After my Zaffiro had its 45 minute 'warm-up' this morning, I flushed some water through the grouphead and something seemed wrong. I touched the grouphead and it was stone cold (funny how I could sense the temp difference having only briefly held the group handle - been doing this for too many years).
I did not do much diagnsotics, but chose rather to catch an earlier bus to work and drink the dodgy full-auto espresso here. However I can tell you that when I flipped up the steam switch, the middle red light (boiler heating indicator) did not illuminate.
Anyway - could someone give me a heads-up on the best diagnostic approach. My understanding is that it is either the thermostat or the element (is there also a fuse in the equation somewhere?). But exactly how to isolate the cause might have me searching electrical text books and doing maths (for which I would need a few espresso's).
I am happy to do everything myself, being an engineer and presently half-way through a Wega Nova rebuild (halfway = I know how to undo things... putting them back together is yet to be demonstrated).
I have seen various posts on various forums for this issue, but the remedies fly in many directions with no conclusions revealed. So it could be: check for continuity on the boiler terminals (sounds fishy); check resistance on the terminals within a range; check resistance between terminal and housing... how to check the thermostat?
Check first things first. Most likely, the over temp safety has tripped. Most machines have a reset button on the safety thermostat but some do not. It should be on the boiler some place. There is a red reset button on the switch if it is resetatable. Press it in and if it clicks, it was tripped.
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Thanks for the info. I will take the hood off maybe tomorrow... going to try things in this order:
unplug the 230V
hunt for that over temp safety button (although I seem to remember reading that for the Zaffiro it's a simple fuse) somewhere under the boiler. If that's intact,
plug in 230V and (carefully) see if there is power at the boiler terminals. If there is, then the element is probably fried, if not, must be the thermostat
hope the pressurestat would not also be a contender, because I haven't thought about that one yet. But I think it's possible that a failed pressurestat may also stop the boiler from firing up from cold.
Will hopefully report back soon...
Good news is I'll be in the US on business next month so I could purchase some affordable replacement parts from Chris Coffee (although I wonder if a boiler element is 110V specific).
and the over temp safety button proved to be a thermal fuse which had indeed blown (according to my no continuity multimeter reading). I wondered whether the steam thermostat had failed, causing the thermal fuse to blow. So I did some further diagnostics:
bridged the thermal fuse terminals, powered up, ran the hot water switch to be sure the boiler was well filled, and then let it come up to brew temp normally, which it did (I released pressure in the boiler a few times via the steam wand due to obsessive thoughts that I was doing something dangerous). -> brew thermostat is working
I then flipped the steam switch (with Iscomac's you really can say that you flipped the switch), and it reached its 4 Bar and then the boiler light went out, much to my relief. -> steam thermostat is working
So I concluded that all is well, and I can continue running the machine with the thermal fuse bridged while I wait for the replacement part. However, the following peculiarities ensued:
When doing a quick backflush, I noticed that max pressure is hitting 14 Bar, instead of the normal 9 Bar that I set about 4 years ago.
After adjusting this back down to 9 Bar (and darn that OVP adjustment was VERY tight requiring 2 pairs of pliers to unstick it)...
I noticed when steaming some milk, that there was a funny gurgling sound... opened the lid, and the OVP was pushing steam out the back.
Well that's about as much living on the edge as I could handle, so I unplugged everything and decided that I'd better order more than 1 replacement thermal fuse, because I foresee popping a few of these before isolating the problem with my machine... although I have a pretty good theory - I believe it needs descaling. We live in a hard water area (25 French degrees; 15 gpg; 100 mg/l Ca) and I've been running the machine for 3 years, only using an ordinary Brita drink water filter (which I know does precious nothing for softening - but it has a placebo effect on my conscience). I have received some good advise on how to descale an Isomac boiler from a qualified technician, only requiring the removal of the T-connector on top and the braided steel hose on the bottom, and thereby avoiding the dangers of chrome flaking incurred when flushing citric acid solution through the whole system.
As this may be of value to some, I hope to update with my results.
A few points of interest gained during my research:
The steam thermostat (which I don't believe I need now) is a little device that is clamped to the outside of the boiler, taking its readings only by contact with the boiler surface, set for 145 deg C. It's lack of availability makes me think these little guys don't give up very easily. The only place I could find (in any part of the world) that sells these, is this German site: Click Here (www.stil-forum.de) >> Pic is attached.
I suspect that one can replace the thermal fuse (167 deg C) with any industry standard variety - I found several for less than 1 $ on ebay and amazon, rated at 167 deg C and 10 or 15 Amps. As long as you put the original insulating sleeve back over it (don't throw it away with the burned out fuse). >> Pic also attached.
I noticed that one can now buy in-tank water softening solutions for machines like the Zaff, very affordably. I say "now" because I am sure that these weren't available a few years ago... or maybe I just never looked, since I'm in a hard water area for the first time.
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