Watlow controller

[Bert Weiss]

Does anybody use the Watlow EZ Zone RM contoller? It looks like a perfect match for a 3 zone kiln, plus a hitemp limit control. It comes with computer interface software and costs considerably less than a comparable Digitry unit. It also can utilize simple SSR relays and make them turn on or off every 3 cycles or 20 times a second. This is easy on the elements, making them last longer.

[Brad Walker]

Contact Brad Shute at handmade-glass.com I believe he has experience with the Watlow.

[Jordan Kube]

They are not stand alone products. You will need an interface. We have these in four large annealers each with one zone on each side plus an over-temp control and they work well.


Watlow EZKB interface: https://www.instrumart.com/products/205 ... -interface
The base unit without any options will work.
$116

Watlow Ez-Zone RMC: https://www.instrumart.com/products/con ... quantity=1
Configured for 3 zone control: RMC3U1U1UAAAAAA
$673
You could add a high limit control for about $90 more. You would also need a contactor rated for the full load of your oven.
This is an inexpensive one that would work for a 60 amp load: http://www.automationdirect.com/adc/Sho ... -E4-110VAC

Watlow Din-a-mite Style A, B, or C: https://www.instrumart.com/products/con ... quantity=1
This will depend on how many amps each bank of elements draws. If each bank only drew 20 amps three style A's would work at $111 a piece. Higher amperage would mean higher prices as you step up to the B or C. You would not be limited to Watlow products for the power controller but they have good documentation and good support.

Total as listed: $1122 plus shipping. Maybe another $2-400 for an enclosure, parts, and wiring.

You would need to configure everything yourself as well.

[Bert Weiss]

I am building a bell kiln with 3 zones drawing 38 amps each (50A circuits). I like the Continental SSRs. I can put the EZ zone together, including display, for $890 plus a power supply $90 and an uninterruptible power supply (cheap computer one?), That includes a 4th high temp limit zone, which also needs a double pole mechanical relay. The computer program comes at no cost.

I am wondering of it might be a better idea to use a stand alone high temp limit controller? With that setup, I put a simple light switch on the power to the high temp limit controller. When you shut that switch off, the double pole relay opens up, and all power is removed to the kiln. That is a great feature. I don't know if there is a way to rig that if I put the hitemp zone in with the EZ Zone.

If you add a USB computer interface to a Bartlett RTC 1000, the cost gets right up there.

[Jordan Kube]

You could absolutely do the light switch with the Ez Zone limit in the controller. Just wire your light switch in series with the relay coil circuit. That's pretty good pricing too, what's your source? What would you need the power supply for? Are you using low voltage controls?

[tob]

...[snip]...Just wire your light switch in series with the relay coil circuit. ...[snip]....

Even if you go with the standalone unit instead of the EZ Zone limit control, what Jordan suggested would be the best way to wire it. By simply killing the power to the relay coil with a switch, instead of the power to the controller, you'll still have a functioning temperature readout on your overtemp control. Although you don't really need that readout due to also having the EZ Zone readout, I think it's still nice to have.

TOB

P.S. And although Brad is right that I have plenty of Watlow experience, it is mostly with their older equipment and their SCRs. I've don't have any experience with their newer EZ Zone products. But Jordan certainly seems to have that covered.

And speaking of Watlow SCRs, if anyone needs some kick-ass 80 amp SCRs, I have a few Watlow Din-a-mite DD Series that are like new, for less than 1/3 the price of new ones. They were installed in, and then removed from, a power panel that was never put into service.

[Bert Weiss]

You could absolutely do the light switch with the Ez Zone limit in the controller. Just wire your light switch in series with the relay coil circuit. That's pretty good pricing too, what's your source? What would you need the power supply for? Are you using low voltage controls?

Pricing is a 10% discount based on that I am reselling it to my client. Tech guy told me I need to ad a 24v 1.6A 31 watt power supply for the EZ zone, and I need to add a UPS to protect the device from losing data in the event of a power loss. I think I can use a cheap computer UPS that puts out 120v and wire the power supply directly to that. I am assuming, with the computer interface setup right, the operator would be able to shut it down from a smart phone (as well as monitor a firing).

[Bert Weiss]

...[snip]...Just wire your light switch in series with the relay coil circuit. ...[snip]....

Even if you go with the standalone unit instead of the EZ Zone limit control, what Jordan suggested would be the best way to wire it. By simply killing the power to the relay coil with a switch, instead of the power to the controller, you'll still have a functioning temperature readout on your overtemp control. Although you don't really need that readout due to also having the EZ Zone readout, I think it's still nice to have.

TOB

P.S. And although Brad is right that I have plenty of Watlow experience, it is mostly with their older equipment and their SCRs. I've don't have any experience with their newer EZ Zone products. But Jordan certainly seems to have that covered.

And speaking of Watlow SCRs, if anyone needs some kick-ass 80 amp SCRs, I have a few Watlow Din-a-mite DD Series that are like new, for less than 1/3 the price of new ones. They were installed in, and then removed from, a power panel that was never put into service.

If TOB is indeed Brad S, I bought some salvage Dinamites from him, maybe 18 years ago, and they are still working perfectly.

In this case, the tech guy at Watlow suggested I go with simple zero cross SSRs, as they will be easier on the elements, cheaper, and the controller has a built in feature that cycles it every 3 cycles (3 times a second) which is sufficient for efficient element control. He told me that the phase angle setup is harder on the elements,and surrounding electronics.

[Jordan Kube]

You could use a 120v ez zone and skip the transformer. Also not all SCRs are phase angle fired. You generally need to specify when ordering. SSRs are good and cheap.

[Bert Weiss]

You could use a 120v ez zone and skip the transformer. Also not all SCRs are phase angle fired. You generally need to specify when ordering. SSRs are good and cheap.

My dad was in the temperature control business. So, when I built my first kiln in 1983, he set me up with a control system including SCR's. In those days, I had this monster analog events programmer that would go haywire if you looked at it funny. When I built my 3 zone bell kiln in 1990, he set me up with a Barber Coleman programmable controller with 2 slaves. That is the one I still use to run both of my kilns (one at a time) The SCR's for that cost $500, and didn't last long. The ones I replaced those with, Watlow Dinamites, I bought as salvage and they are still running just fine. Come to think of it, my center zone is the first SCR I got in 83, and the outer zones are the Watlows.

I miss my dad. When I was a kid he used to bring home optical pyrometers. He sold this stuff to the glass and steel industries in Pittsburgh. PPG would outfit their float lines with his instruments. US Steel was able to figure out how to bend giant I-beams using the optical pyrometers. This enabled them to build curved offramps for highways. Before these instruments, they had to be segmented with straight steel. He got me a tour of PPG research, back in the 80's when I was just figuring out how to mess around with float glass in kilns.

[tob]

...[snip]...Just wire your light switch in series with the relay coil circuit. ...[snip]....

Even if you go with the standalone unit instead of the EZ Zone limit control, what Jordan suggested would be the best way to wire it. By simply killing the power to the relay coil with a switch, instead of the power to the controller, you'll still have a functioning temperature readout on your overtemp control. Although you don't really need that readout due to also having the EZ Zone readout, I think it's still nice to have.

TOB

P.S. And although Brad is right that I have plenty of Watlow experience, it is mostly with their older equipment and their SCRs. I've don't have any experience with their newer EZ Zone products. But Jordan certainly seems to have that covered.

And speaking of Watlow SCRs, if anyone needs some kick-ass 80 amp SCRs, I have a few Watlow Din-a-mite DD Series that are like new, for less than 1/3 the price of new ones. They were installed in, and then removed from, a power panel that was never put into service.

If TOB is indeed Brad S, I bought some salvage Dinamites from him, maybe 18 years ago, and they are still working perfectly.

In this case, the tech guy at Watlow suggested I go with simple zero cross SSRs, as they will be easier on the elements, cheaper, and the controller has a built in feature that cycles it every 3 cycles (3 times a second) which is sufficient for efficient element control. He told me that the phase angle setup is harder on the elements,and surrounding electronics.

Yes Bert, that's me - TOB = The Other Brad

I'm not sure why the Watlow guy told you that the SSRs would be easier on your elements than phase angle firing SCRs. That makes no sense to me. Easier on the surrounding electronics, maybe. Elements, no. Not that it really matters, since either one would be just fine. He's right that SSRs will normally be cheaper though. In fact, I used zero-crossing SSRs to control my 200 lb glassmaking furnace for 14 years and never had an ounce of trouble with them - and got great life out of my SiC elements. I'm using a phase angle firing SCR on my present glass furnace and see no difference in element life. So although I personally don't think that SSRs will give any better (or worse) element life than SCRs, I'm certainly in favor of using them if they will allow you to put together a cheaper system. Just don't neglect proper heat sinking. All SSR power ratings are based on having an appropriate heat sink attached, which will increase the initial price.

There are also two types of both SSRs and SCRs, so a blanket statement about either one is seldom accurate. Both SSRs and SCRs come in zero-cross and phase angle firing styles. (Usually called "random firing" in SSRs, but still phase controllable with the right hardware.) As a matter of fact, the Watlow SCRs I mentioned in my previous post are zero-cross firing, even though they are controlled by an analog 4-20mA signal. So in practice, there would be absolutely no difference in how they deliver power to the elements or how your zero-cross SSRs do it. The primary difference is that SCRs normally include an integral heat sink, firing package, and fusing, while you need to add those things yourself when using SSRs. (Although the need for a "firing package" will usually be handled by your temperature controller.) But in the end, SSRs and SCRs both control the power essentially the same way.

TOB

[Bert Weiss]

Yes Bert, that's me - TOB = The Other Brad

I'm not sure why the Watlow guy told you that the SSRs would be easier on your elements than phase angle firing SCRs. That makes no sense to me. Easier on the surrounding electronics, maybe. Elements, no. Not that it really matters, since either one would be just fine. He's right that SSRs will normally be cheaper though. In fact, I used zero-crossing SSRs to control my 200 lb glassmaking furnace for 14 years and never had an ounce of trouble with them - and got great life out of my SiC elements. I'm using a phase angle firing SCR on my present glass furnace and see no difference in element life. So although I personally don't think that SSRs will give any better (or worse) element life than SCRs, I'm certainly in favor of using them if they will allow you to put together a cheaper system. Just don't neglect proper heat sinking. All SSR power ratings are based on having an appropriate heat sink attached, which will increase the initial price.

There are also two types of both SSRs and SCRs, so a blanket statement about either one is seldom accurate. Both SSRs and SCRs come in zero-cross and phase angle firing styles. (Usually called "random firing" in SSRs, but still phase controllable with the right hardware.) As a matter of fact, the Watlow SCRs I mentioned in my previous post are zero-cross firing, even though they are controlled by an analog 4-20mA signal. So in practice, there would be absolutely no difference in how they deliver power to the elements or how your zero-cross SSRs do it. The primary difference is that SCRs normally include an integral heat sink, firing package, and fusing, while you need to add those things yourself when using SSRs. (Although the need for a "firing package" will usually be handled by your temperature controller.) But in the end, SSRs and SCRs both control the power essentially the same way.

TOB

Brad

I asked the question to my temp control guru. He laughed and said it is a long standing controversy. I have always run my thermocouple wires along with the flexible copper power leads. If there was ever a problem caused by this, I haven't noticed it. He advised me that the zero cross has fewer issues with creating electronic interference, so using the less expensive zero cross SSR is a good choice.

On my own kiln's 3 zones, I have a 30 year old zero cross SCR and 2 @20 year old phase angle fired SCR's. Every thing is in good working order. On the kiln I am building, I will use Continental, zero fired SSRs. I am having a hard time sourcing 240v 50A DPDT NO mechanical (or solid state) relays for my hitemp limit system. I need 3.

[Jordan Kube]

Automationdirect has decent prices on contactors:

http://www.automationdirect.com/adc/Sho ... E2S-110VAC

[tob]

Are you sure you need a double throw contactor Bert? Unless you're doing something fairly unusual, it seems like a 2 pole, single throw should be sufficient.

If you don't need the double throw, here's a Square D contactor rated at 50A resistive, for $34. It's three pole instead of two, but you don't need to connect all three poles. http://www.zoro.com/i/G2315381/

And just in case you were talking about coil voltage when you mentioned 240, here's a 2 pole 50A contactor with a 240 coil for $29 - http://www.zoro.com/i/G1478714/

[Bert Weiss]

Are you sure you need a double throw contactor Bert? Unless you're doing something fairly unusual, it seems like a 2 pole, single throw should be sufficient.

If you don't need the double throw, here's a Square D contactor rated at 50A resistive, for $34. It's three pole instead of two, but you don't need to connect all three poles. http://www.zoro.com/i/G2315381/

And just in case you were talking about coil voltage when you mentioned 240, here's a 2 pole 50A contactor with a 240 coil for $29 - http://www.zoro.com/i/G1478714/

I have to admit my knowledge in this field is not all that broad. What I need is a contactor that opens both poles, removing all power to the system. So it is definitely normally open. When the hitemp limit controller is working and beneath the setpoint, the contactor is closed. If it goes over temp, 2 contactors open up. I thought DPDT meant 2 poles that open up. Typically we turn on and off with a single pole, which leaves a 120v potential should ground be contacted. I am pretty sure this is done with a low voltage DC signal, just like the temp control relays. I do get it that a 3 pole unit with 2 poles connected would suffice. I will need one of these for each of the 3 zones. Perhaps it could be wired with a single 150A relay and a power distribution block, if that was really less expensive than 3 50A relays. I doubt that is cost effective, but it could come close.

[Bert Weiss]

Are you sure you need a double throw contactor Bert? Unless you're doing something fairly unusual, it seems like a 2 pole, single throw should be sufficient.

If you don't need the double throw, here's a Square D contactor rated at 50A resistive, for $34. It's three pole instead of two, but you don't need to connect all three poles. http://www.zoro.com/i/G2315381/

And just in case you were talking about coil voltage when you mentioned 240, here's a 2 pole 50A contactor with a 240 coil for $29 - http://www.zoro.com/i/G1478714/

Thanks Brad. I talked with a few techs and what I have gathered is that 2 - 3 pole120v contactors will do the job for my 6 poles, for 35 bucks each.

[tob]

If you don't need to control the 3 elements independently, then that's the way to go. Two 3 pole relays will do the job for you pretty inexpensively. Zoro is a great place to buy stuff like this. They have a good selection, great prices, and in my experience, ship very quickly. My only criticism is that their site search isn't as good as it could be. But I can live with that for the other benefits. Glad I was able to help.

By the way, if you haven't ordered yet, take a look around online to see if you can find a Zoro discount coupon code. There are usually some available that will save you from 5-15% on your order. Also, since your two relays will total more than $50, you'll get free shipping too. (Can you tell I like Zoro?)

TOB

[Bert Weiss]

If you don't need to control the 3 elements independently, then that's the way to go. Two 3 pole relays will do the job for you pretty inexpensively. Zoro is a great place to buy stuff like this. They have a good selection, great prices, and in my experience, ship very quickly. My only criticism is that their site search isn't as good as it could be. But I can live with that for the other benefits. Glad I was able to help.

By the way, if you haven't ordered yet, take a look around online to see if you can find a Zoro discount coupon code. There are usually some available that will save you from 5-15% on your order. Also, since your two relays will total more than $50, you'll get free shipping too. (Can you tell I like Zoro?)

TOB

The guy at Watlow told me that mercury and solid state are not codeworthy for a high temp limit system, only mechanical. The mechanical relays are only there to prevent a runaway, so they are not often cycled. The 6 pole solution gets the job done. The Watlow hitemp module takes care of the latching feature, that won't let the power come back on after the temp goes below setpoint, until it is manually reset.

Another tricky device I have researched is a power splicer, that makes the transition from flexible copper cables (running from relays on the wall to the kiln) to TGGT hightemp tin plated copper wire. I found a reasonably priced one that has the features I need. It is tin plated copper, 3 poles in and 3 out (I need 2 of these also), made with phenolic resin rated to 300ºF, and is less than 3" wide. When I first set my own kiln up, I connected the copper directly to the elements. Periodically, the copper would disintegrate and fall away. Since I switched to an interface of TGGT, that has not happened even once. The catch here is that Zoro carries Mersen's aluminum block model of the one I want, but not the copper. I found another company, Gordon, who has a really good price on the copper one. Gordon's price on the Square D contactor is double Zoro's. These companies get pricing relative to how much product they actually sell. Shopping around is time consuming, but yields better pricing.

Another interesting thing I have spent too much time researching is the ampacity rating for TGGT wire. With regular flexible copper, they recommend 6 gauge wire. It turns out this is used in the alternative energy game, so it is more common than when it was only used for welding or battery cables. TGGT can get away with 12 gauge. I'm told this is because of the way it is insulated, which can handle around 500ºF. Google provided me with a source for TGGT that costs half as much as the first source I had.

[tob]

The ampacity chart on this page - http://www.powerstream.com/Wire_Size.htm - should help explain the difference you found between the load carrying ratings of regular copper and TGGT wire Bert. The higher temperature rating of the fiberglass insulation on TGGT wire, and the nickel (not tin) coating on the copper, are only part of it. Another difference is that one type of wire is being rated for voltage drop for power transmission (copper cable) and one for temperature rise when used for internal wiring of equipment (TGGT). So the maximum current ratings will be inherently different, with the chassis wiring always rated higher - even when using the same type of wire.

Also note that the figures in the chart referenced above are for the same copper wire, and the maximum ampacities given are based solely on how it is used, whether for power transmission or chassis wiring. As an example of the difference, regular 10 AWG copper wire is rated for a maximum of 55 amps for chassis wiring, but only 15 amps for power transmission (as in a power cord). As also stated on that page, "the rated ampacities are just a rule of thumb. In careful engineering the voltage drop, insulation temperature limit, thickness, thermal conductivity, and air convection and temperature should all be taken into account". So it's more that just the type of wire that matters, the conditions under which it is used make a big difference too.

But when subjected to a potentially very hot environment such as a connection to heating elements, as you said, the high temperature TGGT wire is a better choice that regular copper wire - due both to the higher temperature fiberglass insulation, and the fact that the nickel coated copper can sustain higher heat before it starts to oxidize. In comparison to the copper wire ratings above, 10 AWG TGGT wire is rated for 75 amps in a chassis and has a temperature rating of 250°C http://www.worldwidewire.com/high-temp- ... e-tggt.htm. If you want something even better than TGGT for high temperatures, check out MGT high temp wire. For the same size and chassis wiring as the other two, it is rated for 100 amps, with a max temp rating of at least 450°C - http://www.worldwidewire.com/high-temp- ... re-mgt.htm

TOB

[Bert Weiss]

The ampacity chart on this page - http://www.powerstream.com/Wire_Size.htm - should help explain the difference you found between the load carrying ratings of regular copper and TGGT wire Bert. TOB

Brad, the Powerstream chart is not consistent with other charts I have seen. I am pretty confused. My plan has been to use 6awg flexible welding cable. The zones each draw 38 amps. On one website they have 2 grades of this available, Class K and ClassM, the differences being the number of strands. They rate 6 awg class k at 75 amps and class M at 105 amps. Another website rates their 6 awg cable at 115 amps max.

I believe on my kiln, I used 4 awg, but I have 2 zones that draw more amperage than the one I am building next.