Do PID espresso machines require flushing water before shot?

#1: Post by **matt1203** » February 17th, 2012, 5:48 am

Hi all. i know we do flush some water out on HX machine before making shots, but do we need to do the same on PID machine? since the temp is always at precise point.

#2: Post by **mitch236** » February 17th, 2012, 6:22 am

Yes. On my double boiler, I need to flush to get my group up to temp. The PID really only reduces the dead band (keeps the boiler within tighter temp range) but does nothing to stabilize anything outside of the boiler. On an Hx (correct me if I'm wrong since I don't own one), the flush is to get rid of the overheated water that's been sitting in the pipe within the boiler.

February 17th, 2012, 10:57 am

I'm not sure which direction the question is pointed at - hx or db machines ?

I have a db machine also. I would have to disagree with some of your info. If pid controls the boilers how does that overheat the group head ? (let's use an e61 machine for an example). Thermospyhon transfers temped boiler heat to the group for heat. After the group reaches heat soak that's it - no more.
Using boiler water to hurry group temp is understandable. On an hx machine all bets are off- you have two diff working temps within the same vessel. From what I understand - with no coffee consumed yet.

#4: Post by **mitch236** » February 17th, 2012, 11:00 am

kize wrote:I'm not sure which direction the question is pointed at - hx or db machines ?

I have a db machine also. I would have to disagree with some of your info. If pid controls the boilers how does that overheat the group head ? (let's use an e61 machine for an example). Thermospyhon transfers temped boiler heat to the group for heat. After the group reaches heat soak that's it - no more.
Using boiler water to hurry group temp is understandable. On an hx machine all bets are off- you have two diff working temps within the same vessel. From what I understand - with no coffee consumed yet.

It doesn't overheat the group head. What I said was I flush to bring my group head up to temp. The overheating comment was aimed at Hx type machines. I can't comment to machines other than mine but Lineas are known to have "cold noses".

#5: Post by **kize** » February 17th, 2012, 11:13 am

Ah. Understood.

#6: Post by **JohnB.** » February 17th, 2012, 11:17 am

It would depend on the group design. With a saturated group there is no need to flush the group as it is filled with boiler temp water.

#7: Post by **malling** » February 17th, 2012, 12:06 pm

John saturated groups are not exactly the most commen group in Prosumer machines.

these days you find Them in LM, KvdW machines etc. And they still need a 2-3oz cleaning flush.

The wast majority of us still need to flush our machines even if we have a DBPID, to get the group up to temprature.

#8: Post by **mitch236** » February 17th, 2012, 12:18 pm

JohnB. wrote:It would depend on the group design. With a saturated group there is no need to flush the group as it is filled with boiler temp water.

I've done fairly extensive temperature testing on my Linea (with Piero cap) and find that I need a 6 second flush to get stable brewing temps. I use a Fluke/Scace to make these measurements. The Linea has a saturated group but doesn't stay quite at brew temp.

#9: Post by **genovese** » February 17th, 2012, 12:54 pm

matt1203 wrote:Hi all. i know we do flush some water out on HX machine before making shots, but do we need to do the same on PID machine? since the temp is always at precise point.

This is so highly machine-dependent that it's hard to give an answer specific to your needs unless you also specify the machine. It's also somewhat dependent on what idle temp you maintain. If you had said "Silvia with Auber PID using setpoint 210F and offset 0" my answer would be "no."

#10: Post by **aindfan** » February 17th, 2012, 1:40 pm

On my Elektra HX, the boiler temperature is PID controlled, but I keep the set point such that a flush is required. I do, however, have the option to set the boiler temperature low such that a 1 oz flush would be sufficient to start pulling the shot.

I think there was a thread titled "one and a half boiler HX" but I'm having trouble finding it... please post a link if you know what I'm talking about!