La Marzocco Linea Mini - Erratic Steam Boiler Behaviour

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
JDA1987
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Joined: 2 years ago

#1: Post by JDA1987 »

Hi,

I've had my LM for about 9 months now (Feb 2022 purchase but installed in July 2022) and I've really been enjoying my machine. I've connected it to the latest app and updated the firmware to the most recent version.

Machine is on an auto on/off schedule daily to start at 6:15am since I first installed it. It's been running flawlessly until about 2 weeks ago.

The first time I noticed something was off was when the machine started according to the auto on/off schedule, both boilers warmed up properly and according to expectation. Later in the day, machine turned off. I went to do some errands and started back up the remotely machine using the app. When I arrived home, coffee boiler was up to temp but steam boiler was off. My first reaction was to think that the remote app did not send the right command. I contacted LM IoT team and they confirmed the app sent the right instructions and they could see the steam boiler on. Two hours later, the steam boiler got up to temp.

Then, I noticed that on some mornings, when the machine turns on according to the auto on/off schedule, the steam boiler doesn't start. Or when it starts, it warms up a bit, builds pressure to ~0.8 psi and then doesn't move up. If i open the steam wand, pressure falls back and doesn't build up again immediately. I may have to wait an hour or two and the boiler will restart.

Sometimes, the boiler starts just fine.

Any idea what could cause this? I did contact my LM rep, but perhaps there is a quick fix out there?

Thanks

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Jake_G
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#2: Post by Jake_G »

The mini uses a pressurestat signal to the control board for the steam boiler, so it's a pretty simple circuit. The control board looks to see if the pressurestat stat switch is open or closed and sends power to the heating element accordingly.

Here's a shot of the diagram that comes with the connected retrofit kits:


I'd check to see if the pressurestat contacts are sticking closed and telling the control board that the boiler is already up to temp when it isn't yet.

Otherwise, I'd wager that the output on the board is flaking on you.

Cheers!

- Jake
LMWDP #704

JDA1987 (original poster)
Posts: 8
Joined: 2 years ago

#3: Post by JDA1987 (original poster) »

First, thanks to the mods for moving the thread in the right section.

@Jake_G, thank you for the help, a few follow-ups.
1) I would have to check again, but I believe that when the steam boiler is not functioning, the coffee boiler is. Are they controlled separately and not by the pressurestat?
2) What am I looking for in a faulty pressurestat? I'll get my multimeter, am I looking for a resistance across the pstat contacts?

beans+crumble
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#4: Post by beans+crumble »

JDA1987 wrote: 1) I would have to check again, but I believe that when the steam boiler is not functioning, the coffee boiler is. Are they controlled separately and not by the pressurestat?
Correct... both boilers have separate temperature control. The brew boiler is PID controlled while the steam boiler is controlled by a pressurestat.

JDA1987 (original poster)
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Joined: 2 years ago

#5: Post by JDA1987 (original poster) »

Thanks to both of you.

I checked:
1) No resistance across the pstat terminals
2) No voltage across the two wires (orange and brown) when the machine is turned on

Fried board?



credit to https://support.clivecoffee.com/en/line ... eplacement for pictures

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Jake_G
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#6: Post by Jake_G »

If the machine is cold, that switch should be closed (no resistance across the terminals, meter reads 0.00).

If the machine is hot and your boiler has pressure, the switch should cycle on and off periodically. If the pstat was misbehaving, I would expect you to see the switch open (meter reads O/L, or something along those lines).

So you need to do a little bit more diagnostic work before we look at the board, but it is certainly possible.
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JDA1987 (original poster)
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#7: Post by JDA1987 (original poster) replying to Jake_G »

Hi,

I re-measured and I'm actually measuring something different.

With the terminals wired like the picture above and with my multimeter set on continuity.

1) When the steam boiler is running, I have continuity (i.e.: I measure a resistance, switch is closed / ON)
2) When the steam boiler has reached pressure, I lose continuity (i.e. I measure no resistance, switch if open / off)

I've cleaned the terminal and disconnected / reconnected the wire.

I'll check again tomorrow how the machine behaves.

Datasheet of LMLM pstat: http://www.ma-ter.it/cache/files/XP110.pdf

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Jake_G
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#8: Post by Jake_G »

That seems normal.

Switch closed/On is the same as zero resistance, which is the case when the pressure is below the setpoint.
JDA1987 wrote:2) When the steam boiler has reached pressure, I lose continuity (i.e. I measure no resistance, switch if open / off)

I think you mean you measure no continuity. No resistance would mean you have continuity, which would be the same as switch closed/on.

Anyway, it does look like your pressurestat is behaving, but it also seems like you are measuring it when the steam boiler is heating properly. If you have an intermittent problem, the trick will be to test the switch as you have done here when it should be heating (switch closed), but it is not. If the switch is closed and the boiler isn't heating, I suspect your controller. If the pressure is low, but the switch is open, then I'd look at the pressurestat more closely. (Could be beginning to fail, or you could have some blockage beginning to form on the pressurestat pipe.)

Cheers!

- Jake
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JDA1987 (original poster)
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#9: Post by JDA1987 (original poster) »

Thanks Jake!

This morning the machine is behaving normally, which is a good thing. Now that I know how to monitor the pstat functioning, I'll be able to test it when the steam boiler doesn't appear to be responding.

Anyone has a tip to undo the nuts holding the temperature wheel on the side of the machine?

Unfortunately, I dropped a screw for the top tray at the bottom of the machine...

I used a 7mm socket and my fingers to turn the socket and ended up dropping my socket at the bottom. So I used another socket from another set to try again and I was successful, I was able to loosen the nuts and then I dropped the second socket at the bottom of the machine...

So i finally get the covert removed, find the missing screw and then the missing socket. I put everything back together, but my tools back in my toolkit... and I noticed I had forgotten to to pick up the second socket I had dropped...

beans+crumble
Posts: 126
Joined: 2 years ago

#10: Post by beans+crumble »

JDA1987 wrote: Anyone has a tip to undo the nuts holding the temperature wheel on the side of the machine?
Excellent how to guide and video on the Clive Coffee support page detailing side panel removal including how to remove the temperature wheel. Jump to about 2:45 into the video for the temp wheel removal.

https://support.clivecoffee.com/en/la-m ... el-removal