Post By alexm1
Post By koshari
LA CIMBALI DOMUS CLASSIC - diagnosing electrical problems
I recently picked up a Cimbali Domus classic domestic machine in flawless condition externally. The previous owner said it had an electrical fault / short so now i am hoping to be able to resurrect this machine and put it to work in my shed. There isn't a lot of information out there about these machines but from the little i did find it seems that the classic is the simplest machine - electrically speaking - which hopefully cuts down on the number of possible problem areas.
I understand that I am working with 240V and that this is potentially fatal if i am not very careful, I always use a RCD and a safety switch outlet to help minimise the risks, but i know that these are no substitute for careful planning and checking to make sure the power is isolated and insulated.
Having acknowledged that, I was thinking about how to try and isolate the problem. I haven't even powered it up or taken the covers off yet so I'm not sure of how the electrical fault manifests itself, Im guessing it will just throw the RCD switch. I was thinking that taking the cover off and isolating the various major components such as element, pump, solenoid etc - removing one from the circuit at a time (isolating the wires) then powering it up and seeing if it still throws the switch would be a way to narrow down the cause of the problem. Does this sound like a logical way of going about it all you electrically qualified people out there? any suggestions would be most welcome
I would not try to chase the fault live. As a first alternative put a meter across the active and earth, if you have a short then with the meter still across the same wires go through your isolation procedure. If that gives no joy then try the same across active and neutral and perform your isolation test. Remember that the active and neutral will likely show a fairly low resistance due to the various components that are connected.
If what I am suggesting does not make sense to you then I would suggest you leave the covers on and get someone who is qualified to look at it, you are a long time dead!
Wega Mininova Classic
I had one of these in the late 90's for years and years and I remember an electrical fault it developed which may or may not be what you are experiencing.
The main on / off switch needed replacing after the connections behind the switch fried (couldn't tell you why.... I'm not an electrician but I put it down to over use)
With a bit of luck this is all you're facing
The only other problem towards the end of it's life was some spots on the group head that showed early signs of pitting
Thanks Seeya, and thanks for the advice alexm1, that all seems pretty logical to me. I will report back with my findings once i have had some time to test a few things. Im hoping its not the element as my online research seems to suggest that parts for this machine are pretty hard to come by.
So, i opened the back of the machine today and did some tests with the multi meter.
Upon opening the back I found a couple of loose wires, so it would seem someone had been in here before me. Good thing I didn't just plug it in to see what it would do. I reconnected the wires and started out using Alexm1's advice and looked to see if there was a leak to earth from any of the usual suspects - element, pump and solenoids. everything seems fine. The problem with the machine was described to me as "a short" but it maybe that its something else and that was their only way to describe it to me.
I also measured the resistance of the element and got a reading of 370 ohms..
I am going to double check ever component and all the switches for issues, then i guess i will have to look a little harder at each component
So after failing to find any obvious issues with the machine disconnected using the multi meter, i plugged the machine in. Nothing happened.... the pilot light went on but that was it. I then went to follow the instructions to prime the boiler and here's where i hit trouble. the pump kicked in for a second or two then the RCD cut the power. I tried just running the pump by pressing the brew switch but had the same result. Im going to have to take a break as my wife is sick of me blacking out the house.
I believe this machine has a 1300W element so the resistance of the element should be around 40 ohms, not 370.
Make sure you have disconnected the wires from the element when you measure the resistance to avoid any measurement interference from other components.
You need an insulation tester to properly find an insulation short. Standard resistance tests won't show this.
A good way to stop killing the power to the house is to buy a portable RCD. Bunnings sell them for about $25, they just plug into a powerpoint and hopefully take the hit rather than the house.
Your testing sounds like a pump fault however i've never seen a pump trip an RCD although that doesn't rule it out, there's a first time for everything. I would suspect the pump starts spraying water into the boiler where it hits the element and causes the earth leak.
I actually have an plug in RCD but its at the workshop and I kind of got obsessed with this project and couldn't help myself.
I was thinking of just changing out the pump as I have a spare one and its an easy swap.
as for the resistance on the element, you got it. I didn't disconnect it from the rest of the machine
thanks for a your guidance Noidle22 its helpful to get feedback from other people
I was just thinking about what gets powered up when you flip the brew switch, you have power going to the pump and the group solenoid so i guess these are the first things to look at a little closer.
Yes i just looked at some pics of the internals of the machine. Is there a hot water tap that you can use to fill the boiler or does it need to be the brew switch?
The solenoid could be the problem. I've had a low resistance solenoid on a machine that was blowing the fuse in the machine itself rather than the supply circuit. Yours could just be acting in a different way.
Try measuring the resistance of the solenoid coil. If it looks abnormally low then it'd be worth swapping it. I think you should see around 30-40 ohms on a solenoid coil like the one on this machine, can't quite remember. If you look at the body of the solenoid it could have a power rating marked on it so you can calculate the expected resistance from that.
No, no hot water tap, the instruction manual tells you to press the steam button (there is no steam valve, just a button) then the brew switch and allow the machine to run until a full cup of water is ejected from the steam arm to prime the boiler. I was thinking I could just take the pipe from the pump off and manually fill the boiler. Its a used machine so most likely there would be some water in there.
Common problems with these machines when old are scale, corroded boilers and elements. These machines have an alloy boiler , be extremely carful taking the the top off the boiler , as often bolts can corroded and threads easily stripped.
The on/ off switch can fail and is common, but normally last close to 10 years.
Often I have seen them after being left sitting for a number of years with water in the boiler and corrosion has killed them.
Not really iam afraid, being a reactive load there will be an amount of induction that will create a back EMF that opposes current flow, other than purely resistive loads ( such as the element you correctly calculated previously) reactive loads you need to use R = Z^2/P rather than R=R^2/P and a standard multimeter can only measure R.
Originally Posted by noidle22
thanks everyone for your feedback and suggestions, the machine has sat in its box for the last week as i have had other issues to deal with.
This machine is not what you would call "an old Machine" both inside and out it is in immaculate condition and I would say it couldn't be more than 5 years old, and even then it would have only had light use. there is no wear on the PF, no dust or any kind of coffee remnants internally. By far the cleanest machine I've ever come across.
In order to fill or check the boiler level I was going to take the pump feed pipe off the top of the boiler and fill through the hole. taking the boiler apart is too much trouble at this stage. I have now invested in a second outlet RCD so that should keep the wife happy and me a little safer.
Given your issues are not tempeature related you could always take one of the connector off the element and tape the cable end and element stub up with insulation tape while you troubleshoot the pump/water circuitry. This will eliminate the potential of the element operating whilst the boiler empty protecting the element from overheating.