We have an Isomac Relax Automatica that has stopped working after 5 years perfect service. It suddenly went overpressure starting an espresso. Normaly the pressure rests at approx 1.1 and slowly drops during a brew until the heater comes on. Now it immediately leaps to 2+ even with the Pf removed, less than normal water/pressure at the group, the OPV opens releasing the pressure/water into the tray.
Descaled and backwashed as normal but no change.
After removing the cover I could see that the pressure release at the top of the group is closed during the brew and releases a little pressure on stopping the brew. I assumed this meant the valve at the head is working correctly and the group isn't blocked. I dismantled anyway and all seems ok at the group and group valve.
This is all guesswork as I know nothing of the inside of these machines. Does the excess pressure from the pump return water to the tank as there's no sign of this happening? Could this valve have stopped working? Is it something else completely???
We have an Isomac Relax Automatica that has stopped working after 5 years perfect service. It suddenly went overpressure starting an espresso. Normaly the pressure rests at approx 1.1 and slowly drops during a brew until the heater comes on. Now it immediately leaps to 2+ even with the Pf removed, less than normal water/pressure at the group, the OPV opens releasing the pressure/water into the tray.
Descaled and backwashed as normal but no change.
After removing the cover I could see that the pressure release at the top of the group is closed during the brew and releases a little pressure on stopping the brew. I assumed this meant the valve at the head is working correctly and the group isn't blocked. I dismantled anyway and all seems ok at the group and group valve.
This is all guesswork as I know nothing of the inside of these machines. Does the excess pressure from the pump return water to the tank as there's no sign of this happening? Could this valve have stopped working? Is it something else completely???
Since brew pressure is normally 8-10 bar, I will assume you are referring to boiler pressure. That's why you cant find anything wrong with the group is because the problem is with the boiler's pressure regulation (also known as the pressurestat). Over time the pressurestat wears out and can stick in the closed position causing the boiler to overpressurize/overheat. It will most likely need a replacement.
Just an assumption but the "pressurestat" only controls the heater? The heater switches off ok at the correct pressure and as the heater is off when expresso is brewed the over pressure is caused by the pump, so the "pressurestat" is probably ok.
Just an assumption but the "pressurestat" only controls the heater? The heater switches off ok at the correct pressure and as the heater is off when expresso is brewed the over pressure is caused by the pump, so the "pressurestat" is probably ok.
You are mixing things up. I really think JtothaR has it right, you said....
AuxMemes Said:
.. Normaly the pressure rests at approx 1.1 and slowly drops during a brew until the heater comes on. Now it immediately leaps to 2+ even with the Pf removed, less than normal water/pressure at the group, the OPV opens releasing the pressure/water into the tray.
The PF has NO connection to boiler temp (pressure of 1.1) so are you saying that when you start the brew process, the pressure goes up OR are you saying that just turning the machine ON the pressure goes up?
The boiler pressure of 1.1 is the temp of the boiler and is regulated by the Psat. The only way this static pressure (before starting the brewing process) can rise without you making adjustments to raise it, is for the Pstat to be sticking in the heat position.
If the boiler pressure is 1.1 at static condition THEN rises when you start the brewing process, the HX tube likely has a hole or crack in it and thus the pump is pressurizing the boiler through the leaking HX tube.
You have two gauges on the machine and they each show data that is different than the other.
The static gauge (the one that shows about .8 to about 2 bar) is the temp of the water in the boiler measured in BAR of pressure (not C or F deg)
The gauge that goes from about 6 bar to about 15 bar is the pressure of the pump as it pushes water through the brew system, it should show line pressure of the brew water system when the pump is off. If your supply water pressure is 3 bar, then the gauge will show 3 bar of pressure with the pump off (if you are using a water tank and are not plumbed in, it will show 0 as there is no line pressure in the water tank system) but will rise to the regulated brew pressure of about 9 bar (or whatever you have your brew pressure set at) when you start the pump for brewing.
Two different gauges for two different systems in your machine. If when you turn the pump on, you get a rise in your temp gauge in a HX machine, your HX tube has a split in it where it passes through the boiler (and thus no leaking water outside the machine) and this additional pressure will show on the temp gauge, pegging it and it will cause the safety valve to pop off to bleed of excess pressure that the boiler was not designed to handle.
OH, BTW, it is spelled eSpresso, not eXpresso, a professional would know that ;<P
AuxMemes Said:
Just an assumption but the "pressurestat" only controls the heater? The heater switches off ok at the correct pressure and as the heater is off when expresso is brewed the over pressure is caused by the pump, so the "pressurestat" is probably ok.
The temp of the boiler is maintained by the Pstat and is independent from the brew system, the heater can be either on or off while brewing, it does not turn off for brewing. There is nothing that switches it off when you start to brew espresso so how do you know it is off when you are brewing?
In real life, my name is Wayne P.
Feed the newbs, starve the trolls and above all enjoy what you drink!
BTW it's spelt expresso here in France, by everyone including professionals ;)
I didn't say the heater turned off for brewing, I said the heater was off at the start of the brew. You can tell this because the little green light comes on and the funny boiling noise stops and the lights in the bar get brighter.
It does sound likely that there is a leak in the heat exchanger inside the boiler; so when the pump switches on pressure is leaking out into the main part of the boiler. This will also switch off the heater if it was on to start with, as it will open the pressurestat contacts. I am guessing that the reading of "2" on the gauge is as high as the gauge will go ?
What happens if you open the hot water valve while the pump is running ? Provided the portafilter is in place with either coffee or a blind filter in it, if the heat exchanger is leaking you should find the water comes out with more pressure than normal (please be very careful if you try this !)
I think this is likely to be a repair for the professionals if the heat exchanger is indeed leaking.
After 5 years you might find it difficult to get the manufacturer or supplier to fix it free of charge, even if the law in the EU says that items like this should have a reasonable life. It is worth a try though.
Some machines have one gauge, some have two and others don't have any. I did not look at your specific machine but if you had two gauges they would have reacted the way I described. It does sound like the HX tube has an internal leak buy your description of what happens .. when.
You might get lucky and have a HX tube that can be repaired easily but many boilers have a sealed boiler which would require major surgery on the boiler to repair the HX tube. I hope you are the benefactor of the former rather than the unlucky owner of the latter.
Rob hit the nail on the head with the cycling of the heater in the brew process. The temp is set by the pressure inside the boiler, nominally 1.1 bar. If the boiler is too cold, say 1.0 bar, the Pstat will turn the heater on until the set pressure is reached at which time, the water is at the desired temp. If your HX tube is leaking and you start the brew cycle, the pump pressure will cause a spike in the pressure in the boiler and the Pstat will react to the additional pressure by turning off the heater (it "thinks" the water is hot enough and and the water needs no more heat) which is why the green light for your heater turns off (not all machines have lights that show when the machine is heating). This also explains why the safety valve releases pressure, the valve is set to a pressure that the boiler will never see in normal service but is below the pressure design of the boiler so when the pump adds pressure into the boiler, the safety valve reacts as if the water was too hot and the valve opens, venting the excess pressure to the air before any damage can happen to the boiler.
Often when this happens it is because the machine was left in an unheated space in the winter and the water froze. I know you did not indicate this happened and I have nothing to offer as to why this could have happened when the machine is in service every day, other than possibly a manufacture defect that has taken years to appear. Even if it is a faulty part, it is unlikely that you will get any help with the repair and often when paying a shop to do the work (I don't know if you are able to do the work or not) a repair like this cost will be enough for you to consider replacement of the machine rather than repair.
Good luck!
In real life, my name is Wayne P.
Feed the newbs, starve the trolls and above all enjoy what you drink!
OK I think I understand a little more now. It sounds like the HX could be leaking, but isn't there one other possibility? There must be an inlet to the boiler from the pump to maintain the boiler level. If the valve or whatever controls the flow of water to the boiler from the pump has failed wouldn't that cause over-pressure in the boiler evertime the pump was started and reduce the water flow to the group?
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