I've been using my new Icemaster Max 2 since last winter to regulate temperature of my two Spike CF10 conical fermenters that have attached heaters. I made the mods to power the heating pads directly using the Icemaster's internal power supply with spliced wires from internal extension cords connected to the relays. I only have the female ends of the extension cords sticking out of the unit, so it's a pretty clean look and works pretty well.
I've been able to maintain pretty tight temperature regulation of about +/- 1F, with occasional negative temp deviations, as measured and recorded by my Tilts floating on top of the liquid. I noticed that now that the weather is getting warmer, I've been getting more of the of the negative temp blips so the total temp swings are +/- 2F from the set point (as shown in the chart with the batch that is now fermenting). As some others have noted in this forum, I think that the chiller is cooling the liquid in the fermenter faster than the probe in the thermowell can react to, so the temperature undershoots before the coil pumps turn off. During the cooler months, I guess my fermenters were cooling naturally from the lower ambient temperatures, and just cycling the heating pads to maintain the temp around the set point and maintain a tighter regulation.
To tighten up the regulation, recently I've tried to increase the reservoir temperature to reduce the cooling differential, but it didn't help too much.
I'm considering to try a longer thermowell, one that comes closer to the coils than the 4 inch ones that I'm using now, so that the Icemaster's controller can react faster to turn off the coil pump. Has anyone else tried this? I can live with the temp swings that I'm getting now, but would be happier if they were tighter.