La Cimbali Junior D/1 overheating/overpressure

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
BarcaBere

Postby BarcaBere » May 05, 2018, 5:47 am

Hello all

A friend of mine has been using an older (he says 90's) model Cimbali Junior D/1 for a long time and never has had any problems. Recently however, the device overheats and over-pressurises. While the normal operating pressure used to be around 1 bar, the device now sometimes pressures up to the maximum the pressure gauge at the front of the machine can indicate. The water is also way too hot, even at 'lower' pressures, really burning the coffee.

I've not seen the safety valve open yet, but it has been replaced last year and works if we manually press it open, so at least the boiler will not crack (or worse). For now I've advised him to turn the device off when it starts over-pressurising.

He's asked me (an electrical engineer by profession) to have a look at it. My guess is that the heating element just keeps on heating the boiler. From looking at the electrical wiring diagram this would mean that at least two sensors are broken: the pressure gauge ('pressostat') and the safety thermostat.

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Replacing the safety thermostat seems to be easy, apparently it's just screwed into contact with the boiler/heating element, and not actually inside the boiler. It's also not that expensive. It's the pressostat that worries me more. I'm always wary about touching the pressured sections :P . I probably should replace the whole thing I assume, and also the nut and washer below? Any other things I should pay attention of?

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The resistance of the heating element measures in at around 40 Ohm, which checks out with a 1300W rating. The rest of the machine still looks alright, although it wouldn't hurt replacing some wiring around the boiler section (I probably will do that too).

I've searched this and other forums about similar problems, but didn't not found anyone whose Junior over-pressurises. Mostly it's the other way around (cluncky pressostat which prevents the boiler from pressurising). So I hope I'm doing the right thing by replacing these two components. Any help or tips much appreciated, so we can restore this venerable machine back to working conditions.

User avatar
kolu

Postby kolu » May 05, 2018, 6:38 am

Replace the pressostat. Their membranes hardens over time...

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civ

Postby civ » May 05, 2018, 9:32 am

Hello:
BarcaBere wrote:... older (he says 90's) model Cimbali Junior D/1 for a long time and never has had any problems.

Three things ...
The first one would be to check the D/1's age.
Look under the drip tray and you should see a sticker like this one:

Image

A bad photo but in the lower right hand area you can see the manufacture date.
If the stcker is not there it may be elsewhere on the unit, that info will give you the max age of the machine.

The second would be to ask your friend if he purchased the Cimbali 'new' or not and when and the third (and most important) would be to ask him if the unit has had any maintenance in the span of time he has been using it. If it has, what type.

When I purchased my D/1 (ca. 2000) it had been used for a very short time before the owner grew weary of it and replaced it with one of those Nespresso (!) things, leaving it in a corner to gather dust for a about four or five years till his wife grew weary of it, so it was put up for sale along with an equally unused Junior Max.

US$450 and a cab ride later, a thorough check up of the D/1 revealed that even with very little use, it needed some cleaning up and descaling: the water at this chap's home was sourced from a deep well in the suburbs and quite hard.

It could well be that this D/1 has had litle or no service at all in many years and at this point it would be worthwhile checking out the machine for scale build-up, which depending on the water supply, could be significant for any ca. 90's machine without proper maintenance.

Scale build-up will be found in the boiler, the HX, the boiler level rod, the pipes connecting the boiler to the to the PS and manometer and sometimes even at the manometer's base, all of which which would certainly cause the symptoms it is now showing.

You will also find scale build up in the piping to the 3-way valve and in the valve itself.

Now, all this happens inexorably over time, slower or faster depending on a) the type of water used and b) the maintenance schedule of the unit has had, it is only a question of when.

BarcaBere wrote:... device overheats and over-pressurises.
... water is also way too hot, even at 'lower' pressures ...

Water and pressure are directly related so if the boiler output is 'too hot' at a 'lower' pressure, there is a problem with one of the instruments indicating either that the output is 'too hot' or that the pressure is 'normal' or a combination of both.

BarcaBere wrote:... not seen the safety valve open yet ...

If the safety valve has not blown I'm inclined to think that the valve's operating pressure has not been reached as the safety would have tripped.

BarcaBere wrote:... the heating element just keeps on heating the boiler.

Like kolu has mentioned, pressurestat membranes harden over time.

Actually, what happens is that (in most pressurestats) they progressively lose flexibility and lose their plane, deforming ie: develop a bulge.
When this happens, the deadband increases to the point of making it unrealiable for proper use. With an extra large dead-band, the PS can eventually start to cut off at a point where a safety pressure/temperature limit has been passed, which is what seems to be happening here.

For a Sirai pressurestat you can get a membrane repair kit like the one I posted here:
Sirai pressurestat membrane replacement

It is not a difficult procedure but you have to be careful with the four small metric screws holding the membrane: they can strip easily.
(no, don't ask).

BarcaBere wrote:Replacing the safety thermostat seems to be easy ...

If it is the stock safety TS that came with the D/1 it is probably an auto-reset type one and being so, it has probably tripped and gone unnoticed as it resets itself when the temperature goes back to it's nominal setting. That would be the reason the safety valve has not blown.

I emphatically recommend that you change the original auto-reset part for a manual reset type one like the one I mention in this post:
La Cimbali Junior - Replacement Heating Element Different

As you are aware, mounting it with thermal grease is of good practise.

BarcaBere wrote:... should replace the whole thing ...

The usual Sirai pressurestats you find in older commercial espresso machines like this one are built like Panzer tanks and made to last for a great many cycles under severe conditions, much harsher than the use they have been put to in a Cimbali D/1.

The original unit probably is a model with two sets of contacts.
Check them out and if one is worn or pitted by arching you can switch to the unused one and get many years more service from it.

BarcaBere wrote:... help or tips much appreciated ...


A search here at HB will yield a huge amount of pages related to maintenance of any HX machine, Cimbali D/1, other Cimbali models and even similar rebranded units with common maintenance procedures.

Do keep us posted on your progress.

Cheers,

CIV

BarcaBere

Postby BarcaBere » May 07, 2018, 4:59 pm

civ wrote:Hello:

Three things ...
The first one would be to check the D/1's age.
Look under the drip tray and you should see a sticker like this one:

A bad photo but in the lower right hand area you can see the manufacture date.
If the stcker is not there it may be elsewhere on the unit, that info will give you the max age of the machine.

First of all, thank you very much for your time and advice. I'll check the sticker tomorrow.

The second would be to ask your friend if he purchased the Cimbali 'new' or not and when and the third (and most important) would be to ask him if the unit has had any maintenance in the span of time he has been using it. If it has, what type.

The Cimbali was previously used professionally, but only for a short time (a year or two). It was under a service contract. Once or twice a year a technician came to inspect the machine and descale it with a special descaling agent. The technician was a local guy, and he agreed to keep servicing the machine for my friend without the service contract. He however retired two years ago, and the company he worked for charges a ridiculous amount (€400 just to sign a new service contract!). My friend did keep descaling the machine with the agent though. So I would be inclined to think the insides of the machine will probably be okay.

Some of the wiring has gone stiff though, I'll see to replace it. Some of the metal plates also have some decolouring due to heat, but they appear structurally fine. And everything could enjoy a clean up with some citric acid or so, but that shouldn't affect the operation I guess.

If it is the stock safety TS that came with the D/1 it is probably an auto-reset type one and being so, it has probably tripped and gone unnoticed as it resets itself when the temperature goes back to it's nominal setting. That would be the reason the safety valve has not blown.

I emphatically recommend that you change the original auto-reset part for a manual reset type one like the one I mention in this post:
La Cimbali Junior - Replacement Heating Element Different

Okay, I'll see to replace it with that part.

For a Sirai pressurestat you can get a membrane repair kit like the one I posted here:
Sirai pressurestat membrane replacement

It is not a difficult procedure but you have to be careful with the four small metric screws holding the membrane: they can strip easily.
(no, don't ask).


The usual Sirai pressurestats you find in older commercial espresso machines like this one are built like Panzer tanks and made to last for a great many cycles under severe conditions, much harsher than the use they have been put to in a Cimbali D/1.

The original unit probably is a model with two sets of contacts.
Check them out and if one is worn or pitted by arching you can switch to the unused one and get many years more service from it.

My friend prefers just replacing the whole thing, and optionally fix the original part with the repair kit and have a spare. A new pressostat is not that expensive, and has a higher guarantee to immediately fix the problem.

BarcaBere

Postby BarcaBere » May 12, 2018, 9:18 am

Apparently the device is much older than I thought, probably close to 30 years. It didn't have the sticker on the drip tray, it does have this nameplate.

Image

Last week the behaviour of the machine changed. It now has a too low pressure, but the temperature is still too hot. It also makes loud clicking noises at random interval, which I suspect is the pressostat.

A replacement Sirai pressostat and manual reset thermostat are on their way.

BarcaBere

Postby BarcaBere » May 16, 2018, 4:36 pm

The pressostat has been replaced, and we also descaled the plumbing the between the boiler and the pressostat. The little Junior works like before 8) .

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Unfortunately an old problem with dosing now rears its ugly head again. When setting the dose to two cups, the machine works fine. When setting it back to one cup however, after pressing the dispensing button the pump only works a second or so and then stops, after which the refill light briefly goes on. It requires multiple presses to fill one cup. I hope it's just an issue with the level rods in the dosator and not with the Gicar box. I'll check it next week.