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UNIC Espresso machines- backflushing and more!

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therob
Senior Member

Joined: 21 Nov 2011
Posts: 8
Location: Birmingham, UK
Expertise: Just starting

Posted Thu Dec 27, 2012, 1:57pm Subject: Re: UNIC Espresso machines- backflushing and more!

Hi there, I have just come across this thread, and was hoping you could answer some questions... I bought a Diva Pro on Ebay early 2012 and I have just got it up and running for Christmas. One of the things I had to do was replace the pressure gauge the old original wouldn't zero even while not connected to water and off... what I have found is that the water side tops out when idle and shots are currently coming out at around 11-12 bar on the gauge... is there a way to easily adjust the pressure? Secondly, I am a noob to all this... its a bit of an adventure... all the shots are consistently coming out VERY bitter (undrinkable), I have adjusted the grind and dose and feel I have come to the right combination but I assume the pressure has something to do with it...? It is so difficult to find a great espresso commercially - I need to get this right so that I can just roll out of bed and have one... or two thanks so much R

gucciago
Senior Member

Joined: 6 Apr 2004
Posts: 78
Location: Palm Beach,FL
Expertise: Pro Roaster

Espresso: 07 La Marzocco Linea 3EE/...
Grinder: MAZZER Major with DOSER
Vac Pot: N/A
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Roaster: Custom Gas Drum Roaster/PID...

Posted Thu Dec 27, 2012, 4:21pm
Subject: Re: UNIC Espresso machines- backflushing and more!

therob Said:

Hi there,

I have just come across this thread, and was hoping you could answer some questions... I bought a Diva Pro on Ebay early 2012 and I have just got it up and running for Christmas.

One of the things I had to do was replace the pressure gauge the old original wouldn't zero even while not connected to water and off... what I have found is that the water side tops out when idle and shots are currently coming out at around 11-12 bar on the gauge... is there a way to easily adjust the pressure?

Secondly, I am a noob to all this... its a bit of an adventure... all the shots are consistently coming out VERY bitter (undrinkable), I have adjusted the grind and dose and feel I have come to the right combination but I assume the pressure has something to do with it...?

It is so difficult to find a great espresso commercially - I need to get this right so that I can just roll out of bed and have one... or two

thanks so much

R

Posted December 27, 2012 link

Is your machine designed to use the pods or your own ground coffee? To start with, even if you disconnect waterline you will have residual pressure in machine from the one way valve before the pump ... And similar with vibe pump also... So if your needing to remove all water or depressurize, disconnect waterlne and start pump for 1 second that should depressurize... Now... Back to bad shots... For one you need proper tamper and I beleive yours is a 57mm ... Also good grinder and assming you have these already... They are imparative... Now onto other issues... If you have the rotary vane pump version then facing machine with the right side panel off at back mid way up you havean OPV (over pressure valve) and could possibly need to be adjusted... And on the bottom right side under boiler is the rotary vane pump if so equipped... On the pump body usually facing down on end of motor there is a screw to make adjustments to pump.... One other thing... What is the bar of boiler read? .8-.9? And on your left needle what is it setting at? Also when you pull a shot, what does left needle steady out at during shot pressure and after shot completes does it spike up to over 15?

gucciago
Senior Member

Posted Thu Dec 27, 2012, 4:46pm Subject: Re: UNIC Espresso machines- backflushing and more!

One other thing i forgot to mention... Dont forget the gauges are not super accurate when guessing grouphead pressures which are generally 1-2 bar lower ... My unic for instance has a group head pressure around 8.5 and 10 on body mounted gauge during shot ...

therob
Senior Member

Joined: 21 Nov 2011
Posts: 8
Location: Birmingham, UK
Expertise: Just starting

Posted Fri Dec 28, 2012, 3:54pm Subject: Re: UNIC Espresso machines- backflushing and more!

thanks so much for your quick reply... it is a traditional ground machine The previous gauge was definitely broken, it was the steam pressure that didn't change that really worried me - as I couldn't tell whether it was up or not - or just about to blow up... I have a tamper albeit a really cheap one and I am getting really solid "pucks" (no streaming and fairly level) out after extraction so I think that should be ok but I will look into getting a decent stainless one... I also have a commercial grinder so I think I am able to achieve a reasonable grind... but that said if the water temp is too high and the pressure is all wrong then I assume it doesn't really matter...? when the machine is warming up the water needle would probably go round twice if it weren't for the other needle being in the way! it does spike up after a shot yes... I will double check what the gauge reads during the shot and also exactly what the idle pressure reading is and let you know... sorry if this is obvious but is the boiler bar reading on the front gauge or is there a gauge inside the machine which I have missed? what is the best way to test group head pressure... is there some way to do it while a shot is being pulled? lastly I have seen on some other forums that people have adjusted the water temperature is that fairly simple to do - I assume I should know how to do this in case it is pushing too high? Thanks again R

gucciago
Senior Member

Posted Fri Dec 28, 2012, 4:27pm Subject: Re: UNIC Espresso machines- backflushing and more!

Well first off you need to establish your anti siphone valve is ok... when heating up, is there a little valve that may spit a littl water until boiler is hot then seals itself? This is very important to get proper and not false pressure readings... If it is not working ( probably located high on the left side back of machine if like mine) opensteam wand a coule times during warm up and if gauge drops really quickly when you thoughtit was hot then its the false pressure and maybe the anti siphon isnot working correctly also on the right needle does it go up and down by.1 bar and y canaudibly hear it coming on and off with a click from the pressurestat? Leftneedle is line pressure when idle and shot pressure when pulling shot and then might spike a little but then if OPV over pressure valve is working correctly you will see some drips inthetray andtheleft needle should not go past around 12 ... If during shot its round 8-9 thenthat should be okk... You cangoto espresso parts and look for an adapter for a portafilter you may have extra to look atgroup pressure... Gauge on machine is not accurate its just a genral reading comeing from line pathway... If pressure it too high or OPV not working correctly you would be hittingthe grounds very hard with pressure not allowing ground to blossom and saturate in the basket thus overextracting espresso... Pressure control is very important and you could have several issues or just one... What coffee are you using?fresh roasted?

therob
Senior Member

Joined: 21 Nov 2011
Posts: 8
Location: Birmingham, UK
Expertise: Just starting

Posted Sat Dec 29, 2012, 6:06am Subject: Re: UNIC Espresso machines- backflushing and more!

Ok... Posted a video and pic here: Video: https://www.dropbox.com/s/d4txnocf9kx79mt/IMG_1406.MOV is this the OPV?: https://www.dropbox.com/s/npbj7tvg77l4w4g/IMG_1407.JPG So I think the siphon valve is working... see video (sorry its so long - 3.5mins) I assume the OPV adjuster is the flat head threaded nut that goes into the brass housing (see image - or is it the upright valve on the left?)... to be honest it doesn't seem to make any difference at all... right in and pressure is high (off the scale) and shot comes through at about 15bar and right out and I get the same readings... on both occasions there is a slowish steady drip into the tray straight after the shot for about a minute... seen the adapter for the portafilter on ebay for £20 so will get one of those. Thanks R

gucciago
Senior Member

Posted Sat Dec 29, 2012, 7:06am Subject: Re: UNIC Espresso machines- backflushing and more!

Ok before going any farther you need to disconnect the brew pathway side of manometer ( gauge ) and put a new good test gauge on it and see what the heck is really going on... Also was this machine considered fully warm? On right side of gauge you are sitting way too low at around 5 bar it should be around .9- 1.0 bar ...if gauge reading is too low then that little spitting valve top left of boiler called the antisiphon valve is releasing false pressures as tank water expands and heats to full temprature and its obviously not there yet lol ... The hot water does come out strong like in video so thats ok And in the video, the all brass cylidrical valve with wide flat screw on top with 2 divot holes is your OVP that should terminate via a copper line into rear of drip tray... Now if your hearing the pressurestat cycle on and off ( big box on back of boiler usually branded" sira" with screw on top) . Then you need turn that up until it cycles in .9 range on right gauge (via screw on top of pressure-stat) but you really should also look around for scale,especially coming from the safety valve on top.. id say honestly, you really have to get these readings correct before you can go further... If you fracture the brewpath into the boiler or safety valve is scaled up you could blow that thing to peices... However its more likely stil too low on heat... The other thing is that it could be full of scale and not much room for boiler water but then id doubt you'd have that much hot water... With a tank of 6.5liters the is plenty of hot water when running properly and should never drop low enough to cause the antisiphon valve to unseal from low pressure... So... Recap... Check for scale and put a good working gauge on connector even if generic one just a good one to know truely whats going on.. And... Listen for the Siria pressurestat top back for cycling on and off and if so you may need bump up that pressure And.. Dial down the screw on the pump 1 turn and make note of change... OPV could still be ok since you did see water coming out of it behind font panel into back of drip try after shot... Send another video once you detrmine machine is actually fully warmed up... (Pressurestat cycling on and off, gauge showing .9bar to start, antisiphon valve top left of boiler that was hissing has stopped and a little stem sticking out the top of it sealing it tight) :). Good luck :D

therob
Senior Member

Joined: 21 Nov 2011
Posts: 8
Location: Birmingham, UK
Expertise: Just starting

Posted Sat Dec 29, 2012, 8:25am Subject: Re: UNIC Espresso machines- backflushing and more!

You are a legend thank you so much - I will look at all those issues it had been running for about 3 hours but I had also just released about 1.5 litres out of the tank, to try and show you what the gauge was doing. When fully warm and idle the right side of the gauge sits in the 1.0 bar range - the red section. to check for lime scale on the release valve on top of the tank should I just take it out? when I pull the pin it moves freely... and there is no obvious scale from the outside... saying that it would all be on the inside... how do I release all the pressure in the system so that I can remove the safety valve? LOL ... I am beginning to think I should have got one of those plastic £50 nespresso machines!!! I know it will be worth it in the end though... Will update once I have worked through those bits... R

gucciago
Senior Member

Posted Sat Dec 29, 2012, 8:46am Subject: Re: UNIC Espresso machines- backflushing and more!

Hahaha well your getting a quick education in why commercial machines are commercial however if you take time and hopefully not too much money you will be enjoying some of the best espressos! And worst! Hahaha anyway, that clicking of gauge was odd so you need determine if that is accurate from a good test gauge, which I doubt ,or it is actually accurate, l but who knows at this point, the boiler temp side is usually ok but the brew circuit seems to fail more often on those gauges... Ayway, cool machine til cold, unplug wateline, turn on pump for 1-2seconds no more and you should be depressurized... Then you can attempt to remove seafety valve and look in with flash light... If it looks ok then still could be at any fittings or valves but still coud be ok... Its possible its only that gauge giving you faulty and previous owner, readings and they tried to adjust pump pressure according to bad gauge... So plug on a new gauge, warm it up, pull shot... Watch for OPV ( one way valve) to drip into rear of tray after shot and do not confuse this with 3 way valve that will gush water into rear of tray... The opv will just drip usually not gush.... If new gauge showes that evything is actually ok then id start looking at grind and tamp and coffee your using... Bad coffee makes bad espresso even with best equipment... This is the general order of making good coffee or espresso... Quality of coffee and blend or verital using for specific outcome Grinder Barista ( human factor usually) Machine This is most important when dealing with espresso making... Its like a bunch of doors locked and only one is open and you have to find that unlocked door and remember where you found it! Lol Look here this may help see what is happening at group pressure http://www.espressoparts.com/V_512

therob
Senior Member

Joined: 21 Nov 2011
Posts: 8
Location: Birmingham, UK
Expertise: Just starting

Posted Sun Dec 30, 2012, 5:35pm
Subject: Re: UNIC Espresso machines- backflushing and more!

gucciago Said:

Ok before going any farther you need to disconnect the brew pathway side of manometer ( gauge ) and put a new good test gauge on it and see what the heck is really going on... Also was this machine considered fully warm? On right side of gauge you are sitting way too low at around 5 bar it should be around .9- 1.0 bar ...if gauge reading is too low then that little spitting valve top left of boiler called the antisiphon valve is releasing false pressures as tank water expands and heats to full temprature and its obviously not there yet lol ... The hot water does come out strong like in video so thats ok And in the video, the all brass cylidrical valve with wide flat screw on top with 2 divot holes is your OVP that should terminate via a copper line into rear of drip tray...

Now if your hearing the pressurestat cycle on and off ( big box on back of boiler usually branded" sira" with screw on top) . Then you need turn that up until it cycles in .9 range on right gauge (via screw on top of pressure-stat) but you really should also look around for scale,especially coming from the safety valve on top.. id say honestly, you really have to get these readings correct before you can go further... If you fracture the brewpath into the boiler or safety valve is scaled up you could blow that thing to peices... However its more likely stil too low on heat... The other thing is that it could be full of scale and not much room for boiler water but then id doubt you'd have that much hot water... With a tank of 6.5liters the is plenty of hot water when running properly and should never drop low enough to cause the antisiphon valve to unseal from low pressure...

So... Recap... Check for scale and put a good working gauge on connector even if generic one just a good one to know truely whats going on..

And... Listen for the Siria pressurestat top back for cycling on and off and if so you may need bump up that pressure

And.. Dial down the screw on the pump 1 turn and make note of change...
OPV could still be ok since you did see water coming out of it behind font panel into back of drip try after shot...
Send another video once you detrmine machine is actually fully warmed up... (Pressurestat cycling on and off, gauge showing .9bar to start, antisiphon valve top left of boiler that was hissing has stopped and a little stem sticking out the top of it sealing it tight) :). Good luck :D

Posted December 29, 2012 link

Right...

The front gauge that is on it is brand new... I havent had a chance to get a new one to use... this one should be fine.... I hope...

There was no limescale that I could see in the tank (but the hole is pretty small), and there is a definite clear pathway to the safety valve, and the siphon is coming on and clicking in as the pressure builds.

Pressurestat seems to click on and off and needle for the steam pressure is fine is sits in the 1.0 range all the time.

I had to take the OPV off the line to turn it, it was locked into place with some limescale - I soaked it in vinegar and beat it with the back of a big screwdriver and it eventually started turning (what kind of tool was I supposed use for that? only thing I had was circlip pliers but that only gives 1/4 of a turn when it is on the machine) so I took it all apart soaked pieces individually gave them a scrub and put it all back together and stuck it back on, but dialed out 1 turn... at that stage I also dialed the screw underneath on the pump in one turn...

When I turned the machine on it all seemed fine, idle pressure sat around 12-14 bar and I thought it was fixed... NOPE. Brew pressure dropped to 6 bar, so I undid the pump pressure adjustment and dialed in the OPV back to where it was before I took it all apart... NO CHANGE... it sat like that for hours... so I filmed this:

https://www.dropbox.com/s/x8gtd5xo8klujq3/IMG_1415.MOV

(sorry the sound quality drops out on this half way through... my hand may have been on the microphone)

I thought maybe I had turned the pump pressure the wrong way so I dialed the screw back in 3 turns, and that changed everything... idle pressure shot up to peak and shots were coming out at 15 bar... so I turned the screw back out in increments of half turns and worked it back to a shot pressure of about 10bar but now the idle pressure is back up to peak... video here:

https://www.dropbox.com/s/udneyvi2akzuz9l/IMG_1417.MOV

Would the fact that I was having to turn the machine virtually onto its side, while it was running, to adjust the pump pressure have any effect on this?
One of the issues I will have is the double shot is coming through with 120ml of water... so I will need to adjust that - is there a way to adjust the flow without changing what I have achieved so far?

I have just had another look and it was resting idle around 11 bar and an empty shot (just water) was still around the 10bar mark - as soon as I had pulled the shot the gauge maxed out again... I am happy with that, I think it will settle as I use it... the OPV only drips so it will take a while for the pressure to drop.

Now onto beans... I see you are a pro roaster... what blends do you recommend?

Thanks again - I really appreciate your help

R

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