Post By MattyRay
Post By artman
Post By MattyRay
Boiler element - earth leakage issue
The machine is a microcimbali liberty, but I guess this could be on any machine.
I picked this up recently, was told it was stripped and cleaned, new seals etc. Worked a few times then was tripping the RCD.
The machine looks in great condition overall.
I separated the boiler/group from the base to get to the element terminals. I am getting 37 ohm across the element terminals (seems perfect to me) but also getting about about 15 Mohm across the element terminal and earth (not good).
I haven't open the boiler yet to see inside.
I have not plugged the machine in yet. Is there a minimum resistance required between element and chassis (ideally open circuit)? The boiler is empty and dry.
Would this be fixable in any way (I recall someone using some compound to insulate element on one of these machines?) or would it need a new element? Or are the readings to chassis ok?
I also noticed there is a combines capacitor/resistor across the microswitch that is controlled by the boiler pressure, this looks like it has been a touch hot.
Last edited by artman; 28th April 2017 at 12:25 AM.
Reason: added info
15 megohms from element to earth is a fantastic reading, anything over say 100Kohms is no cause for concern. However, there is a right way and a wrong way to measure. If using a low voltage source to test, such as a normal multimeter, then the element may show up fine, but when put onto a higher voltage source, such as 240V power, the insulation may break down and cause a short. The correct way to test the element would be to use a high voltage tester, such as a "Megger", which is capable of putting 500VDC or 1,000VDC across the element. Using a tester such as this will tell you for sure what state your element is in. Before high voltage testing, make completely sure that any electronics, controllers etc are totally disconnected first to prevent damage to them.
If the element just has a tiny bit of moisture in it, then it is possible to drive the moisture out by the application of heat, starting from the centre of the element and working outward to the ends. However, if moisture has got in there before, then it is likely it will get in there again, as the seal on the end of the element is probably compromised.
If the power has tracked across the insulation inside the element and caused a little damage, then an element replacement is the only option as the element will fail completely in the near future.
Regarding the resistor/capacitor, can you post a pic? It is probably there to suppress any arcing and electrical noise caused by the contacts opening and closing under load.
Thanks for the info, yes I tested it with a normal multimeter.
Anyway, I plugged it in and the machine is heating up fine! Woohoo!! Hopefully it will keep working, otherwise I will track a new element down.
There are some other bits I need to sort out and info I need, I will start another thread.
The electrics of this machine are as simple as it gets. A main switch, an over temp resetable safety switch, and a mechanical pressure stat clicking a micro switch. There is a cap across the supply in the base, and this cap/resistor combo across the micro switch on the pressure stat.
pic below pf the resistor/cap combo.
cap resist 2.JPG
Good to hear it's working.
Yes, the little RC (resistor/cap) would be for arc/electrical noise suppression. Not sure why it should appear burnt though, unless an electrolytic capacitor has been used in it's construction and it has leaked/failed.