Troubleshooting Starbucks Barista tripping GFI

#1: Post by **LMO** » December 16th, 2009, 6:47 pm

For a few weeks the pump has been sounding a bit off, so it was not a surprise when it slowed and then died altogether. I checked the thermal shutoff, which was still good, so I ordered a replacement pump. Meanwhile I discovered that the machine had tripped the GFI, so I hoped that was related to the pump as well.

I installed the new pump, checked operation and fixed a leak, and then put the cover on. Immediately it tripped the GFI. I suspected the heater element, and if I remove the ground connection from the boiler assembly the GFI does not trip. However, if I remove all electrical connections to the boiler other than ground, the GFI still trips.

Tracing wiring I can track down one wire coming from the lower (steam) switch that has a path to ground, although greater than 1 megohm. At the moment I haven't figured out how to go any further as I haven't figured out how to disassemble the switches.

I'm hoping someone can suggest how to troubleshoot further. Is the machine unsafe to run on a non-GFI circuit?

TIA,
Lynn

#2: Post by **tsenfw** » December 16th, 2009, 6:56 pm

http://kitchen.manualsonline.com/mdownl ... 034a94.pdf

Hopefully this wiring diagram helps.

http://users.rcn.com/erics/ · #3: Post by **erics** » December 16th, 2009, 6:58 pm

Is the machine unsafe to run on a non-GFI circuit?

For now, YES. If I remember correctly, the ONLY function of the switch on the steam valve shaft is to initiate the pump when the hot water switch is depressed. So, disconnect the leads to the switch on the steam valve, connect all previously removed wires and see if everything is OK when plugged into a GFI outlet.

December 17th, 2009, 2:51 am

Thanks for the wiring diagram. It should be a big help in figuring out what the individual wires are doing.

Looks like I'll be tearing it completely apart tomorrow...

Lynn

#5: Post by **stefano65** » December 17th, 2009, 8:20 am

it is common that those heating element coil will create a pim hole and short into ground
to single out the problem to that
remove the heater terminals wire and attach another load ( light bulb for example )

December 17th, 2009, 1:57 pm

The wiring diagram was interesting, although I don't see how it could work as shown. In any case it doesn't match the wiring on my unit.

I started troubleshooting it this morning, but couldn't reproduce the readings I took yesterday. Sure enough, it is not tripping the GFI today, and the real test: I put the cover back on, and it still doesn't have the problem. Not much I can do with it unless it starts to fail again.

Thanks again,
Lynn