# Help understanding E61 group thermometer with HX



## JonathanK (Feb 12, 2020)

Hi all,

I need help in understanding how to use a group head thermometer to achieve a specific brewing temperature on an HX machine.

I understand that when the lever is down the temperature that is displayed represents the group's temperature.
I also understand that when the pump is on and the lever is up the displayed temperature represents the temperature of the water coming from the HX.

However, i don't know how these two temperatures correlate to the brewing temperature.

For example:
* When the machine is idle for 30 minutes, the group head temperature is at 210F.
* When I start the pump, the temperature rises to 214F.
* No doubt a flush is needed.

* I flush until I see 193F, and start the preparation of the puck.
* Before I start brewing the idle temp is 195F
* I so another quick flush and the water temp is at 210F
* What will my brew temperature be ? I mean the temp of the water hitting the puck.
** will it be closer to 195 ?
** will it be closer to 210F ?
** will it be right in the middle ?

Any help and explanations would be great.
Thanks.


----------



## kennyboy993 (Jan 23, 2017)

It will be somewhere in the middle.

There's no accurate way of achieving a set temp with an e61 HX unfortunately - though you can get close with lots of practice and the temp probe you have.

Lots of discussion on here though generally comes down to:

1. If the group is hotter than the water in the hx then the brew temp will be higher than stated on the probe. 
2. If the hx temp is hotter than the group then the brew temp will be lower than stated.

This is because the big hunk of brass always wins thermally when water comes in to contact with it - indeed this is how a well tuned HX should never be that far away from a good temp.

In my experience the probe is more useful for determining what sort of flush the machine needs. For example if it's a modern ECM then it will be flush-and-go

Sent from my iPhone using Tapatalk


----------



## NJD1977 (Dec 16, 2014)

There are 2 ways of using the thermometer.

1. Flush and Go
2. Flush and wait

Erics did a lot of articles and study on how to use it. Just google that.

In option 1 the group is hotter than the water entering it and will heat the water before it hits the puck. (Thermometer reads lower than the water hitting the puck)

In option 2 the group is colder than the water entering it and will cool the water before it hits the puck. (Thermometer reads higher than the water hitting the puck)

I use option 2 which Erics recommends. Flush to 184degF. Wait around 3mins, pull when thermometer reads 197degF. The downside is you have to flush a lot to get down to 184 but it's more stable in outcome than using option 1.


----------

