# Bezzera BZ02 test..



## Rhys (Dec 21, 2014)

I asked the seller if he'd undone the connector on the boiler, he said no. So, I've decided to switch it on and try it (after putting the connector back on).

Filled it with tap water (no point wasting bottled for a test) and plugged it in. It clicked the lights on the front (test mode?) and the whiny/buzzy pump started (apparently a trait of these machines, annoying..) hopefully this was filling the boiler. It might be the boiler already had some water in it as I could see it in some of the pipes. One of the return pipes to the tank had a little bit of water come out (why has it got two? OPV abd boiler pressure stat maybe?). Anyway, pressed the brew button and water came out. Turned the steam and water wands but nothing happened. After a while, all went quiet and the brew head stopped working. I've since emptied the tank and tipped it up to feel underneath, the boiler is very slightly warm. I don't know if the pump is supposed to kick in when its hot or not but I would've thought it would at least pump water from the boiler when the wands are turned on. So I don't know.. The seller said it tripped the RCD after 15 minutes of being switched on (I didn't want to leave it this long as it evidently has something wrong with it). I've not had a HX machine before.

Can anyone help? The local service centre to me charges £35 an hour, and I don't fancy him prodding about to find out what's wrong and it costing me a fortune before he's even sussed out what's wrong. At least the Official Bezzera service centre near Edinburgh said they'd look at it for free if I was local to them (which I'm not).

Here's a quick vid anyway, up to it stopping working. If anyone has any ideas that'd be great! Thanks.

[video=youtube;Tt6nzt-75JA]


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## Kyle548 (Jan 24, 2013)

It works by pulling water into the boiler, heating it and then pulling extra water to keep pressure up.

Pulling water from the wand or hot water eventually turns the pump on, but only after it can't maintain pressure.

I only have one return into my tank.

Bear in mind, also, it creates 1 bar +\- in steam pressure- which is roughly atmospheric pressure.

At less it will continually heat, at higher it won't heat at all.

(If the pstat works).

Also the tank is weighted- if the tank is not heavy enough - about 1/4 full, the pump and boiler won't run to avoid cracking the element.

Looking at it- the lights are acting funny.

Even the Orange light should be on pretty much all the time and the green light for heating.


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## Dylan (Dec 5, 2011)

Steam pressure causes both the steam and hot water to work on HX machines, so you wont get anything unless the boiler is at temp


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## Rhys (Dec 21, 2014)

I filled the tank well over the sensor height. I'm wondering if one of the pipes is for filling the boiler as I have a large water filter that looks like it should fit on the end of one of the pipes. There's a small filter at the bottom of the tank, and I'm also wondering if this is for the brew head only? I'd see some sense in having a water filter on the boiler intake to reduce scale in the boiler itself. I noticed one of the pipes looks like its been stretched a bit. Maybe it stops working as no water is going to the boiler and a thermal cut-out trips in?


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## Dylan (Dec 5, 2011)

If there are no other exits from the tank, then one of those pipes will be the inlet, and should indeed be attached to the filter. I expect it splits off at some point to feed the HX and boiler.

Same design as my Expobar office pulsar.


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## Rhys (Dec 21, 2014)

I've just downloaded a manual and it says..

"A safety device allows to stop the pump after 120 seconds if the water minimum level is not supplied to the boiler. The machine, as alarm signal, turns off the yellow light"

I'll have another look after and connect one of the pipes to the filter. I can guess at which one by immersing them bother and seeing which one draws any up - the other by deduction will be the OPV return.


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## Dylan (Dec 5, 2011)

I'm not sure on this, as Kyle said the boiler is weighted, but looking at parts diagrams there are water level probes that will detect the water and tell the electronics to run the pump.

They work on a ground loop, when the water touches the end of the probe it connects it to the boiler body and thus to ground, this tells the machine to turn off the pump.

You can test if the probe is working properly by removing the wire from the top of the probe, this will break the ground loop and cause the boiler to start filling, touching this wire to the boiler body should stop the pump.

It could, of course, be one of many other problems, but this is one I came across before so thought I would share.


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## Rhys (Dec 21, 2014)

Found this yesterday.. https://drive.google.com/file/d/0BzvJZ_9Mhsq2Z0lFVHprOTU0T2dhV1R5ZnBrbEFmdVg0bExN/view?usp=sharing


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## Dylan (Dec 5, 2011)

Yea, so on page 23, 19 and 8 are level probes, no idea why there are two.


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## Rhys (Dec 21, 2014)

Dylan said:


> Yea, so on page 23, 19 and 8 are level probes, no idea why there are two.


Upper and lower levels?


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## Dylan (Dec 5, 2011)

I can't see why you would need 2 levels, the boiler fills X amount and then the pressure determines the heat.

It probably just a feature that is foreign to my limited experience, hopefully someone can shed some light.


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## Dylan (Dec 5, 2011)

From looking at other machines and googling I think its a safety level probe, maybe to prevent overfilling in the case of the first probe failing.

From a post about a strega on HB:



> The Strega is fitted with two probes because one acts as a safety device to not allow power to the heating element until the probe is covered or to (obviously) cut power to the heating element should the water level fall below the tip.


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## Rhys (Dec 21, 2014)

I think I might've found something significant (then again it might not be..)

The two silicone pipes going into the tank are both snapped, they have both been taped up.

I removed the tape and tried putting some more on to hold the ends together. It didn't work.. Well it wouldn't would it.

Anyway, I just wanted to try holding the ends in the tanks to see if one of them drew water up. Nothing happened, except one started leaking.

So now, I need some silicone tubing..


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## El carajillo (Mar 16, 2013)

Check the ends of the tubes, you may / will need new olive's or inserts for the connections. Also make sure you obtain the correct grade/ hardness of tubing.


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## JohnPrime (Nov 2, 2014)

Rhys said:


> to see if one of them drew water up. ...


No, one of the silicone tubes is the OPV bleed (from the OPV). It just dumps into the water reservoir. The other does a similar thing from the other valve. I don't (wish I did) know the functiion of this valve.

The water filter on mine is a film-canister sized jobbie with a tube that connects to the water output in the base of the tank.

The 2 probes are minimum ( you always want the element submerged) and maximum (you don't want the boiler over-filled).

The video shows that the heater is switching off before the water's barely warm: that's why there's no steam and no water (which is forced out by steam pressure). I noticed that the heater light went off as soon as you switched the pump off. I'm no expert but some possibilities are: thermal cutout is f***ed, control unit ditto, wiring to element dodgy, element not well. Please can a clever technician help?

Also, FFS please stop touching a live machine that's known to be unwell and is said to trip the RCD; switch it off and pull out the plug before you feel if it's warming up.

HTH

John


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## Dylan (Dec 5, 2011)

JohnPrime said:


> The 2 probes are minimum ( you always want the element submerged) and maximum (you don't want the boiler over-filled).


So on most machines does the water level probe simply acts as a cut out for the pump, and the element is on regardless?

That would make sense as to why some machine have 2 stage switch to fill the machine, and then turn on the element... the extra probe in the BZ02 must essentially automate this process...?


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## JohnPrime (Nov 2, 2014)

TBH I don't know. This BZ02 is the only machine I've ever had (except a psychopathic Europiccola) so I don't know how others operate. The element is switched on if the following statements are all true: mains power is on via main power switch, pressure stat is on (ie boiler pressure is under set-point), controller (gicar) is signalling 'OK to heat'. This last requires at least that there's enough water in the boiler.

Attached is a circuit diagram I made from the official one; I found it unpleasantly labyrinthine so did my own. Obvs I don't guarantee that it's accurate. Your risk etc ...BZ02 diagram.pdf


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## Norvin (Sep 10, 2014)

Now then Rhys.

I've just got around to looking at this machine.

I found that the boiler fill solenoid plunger was seized in its housing. It was seized closed so no water was being diverted to the boiler.

The brew system was being fed by the pump as it bypasses the soleniod, hence water was coming out of the group head.

The water in the boiler would have been very low due to losses from steaming, leading to the boiler overheating, hence the tripping.

At least that's my interpretation. Its been on for about three hours now, seems to be working fine.


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## Rhys (Dec 21, 2014)

That's great news! Glad it's working ok now. It's a shame that the people I contacted to have a look it wanted stupid amounts of money, as they mainly do commercial. More than the machine was worth in fact. I could've started pulling things apart, but knowing me I'd've either broken it or blown myself up!

Does it make coffee now?


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## Norvin (Sep 10, 2014)

Rhys said:


> Does it make coffee now?


That will have to wait 'till tomorrow.

I've read that with HX machines you have to do a water dance before pulling a shot. I've not danced for years and don't know the steps, will a dad shuffle do?


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## Rhys (Dec 21, 2014)

Norvin said:


> That will have to wait 'till tomorrow.
> 
> I've read that with HX machines you have to do a water dance before pulling a shot. I've not danced for years and don't know the steps, will a dad shuffle do?


Don't get confused with a rain dance, otherwise your kitchen might get a bit wet..


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