Thermal safety switch fail? (Cremina)

by **roadman** on Thu Feb 17, 2011 2:13 am

Here's what happened. I walked up to my Cremina, pulled a shot and all was well.

Left the machine on, tried pulling another shot 15 minutes later and no pressure. The power light was still on but the pilot light for the heating element was off and it failed to heat up. There was plenty of water in the boiler so it was not an issue of the boiler running dry.

Opened up the machine and saw that the insulation on every one of the wire terminal covers had melted. Pressing the reset button did nothing.

Put a multimeter to the heating element and no short was detected.

I swapped the thermal safety switch and now the heating element works again.

Before I put this machine back into service I'd like to know what happened. I'm guessing that the thermal safety switch failed causing the meltdown, but I'm no expert. Could the problem lie elsewhere like in the heating element itself or in the wiring? Or did the thermal switch simply fail?

Jon

by **michaelbenis** on Thu Feb 17, 2011 3:56 am

Others with more experience in Cremina repairs will hopefully chime in later, but I wonder if it is also possible that the cutout did its job and you have a root problem with the pressurestat. Have you checked that out?

Lucky that the element is OK one way or another....

Cheers

Mike

by **roadman** on Thu Feb 17, 2011 4:01 am

Yeah, I swapped the pressurestat before I swapped the swapped the thermal safety switch. Didn't make a difference.

Thanks for the input.
Jon

by **orphanespresso** on Thu Feb 17, 2011 5:54 am

the question would be....were the terminals melted before this mystery event? So let's say they were melted, which happens when the connections become contaminated and dirty and the terminals act as a small resistor and produce heat thus melting the cover, which is usually nylon or other fairly low temp plastic. Let's say that the thermal switch developed a dead short, which in effect replicates touching the two wires of the power cord together, which usually draws enough amps to blow the circuit breaker...most are rated at 15 amps for home current. Let's speculate that you perhaps have 20 amp circuits in the kitchen and the thermal switch dead shorted....the amperage on such an event would have to exceed the 20 amps in the breaker box to throw the breaker, which it did not, but the components of the machine are mostly rated at 15 amps and the wires of the machine likely 30 amps, but the terminals plastic covering not so high a rating. Let's say you have a 15 amp circuit in the box....this would protect the 15 amp components of the machine and likely throw the breaker thus protecting the parts.
It is frustrating when there is no obvious causal event to make a part fail like this but there is always the outside possibility of a power surge on the line, which usually fries the heating element, if the heating element was in the ON mode when the surge happens, such as when first turning on a cold machine. So if there was a power surge and the pstat was OFF, then no current would reach the thermal switch OR the heating element. If there was a surge and the pstat was in the ON the current would go through the pstat to the thermal switch and possibly over amp the switch BEFORE getting to the element, thus giving a sort of fail safe fuse .
I bet that if one inspects all of the amperage ratings that the thermal safety switch has the lowest rating of all the switches on the machine and would act as a sort of internal surge protector to keep the element protected for any over amperage event.
Of course it is possible that the switch decided to crap out just at that moment and it has nothing to do with anything other than timing.

by **roadman** on Thu Feb 17, 2011 3:34 pm

Hi Doug. Thanks for checking in on this.

orphanespresso wrote:the question would be....were the terminals melted before this mystery event?

The terminal covers on machine in question were in good shape before the event. After the meltdown some terminal covers melted completely, others stayed intact.

Both sets of terminal covers to the p-stat and thermal switch melted off. Three of the four terminal covers to the power light also melted. The remaining covers to the pilot light, heating element and the one undamaged terminal from the power light to the pilot light are still in great shape.

orphanespresso wrote:So let's say they were melted, which happens when the connections become contaminated and dirty and the terminals act as a small resistor and produce heat thus melting the cover, which is usually nylon or other fairly low temp plastic. Let's say that the thermal switch developed a dead short, which in effect replicates touching the two wires of the power cord together, which usually draws enough amps to blow the circuit breaker...most are rated at 15 amps for home current. Let's speculate that you perhaps have 20 amp circuits in the kitchen and the thermal switch dead shorted....the amperage on such an event would have to exceed the 20 amps in the breaker box to throw the breaker, which it did not, but the components of the machine are mostly rated at 15 amps and the wires of the machine likely 30 amps, but the terminals plastic covering not so high a rating. Let's say you have a 15 amp circuit in the box....this would protect the 15 amp components of the machine and likely throw the breaker thus protecting the parts.

Makes sense. The breaker in question is 20 amps, which seems to be a reason that it didn't trip.

orphanespresso wrote:It is frustrating when there is no obvious causal event to make a part fail like this

You got that right!!

orphanespresso wrote:but there is always the outside possibility of a power surge on the line, which usually fries the heating element, if the heating element was in the ON mode when the surge happens, such as when first turning on a cold machine. So if there was a power surge and the pstat was OFF, then no current would reach the thermal switch OR the heating element. If there was a surge and the pstat was in the ON the current would go through the pstat to the thermal switch and possibly over amp the switch BEFORE getting to the element, thus giving a sort of fail safe fuse.

Could it be that the path of melted terminals described above favor the surge/p-stat ON scenario?

orphanespresso wrote:I bet that if one inspects all of the amperage ratings that the thermal safety switch has the lowest rating of all the switches on the machine and would act as a sort of internal surge protector to keep the element protected for any over amperage event.

Yep, the thermal switch is rated at 10 amps.

orphanespresso wrote:Of course it is possible that the switch decided to crap out just at that moment and it has nothing to do with anything other than timing.

Anything's possible.
Looks like I'll be placing an order with you very soon!
Thanks again,
Jon

by **TUS172** on Thu Feb 17, 2011 9:51 pm

Hi Jon,
You said that you swapped out the P-stat. Did you swap it out with another Olympia P-stat or something like a Ceme P-stat or what?
B Cullen

by **roadman** on Thu Feb 17, 2011 9:59 pm

Hi Bob,

They are both Olympia p-stats. I've got a backup Cremina, so I've been swapping parts from the second machine in order to run down the problem.

I've never used a Ceme in a Cremina. Have you used one?
Jon

Ps bet you miss those New England winters about now :wink:

by **TUS172** on Thu Feb 17, 2011 11:11 pm

Ya I miss the weather in Vermont, about as much as chewing aluminum foil! :lol:

I put a Ceme in the C Lever and it works flawlessly.
Hm... I am kinda stumped on why the unit won't fire up if you replaced the P-stat and and the Switch.
How does the terminal block look if its shorted somehow, current may not passing through it to the rest of the maching including the switch or perhaps the fix would be to run all new wiring.
Perhaps the element took the hit... But you have already tested the heating element with a multimeter. You might want to bypass the P-stat and try putting the multi meter across the the switch in the on position (while unplugged) and test the switch and heating element to the correct ohms. Or perhaps just test it from the wiring that leads up to the switch (take the swich out of the line) with the switch out of the line to test the wiring. In other words try to narrow down where the failure is.
Sounds as if you have a nice project on your hands.
Bob C

by **roadman** on Thu Feb 17, 2011 11:52 pm

Thanks for your thoughts on this conundrum.

TUS172 wrote:Hm... I am kinda stumped on why the unit won't fire up if you replaced the P-stat and and the Switch.

The heating element powers up fine with the substitute switch:

roadman wrote:I swapped the thermal safety switch and now the heating element works again.

As I'm down to my last switch I'm reluctant to leave the working switch in the suspect machine until I have a better handle on why it died. At least I know that the heating element and pstat work and that for whatever reason the switch is the part that failed or got fried.

Until I order a new switch I'm leaving the functional switch in the backup machine. The middle of February is no time to be without a working espresso machine! Don't want to end up with two borked machines.

Jon

by **TUS172** on Thu Feb 17, 2011 11:58 pm

Oops I misread... Youwere talking about the reset on the bottom of the boiler now I got it... :oops:

So Doug has them for around $15. I am sure you already know. Well have fun... Could be that the reset was your problem to begin with... Right? Well I guess that wAs your question from the first.
Bob C


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