Thermometer temp errors out in my cold shop

[pswindler]

In the mornings my shop is cold, and it errors out my temperatures. so i have to pre-warm the hotend and bed with a heat gun before it will let me print. the led screen says "def" for both temps. it looks like it errors out at temps below 18*c. is there a way i can lower the temp it errors at so i can start prints in the cold?

[geneb]

It's probably better in the long run to pre-heat a bit as you've been doing rather than disable a safety feature.

g.

[IMBoring25]

It could be worth at least looking to see what MIN_DEFECT_TEMPERATURE is in configuration.h. The default for 0.92.9 is -10, which shouldn't be problematic.

[Xenocrates]

I've faced the same issue. I believe the setting is MIN_DEFECT_TEMPERATURE, which is set to 18. Note that the way we've adjusted the thermistor profiles, they are quite inaccurate at room temperature and below. I also agree with Geneb that disabling the feature, or reducing the sensitivity is a bad idea. I recommend that you build an enclosure with a separate temperature controller and some form of heater (reptile warmers, flat panel ceramic convection heaters, ETC, just not propane or something please), and leaving that running at a relatively low temperature overnight, and turning it up while actually printing. You'll have less trouble, and better quality prints.

If you install PEI, do not use a heatgun on it. I learned that the hard way, and now said PEI sheet was given away to be turned into a bed for a smaller printer. Instead, unclip the bed surface, and put your thumb over the thermistor location. Then once it stops erroring, get it to start pre-heating and up to ~50C before you put the build surface back. I also dis-recommend it for the hotend, due to the potential to warp the effector, ball joints, or tensioning springs.

[pswindler]

So why would lowering the temperature it errors at, effect the temperature accuracy while printing? not sure i understand that??

[IMBoring25]

It wouldn't affect anything while printing except it would reduce the instances when the protection would trigger. If the thermistor went to a dead short you'd still be fine but if the short had a resistance between the resistance that corresponds to your current setting and the resistance that corresponds to your alternate setting the protection would not trigger and you risk thermal runaway.

[pswindler]

ah i get it, if the thermister broke and no current was going though it it would show a very low temp, that 18*c is just high enough that the thermister has to be working to go to that range in resistance. Do you think it is safe to just lower it a few degrees? what is the safety margin they used?

[IMBoring25]

SeeMeCNC is usually pretty conservative with stuff that has the potential to affect safety. As I said, the default on the Repetier 0.92.9 configuration tool is -10. Personally I'd probably follow the advice to let it nudge you to a heated chamber. Printing in ambient temperatures below 18, you're going to have a lot of problems with warping, peeling up, and cracking.

[pswindler]

so i just plugged in a completely open lead into the thermister slot, and it came back as 7* c so -10 would be pointless as a safty, so it looks like they put a safty margin of 11*c so i feel comfortable lowering it to 15* c.