DanJ Senior Member Joined: 1 Dec 2012 Posts: 2 Location: Calabash NC Expertise: Just starting
Posted Sat Dec 1, 2012, 4:31pm Subject: Cremina 67
I've rewired, new switch, new thermostat and the heater reads 12.5 ohm and no current when each post is checked with ohm meter. with 120 v at both element posts, no heat. Cold as a dead fish. Any thoughts would be greatly appreciated. thanks, dan
SStones Senior Member Joined: 24 Nov 2012 Posts: 506 Location: Canada Expertise: Professional
Espresso: Giga 5, ECM Giotto, Rocket... Grinder: Anfim Milano-Best Vac Pot: No :( Drip: Some $30 thing from Walmart Roaster: I buy pre-roasted.
Posted Sat Dec 1, 2012, 6:38pm Subject: Re: Cremina 67
Sorry, I'm not sure I'm correctly reading your post... With it turned on, plugged in you clearly read 120VAC across the heating element, right? And with it unplugged, you read 12.5 ohms resistance across the element? That sounds like the element is okay. I'm not familiar with the cremina 67, but re-do the tests. There is something breaking the circuit, measure right at the element when measuring the voltage. If a good 12.5 ohm element is getting 120 VAC, it will heat up to painful in seconds if there's no water conducting the heat away.
Is there any conductivity to ground? Set the ohmeter to maximum range, ie. 20 million ohms, or whatever the extreme is, and check each element connection to boiler body. It just seems impossible for a 12.5 ohm conductor to not heat up when supplied with enough juice to register a 120 volt voltage drop.
dspear99ca Senior Member Joined: 17 Jan 2013 Posts: 93 Location: BC, Canada Expertise: I love coffee
Espresso: Gaggia Coffee Grinder: Mazzer Mini
Posted Thu Mar 7, 2013, 9:38pm Subject: Re: Cremina 67
Electricity, like everything else, seems simpler when broken down into parts.
I think what you are saying is that you measure across the element and read 12.5 ohms which is a pretty high reading for a cold element. One meter probe goes on one end of the element and one end goes on the other. The unit is unplugged during this test. Yes? If so this is just telling you that the element is neither shorted (zero resistance) or open (infinite resistance) UNDER THE CONDITIONS OF THE TEST. The ohm test uses a small voltage, less than 9VDC, to achieve its' measurement. Unfortunately it does NOT guarantee that the element will behave similarly when exposed to 120VAC, so be careful not to jump to conclusions. The way elements behave is they have nearly zero resistance when cold, and the resistance increases with temperature. Hence, when you turn first turn on power to the element it will draw a spike of current through it. As it warms up the current decreases to a steady-state level equal to the rating of the element. I.e. a 1200W element connected to a 120V line will draw 10 amps of current continuous, but will draw several amps more at startup. That's why if you plug it into the same circuit as an incandescent lamp, the lamp will momentarily dim when you turn on the machine... it's that current spike.
Next you say that while plugged in, you read 120VAC across the element terminals. Again one probe on one end of the element and one on the other.
I'm not familiar with the wiring of your exact machine, but I know it's a SBDU and it's built like a tank with simple, easily replaceable parts. current flows from one plug prong through the power switch, a thermostat (two thermostats actually, one for steam and one for water), and possibly an overtemp thermal fuse or fusible resistor, back to the other plug prong.
Regardless of the ohm test, if you have voltage (120VAC line voltage in this case) across the element and no heat, either the element is bad or there is something in the circuit that is restricting current to such an extent that no heat is developed. The only things in that circuit are the power switch and the boiler temperature thermostat, the water one not the steam one. The switch is new. The thermostat is new. The cold resistance is high, my money is on the element being bad.
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