Hi there,

First post so be gentle and boy do I need some help!

Got hold of an old Zaffiro with a known dead heater. Thought it would be easy to replace - it wasn't that difficult actually.

Whilst the boiler was out, I removed a lot of gunk and scale, but it could have been much worse!

Gave her a good cleanup, inside and out and proceeded to start her up. All was well apart from a small leak from the braided steel pipe. Oh well, continued the clean up while I awaited a new braided steel pipe. Gave her a proper descaling as the pipe wasn't leaking that badly.

Fitted the new pipe this morning and fired her up with the casing off. All appeared well. No leaks, even under pressure. Thermostat appropriately clicking on and off at what appeared sensible intervals.

Decided to pull the first shot, still with the case off (paranoid about leaks!) It looked beautiful, but didn't fancy tasting the first!

I then reassembled the case and decided to do a chemical backflush to get the last of any built up gunk out - worked a treat and I was getting quite excited about having a 'proper' espresso machine at long last.

I then pulled another shot to cure the group after the backflush. Another great looking shot.

Right, time to actually taste one. As I was grinding for my first taste, the pressure gauge went really high and water was released through the pressure release valve into the water reservoir. Oh no, what now I quickly powered off the machine.

Case off again I tested the resistance of the heating element to the outside of the boiler. 3-400 ohms from either leg. I knew what this meant as i removed the boiler.

Unscrewed the element and it had burst quite badly. The question I need help with is why?

Brand new element - was it faulty?

Did the boiler overheat - if so why. It seemed to be holding a reasonable temperature. If the coffee brew thermostat had failed, surely the steam thermostat would have cut off the heater before it blew?

if that was faulty too (hadn't tested the steam function as I only drink espresso) surely the thermal fuse should have blown??

The boiler was obviously full of water as I'd just pulled a shot and flushed the group immediately afterwards!

All of the confidence I'd gained over the last couple of weeks restoring this machine have evaporated. I'm obviously going to speak to the supplier of the new heating element, but regardless I'd hate for another one to blow almost immediately after fitting.

In case its not clear from the above ramblings, the machine had been powered on and appeared to be correctly regulating the water temperature for over an hour before the heater blew.

Any thoughts gratefully received (even if I've done something stupid!!)

See this for a little more info: http://www.bellabarista.co.uk/pdf/Isoma ... lookv5.pdf

Did you remove the boiler from the machine when you initially replaced the element? Did you replace the brew thermostat temperature probe soundly?

I do concur with your thoughts as regards the brew thermostat, steam "button style" thermostat and safety thermostat. BUT, are you sure that these devices are wired correctly? For lots (all?) single boiler machines, the current for the heating element flows through the steam thermostat and is switched by the brew thermostat even when NOT in the steam mode. When you switch to the steam mode, the brew thermostat is bypassed.

I would recommend you try to get an electrical diagram from Isomac and see this for their info: http://www.isomac.it/writable/machine/p ... affiro.pdf .

But, in any event, attaching a simple temperature probe to the boiler's external surface would be a nice safety mod - expected reading would be in the 225-230 F region.

Eric,

Thank you for taking the time to respond to my questions and providing the useful links - much appreciated.

I did remove the boiler from the machine during heater replacement, interestingly the 'original' heater that was not working showed no signs of rupture from overheating and had simply gone open circuit!

The temp probe was fully re inserted in the thermal well and the wiring is correct (have triple checked it!)

I have received an informative response from the new heating element supplier who suggests that the brew thermostat may have been set a little too high (likely as I foolishly didn't check temperatures) and that over time the water level in the boiler was slowly being 'boiled away' so that a 'heat spot' occurred on the tip of the element that subsequently caused it to blow completely. The element had certainly failed at the top, so this is a likely explanation.

I guess I now need to get another element and thoroughly check the boiler temperature, starting with the adjustable brew thermostat on lowest setting.

Any further insight gratefully received - I cant afford to keep blowing elements at £40 a pop (pardon the pun)

Thanks again

Keith