For those that own GS/3's I'm curious what the offset is? I have had to make a few adjustments to mine but I still don't think that it is correct. From the factory mine was at 2.5F, but shouldn't it be more like 5-7F?

Mine from the factory is set to -1.4C (-2.5F)

No, unfortunately I don't have a Scace. Im measuring with my taste buds only. I was playing around with a dark roast coffee the past few days with a friend of mine, and we both confirmed that the coffee was indeed better at 205 than at lower temps. The shots were much richer, fuller and more nuanced. l've also found this to be the case with other coffees. I have this belief that shots will be scorched and bitter if they are pulled above 204F. Maybe some blends/beans are just more tolerant to higher temperatures than others. Has anyone else had this experience?

The GS3 offset should only be set using a Scace device or something at least as precise. The offset is only in the software to allow you to match the display temp with the temp of the water exiting the group.

There is a slight difference in temperature from where the temperature probe is to the water exit of the group. Additionally the offset is a bit subjective also because measuring temp in the 1/10 range is really not that easy. It may display in the 10's on the measurement instrument but that alone does not guarantee precision to that level.

Bill

danetrainer wrote:Are you measuring your brew temp with a scace.

That's how you have to do it. The offset is a measure of the heat loss between the sensor location, which is at the top of the brew boiler, and the group head. That can vary from machine to machine, so LM measures it at the factory and adjusts the offset accordingly.

Generally speaking, it should be a negative number. It would be unusual for the group water to be hotter than the boiler water. Mine was set to -4F. At one point I measured it with a Scace and found that -3F was closer to the actual temp at the group head.

I wouldn't obsess about the offset. The issue isn't so much the absolute temperature number as the stability and predictability of the temperature through the shot. On my machine, the temp actually rises a bit during the early part of the shot, then levels off. That makes sense, as hotter boiler water is coming into the group at that point.

In theory, the absolute temperature might be useful for setting your machine to the brew temperature recommended by the roaster. But it's unlikely that they're brewing under exactly the same circumstances as you are, and who knows what machine they're using, how its temperature is calibrated and how stable the brew temperature is through the shot?

I use the roaster's recommended temperature as a guideline for setting the ballpark temperature. I know if they recommend 200F-201F, I need to set the GS/3 towards the higher end of the scale, and if they recommend 196.5F, I need to set it to the lower end of the scale. From there, the fine tuning has to be done by taste, and then the absolute temperature reading is only important for being able to return to the same setting later. It could, in fact, be off by a degree or two from the actual temperature at the group head, but that doesn't matter.

Javacat wrote:No, unfortunately I don't have a Scace. Im measuring with my taste buds only. I was playing around with a dark roast coffee the past few days with a friend of mine, and we both confirmed that the coffee was indeed better at 205 than at lower temps. The shots were much richer, fuller and more nuanced. l've also found this to be the case with other coffees. I have this belief that shots will be scorched and bitter if they are pulled above 204F. Maybe some blends/beans are just more tolerant to higher temperatures than others. Has anyone else had this experience?

Important question: when you say 205F, are you referring to the temperature you set the brew boiler to in the menus or to the temperature reading displayed on the panel just before you pull the shot?

What you say makes sense if you're talking about the temperature you set the brew boiler to, because it's going to be a few degrees cooler at the group head. Probably an actual temperature there of 201F-202F. That would make sense for a typical blend, somewhat updosed.

But if you're referring to the temperature displayed by the GS/3 on the panel before you pull the shot, then 205F is quite high. If that's the case, then your temperature offset needs adjustment. Despite what I said above, it's best to try to get the offset in the ballpark so your temperature number at least makes sense relative to temperature guidelines published by roasters. For that, you'll need a Scace. You may be able to borrow or rent one. If you can't do that, my guess is that an offset of -2 to -5 is probably correct.

To answer your question, some blends/beans/roasts may be better at higher temperatures. Temperature tolerance is also influenced by contact time and thickness of the puck, which are functions of dose, grind setting and basket geometry. The thinner the puck and the longer the contact time, the greater the chance of burning the coffee.

Most of the roaster guidelines I see fall into the 199F-201F range, usually with doses in the 18g-22g range. With some of the light-roasted Terroir coffees, the recommendation has been to dose low, say 14g, and set the temperature to about 196.5F. That range, roughly from 196F-202F is where I pull virtually all coffees. The only departure has been for Vivace Dolce, where the consensus was to pull it at around 203F. That's a dark roast and some of the beans in the blend aren't of premium quality.

Peppersass wrote:In theory, the absolute temperature might be useful for setting your machine to the brew temperature recommended by the roaster.

But strangely you have to do the compensation yourself when entering the value!?

For years I ran with an offset = 0. Now I use the nice (easy) round number of -2dgC just to have some more 'trustworthy' numbers to look at (and it's close enough as a starting point when following recommendations).

The 205F is the reading on the display. The boiler is set at 209F. I do run my machine in the basement which tends to be a bit cooler than the rest of the house. Last time I checked it was around 68F which might be causing more heat loss at the head than the factory where it was tested.

I would not say that the offset is for heat loss. It is really there to compensate for errors in the electronics and probe and also to account for a temperature differential. The differential is not because of heat loss it is the result of a different location. There is a temperature gradient throughout the boiler and is a different temperature every place you measure.

The electronics have some adjustment and are calibrated at the factory. The probes have some error associated with their manufacturing also. There is even some error associated with where the wire is routed. These errors do not necessarily affect the precision of the system but they do affect the accuracy. Therefore there is an offset in the software to account for this. The number can be + or -. Normally it is a negative.

BillC