is for the AL1 alarm. I'm going to use just the PDI with no SSR and see what happens, like you say, worse case I'll have to deal with a dead relay and bypass it. I did order the SSR the same day as the PDI and thermocouple, that SSR is much bigger then I thought it was going to be. I have a nice big heatsink from one of my old computer builds, came off a CPU fan/heatsink. But I like the idea of a small box for the PDI, it will be a much cleaner setup, power cord in, power cord out and the thermocouple wire, that's the route I'm going.

[leadman]

I have built around 10 PIDs for my use and friends. I would not trust the pid relay to last due to the high cyclic rate. I also found that the 40 amp SSR lasts much longer than the 25 amp SSR. I had 4 of the 25 amp ssrs give up after only a month or so of service. I still am using the pid with an original 40amp ssr that is over 2 years old.
I use the pid on my RCBS pot and 3 toaster ovens for curing Hi-Tek boolit coating. If I use my Lyman heater on the luber/sizer I move a pid over to it .

I buy my Chinese made pids and ssrs off E-bay from sellers that are here in the USA because they have stock here to ship. Cost is usually only a couple dollars more, time to receive the product is much shorter.

[benellinut]

Well, most PID's can be opened. You will find the relay on the board. Most have two or three relays for current and alarms. It's easy to solder two wires on the two input pins running the relay.
So, if the relay breaks, just solder the wires and use them to run the SSR. For safety, use a multimeter and measure the current running the relay. (most is 3-5V or so)
I have this sorted out on my Omron PID's the day the relay is gone...

Lars, I wired the PDI up with jumpers, ran it through it's paces and checked the voltage to the coil of the relay, it's 24V DC so I could run an SSR off the relay signal but I'm going to use it with the internal relay. I can get these relays off ebay, two for $4 shipped, for that price I'll get a couple to have on hand. I should have this in a box, up and running within a week after I knock down a few more honey-do projects, I'll post up some pics of the set-up once done.

[benellinut]

OK, as promised here's photos of my simple and compact PDI unit using the internal relay instead of an SSR. I think the photos will pretty much explain, I added text notes to two photos to point out the fuse I used to protect the PDI and the fact I had to change the thermocouple extension wire because the temp floated with the first wire I used.

Other notes, the screens are to allow air flow in and keep the spiders out. The light I added lights when the relay contacts are closed and feeding power out. The output indicator LED on the PDI itself only shows when power is being sent to the relay coil to close the relay contacts, the light I added is showing power is flowing through the contacts. Should the relay fail, I'll see the indicator LED on the PDI ON and the light I added OFF. I ordered two more of the identical relays from ebay, should the relay fail I have two spare that cost me $4 shipped and I'll just solder a new one on the board.

This is to show you don't have to use an SSR and a big box with extra components, heat sinks and connections. I know some won't have anything good to say about this setup, that's OK, to each their own or as my buddy use to say, "If I'm happy, I'm happy"

http://i274.photobucket.com/albums/jj274/guywil/PDI/DSC01752_zpszitvhmom.jpg

http://i274.photobucket.com/albums/jj274/guywil/PDI/DSC01751_zps5muja4sr.jpg

http://i274.photobucket.com/albums/jj274/guywil/PDI/DSC01750_zpskrpufofz.jpg

http://i274.photobucket.com/albums/jj274/guywil/PDI/DSC01749_zpsnx5hhreg.jpg

http://i274.photobucket.com/albums/jj274/guywil/PDI/DSC01748_zpsy2gf0tan.jpg

http://i274.photobucket.com/albums/jj274/guywil/PDI/DSC01747_zps5ixiqmov.jpg

[benellinut]

The rest of the photos

http://i274.photobucket.com/albums/jj274/guywil/PDI/DSC01746_zpscw9m7xmk.jpg

http://i274.photobucket.com/albums/jj274/guywil/PDI/DSC01745_zpsx5y35tud.jpg

http://i274.photobucket.com/albums/jj274/guywil/PDI/DSC01744_zpsx1skyma2.jpg

http://i274.photobucket.com/albums/jj274/guywil/PDI/DSC01743_zps3xrohghe.jpg

http://i274.photobucket.com/albums/jj274/guywil/PDI/DSC01742_zpsnsmjyjiz.jpg

[JonB_in_Glencoe]

Looks alright,
How does it function ?

[benellinut]

Looks alright,
How does it function ?

Works great!

[edctexas]

The Relay outputs switch slowly. Power relays typically take 10 milliseconds or more to energize or de-energize. Each half cycle of the 60 herz power is 8 milliseconds. The relay also may switch on or off near the peak which is harder on the contacts of the relay. If you use a sufficiently robust relay, you might have a good life on the contacts.

The SSR module always switches when the AC power is near 0 volts. It can provide as little as one half cycle of AC power. There are only three things that kill the SSRs: over current (which can happen with heater on startup); Over voltage (usually from some sort outside the PID box); or over temperature.

Ed C

[benellinut]

The Relay outputs switch slowly. Power relays typically take 10 milliseconds or more to energize or de-energize. Each half cycle of the 60 herz power is 8 milliseconds. The relay also may switch on or off near the peak which is harder on the contacts of the relay. If you use a sufficiently robust relay, you might have a good life on the contacts.

The SSR module always switches when the AC power is near 0 volts. It can provide as little as one half cycle of AC power. There are only three things that kill the SSRs: over current (which can happen with heater on startup); Over voltage (usually from some sort outside the PID box); or over temperature.

Ed C

Ed,

As I put in the first post of the thread the pot draws 6.36 amps, the relays is rated for 10 amps so I'm not too worried about the relay being able to handle the load. If it does fail, I'll just replace it with one of the $2 spares, I could even switch the AL1 relay that's on the board seeing it's not being used. As far as cycle time, these Lee pot's have run for many years on the temp switch before these PDI's came into the picture, granted the PDI cycle much more often then the Lee switch (and that varies widely depending on the settings one inputs to the PDI) but I'm sure the relay can out last the old Lee temp switch contacts.

I can see using an SSR for some applications but I think to run a Lee Pro Pot it's just overkill and not necessary. To each their own.

[benellinut]

Ed, I forgot to add, I looked up the rated life cycle for this very relay before I went down this path. I'll have to dig to find the link again and post it later, it was not a low number by any means and gave me confidence that unless I get a bad relay it should hold up for many years. And for $4 shipped for two relays, I just went ahead and ordered them up, by the time I may need them I'll probably forget where I put them LoL.

[JonB_in_Glencoe]

Works great!
Be sure to keep us updated.
Like say after about 10 hours of use.

[benellinut]

Ed,

Here's the link to the relay at Hongfa Mfg http://www.hongfa.com/pro/HF32F_en.html
*note the old part number JZC-32F now changes to this relay HF32F http://www.hongfa.com/productsnold.asp?sid=6&lm=3

Here's the spec sheet in a PDF, http://www.hongfa.com/pro/pdf/HF32F_en.pdf Rated life rating depending on the relay contact material, the lowest rating is 1 x 105ops and that's 5amp 240vac

Like I say, unless I get a bad one, it should hold up for many years of my use. And here's where I bought the relays off ebay http://www.ebay.com/itm/390649654399

[benellinut]

Be sure to keep us updated.
Like say after about 10 hours of use.

I will do that.

[benellinut]

Be sure to keep us updated.
Like say after about 10 hours of use.

On second thought, no, no I won't update you. With a comment like that, after the info I have referenced it's clear your not willing to accept that an SSR isn't needed to run the Lee Pro Pot. You have already made up your mind so I know you wouldn't believe me even if I told you it's still working years later. I'm not trying to convert anyone, I'm showing someone new to these PDI's that they should do their homework for themselves and figure out what's really needed and necessary. This isn't rocket science, it heating a lead pot with a small heating coil.

And as far as milliseconds lost between a SSR and a physical contact relay, well the PDI will learn that delay and take it into account, not that milliseconds really matter when melting lead..... gheez guys, really? How'd our forefather's ever survive casting mini-balls over a campfire....

[Springfield]

If it works, it works. I run a 1500 watt 220 volt Magma pot. The first 2 20 amp SSR's burned out within a year and a half. I put in a 40 amp and it has been going for 3 years now. All 3 had a heat sink. I prefer to err on the side of caution myself, I have enough room on the bench for a larger PID box.

[benellinut]

If it works, it works. I run a 1500 watt 220 volt Magma pot. The first 2 20 amp SSR's burned out within a year and a half. I put in a 40 amp and it has been going for 3 years now. All 3 had a heat sink. I prefer to err on the side of caution myself, I have enough room on the bench for a larger PID box.

Yeah you need an SSR for that one for sure, my Lee pot only draws 6.36 amps at 120 volt. I have an SSR, I'll be using that when I set up another PDI for a stove for coating bullets.

[JonB_in_Glencoe]

On second thought, no, no I won't update you. With a comment like that, after the info I have referenced it's clear your not willing to accept that an SSR isn't needed to run the Lee Pro Pot. You have already made up your mind so I know you wouldn't believe me even if I told you it's still working years later.
...snip
Wow, I'm not sure how you read all that into my comment? Please don't assume my mind is made up, while I am a bit skeptical, I surely have an open mind. But, as edctexas has pointed out to you, there are other factors involved than just powering a heater that is running at about 6.36 amps. Those other factors are seemingly better served by a SSR. Now you can share your experience or not, It doesn't really matter to me. But if you were to get 10 hours of service, without having a relay fail, especially if your casting procedure is like some here, that dump the sprues back into the pot, which works the heater more, than not doing so...Then I would surely be convinced that your simple design works, and I'd recommend it.

[benellinut]

Wow, I'm not sure how you read all that into my comment? Please don't assume my mind is made up, while I am a bit skeptical, I surely have an open mind. But, as edctexas has pointed out to you, there are other factors involved than just powering a heater that is running at about 6.36 amps. Those other factors are seemingly better served by a SSR. Now you can share your experience or not, It doesn't really matter to me. But if you were to get 10 hours of service, without having a relay fail, especially if your casting procedure is like some here, that dump the sprues back into the pot, which works the heater more, than not doing so...Then I would surely be convinced that your simple design works, and I'd recommend it.

What factors has ed pointed out that leave you skeptical?
Did you read all my posts?
Did you look at the spec sheet for the relay I posted?
Where does the ten hour mark come from and what would that prove?

[dragon813gt]

So I just read the specs on the relay. Did you read the electrical endurance cycle? It's assuming a one second cycle time. Your PID will be switching faster than that when you're close to set point. I understand why you're doing this and more power to you. But I wouldn't expect the relays to last long.

Is there a reason you keep typing PDI instead of PID?

[benellinut]

So I just read the specs on the relay. Did you read the electrical endurance cycle? It's assuming a one second cycle time. Your PID will be switching faster than that when you're close to set point. I understand why you're doing this and more power to you. But I wouldn't expect the relays to last long.

Is there a reason you keep typing PDI instead of PID?

"Did you read the electrical endurance cycle? It's assuming a one second cycle time. Your PID will be switching faster than that when you're close to set point." What does the life cycle rating at one second on and off have to do with how fast the PID switches? Did you read the closing and opening time for the contacts? Close 8ms max, Open 5ms max, the relay will keep up with the PID.

Did you look at the life curve chart at the bottom of the PDF? If your right and the relay doesn't last, it will take me maybe ten minuets to solder a $2 spare on the board, I'm not worried about it. I also have a spare thermocouple, because we all know these cheap parts may fail at anytime.

PDI instead of PID, just a bad habit, one of many I have.

[benellinut]

I am using a PID with an internal relay and was told, authoritatively, by members here that it would fail. It probably will. But, the last three years have been trouble free. I also use it with a Pro-melt that draws quite a lot more current. I play with electronics for a hobby and have a pid running an ssr that drives an oven for making circuit boards. Cooling the ssr was mandatory as it gets pretty warm. When/if the relay in my first unit cacks, I have a ssr to replace it with but will have to rebox as there is no room for the heat sink.

What I'm doing is nothing new, OuchHot posted early in the thread his PID has been running for three years without a problem AND he's using it at times on another pot that draws more then my Lee. Ouch, if your relay does give out someday, just get a new one off ebay for a couple bucks and solder it on the board. I'll be doing the same as you, a second PID for an oven, that one I'll use an SSR because of the higher amps.

I see I'm getting the same negative feedback you got LoL.

[JonB_in_Glencoe]

The Relay outputs switch slowly. Power relays typically take 10 milliseconds or more to energize or de-energize. Each half cycle of the 60 herz power is 8 milliseconds. The relay also may switch on or off near the peak which is harder on the contacts of the relay. If you use a sufficiently robust relay, you might have a good life on the contacts.

The SSR module always switches when the AC power is near 0 volts. It can provide as little as one half cycle of AC power. There are only three things that kill the SSRs: over current (which can happen with heater on startup); Over voltage (usually from some sort outside the PID box); or over temperature.

Ed C


What factors has ed pointed out that leave you skeptical?
Did you read all my posts?
Did you look at the spec sheet for the relay I posted?
Where does the ten hour mark come from and what would that prove?
>I did read all your posts.
>the alibaba link? that told me nothing
>10 hours ...Just a guess. My thought is, if the inrush current during "turn on" of the heating element exceeds the rated value of 10 amps, even though the time of that higher current is measured in miliseconds during each occurrence, when the PID starts switching faster, the heat generated at the contact surface by each over current occurrence will build...at some point the heat will degrade the contact surface, creating resistance, which will create even more heat...sooner or later failure will occur. Now I could surely be wrong about how high the inrush current is going to be, I'd need to borrow a curve tracer from my old job, to measure it and I'm not smart enough to calculate it. So my mind is open, it may work, BUT if my thought of overcurrent is correct, I'm bettin' it will not last over 10 hours of use. So, then if you can run that PID with 10 amp relay 'troublefree' for 10 hours of use, I'm bettin' it'll last a good long time.

FYI: from 1985 til 1993, I worked for a manufacturer of electronic industrial DC motor controllers, in the PCB (Printed Circuit Board) department. Every assembled PCB would go through a 24 hour "Burn in test" (a test under load) and would work with the engineers if a common failure was found and needed to be corrected. Among other duties, I was in charge of that for 6 years, so I have a little experience.

[benellinut]

I can always upgrade the relay on the board if I see repeated failures, no reason why this can't be doable as Ouch has already proved.

[MT Chambers]

I didn't read all the posts but why all that wiring for a cheapo Lee pot, is it to time the drips better?

[benellinut]

I didn't read all the posts but why all that wiring for a cheapo Lee pot, is it to time the drips better?

How's the weather up there on that pedestal?

[alfloyd]

If you will read the instructions manual, it will say that the "Main Output" for the relay model - normal open - AC 250V/3A - DC 30V/3A.

I would take this as saying that the PID is rated for a load not to exceed 3 amps.
You can run it at a 10 amp load, but it is not rated for that.

The output for the alarms is rated the same as the main output, 3 amps.

Yes, I do read the instructions.

Lafaun

[William Yanda]

'Cause bigger is better. Everybody knows that.

Duckin' and runnin'

[benellinut]

If you will read the instructions manual, it will say that the "Main Output" for the relay model - normal open - AC 250V/3A - DC 30V/3A.

I would take this as saying that the PID is rated for a load not to exceed 3 amps.
You can run it at a 10 amp load, but it is not rated for that.

The output for the alarms is rated the same as the main output, 3 amps.

Yes, I do read the instructions.

Lafaun

I don't know what you read but the relay in this PID is rated for 10 amp at 125VAC, all this info is in this thread, I'm sorry but you are wrong.

[benellinut]

'Cause bigger is better. Everybody knows that.

Duckin' and runnin'

That what "they" say.

[Handloader109]

If it works, it works. I run a 1500 watt 220 volt Magma pot. The first 2 20 amp SSR's burned out within a year and a half. I put in a 40 amp and it has been going for 3 years now. All 3 had a heat sink. I prefer to err on the side of caution myself, I have enough room on the bench for a larger PID box.
Well at 1500 watts @220v it only draws 6.8 amps..... You just had **** 20 amp ssrs. I think this only reinforces Benellinut's argument for leaving out the SSR. Extraneous, same as others putting in a fuse. But to each his own. I've an SSR as that is what I thought I needed when I jumped on the PID.

[Cmm_3940]

Well at 1500 watts @220v it only draws 6.8 amps..... You just had **** 20 amp ssrs. I think this only reinforces Benellinut's argument for leaving out the SSR. Extraneous, same as others putting in a fuse. But to each his own. I've an SSR as that is what I thought I needed when I jumped on the PID.


Keep in mind the internal relay comes from the same source as the SSRs -China. There are no guarantees that the QC of the internal relay is any better than the SSR.

The SSR is the more appropriate part for this application. Mechanical relays are not meant to be used in high cyclic rate applications for all the reasons previously mentioned. Will it work? Sure. Probably. For a while.

All these Chinese parts are only somewhat expected to work at their rated values at the time they leave the factory, with no guaranteed lifetime once deployed. I and others prefer to go overkill on the SSR because it is a cheap part, and it makes sense to do so to hopefully gain a reasonably long service life. A cheap "40" amp Chinese part is likely to last longer than a cheap "20" amp part at a steady ~6A draw. If you expect 100% duty cycle at the rated value from one of these things, you're dreaming. It's worth the $8-$10 to me to not have to be tearing my PID apart to replace cooked parts.

Also, don't forget about the inrush current, which will be higher than the steady-state current draw, so it's best to leave yourself some headroom in any case. This will have more of an impact with the constant rapid on/off cycle of the PID than it will with the factory thermostat.

[benellinut]

Keep in mind the internal relay comes from the same source as the SSRs -China. There are no guarantees that the QC of the internal relay is any better than the SSR.

The SSR is the more appropriate part for this application. Mechanical relays are not meant to be used in high cyclic rate applications for all the reasons previously mentioned. Will it work? Sure. Probably. For a while.

All these Chinese parts are only somewhat expected to work at their rated values at the time they leave the factory, with no guaranteed lifetime once deployed. I and others prefer to go overkill on the SSR because it is a cheap part, and it makes sense to do so to hopefully gain a reasonably long service life. A cheap "40" amp Chinese part is likely to last longer than a cheap "20" amp part at a steady ~6A draw. If you expect 100% duty cycle at the rated value from one of these things, you're dreaming. It's worth the $8-$10 to me to not have to be tearing my PID apart to replace cooked parts.

Also, don't forget about the inrush current, which will be higher than the steady-state current draw, so it's best to leave yourself some headroom in any case. This will have more of an impact with the constant rapid on/off cycle of the PID than it will with the factory thermostat.

Finally, someone with reasonable and valid points. Your right on the money with everything you said and we each have to decide which way we want to go. I'm just offering up an alternative, one that gives you a much smaller and simpler unit, there is a trade off for everything. For me, I'll take the chance I may have to solder a new relay on the board, it takes me less then one minute to take the unit apart to this condition (pic below) and a few minutes to get my tools out and solder a new relay on the board. Probably no longer then it would take to replace a failed thermocouple and no more time to replace a failed SSR.

BTW Note the amp rating printed right on the relay.

http://i274.photobucket.com/albums/jj274/guywil/PDI/DSC01743_zps3xrohghe.jpg

http://i274.photobucket.com/albums/jj274/guywil/PDI/DSC01742_zpsnsmjyjiz.jpg

[leadman]

You may get this to work ok depending also on the ambient air temperature that the unit is in. I use mine here in Phoenix and they get plenty hot in the summer. The unit can get over 120 degrees without being switched on.
The internals of the relays have contact points just like the ignition system on old gas engines. There was a reason the tune up schedule was 10,000 miles on most of these.

I do have a Bosch 30a fused relay and have thought of installing this if I have an SSR go out just to see what happens. The PID to run a relay versus a SSR is different and not interchangeable though. Found this out the hard way when a vendor on EBay sold me some mismarked PID units.

I have added heat sinks and on one unit an electric fan like a computer uses and performance is much better. The unit on my pot has run for more than 8 hours many times without being shut off.

[alfloyd]

Yes, the relay is rated for 10 amps but, the PID is only rated for 3 amps.
Look at the spec sheet.

Lafaun

[JonB_in_Glencoe]

Yes, the relay is rated for 10 amps but, the PID is only rated for 3 amps.
Look at the spec sheet.

Lafaun
I wonder if they downgrade the rating to 3 amps, due to the delicate connections between the PCB and the terminals in the chassis ?

It might be prudent to add some 'hard wiring' between the Relay contacts and the terminals.

[benellinut]

Yes, the relay is rated for 10 amps but, the PID is only rated for 3 amps.
Look at the spec sheet.

Lafaun

OK, I'll agree that's what's printed on the MYPIN spec sheet --> http://www.mypinchina.com/uploadfiles/201161494651265.pdf
but as you can clearly see the relay is rated for 10 amps at 125 volts. The relay is what's sending volatage to the pot, the PID is just switching the relay on and off.

A couple other things, that 3 amp rating your talking about is at 250 volts ac, not 125 volts ac, again look at the ratings on the pic of the relay I posted above and you'll see printed on the relay (and also on the relay spec sheet linked prior)
10 amps at 125 v ac
5 amps at 250 v ac
5 amps at 30 v dc
Amperage ratings change depending on the voltage and if it's being used to control AC or DC.

I have already run the pot for a couple hours, if the PID connectors or the board connections from the relay to the connections couldn't handle the 6.36 amps of the pot it would have gotten hot or smoked and it did neither as I kept a very close eye on it.

Take a look at the comparable PID made by Auberins and you'll see the output is rated for 10 amps at 125 volt ac
http://auberins.com/index.php?main_page=product_info&products_id=1 There isn't any reason why a PID with an internal relay can't be used to run this Lee Pro 4 20lb pot that draws a max of 6.36 amps, this is doable.

Lastly, I'll once again point out, I'm not the first one to do this. Ouch has been using his for three years and sometimes to run another pot that draws even more amperage. Read his post on the first page of this thread, #13 linked below.
http://castboolits.gunloads.com/showthread.php?278033-Why-use-an-SSR-when-Lee-states-the-Pro-4-20lb-pot-(100v)-only-draws-6-36-amps&p=3250816&viewfull=1#post3250816

[JonB_in_Glencoe]

Yep, your PID should be good to go.

I do, however, find your thread title a bit curious. In it, you ask a question...
Then, when myself and others offer our reasons why, you get defensive ?
(and while I was skeptical, I remained tactful and open minded..and gee, we were just trying to help)

Then in your last post, you state the following...

There isn't any reason why a PID with an internal relay can't be used to run this Lee Pro 4 20lb pot that draws a max of 6.36 amps, this is doable.
hmmm, maybe your title question was rhetorical ? IDK ?
ANYWAY, Good luck and I will avoid your questions in the future.

[benellinut]

Yep, your PID should be good to go.

I do, however, find your thread title a bit curious. In it, you ask a question...
Then, when myself and others offer our reasons why, you get defensive ?
(and while I was skeptical, I remained tactful and open minded..and gee, we were just trying to help)

Then in your last post, you state the following...

hmmm, maybe your title question was rhetorical ? IDK ?
ANYWAY, Good luck and I will avoid your questions in the future.

I think the title was appropriate, potato, patata. Remember this thread is now two months old, I've done a lot of research since so when I now say it's doable that opinion is a conclusion that evolved over that time and backed up by someone who had already proven it.

BTW, It wasn't the reason's offered, (none that I saw as valid nor swayed me) that made me defensive, it was the offensive nature of some of the posts.

[Mal Paso]

Also, don't forget about the inrush current, which will be higher than the steady-state current draw, so it's best to leave yourself some headroom in any case. This will have more of an impact with the constant rapid on/off cycle of the PID than it will with the factory thermostat.

No inrush current with a resistive load like a heater. I agree with the rest though. That relay will be chattering like a telegraph close to operating temperature.

[benellinut]

No inrush current with a resistive load like a heater. I agree with the rest though. That relay will be chattering like a telegraph close to operating temperature.

Not as much as you think, I'll back off the dwell time a little to reduce that chatter. Letting it overshoot and undershoot a little isn't going to hurt.

[benellinut]

From here on in I'll let you guys chat it up, be it good or bad, if you want to knock it or me feel free, I don't care. There really isn't anything more I have to add, pretty much any info relevant to my build has been posted and my points posted. I'm done defending my reasons, disproving & correcting bad information and myths.

For the folks looking to build a PID, all I can say is don't take everything you read on any forums as fact, including my opinions. Do your own homework, understand the trade off's and do what makes you happy.

[OuchHot!]

benellinut, you are starting to see why I don't bother with this site much. In three plus years, I am sure I have better than 20hrs on a pro-melt and at least that on the lee. The unit I use appears identical to yours. I have some more demanding applications for PID where I did use an ssr and found the run of the mill ssr to be very sensitive to temperature and needful of careful heatsinking. My spare bedroom is an electronics lab, I make my own choices and learn from my own mistakes. I put two of these PID in a box, the other runs the hotplate for my mold warming. I have no problems with that use either. Given the entire electronics suite in your automobiles is straight from China, I suggest everyone stay home or at least not drive any further than you want to walk.