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

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/elec...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

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.

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.

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-detai...174339563.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!

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.

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.

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.

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.

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.

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 :-)).

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Originally Posted by 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 :-)).

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"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

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.

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.

Just buy the SSR.

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.

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

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...

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.

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Originally Posted by 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...

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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.

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.