# Noob PID/flush question



## NJD1977 (Dec 16, 2014)

Without really thinking why I'm doing it, I have still been giving the group head a short flush (2-3seconds) 60seconds or so before pulling a shot on my classic. I have a PID fitted, and seem to regularly encounter sourness in my shots despite trying tons of different brew temps. This may be a result of introducing fresh cold water into the boiler shortly before pulling a shot.

So my question is, is a group head flush needed on a classic with PID fitted immediately before pulling the shot......and if so why? I seem to recall the main purpose of the flush was when temp surfing to force the boiler to kick back in etc.


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## Mrboots2u (May 10, 2013)

What does the water coming out look like when you flush ? Flash boiling ...

What is the PID set to ?

Sourness = under extraction, could be channeling, extraction temp to low.....or a combination of all three...

What happens if you don't, prior to extraction flush, and pull the same bean , same sourness in the cup ?


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## NJD1977 (Dec 16, 2014)

I have the PID set to 93deg with a SC of -9.8degC, so its set to 102.8deg at the boiler casing.

The water just looks like water, obviously very hot water, with some steam etc.

I'm going to try a shot without a flush and report back.


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## Mrboots2u (May 10, 2013)

NJD1977 said:


> I have the PID set to 93deg with a SC of -9.8degC, so its set to 102.8deg at the boiler casing.
> 
> The water just looks like water, obviously very hot water, with some steam etc.
> 
> I'm going to try a shot without a flush and report back.


Ok cool ...try same dose - weight out - time if possible , note it all down , plus don't forget to taste ....


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## NJD1977 (Dec 16, 2014)

Test done. Problem found. The shot was waaaaaay nicer. Almost no sourness (I suspect what little there was, was maybe just the slight citrus notes of the LSOL beans I'm on).

I will have to have another now!


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## Mrboots2u (May 10, 2013)

NJD1977 said:


> Test done. Problem found. The shot was waaaaaay nicer. Almost no sourness (I suspect what little there was, was maybe just the slight citrus notes of the LSOL beans I'm on).
> 
> I will have to have another now!


Problem was.......?


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## NJD1977 (Dec 16, 2014)

Mrboots2u said:


> Problem was.......?


The flushing pre shot. Its cooling the water inside too much.

I thought this was a standard procedure for the classic but now I'm going to flush when I first fire up the machine and then not again until I pull the shot.

Amazing difference.


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## marcuswar (Aug 19, 2013)

Moot point, but my guess would be it's not the flushing per sea but the fact that you're not then allowing anytime for recovery after the flush.

When I flush my ISOMAC E61 (non PID) machine (to cool down the brewhead) I have to then wait 6-8 seconds after the flush for the brewhead to recover some heat from the thermo syphon.

On the classic the flush is only part of the ritual. The flush is to lower the temp enough to cause the heating elements to kick in and then to wait for it to get to it's top temperature (elements off) so yo are at known point in it's heating cycle ; at that point I would then flick the steam switch for a few seconds to bring the water even higher to compensate for the sudden inrush of cold water when the brew switch was flicked.


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## bronc (Dec 10, 2012)

There is no need for him to flush his Classic as it has has a PID.


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## NJD1977 (Dec 16, 2014)

marcuswar said:


> Moot point, but my guess would be it's not the flushing per sea but the fact that you're not then allowing anytime for recovery after the flush.
> 
> When I flush my ISOMAC E61 (non PID) machine (to cool down the brewhead) I have to then wait 6-8 seconds after the flush for the brewhead to recover some heat from the thermo syphon.
> 
> On the classic the flush is only part of the ritual. The flush is to lower the temp enough to cause the heating elements to kick in and then to wait for it to get to it's top temperature (elements off) so yo are at known point in it's heating cycle ; at that point I would then flick the steam switch for a few seconds to bring the water even higher to compensate for the sudden inrush of cold water when the brew switch was flicked.


The last bit was my question really. If the flush is purely for temp surfing purposes then it makes no sense to do it on a PID modified machine. Am I correct? Or does the flush serve some other purpose?


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## marcuswar (Aug 19, 2013)

As far as I know the flush on the Classic is purely for temp surfing. Although if yours was PID'd as bronc says, then there was no need for it at all.

On an E61 HX machine, my understanding is that any flush is to stabilise the temperature of the E61 brewhead. which depending on the machines design could run hot (or cool).


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## marcuswar (Aug 19, 2013)

Eric's E61 thermometer would show you the behaviour of the temperature of the water at your E61 brewhead. They are a bit expensive to buy (~£80-100) just to have a look see though.

http://www.chriscoffee.com/E61-Group-Digital-Thermometer-Adapter-p/sss-04.htm


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