# Loud bang from heat exchange machine during descale!



## alip_93 (Feb 28, 2015)

Hi all,

I was performing my first descale on my Quick Mill Andreja. As I was flushing through clean water to get the descaling water out of the machine, I noticed some steam coming from the top of the machine and a couple seconds later a loud bang. I immediately turned the machine off at the mains. Upon looking inside, there is some water around a valve on the top of the boiler and some at the bottom of the machine. I haven't turned it back on. Could this be the pump over heating or electrical short circuiting due to the water?

Bit of a nightmare!


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## Jon (Dec 3, 2010)

I'm no expert* but sounds 'shorty'

*on anything


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## garydyke1 (Mar 9, 2011)

Perhaps the boiler overfilled and triggered the pressure relief valve?


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## espressotechno (Apr 11, 2011)

Probably the safety valve popping. Maybe due to overfilling.

Remove saftyr valve & look inside the boiler: If it's full, syphon some water off & refit the valve.

Dry everything off (use hairdryer...), use a powerbreaker adaptor, plug in & switch on again.

If the steam gauge keeps rising after 1.5bar, switch off: You have a faulty pressure switch & need a new one.


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## urbanbumpkin (Jan 30, 2013)

Was the pump kicking in when you were flushing the descale out?

Were you flushing out via the HW or via the group?

The bang could just have been the safety valve going off. This may have been caused by the boiler not refilling.

Try mopping up the excess water first before doing anything and see if there's a clear sign of a short.

I believe the newer Andreja's have a switch on the front to switch off the heating element. It might be worth switching this to off before firing up the machine.

If you have an older machine like mine you can disconnect the heating element at the bottom of the machine. The should be a little square plate with 2 screws.

Once off try the machine and see if the pump kicks in. If it doesn't repeat a few times.


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## urbanbumpkin (Jan 30, 2013)

Have just seen Gary's and espresso techno's post. Sound advice, re hairdryer / power breaker. I hadn't thought about overfilling.

Was the pump running at the time?


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## garydyke1 (Mar 9, 2011)

Could be scale build up/damage to the fill sensor ?


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## urbanbumpkin (Jan 30, 2013)

garydyke1 said:


> Could be scale build up/damage to the fill sensor ?


Isn't the fill sensor disconnected during descale? Has it been re-connected properly?

Questions questions questions.


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## 7493 (May 29, 2014)

My understanding is that, for a normal descale, there is no need to disconnect the fill sensor since no scale forms above the usual fill level. If the OP did disconnect the fill sensor then this might well cause problems if it was inadvertently forgotten.


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## El carajillo (Mar 16, 2013)

How old is the machine ? Is it "new" OR Is it "new" to you ? I would agree with espressotechno, possibly over fill and safety valve releasing excess pressure or pressure stat allowing it to over heat /over pressure. Thoroughly dry internals, especially wiring and electrical's before trying anything else


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## urbanbumpkin (Jan 30, 2013)

How are you getting on........................... Silence isn't a good sign


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## alip_93 (Feb 28, 2015)

Hey all, Thanks for advice. I've been away at glastonbury for the week so I left it to thoroughly dry out before turning it back on again. Checked the internals and all seemed to look completely dry. Plugged it in, flicked the switch and there was another loud bang and it blew a fuse. It's unplugged again for now. The fill sensor was disconnected for the descale, but reconnected before the flushing took place. I was following the instructions on this video: https://www.youtube.com/watch?v=iuODdWm7oJQ.

All cables are connected firmly. Would turning off the heating element help?

Any advice is appreciated!


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## urbanbumpkin (Jan 30, 2013)

alip_93 said:


> Hey all, Thanks for advice. I've been away at glastonbury for the week so I left it to thoroughly dry out before turning it back on again. Checked the internals and all seemed to look completely dry. Plugged it in, flicked the switch and there was another loud bang and it blew a fuse. It's unplugged again for now. The fill sensor was disconnected for the descale, but reconnected before the flushing took place. I was following the instructions on this video: https://www.youtube.com/watch?v=iuODdWm7oJQ.
> 
> All cables are connected firmly. Would turning off the heating element help?
> 
> Any advice is appreciated!


Possibly, how soon between the switch on and the bang?

Did the pressure suddenly shoot up?


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## alip_93 (Feb 28, 2015)

Pretty much instant. Fuse blew as soon as I flicked the switch and scared the shit out of me. Hahaha.


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## urbanbumpkin (Jan 30, 2013)

If there's a bit of a delay then it could be the boiler not being full of water or overfilled. In that case the bang would probably be the boiler safety valve going off.

If its immediate then it sounds like something electrical.

Does the switch on the front look like this? If so try it in just the fill position.


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## urbanbumpkin (Jan 30, 2013)

alip_93 said:


> Pretty much instant. Fuse blew as soon as I flicked the switch and scared the shit out of me. Hahaha.


Sounds more electrical than anything else.

He's were I hand over to more qualified people that me.

Is it worth opening it up, taking a photo of the top of the boiler and indicating what you disconnected. Just to rule out what you've done and re-connected in the de-scaling process.

I'd try disconnecting the heating element and then trying it.....but i'd prefer the advice off someone with electrical know how before you do.

Any thoughts anyone?


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## DavecUK (Aug 6, 2013)

It could well be the limit stat, on Andrejas, especially the early ones, they had a habit of shorting out. If the autofill sensor is disconnected to descale (which I never advise), there is a good chance this got wet and shorted out. if you bypass the limit stat on top of the boiler and it works, then it almost certainly is shorted. Sometimes, not always, there are burn marks visible.


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## alip_93 (Feb 28, 2015)

Would having it completely dry not prevent the shorting out? The limit stat sounds like a likely candidate. I've got the simple on/off switch andreja. This pretty much describes my issue.

http://coffeetime.wikidot.com/andreja-goes-pop

Looks like i'll be taking this baby apart. Would I need a new limit stat or is the old recoverable? Also best place to get one? Cheers All! It's so damn hot!


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## alip_93 (Feb 28, 2015)

Right. I've bought a new limit stat from Bella Barista. I'll see if replacing that fixes the issue. Anything else to suggest in the meantime?


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## DavecUK (Aug 6, 2013)

alip_93 said:


> Right. I've bought a new limit stat from Bella Barista. I'll see if replacing that fixes the issue. Anything else to suggest in the meantime?


I'm reluctant to suggest more, because I thought you might have tested it to see if it was indeed the limit stat....so don't want to risk incurring you unnecessary expense.


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## Dylan (Dec 5, 2011)

DavecUK said:


> It could well be the limit stat, on Andrejas, especially the early ones, they had a habit of shorting out. If the autofill sensor is disconnected to descale (which I never advise), there is a good chance this got wet and shorted out. if you bypass the limit stat on top of the boiler and it works, then it almost certainly is shorted. Sometimes, not always, there are burn marks visible.


Is the autofill sensor you mention here a regular level probe?


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## DavecUK (Aug 6, 2013)

Dylan said:


> Is the autofill sensor you mention here a regular level probe?


Yes..rod of metal in a teflon sleeve.


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## Dylan (Dec 5, 2011)

DavecUK said:


> Yes..rod of metal in a teflon sleeve.


Just wondering how that could short and cause another electronic problem? Do you just mean it as in it allowed the boiler to think it was full when it was not?


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## DavecUK (Aug 6, 2013)

Dylan said:


> Just wondering how that could short and cause another electronic problem? Do you just mean it as in it allowed the boiler to think it was full when it was not?


It was only mentioned because I believe the OP disconnected it to descale the machine.....a practice I don't recommend.


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## Dylan (Dec 5, 2011)

Fair enough, I broke a fill probe when re-assembling a machine so there is good enough reason to not tamper unless necessary. I just wondered how it could be considered to cause a short, if the OP is fault finding it could be misleading to think the fill probe could have caused an electronic short.


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## urbanbumpkin (Jan 30, 2013)

DavecUK said:


> It was only mentioned because I believe the OP disconnected it to descale the machine.....a practice I don't recommend.


What's the practice that you would recommend to de-scale an Andreja / a HX Dave?

The last one I did on mine was to remove the heating element, invert and filled manually fill with descaler. Only because it was 7 years old and to completely strip the boiler and get rid of the sediment that builds up over time. Not the standard descale I agree.


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## alip_93 (Feb 28, 2015)

Okay so I've replaced the limit stat (the old one was definitely fried), put a bit of dish cloth around the valve to prevent any further splash and switched it on. No bang this time thankfully but no sign of life either. Is there anything else I need to check/reset?

Thanks all!


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## urbanbumpkin (Jan 30, 2013)

alip_93 said:


> Okay so I've replaced the limit stat (the old one was definitely fried), put a bit of dish cloth around the valve to prevent any further splash and switched it on. No bang this time thankfully but no sign of life either. Is there anything else I need to check/reset?
> 
> Thanks all!
> 
> View attachment 15258


Fuse in the plug?


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## MrShades (Jul 29, 2009)

Any lights on or sign of any power at all when you turn it on? Can you easily check to see if power is being applied to the heating elements, or at the very least check the impedance of tthe heating element? ((These two tests, ideally, would cover the "Is power being applied to the elements?" and "Do the elements actually work?" - cus an answer of "Yes" to both would result in the water heating up, and that isn't happening, so one or both will be a "no").

Dummy question, but have you checked the fuse in the plug?


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## alip_93 (Feb 28, 2015)

Haha. Just stole a 13A fuse out the kettle. All fixed. Thanks all for your patience with an electrically clueless coffee lover.


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## MrShades (Jul 29, 2009)

You're not the first and certainly won't be the last - glad it's (now) an easy fix!


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