60L Fermenter temperature control

[BrewerBen]

I'm in the middle of some brewery upgrades and am currently testing out the heating part of my 60L fermenter and i am measuring quite a large temperature differential between the top of the fermenter and the bottom 14C at the thermowell and 18C towards the top. What i'm using for heating is 2 flexible reptile heating mats of 25W each strapped to the side of the fermenter. I currently use a 25W heat mat for my 30 litre fermenter and it works very well so i thought 50W would be enough for a 60L fermenter. The problem is the mats are stuck on the fermenter a bit higher than i'd have liked as they were not as flexible as i expected so had to put it on the least curvy part and the thermowell is fitted towards the bottom as there is a convenient flat recess. Pic of the fermenter is below:

Cant really see the heaters but they are between the 2 straps:


I guess my question is do i need to worry about this and fix it? The water went in at at the temp it came out the tap and i have the heaters on to see what temp i can get it up to just as a test but when i brew a beer the wort will be going in at the target temp and the heaters are just there to maintain it, also would fermentation help even out the temp?

[Donald]

I think the key thing here is to reduce heat that the fermenter loses in the first place: Insulate the sides with camping mat etc and the temperature throughout will be far more even.

[BrewerBen]

Ok so i wrapped it up as below and got the water temp to 20C and gave it a good stir until the temp was even and left it overnight without the heaters on. The next morning the temp from the thermowell was 16.8 and 17.2 from the top of ther fermenter. I turned the heaters on for a few hours and the temperature from the thermowell was still 16.8 where as sticking the probe in the top of ther fermenter gave 22C.



I think i'm going to abandon the heater mats and switch to using a heater cable then i can spread it more evenly and towards the bottom of the fermenter so that the thermowell gives a more accurate reading of the wort temperature (i hope).

[Rad]

Since heat always raises up, I would try to lower the mats. Let the physics take care of the rest. Have you tried putting the fermenter on the mat? Don't know how flat the bottom is.