# Problem with MaraX + flow control



## Tjyven (Jun 14, 2021)

I installed the flow control from Coffee-Sensor on my MaraX and now I have big problems with my machine. The installation was simple (did not change the preinfusion spring) and at first everything seemed ok. The normal stock flow is about 5ml/s and with the flow control I could reach about 8 ml/s. After just a short the while I noticed that the flow rate started to decrease and the machine also got hotter, you could say that less water came out but more steam. I stopped using the flow control and changed back to the original set up. However the machine is still too hot and most steam comes out when starting the pump so it is impossible to use it. I have the machine in brew mode (1 on the side) and temperature at 0.

Anyone knows what went wrong and how I can solve this?


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## DavecUK (Aug 6, 2013)

Is this straight after warming up or after the machine has been on 35m


What pressure shows on the boiler pressure gauge


Does your phone do video? If you have the YouTube application to video/upload an unlisted video to YouTube and link to it here. It's free, so don't worry about having a video longer than 10s or of high quality.


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## Tjyven (Jun 14, 2021)

Thanks for answer!

During warm up the pressure can go very high (guess 2,5 bar) but that is normal for this machine but after warm up the pressure is constantly at about 1,5 bar which is not normal in brewing mode, usually drops down to about 0,5 bar.

I will try to do a video later today, is there any specific things you want me to do while recording?


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## Tjyven (Jun 14, 2021)

Here is a video:


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## MediumRoastSteam (Jul 7, 2015)

The pressure is at 1.5 - suggesting, to me at least, the machine is not stable just yet. I'm not surprised that's happening. Does the same happen if you leave the machine idling for 30 minutes from turning on?

Also, to me, it seems you have a very restrictive flow on the group.


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## Tjyven (Jun 14, 2021)

The pressure at the machine is still the same, just little below 1,5, since the problems started the pressure stays there. The flow rate is also very low, that is another symptom.


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## MediumRoastSteam (Jul 7, 2015)

Are you sure there isn't any residual/blockage on the jet? Doesn't seem normal.

Also, you say your machine stays at 1.5 bar (just below). In coffee mode, it should fluctuate. Are you sure it's in coffee mode? What happens when you flip the switch?


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## Tjyven (Jun 14, 2021)

Yes I am sure it is coffee mode, Ive had it on 1 all the time and has worked until now. I changed to steam mode now and there the pressure is little lower, around 1 bar, but still very low flow and lots of steam coming out.

Where should I look for residual/blockage? That could probably be the reason for this behavior.


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## DavecUK (Aug 6, 2013)

@Tjyven Just an initial guess, but the HX looks as if it's empty....hence all the steam, the temperature sensor in the thermosyphon circuit might well not read right because of that. Especially as it will flood the HX with cold water....everything gets thrown off.



Do another Video and run that pump until you get a flow with no steam (that will show what the flow rate looks like


Then try it again in HX mode on zero (as on this mode you should definitely be able to flush the HX down)


Also run a shot against a blind filter


At the moment I think the HX may not be completely sealed, and gradually emptying...especially as the behaviour coincided with doing something to the group.

*P.S. if you can never get enough flow to flush it down...then there may be a blockage, which would cause the HX to be empty, or have a lot of steam...and similar problems around temperature control, because the HX temp sensor is seeing weird stuff. *e.g. not enough flow, no pressure in HX, water flashes off to steam...etc.. etc..


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## MediumRoastSteam (Jul 7, 2015)

@Tjyven - I take there isn't a puddle of water under your machine? Have you done the OPV divert mod?

The reason why I ask about the puddle of water is that the machine has a tap to drain the HX. It is accessible via a hatch under the machine. I was wondering whether the tap could be open, but I assume you'd have spotted it by now.


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## Tjyven (Jun 14, 2021)

@MediumRoastSteamI have not done the divert mod and no water under machine.

@DavecUK Here is video where I run it longer. What actually happens is that after about two and a half minute the flow stops even though there still is water in the tank.


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## Tjyven (Jun 14, 2021)

After this last video the pressure dropped to about 0,5 bar but when starting the pump there were still no flow.


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## DavecUK (Aug 6, 2013)

don't run the pump that long again, there is a thermal fuse on the pump. By flushing down I meant in under one minute you should have been down to just water, no steam. to me it looks as if water simply isn't getting into the HX. The whole temperature issue is potentially a red herring at the moment, and probably an effect of the HX being empty.

*If you have not done the expansion valve divert mod, is water pissing out of the expansion valve tube into the drip tray with nothing much coming out of the group?*

If you don't know, remove the drip tray grid and video that area for us.


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## Tjyven (Jun 14, 2021)

@DavecUK Not sure if I understand correct, you want me to just remove the drip tray grid so you can see how much water there is in the drip tray, and start the pump also?


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## MediumRoastSteam (Jul 7, 2015)

@Tjyven - Empty the drip tray. Run the test. Catch the water from the group with a container. While you are doing that, do you see water entering the drip tray?


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## DavecUK (Aug 6, 2013)

It will indicate the probable location of a blockage...or even the possibility of a failed pump.


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## Tjyven (Jun 14, 2021)

@DavecUK There is no water entering the drip tray. Lower pressure now.


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## DavecUK (Aug 6, 2013)

Do you have a filter installed, if so, remove it. Try again.

If that doesn't help, check the water tube from pump (inside machine) is not kinked or pinched. Also remove the tank and check that there's no debris or anything blocking the inlet where the tank plugs in.

Finally, draw some water from the hot water tap about 200ml and when it tries to refill see if the water level in the tank drops.


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## Tjyven (Jun 14, 2021)

@DavecUKI have looked inside it and as far as I could see it looked ok. I removed the filter and started the pump and the flow was still very low. Then I flushed about 200ml from the tap and after that the machine seems to work normal again. Got flow rates of about 5ml/s and not a lot of steam as earlier. Do you have any idea what could have been wrong and how could that have solved the problem?

All the problems started when installing the flow control so now I dont know if I dare to install it again even though I really would like to try using it. Saw someone saying that you should not use a flow rate that is higher than the stock flow. Is that correct? Since the MaraX has a very low flow rate, about 5ml/s (which I usually think is good) it limits the use of the flow control if I cant go up to flow rates of about 8 ml/s which is possible with the flow control.

I am very thanksful for the help you are giving me @DavecUK and @MediumRoastSteam.


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## MediumRoastSteam (Jul 7, 2015)

Tjyven said:


> Then I flushed about 200ml from the tap


 You are welcome. When you flushed water through the tap, did you hear the pump filling the boiler? I'm wondering whether you had a sticky diverting solenoid or something? Dave is the best person to give you possible insights as he knows the machine like the back of his hand.


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## Tjyven (Jun 14, 2021)

@MediumRoastSteamI actually dont remember if I heard the pump but the water level in the tank immediately dropped.


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## DavecUK (Aug 6, 2013)

@Tjyven As you asked, yes, I do have some educated guesses as to the problem...which was definitely an empty or almost empty HX. When empty, everything inside simply trieds to flash off to steam when you lift the E61 lever.

Probably a bit of something caught in a solenoid valve perhaps and has hopefully entered the steam boiler (where it will most likely stay forever, doing no harm). It was probably blocking the beginning of the brew circuit before.

In the screenshot from my review



A is the solenoid that depressurises the brew circuit (so the gauge flips back to zero) one of those Lelit things they do


B is the expansion valve


C is the autofill solenoid


If C had been blocked to the brew circuit, water would have pissed out of B (but you said it wasn't doing that)?

If A was blocked to the brew circuit, *then water wouldn't come out of B, which is what you observed*.

By rights, if A was blocked, then C shouldn't have been able to autofill the main boiler. *It's possible though that the decreased resistance of filling the main boiler dislodged any obstruction from A.*









P.S. Probably clear as mud but if you work through it, the logic is there.


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## Tjyven (Jun 14, 2021)

@DavecUK I dont understand all the details but I see it as a circuit and depending on where in the circuit there is something wrong we will get different symptoms. Will try to find some sort of blue print and get a better understanding.

Do you think it was just coincidence that this happened just after installing the flow control or could that have caused this error?


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## DavecUK (Aug 6, 2013)

@Tjyven Coincidence


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## Doram (Oct 12, 2012)

Tjyven said:


> @DavecUK I dont understand all the details but I see it as a circuit and depending on where in the circuit there is something wrong we will get different symptoms. Will try to find some sort of blue print and get a better understanding.
> 
> Do you think it was just coincidence that this happened just after installing the flow control or could that have caused this error?


 FWIW, I am running the Coffee Sensor on the Mara X and didn't have this issue. I understand your concerns after this experience, but if Dave says it has nothing to do with the flow control then that would be enough for me to give it another try. If the issue does return, hopefully you can solve it again by flushing water from the wand.


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## Tjyven (Jun 14, 2021)

@Doram Yes I will give it a try again soon.

May I ask if you have any favourite profiles so far? Also curious how high flow rate you have at maximum? Guess the stock flow rate of the MaraX is very suitable for the medium roasts I prefer but maybe sometimes it would be good to get a little higher flow rate.


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## Doram (Oct 12, 2012)

Tjyven said:


> @Doram Yes I will give it a try again soon.
> 
> May I ask if you have any favourite profiles so far? Also curious how high flow rate you have at maximum? Guess the stock flow rate of the MaraX is very suitable for the medium roasts I prefer but maybe sometimes it would be good to get a little higher flow rate.


 I am still playing, but this is what I have been doing so far:

The first thing I can say is the range I use is about 3/4 of a turn of valve, not more than that. The max I go on the open side is about one full turn from the fully closed position, which I think gives a flow similar to the stock mushroom. The max I go on the closed side is about 1/4 of a turn from the tap being fully closed (when I say fully closed, I mean when you can't turn the tap anymore, not when you don't have any flow. I find that for about 1/4 of a turn from the fully closed position there is no-to-very-little flow, so I just go down to the 1/4 turn position, as I never actually want no flow at all. Also note that when I say fully close - I mean when I just start to feel resistance from the valve. I never close it hard, and I always try to be gentle with it).

As to profiles I use, it depends on the coffee and what I want to achieve with the flow control. If I use a very dark roast, for example, and want to tame down harshness/bitterness, I will ramp up the flow quite quickly and then gradually reduce the flow (is this lever-style profile?) to avoid the bitter/burnt flavour.

For a medium roast I will try to extract more from the coffee, so would lift the lever and after a couple of seconds almost close the tap to get a nice, long pre-infusion (10-20 seconds to first drops). I would then ramp up gradually and maybe just reduce flow a little once the puck starts to degrade and shot speeds up, to try and keep it at a steady flow.

Grind and channelling can also be a factor. If the shot doesn't come to one stream, or looks like it's degrading in some way, I will slow the flow to try and reduce the damage and get a nicer pour - this sort of thing.

As I said, this is all preliminary play. I am not an expert and just playing with it. If anyone knows more, or if I am doing it all wrong, please give me a shout.


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## DavecUK (Aug 6, 2013)

@Doram Try, opening it to your maximum and ramp to 10 bar, then gradually drop it to 7 bar of 30 sec (set the grind to give you the ratio required in thet time, I use 1: 2 ish, but not less).


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## Doram (Oct 12, 2012)

DavecUK said:


> @Doram Try, opening it to your maximum and ramp to 10 bar, then gradually drop it to 7 bar of 30 sec (set the grind to give you the ratio required in thet time, I use 1: 2 ish, but not less).


 Thanks Dave. I can't go to 10 bar, OPV is set to 9... 🙂

It was interesting to learn the relationship between flow and reassure. For example, I can open the valve to a very low flow and still the pressure goes all the way up to 9, just takes a little longer to get there. So now I shifted from thinking about pressure to thinking about flow - lowering the flow does decrees the pressure, of course, but it is like the pressure is a secondary variable to the flow, if that makes sense.


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## DavecUK (Aug 6, 2013)

Doram said:


> Thanks Dave. I can't go to 10 bar, OPV is set to 9... 🙂
> 
> It was interesting to learn the relationship between flow and reassure. For example, I can open the valve to a very low flow and still the pressure goes all the way up to 9, just takes a little longer to get there. So now I shifted from thinking about pressure to thinking about flow - lowering the flow does decrees the pressure, of course, but it is like the pressure is a secondary variable to the flow, if that makes sense.


 I understand what you are getting at, but there needs to be a little care taken. A liquid is incompressible at the sort of pressures we are talking about. Even at the bottom of the Mariana Trench, water density is only increased about 5% due to the extreme pressure over 1000 bar (16000 PSI).

This means theoretically, if you imagine a "ideal" espresso machine with a blind filter loaded and set to 9 bar via an expansion valve with no leaks, or metal expansion, or temperature change. It would go from 0 bar when full of water, to 9 bar as the next *drop* is added. If the expansion valve was set to 100 bar and the pump capable of it...then it would go to 100 bar when the next *drop* is added. The relationship between pressure and flow breaks down in that respect in a static system. *An espresso machine with coffee is essentially a dynamic system, with an extra "expansion valve" made out of coffee.*

Now imagine an "ideal" the coffee can only flow 0.5 ml per sec. In a machine with an expansion valve set to 9 bar, if your pump delivers (with the excess dumped via the expansion valve):



0.5 ml per second, your pressure is 0


0.6 ml per second, your pressure is 9 bar


0.7 ml per second your pressure is 9 bar


1 ml per second your pressure is 9 bar


The problem comes with the increasing permeability of real coffee and the compressibility of the puck, especially when dry, it compresses much less easily when wet. The same chart might look like this as the flow rate remains the same but the shot progresses



0.7 ml per second, your pressure is 9 bar


0.7 ml per second, your pressure is 8 bar


0.7 ml per second your pressure is 7 bar


0.7 ml per second your pressure is 3 bar


You can reduce or increase flow to *maintain* pressure, but when at 9 bar, you cannot increase flow beyond what the puck will transmit, as it simply shunts out of the expansion valve.

You cannot know *where you are with flow *in the first list when the pressure is at 9 bar, without experimenting with the paddle. When you do, you are chasing a dynamic situation that changes all the time. If you try and control purely by flow using some sort of theoretical meter...then the pressures would be completely dictated by what was happening in the coffee puck

=====================================================

It's always going to be a balancing act....if you want certain pressures at certain points within the extraction, you have to measure the pressure using the MK1 human eyeball (MHE) and adjust the flow as required to maintain or reduce those pressures. Here, you don't care about flow, you care about pressure

If you don't care about pressure, you can use any grind you like and just alter the flow to get whatever volume you want over any specified time. Here, you only care about flow and disregard pressure

====================================================

now comes the issue of "normalisation", without this, grind, flow rate and results can be way out of the ballpark....in a sense the "expansion valve" setting of the coffee puck can be way out.

take an "average" coffee, set an average flow rate 3ml per second ish (because 90ml of water might be used to make 40g of espresso)...then set your grinder to maintain 9 bar for almost the whole extraction...it might drop a little towards the end. Note the position of the paddle..*.you are now in the ballpark for grind, pressure and espresso production.*

Then try and make your variations around that point. If you don't do this, you might find your grind/flow are so far from a reasonable range that the results are not as expected or desired. This is because a certain pressure is required to make espresso and that "desired|" pressure changes as the extraction progresses. *Arguably pressure is the most important variable to control, as long as you are maintaining sufficient flow (a product of grind)*

*Ideal (perfect)*: used to describe an espresso machine, coffee, or other thing that works theoretically perfectly, with no loses, leaks, hysteriesis etc.. Such a system does not exist and is just used to illustrate the physics


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## Tjyven (Jun 14, 2021)

I still of course havent any experience of flow controlling. Mostly been watching som videos on youtube and even though I think the MaraX stock flow rate of 5ml/s often is very good I think we can gain by sometimes using a higher flow. I dont know if you seen this movie 



? Is rather long but you could jump to about minute 20 when they start talking flow rate. They talk about both roast and age of the beans and to put it simple it seems as darker and older beans need higher flow rate and then the opposite for fresher and light/medium beans.

@Doram Did you change the preinfusion spring?

@DavecUKDo you know if changing the preinfusion spring to a stiffer one also will give a higher flow rate?


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## DavecUK (Aug 6, 2013)

Tjyven said:


> @DavecUKDo you know if changing the preinfusion spring to a stiffer one also will give a higher flow rate?


 It will not give a higher flow rate.


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## Doram (Oct 12, 2012)

Tjyven said:


> @Doram Did you change the preinfusion spring?


 I did change the bottom spring. I am still learning how to use the flow control device. I think I can reasonably imitate the original pre-infusion with the stronger spring, or go for a slower pre-infusion if I want to. I didn't try light roasts yet (usually prefer darer coffee), so can't say if I get better results from it compared to the stock spring, but I think it isn't worse either.


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