Back-up heat lamp system for Nyle controllers

[blackhawk]

If you have a Nyle L53 or L200 kiln, you hopefully know that the controllers cannot get below freezing.  I have my Nyle L53 mounted in an insulated Tractor Supply truck toolbox on the side of my kiln.  So, I run a light bulb off a digital temperature relay to cycle the bulb on and off to keep the toolbox above freezing.  The problem is that light bulbs or heat lamps burn out.  This happened to me the first cold snap a couple of months ago in the middle of the night so the toolbox got below freezing.  Luckily, I caught it early and my controller was ok.  My kiln is too far away for bluetooth or wi-fi alarms, but those don't do any good if the temp drops in the middle of the night or you are 20 miles away and can't change the bulb in time.  I decided to come up with a circuit to turn on a back-up bulb in the case that my main bulb burns out.

I am not an electrician or electrical engineer, so fair warning if you would like to try this.  I attached pictures and wiring diagrams of my setup.  I kept my original temperature relay, but I added a N.O current sensing relay to the hot wire feeding my main lamp.  When that relay senses current to the main lamp, it opens a standard N.C. relay that goes to the backup light bulb, so the backup bulb is off.  If the main bulb burns out, the current sensing relay drops power to the N.C. relay's coil causing it to close, allowing power to the backup bulb.   

I had to add a time delay relay into the circuit going to the backup lamp.  Without this, the backup lamp was flashing for a half second every time the temperature relay called for heat because there is a slight delay for the current to be sensed.  This would inevitably shorten the life of the backup lamp.  I don't 100% like running the circuit directly through the time delay relay, but it is rated for 1.5 amps and my 75 watt bulb is only pulling .63 amps and that relay is UL listed.

The 3 way light switch is just for my convenience when I am checking the kiln at night.  I flip the switch and that bypasses the temperature relay so my bulb is on all the time and I can see to write down readings.  This bypass will turn on both bulbs, but I can simply turn up the timer to its max of 10 minutes to keep the backup bulb from turning on.  I just didn't want to add another switch, but you could.

I also added a red LED with buzzer that turns on when the backup bulb turns on.  This way when I walk by the kiln I have the audible warning that my main bulb has burned out.  

[blackhawk]

Here are some links to the parts that I used.   I bought the electric boxes, light switch, 3 prong plug and lamp holder from Lowes.  Altogether, I've got about $140 into it, not counting wire which I mostly had already.  You can sign up for Zoro emails and they send out 20% off coupons all the time which is what I used.  I really like Zoro if you haven't used them before.

https://www.amazon.com/gp/product/B07Y2FDR4K/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

https://www.zoro.com/functional-devices-rib-current-sensing-relay-05a-120vac-ribxghf/i/G5174881/?q=ribxghf

https://www.zoro.com/functional-devices-rib-enclosed-pre-wired-relay-10a277vac-spdt-ribu1c/i/G1045256/

https://www.amazon.com/dp/B0BCF2ZBHH?ref=ppx_yo2ov_dt_b_fed_asin_title

https://www.amazon.com/dp/B01LYA0LJX?ref=ppx_yo2ov_dt_b_fed_asin_title