Posted Thu Nov 15, 2012, 2:32pm Subject: NS Ellimatic's T-Stat failure - replace with a manually reset equivalent?
I'd raised the p-stat on my old Ellimatic to improve the extraction temps on my shots. With the higher temps in the boiler my steam power also improved and I was pulling good shots more consistently. However I was also tripping the safety thermostat more frequently, especially while I was going through the process of warming up the machine. I took the skins off of the Ellimatic to get a look at the safety thermostat underneath the boiler and noticed that the insulation on one of the quick connects connected to one side of the thermostat had melted a bit. Not good news. The terminal of the thermostat was a bit corroded as was the quick connect so I polished up the thermostat contacts and replaced the quick connects with new ones and that was working fine until two mornings ago when the thermostat started tripping again before failing completely. Once again, one of the thermostat leads had melted prior to the thermostat failing.
I looked up the part number for the proper replacement thermostat (thermodisc style bimetallic, 135° C, autoreset) and wrote up a request but my NS repair depot no longer stocks them and has suggested a more expensive manual reset part. If I can mount the manual reset thermostat, I'm going to want back off on my boiler temps because if the thermostat trips, it will be a real pain to reset. My question is: do I take the advice to go with the manual reset 135° C or use a readily available auto reset 125° C look alike part in stock at a major online Espresso Parts retailer? With the manual reset 135° C part, I'll get higher boiler temps and easier extractions but with the 125° C part resets will be more frequent but less of a pain. Either way I'm going to have to back off on my boiler temps.
Note: The Ellimatic is a fairly basic HX machine with the solid brass brew group directly attached to the boiler and heated passively by conduction through the brass and by contact with brew water moving out of the head. (Coffeegeek forum member GVDub points out that the trick to getting acceptable brew temps with the Ellimatic is to heat up the passively heated brew head by flushing a lot of water through it just prior to attaching the portafilter as he illustrates in a recent video that he's posted of his newly restored Ellimatic.)
Posted Thu Nov 15, 2012, 4:35pm Subject: Re: NS Ellimatic's T-Stat failure - replace with a manually reset equivalent?
Now if it were me, I'd rig a little pivot/see-saw type thing that could be accessed by merely removing the drip tray. You press down the end closest to you and the other end swings up to hit the reset button on the thermostat. No need to remove anything other than the easily removable drip tray. Might have to drill a hole in the bottom plate to mount a pivot point, but that would be about it.
Just an idea. As they say, though, "Ideas are easy - implementation's a bitch."
Posted Mon Nov 26, 2012, 12:36pm Subject: Re: NS Ellimatic's T-Stat failure - replace with a manually reset equivalent?
The Oscar Manual Reset 135 deg C T-Stat has been working without problems for two weeks now. In swapping out the old T-Stat I noticed a lot of corrosion on the 18 gauge wires at the T-Stat terminals. You see, one of the T-Stat terminals had gotten really hot and had melted the insulation even with the new T-Stat installed, the resistance between the crimp on quick connect and the corroded copper wire was probably the cause of the whole problem which had caused the original T-Stat to fail. I cut off about an inch of the 18 gauge wire and made sure it was shiny before crimping on a new quick connect and there haven't been any problems since.
For now I'll settle for having to take off all the skins in order to manually reset the T-Stat since it doesn't seem to trip in normal operation.
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