# Modded Severin: Struggling to reach high temps with fan over 50%



## jamie723 (Jan 2, 2021)

Having just modded my Severin according to the instructables article below, all is working apart from I am struggling to reach higher temperatures when the fan is above about 50%.
https://www.instructables.com/Arduino-controlled-DIY-Coffee-Roaster/

This is problematic as I really would like the fan on high to keep the beans moving, but am having to turn it down and then stir manually to get over about 120 degrees C and towards first crack.

Just wondering if this is to be expected with the modded popper or if I may have done something wrong in the build.

A bit more info for reference (measured with DMM):
18V PWM going to the fan
230V going to the primary heating coil (42 Ohm) controlled by the SSR

An image of my first roast profile as well here as well -


http://imgur.com/m5t2PJN


Naturally this went longer than I would have liked but was cut off at about 15 mins. You can see though that I had to keep stepping down the fan in order to push the heat up whilst the heat was set to 100.

Also was using about 70g of beans.

Thanks in advance


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## El carajillo (Mar 16, 2013)

Possibly the fan is too powerful for the heat source ? and over cooling. Is it being used in a cold area ?


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## jamie723 (Jan 2, 2021)

Hey. Being used at room temp in my kitchen so I think should be OK. My first attempt was without the plastic housing. I've added that back on now for some extra insulation but it doesn't seem to make much difference.

I agree it looks like the fan is cooling too effectively for the heat source. Before modding it would get to first crack in about 4 mins indoors though which if I am correct should be approximately equivalent of both fan and heater on full power in my current setup.

The major difference on the heating is that I'm now putting mains voltage across only the primary coil, whereas before the mods it was split across the primary and secondary coils at 42 and 7Ohms respectively.


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