How do I set the TCR for my ceramic donut coil?
The Crux: Lower TCR numbers provide power for a shorter amount of time, higher ones for longer. If your wattage and temp are set at the desired level but there's not enough vapour the TCR number needs to be increased. If there is too much vapour or it is burning material it needs to be decreased. When searching for a TCR always start with lower numbers, at a lower wattage within the manufacturer specified range and at a lower temperature. This will protect your coil from damage as you will be working from cooler, lower power settings settings upwards. When your coil or bucket is reaching the set temperature and staying relatively stable it is time to turn up your wattage and temperature to the desired settings to improve heat up time and reach vaping temperatures.
The resistance or Ohms of your coil is set when screwing in the atomizer and coil - this is your baseline resistance reading. This will vary slightly depending on the temperature of your coil, mod box and minor variations in coil production. Glossary of terms at the bottom.
It should be noted that TCR temp control is not completely accurate. The TCR number describes to the mod how the resistance will increase as the coil heats, helping it fairly accurately reach set temperatures by providing power in short bursts to avoid overheating the coil . To start from the right place the coil resistance should be locked when cold (room temperature - around 20c) to provide a baseline for the mod box to work with. Most mods will do this automatically when you install a new coil. The TCR number should be found when the coil is new. Over time (weeks to months) the resistance of the ceramic coils increase, as the resistance increases the coil will start to reach higher temperatures more quickly and the TCR number will need to be decreased slightly. To avoid doing this too regularly you can simply decrease the temperature setting on your mod box as you notice this change. When the coil is not effectively heating to your liking, wait until it's cool and then recalibrate, decreasing the TCR appropriately. If you don't use a resistance lock and allow the mod to read the new resistance each time you can follow the same method, leaving the TCR number the same as before but turning down the temperature a little. With some mods like the Aegis Solo or Wismec Tinker 2 changing the TCR is so easy you might choose to lower this slightly as you see the resistance increase, if changing the tcr it's always best to use a thermocouple to check your results.
For any given material there will be a TCR value which helps the mod box fairly accurately predict how much power to provide and how to respond to the increasing resistance of the coil, appropriately heating and maintaining the set temperature. For single wire coils such as titanium wrapped quartz rods there will be a TCR number that will accurately heat the coil, these numbers differ slightly between mod boxes. This is no different for the ceramic donut coils as there is one number which accurately reflects the relationship between "power" and heat, however due to the way they're made these coils function with a wide range of TCR values. As you increase the TCR number the mod box will power the coil for longer, reaching a higher temperature. Lowering it will reduce the maximum temperature. The main issue when using these coils is then finding a tcr value that accommodates for the heat being lost in transfer to the bucket or crucible. There are small gaps in between the coil and crucible and the crucible itself needs to be heated. Because of this the TCR number that heated your coil up will no longer effectively heat the bucket in a timely manner as there is more loss and more material to heat, the bucket will eventually stabilize a few degrees below the set temp but this can take a long time.
For the Sai atomizer it is often possible to leave the TCR value for the coil (TCR 260) and increase the temperature on the box by around 20c since the coil and bucket make such good contact. The increased temperature setting is required because the bucket is also in contact with the base of the atomizer which acts as a heat sink, sucking heat away from the bucket. This method stabilizes the bucket around 20c under the set temp and while drawing air through it will not overheat the bucket to the temp set on the box. We've found this is a better way of heating the Sai than using a TCR Value for it calibrated with the bucket as it more effectively avoids overheating the material. If you weren't happy with this the common TCR range for the Sai with Titanium bucket is between 300-340. We don't turn the temp up over 260c so avoid burning material even if we forget to take a draw from the atomizer! Resistance readings for these coils are usually between 0.68 and 0.72 depending on the mod and temperature everything was when you put it together. Our TCR number were calibrated at 0.7 ohms.
The DC V4 Crucible is a little different in the way we set it up. This is because it has slightly bigger gaps between the crucible and coil. The titanium crucible sits fairly close to the coil, is very thin and heats up quickly however the quartz crucible has slightly larger gaps and thicker, heat resistant material (the quartz). Due to these differing and larger gap sizes and different materials the same TCR does not effectively heat both crucibles in the same way... As this is an imperfect system there is a little compromise that occurs here between heat up times and temperature accuracy. For the quartz using a lower TCR number will mean it takes much longer to heat up, we've found 560 at 33w to be effective as it reaches around 200c in the first 10 seconds, then climbs up to the set temperature. While drawing air through it; in the next 10 seconds (a fairly long draw time) it will not overheat much past the temperature. To avoid burning the material with longer draws we leave the temperature set to 220c as this provides a range within 220-240c. For the titanium crucibles we use a TCR of 315- 345 at 33-40w and stick to the same temperature range, this heats the crucible up to temperature in around 5 seconds then slowly climbs by no more than 10-20c while drawing air through it over a 10 second draw. Left to heat indefinitely without air being drawn over the crucible these final temperatures will be higher. If you don't account for this and heat loss from contact issues the coil will struggle to heat the bucket especially while drawing air over it. If you have a coil that has particularly good thermal contact with the titanium bucket you can use a TCR of 270-280 at 40w, it will take a little longer to heat up but will get there and provide the most accurate temperature control. Resistance readings for these coils are usually between 0.45 to 0.51 depending on the mod and temperature the coils and mod were when installed. Our TCR numbers were calibrated at 0.48 ohms.
The DC V3.5 Atomizer is very simple as you're only working with the ceramic coil. For this setup we use a TCR number of 270 at 0.48 ohms set to 33w with the temperature between 220-260 depending on desired vapour production and material. With this setup it reaches set temperatures within two seconds and fairly accurately maintains them..
To revise - if your coil isn't getting hot enough or producing enough vapour due to having a lower coil resistance reading you need to increase your TCR number, usually by around 10-15 per 0.1ohms difference (from our stated ohms reading, above). If it's overheating and burning material due to a higher resistance reading the TCR number needs to be turned down. Remember to always start low and stick within the manufacturer recommended wattage settings while calibrating to avoid overheating your coils. If you're still having trouble please send us a message through whatsapp or our contact page (in footer).
Glossary of Terms
TCR number - thermal coefficient of resistance number - This tells the mod how the resistance of the coil changes as it heats allowing the mod to control the amount of input energy to control temperature.
Ohms/Coil Resistance - The ohms or resistance of the coil affects how much energy is required and for how long. This reading will affect the TCR number that needs to be input and is set automatically when attaching your coil and atomizer to your mod box.
Wattage - This affects the heat up times, higher Wattage settings increase heat up speed for any given TCR setting. The wattage should only be turned up one the TCR number has been found .
Temperature - We know you know this one but since we're here... The set temperature is the limiting factor when you're set up. Depending on your material vaping temps tend to range between 190-260C. At the lower end you will barely produce any visible vapour, if any; flavours will be at their best and any effects from your chosen aromatherapy material will be minimal. At the higher end you will achieve more complete vaporization with lots of vapour and stronger effects. Many people like mid-range settings between 225C and 240C which is where we generally advise people to start out..
Sneaky trick - if you don't have a thermocouple but make your own vape liquid or if you have it, you can put a single drop of PG into your crucible or bucket or a smear on your ceramic coil and set the temperature to 190C. If it starts to boil as it reaches 190C on the donut you know your temperature settings are within a fairly accurate range as PG boils at 188C. In a crucible or bucket you'll need to wait longer as the crucible material is heated by the coil, but you once again want it to boil gently in the crucible with the temp set to 190C. Always use PG first as it has a lower boiling point so if you've overshot your settings there's far less chance of damaging your coil. Once you're satisfied you can check it is fairly accurate over a range of temperatures by wiping the donut coil or bucket clean and adding a little VG in the same way; set the temperature to 295C (as VG boils at 290C) and wait for it to gently boil. If it goes crazy instead of gently boiling you'll need to turn your tcr down a little and try again.
Our hope is with the settings provided on product pages and this guide people will have a better understanding of their setups enabling them to accurately set up and customize their settings as desired. If you need further help or think we've missed something please message us either through whatsapp or our contact page (both in page footer).