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Old 05-30-2019, 05:21 PM
Eddie Bernard Eddie Bernard is offline
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Sluggish Electric Furnace--Possible Fix

If your electric furnace is more than eight years old, uses a Watlow Power Series SCR, and is excruciatingly sluggish, there's a function that can be disabled in the SCR which is likely the cause. The function is displayed as HCYC, and it was set up to solve a theoretical problem that never materialized. Instead, this function causes near-debilitating sluggishness.

A little backstory--Wet Dog Glass stopped using these SCRs after only using four of them 10 years ago when Watlow admitted that they use cheap current transformers because the vast majority of customers for this product use it for burst firing--not phase angle, and that the cheap current transformers were indeed the cause of the problem I was having. After having another brand new furnace fail to function properly, Watlow had me disable the HCYC function. That adjustment worked immediately. A few months ago, I remembered this fix when a furnace that previously functioned well began to drag on its way to melt temp after ten years of service. Since then I've helped a number of non-Wet Dog Glass furnace owners who were at wit's end over how slow the furnaces were, and those who found the HCYC function enabled and then disabled it reported that their furnace was like "a whole new animal!"

Attached is a .pdf file with instructions on disabling this feature.
Watlow Power Series_HCYC disable.pdf

Last edited by Eddie Bernard; 05-30-2019 at 05:23 PM.
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Old 05-30-2019, 06:31 PM
Larry Cazes Larry Cazes is offline
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Probably a hysteresis function
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Old 05-30-2019, 06:33 PM
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Pete VanderLaan Pete VanderLaan is offline
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This goes straight to "Antiques and Classics". Thanks Eddie.
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Old 05-30-2019, 08:52 PM
Rick Kellner Rick Kellner is offline
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Quote:
Originally Posted by Larry Cazes View Post
Probably a hysteresis function
I concur. That's exactly what came to mind when I saw the acronym.
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Old 05-30-2019, 09:55 PM
Lynn Read Lynn Read is offline
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Hi Eddie

Thanks for making this suggestion at the GAS conference. After tuning off this alarm it seems my furnace is running about 10 % lower on output. I was able to reach higher melt temps with the same output.
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Old 05-31-2019, 01:35 PM
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Richard Huntrods Richard Huntrods is offline
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Some modern controllers have an 'auto tune' function that saves data on the performance of the controller over time, and can adjust the response of the controller over time if it sees a change. (i.e. elements getting old and response to X power slowing down).

It works pretty well until you do something stupid, like maintenance with the shutoff switch blocked (i.e. in the off position) while the system is running. In my case it kept trying to hold the temp setting (1900F) while the door was open and temp was falling. After I was done and returned things to normal, I had a severe case of "temperature overshoot" for many days until the system auto-tuned itself back into normal behavior.

But the tuning curve can get in the way and it sounds like this is a quick way to reset the data and restore factory response times.
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Old 06-01-2019, 06:24 AM
Eddie Bernard Eddie Bernard is offline
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The HCYC prompt stands for “Half Cycle Line Loss.”. The theory as explained to me by Watlow was that if supply voltage on any phase was disrupted to the degree that it lost half the cycle, meaning the positive or negative half of the sine wave, the resulting DC component could have caused damage to the transformer. As a matter of fact, these very instructions originally stated that the user should not disable the HCYC function when the SCR was firing into a transformer. I retyped it and added a few notes to clarify the steps to get to the setup and factory pages based on feedback from some users who went through the process. I did speak with Watlow in March and asked them again to confirm that we should ignore the note about not disabling HCYC when using a transformer, and they did confirm without hesitation.
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Old 06-01-2019, 07:25 AM
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Pete VanderLaan Pete VanderLaan is offline
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Is it not the case that all Moly SCR relationships fire into the transformer?
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Old 06-01-2019, 12:31 PM
Eddie Bernard Eddie Bernard is offline
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As far as I know, the vast majority of furnaces using Moly-D’s in our art glass community also use transformers. I know some of you who have been on CraftWeb for years will recognize some of the conversation Steve Stadelman used to have with others here—It’s not exactly necessary to use transformers, but it’s the responsible thing to do in terms of power factor (for the sake of the power grid) when the resistance of the elements added up in series won’t be enough to resist full line voltage without self-destructing. Some people use 120V single phase and put the elements all in series and let the phase angle SCR take care of the discrepancy in voltage needed, and there are also interesting arrangements that can be done with contactors to change the element arrangement from Series Wye to parallel Wye to Series Delta to Parallel Delta as they heat up. That’s a lot to go through to avoid using a transformer.

Another key advantage we have with transformers is the safety it can provide the user when it is an isolation type with the X0 tap not grounded and secondary voltage lower than 48V. For production shops where the door is opened more frequently than the furnace can recover the heat lost while open, the user can safely bypass the door safety limit switch without risk of electrocution. This is known as SELV, or “Safety Extra Low Voltage.”. The elements remain energized while the user is gathering glass from the furnace.
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Old 06-01-2019, 02:15 PM
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Pete VanderLaan Pete VanderLaan is offline
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I don't know of any that use line voltage. I always viewed that as the downside of SiC. When Steve was building the very early ones, it was all salvage transformers which were virtually all 440V. One could trick the transformer and run 240V into it and it created two 120V taps and one 60V tap which worked great with the 6/12 type elements drawing 20 Volts. The downside was serious fragility.

My furnace, which we put together back around 2001 did not have a kill switch. I tend to think any commercial unit would be nuts to not have one just for the liability. It did not take long for commercial transformers from Marcus to become mainstream. Then the beefier 9/18 elements could be used easily and secondary voltage could collapse to 36V.

While they are still built a fair amount, it never bcame the hot tool I thought it would. The initial belief was that it would be so low maintenance and it was far from that as it turned out. Then. Electric rates where I live made it impossible to justify not using Propane or natural gas. I prefer the gas actually although it's not as safe. I just can't get the colors I want with moly. If I ran electric now, a 28 inch pot would cost close to 3K per month to run. Propane is about $600 and I think that's a lot.
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