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Thread: HX machine on a timer

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    HX machine on a timer

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    My previous machine, PID Silvia, was on a timer I could set to come on in the morning. Id like to run my HX Bezerra a similar way (indeed probably even more so as at least Silvia heated up quickly if I forgot). However I find that with the steam wand closed, as air in the boiler heats up, the pressurestat turns off the heaters before the machine is at full operating temperature. Clearly if its on a timer, leaving the steam wand open and closing it once it begins to steam is not an option.

    Is there any way around this issue, short of replacing the presurestat with a PID?

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    Re: HX machine on a timer

    clean or replace the anti vaccuum valve
    so that the machine works correctly
    then it can be fitted to a timer
    you will still need to bleed the steam and run hot water through the group head before making coffee

    graham

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    Re: HX machine on a timer

    Quote Originally Posted by fix link=1228944909/0#1 date=1228945611
    clean or replace the anti vaccuum valve
    so that the machine works correctly
    then it can be fitted to a timer
    you will still need to bleed the steam and run hot water through the group head before making coffee

    graham
    Thanks Graham. Its a Bezerra BZ-40E and I recently completely rebuilt this machine, where it was stripped to component level. While the boiler/hx/elements were out I cleaned the boiler to within an inch of its life *;D No scale etc in there. Now while the OP/anti-vacuum valve was one of the very few components I didnt remove and strip, I feel it is operating correctly. If I grab the shaft of it with the boiler pressurised I can release pressure through it (obviously I cant determine at what pressure this would be, just that it does release in an over pressure situation). On the other side of the equation, I havent seen any obvious signs that its not allowing a vacuum to equalise after the machine has cooled down. I normally leave the steam wand closed however if I open it up after the machine has cooled theres no in-rush of air, the machine is completely dead, but Ill certainly check very carefully next time to be absolutely sure. I also dont think its sucking up water past the solenoid either. I just had that solenoid apart a few moments ago as a matter of fact as I had an extremely weeny drip past the seal (out into air) and the solenoid seal looked good. Incidentally, as a complete aside, if anyone wants to REALLY know their machine do a strip and rebuild ;)

    This is the first HX machine Ive owned however was told on a "Barista course" I did that with the commercial machines we were using to leave the wand open after turning the machine on until it begins steaming, then close the wand. I presumed that was the fastest way to get the machine up to temp, but its hard for me to know when N=2 *;D

    So is this behaviour Im experiencing therefore not normal on a pressurestat machine? I should be able to turn it on and it come up to normal operating temperature with the machine fully closed from the start? The bleeding of the steam you mentioned was exactly what I needed to do, unless you just mean bleeding the condensed water from the wand. If I did that, the pressure dropped to zero and took a few moments to come back up to normal steam pressure. ie it wasnt at full operating temperature.

    Pete

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    Re: HX machine on a timer

    Pete,

    Yep, those anti vacuum valves are often dodgy - even when new or serviced. They generally have a O ring which seals when the boiler is under pressure - and should release when the boiler cools down...

    However in my experience they have a habit of sticking..... and then when the unit heats up - the air is not expelled by the expanding steam..... you then have a boiler with lots of air in it..... and the pressurestat also detects "false pressure"..... and doesnt allow the water to fully heat (when you go to texture milk the pressure falls to zero - almost instantly)....

    The solution to this (as you were told at the commercial machine course) is to open a steam wand at cool down and leave it open until you get a strong stream of steam coming out a heat up.....


    The anti vac valve SHOULD do this automatically for you..... but Ive found even a new one (on my La Cimbali) often doesnt.....

    So I always use the "steam wand trick"

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    Re: HX machine on a timer

    Quote Originally Posted by PeteF link=1228944909/0#2 date=1228957130
    I should be able to turn it on and it come up to normal operating temperature with the machine fully closed from the start?
    Yes. My Faema does. I have mine on a timer and have had no problems with the machine fully closed.

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    Re: HX machine on a timer

    Quote Originally Posted by JavaB link=1228944909/0#3 date=1228958972
    However in my experience they have a habit of sticking..... and then when the unit heats up - the air is not expelled by the expanding steam..... you then have a boiler with lots of air in it..... and the pressurestat also detects "false pressure"..... and doesnt allow the water to fully heat (when you go to texture milk the pressure falls to zero - almost instantly)....

    So I always use the "steam wand trick"
    Yeah thats whats happening. Whats worse is that if I forget (as I did when I first started using the machine), Id pull the shot, THEN go to do the milk and realise that the machine wasnt up to temp so it goes down the drain.

    I must admit however that Im confused with what you guys are saying regarding the anti-vac valve. From my understanding it is there to break a vacuum that may form as the machine cools. If theres no vacuum the valve is simply closed (except in an over-pressure case in my machine, but thats irrelevant). So if the wand is closed and the anti-vac valve is closed the boiler becomes simply a pressure vessel and will build pressure in it as it heats. However there was ambient air in there to begin with (let in by the AV valve) and I cant understand how the anti-vac valve would affect the boiler once it begins heating and allow air to be "expelled", unless of course it was leaking. Indeed it seems to me quite the opposite, if it were stuck closed and allowed a vacuum to form the machine could heat back up to its normal temperature from whence it came. Is the anti-vac valve supposed to remain open until pressure begins to build? If so that would make sense.


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    Re: HX machine on a timer

    I have had my Expobar on a timer for almost two years now with no problems.

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    Re: HX machine on a timer

    Quote Originally Posted by PeteF link=1228944909/0#5 date=1228962955
    I must admit however that Im confused with what you guys are saying regarding the anti-vac valve. From my understanding it is there to break a vacuum that may form as the machine cools. If theres no vacuum the valve is simply closed (except in an over-pressure case in my machine, but thats irrelevant). So if the wand is closed and the anti-vac valve is closed the boiler becomes simply a pressure vessel and will build pressure in it as it heats. However there was ambient air in there to begin with (let in by the AV valve) and I cant understand how the anti-vac valve would affect the boiler once it begins heating and allow air to be "expelled", unless of course it was leaking. Indeed it seems to me quite the opposite, if it were stuck closed and allowed a vacuum to form the machine could heat back up to its normal temperature from whence it came. Is the anti-vac valve supposed to remain open until pressure begins to build? If so that would make sense.

    What happens is that the anti vac valve doesnt fully open.... it just allows air to slowly leak in as the machine cools down.... so yes, there is no vacuum in the boiler.... but the boiler does actually fill with air slowly!

    When you heat up the machine.... the smallest pressure causes the valve to close in this case (where if it had opened correctly it doesnt close until there are quite a few PSI in the boiler). So the boiler is virtually full of air (where it should be full of steam had the anti-vac worked).....

    Whilst some people seem to be lucky (possibly some anti vac valves are a slightly better design)..... It is, in general, known to be an issue.... and that is why on the commercial machine courses they insist on the operator using a steam wand.

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    Re: HX machine on a timer

    the bezzera OP/ AV valve needs pulling apart and a new oring being fitted

    doing a strip down and rebuild with out servicing the safety valve or anti vac valve is only doing half the job

    the anti vacuum valve needs regular service, just like the rest of the machine

    tooo many so called repairers dont even take the top off the machine when doing a service

    the operation of the av is a very important part of the operation of the machine. people talk about the importance of temp or pump pressure. but checking and cleaning av valves or OP valves gets neglected

    graham

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    Re: HX machine on a timer

    Ok, ta. I edited my previous post to add the last part where I suspected that may have been how they worked but obviously wasnt sure, just a guess. I think the thing Ive learned from this rebuild is that if it warrants rebuilding then while its apart do EVERYTHING! At the time there was also a couple of solenoids I hadnt stripped and wouldnt you know one was partially blocked. I wouldnt have found it was blocked had I not accidentally got some Loctite thread sealer in the line which then blocked it completely. Looks like this valve also should have had the once over. With a basket case, as this machine was, dont assume anything will be "ok". Oh well, fortunately the Bezerra is a dream to work on so hopefully no big deal to whiz the AV valve off.

    I can imagine various makes/models may be better or worse in this regard, but will certainly see how I go.

    It looks like its otherwise good to bottle up. As I type Im enjoying a sensational latte off it, and the other half of the double was a magnificent espresso so I have to say it does a great job. Looking forward to having it finally fully plumbed in final resting place!

    Pete

    Edit: Thanks Graham, we posted at same time. I figured Id got the valve ok in situ as the whole boiler got a full immersion cleaning (outside looked great too, shame the heat so quickly oxidises the copper). However it seems I was mistaken. As mentioned, no biggie, can be done any time.

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    Re: HX machine on a timer

    As a matter of interest Graham,

    Is there such a thing as a combination AV/OP Safety Valve :-?? My old Bezzera only has an OP Valve, no location to fit an AV Valve. Im not concerned about putting the Bezz on a timer, just thought that if such a combo valve was available Id think about fitting it..... :)

    Mal.

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    Re: HX machine on a timer

    Pete,

    I suspect this anti vac problem is more of an issue with larger boiler machines (mine has a 17L boiler)...

    When you switch it off, it cools very slowly - steam pressure takes several minutes to drop to zero.

    The anti vac valve is held closed by boiler pressure.... and only gravity (and the vacuum in the boiler) causes the valve to drop and the O ring to move from its seat. With the slow cool down, it appears to open just a little.... allowing just enough air in to prevent a vacuum. I have observed even a new O ring remaining adhered to its shiny seat in the valve (the valve was initially cleaned and a new kit put in it - still failed occasionally - replacing the valve - same story.... worked sometimes... failed to open other times).

    When this happens, virtually zero pressure is required to fully reseat the O ring and seal the boiler.... and you then retain air in the boiler.

    Give it a very slight tap..... the valve drops and heat up continues until some steam starts to exit the valve - it then snaps shut and everything works normally.

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    Re: HX machine on a timer

    Quote Originally Posted by Mal link=1228944909/0#10 date=1228980969
    As a matter of interest Graham,

    Is there such a thing as a combination AV/OP Safety Valve :-?? My old Bezzera only has an OP Valve, no location to fit an AV Valve. Im not concerned about putting the Bezz on a timer, just thought that if such a combo valve was available Id think about fitting it..... :)

    Mal.
    Ergh, I see! My advice not good enough hey Mal! *::) Not sure about your Bezzera however I understand its typical Bezzera and its certainly the case with mine. It will definitely have some sort of vacuum breaking system and if you cant see another one it will be a combo. As I recall you have a 35 and they are very similar to the 40.

    Ive taken mine out and you guys were right, the OP part looks fine, but the vac breaker is stuck closed. Its soaking now but dont hold up my hopes of freeing it up without disassembling further, a job thats going to be a PIA by the looks of it as its designed to just drop out and theres nothing to drive it out that I can see. Gotta love the Italian engineers *;)

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    Re: HX machine on a timer

    Woo Hoo! It did just drop down after all! My lucky day. Is there anything that can be done to help prevent this valve sticking? I cant see any way of lubricating it, given that steam is basically going to and from with each cycle.

    Mal, I was of course just messing with you. Ive had a look at the BZ-35 manual and it looks like its identical to the -40 as I suspected. The valve is #16 on page 4, they call it a safety valve. For the OP side imagine a plunger working against a spring within the casing you see from the outside. The boiler has a seat on it so the spring pushes the plunger down. Now if you can picture this plunger as actually hollow, and inside IT is a weeny little chuppa chup dangling from its stem. Gravity un-seats it and a cross pin stops it falling in to the boiler. Once the steam pressure rises enough it will overcome the weight of the "chuppa chup" and force it back up against its seat (which is inside the OP "plunger").

    Hopefully that all makes sense, it certainly does once you pull it apart. It looks as if Bezzera only sell the complete assembly however so if a seal needs replacing (or the Vac valve gets REALLY stuck) then youre probably fresh out of luck.

    Pete

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    Re: HX machine on a timer

    Quote Originally Posted by PeteF link=1228944909/0#12 date=1228985036
    Ergh, I see! My advice not good enough hey Mal! ::) Not sure about your Bezzera however I understand its typical Bezzera and its certainly the case with mine. It will definitely have some sort of vacuum breaking system and if you cant see another one it will be a combo. As I recall you have a 35 and they are very similar to the 40.
    I had a laugh Pete.... ;D

    I must have overlooked your reference to this valve (sorry) as I didnt see anything there specifically about a combination job. Anyway, not to worry.

    My Bezz is a very old machine (20+ years) and is already stripped down to component parts, including the Safety Valve (their nomenclature, not mine). It is most definitely not a combo valve though, just a straight forward OP Safety Valve that is nice and clean and also seems to be working well enough, one has to suppose, at the correct pressure. Given the age of my machine, it is quite possible that the original valve assy was replaced with the current OP Valve some time back in its history. Ill have a look through my various Bezzera parts catalogues to see if I can spot a combo valve that can be directly swapped. Must admit that I never considered that a combo valve might have been fitted originally so that would be a good fix if I can find one. 8-)

    Just so happens that my background is in engineering (Electrical) too Pete so understand hydraulics and pneumatics pretty well but appreciate your taking the time to explain. Will be quite useful to people who may not have had exposure to this type of hardware before. All the best mate..... :)

    Mal.

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    Re: HX machine on a timer

    Quote Originally Posted by Mal link=1228944909/0#14 date=1229001179
    I had a laugh Pete.... ;D

    I must have overlooked your reference to this valve (sorry) as I didnt see anything there specifically about a combination job. Anyway, not to worry.
    Pffft, no way buddy, youve done you dash with me! *:P

    I could see this little valve was going to be a big PIA, even after reassembling it got stuck closed immediately. It clearly either needed to be replaced or needed some sort of lubricant to help it along its way. I didnt fancy my next latte tasting like ezy glide (could they possibly make a product STINK more than it does, even I wont use it!!), so after the benefit of a poor nights sleep decided I needed to think laterally and it would have to come from the kitchen. Enter Mr Spray Olive oil. Whiz the top off him, exchange a nozzle off a can of WD-40 and there you have it, a can of food safe spray lube. Ok on the lubrication front it probably doesnt rate too highly, but it seems to do the job and Im sure would bring a tear to the eye of any red blooded Italian!

    Anyway, not sure if this will work, but for the benefit of anyone other than Mal, I took a photo of an "exploded view" of what a Bezzera "safety valve" looks like. Ive often read people say that their Bezzera doesnt have an AV valve, but you can see it in the middle of the photo. Inside that is another valve; the "chuppa chup" that hangs down. I probably should have taken a close up of that but managed to bugger up the focus on this shot so will leave it at that.

    BTW Mal, my background was similar, in my case electronics. Actually I was just toying with the idea of putting some form of soft-start on this pump motor but think it will go in my (now over-flowing) couldnt be buggered basket.





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    Re: HX machine on a timer

    hi
    this valve has an Oring and ball located in the bottom of the shaft

    to service it, replace the oring, lubricate with Molycote grease, clean the ball and the hole, replace oring on safety valve side reinstall
    you need to adjust the release pressure of the OP valve

    even a new av valve needs the seal being lubricated,
    we use Molykote valve and oring Lube, this lube is suitable for up to 200*c and steam

    Hi Mal

    your bezzera only has an OP valve, not a OP/ AV combo

    if you contact chris at Barazi he can help with the right one

    graham

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    Re: HX machine on a timer

    Ok thanks Graham, I didnt expect this part to be technically "serviceable" and guessed it was just considered a replacement part. Having said that, that certainly wouldnt stop me pulling it apart anyway. Theres a cross pin that will need to be driven out and I decided that, given how easy the unit is to service, Id see how it went.

    Molykote, pfft, what, you didnt like my olive oil trick? Fine Ill go get some Molykote then! *::) Unfortunately that will no longer give me any excuse as to why I reinstalled the steam and water valves without similarly lubricating them *>:(

    As its turned out, with the valve now functioning I can hear it leaking ever so slightly so will take it out and do it properly. Regarding setting the release pressure on the OP valve I presume its done with a spring gauge and screwing the outside sleeve up or down to get the correct tension, or replacing shims/washers? Is that correct and if so can you tell me what the tension is? Unfortunately this machine had been to hell and back by the time I got it and so just reassembling the way I found something is absolutely no guarantee at all that its anything like correct.

  19. #19
    Mal Dimal's Avatar
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    Re: HX machine on a timer

    Quote Originally Posted by fix link=1228944909/0#16 date=1229039996
    Hi Mal

    your bezzera only has an OP valve, not a OP/ AV combo

    if you contact chris at Barazi he can help with the right one

    graham
    Good one Graham,

    Thanks very much for that mate... [smiley=thumbsup.gif]

    Mal.

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    Re: HX machine on a timer

    Quote Originally Posted by PeteF link=1228944909/0#15 date=1229029680
    Actually I was just toying with the idea of putting some form of soft-start on this pump motor but think it will go in my (now over-flowing) couldnt be buggered basket.
    Ahh, know that feeling very well indeed :P .... I keep a hard-bound log for all the things I dream up and want to get around to dealing with someday; but you know what they say about someday..... ::)

    Mal.

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    Re: HX machine on a timer

    morning pete
    generally i dont service them, just replace them
    (Most new ones are preset)

    but sometimes this is necessary
    to set OP,
    wind all the way onto the base thread, adjust pressure switch to 1.7 bar, back of OP until it leaks steam, Tighten
    test by winding pressure switch down, then back up to ensure it lets of steam
    Dont burn yourself

    Graham

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    Re: HX machine on a timer

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    Yeah it seems the Bezzera is designed to be replaced but still looks quite easily serviceable inside. Ill adjust that after Ive serviced it, thanks for that. As with the rest of this machine when I got it, it was totally butchered and somebody had just screwed the whole assembly down hard.

    Thanks for that.

    Pete



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