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Classic Pressure?

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  • do-ob
    replied
    Re: Classic Pressure?

    just thought id post the documentation for anyone with an invensys pump, had to trawl some other forums to get the info seeing as noone has posted it on this forum.

    spanglefish.com/avicennassolution/documents/Parts%20List/CP03A-120V.pdf

    consensus of other posts around the net is that flow rate is 125ml/30sec for 9 BAR for the invensys cp3a pump (but its actually 240cc/60sec if you look closely at the graph above), and 100ml/30 sec for the ulka.

    hope this saves some people some time!

    Leave a comment:


  • giacomotaylor
    replied
    Re: Classic Pressure?

    Finally some good shots -- that Sparky bloke is brilliant.  Thank you so much! 

    Originally posted by 3B2F20252D214C0 link=1143118905/115#115 date=1298859799
    Ive adjusted the opv so that Im getting 100ml in 30 seconds, down from about 130ml out of the factory. Perhaps Ive completely misunderstood the above posts, but I found tightening (turning the opv clockwise) reduced the flow, and loosening (counter-clockwise) increased it.
    So I had the same experience (with a one month old Gaggia Classic).  Didnt have a blind filter, so just did the 270 degree turn blindly.  Now that I have one, I found I had to rotate it clockwise to get to 100ml in 30 seconds.  Im not sure how much, because I kept rotating it counter clockwise and I kept getting more and more water (up to 200ml/30 sec).  Once I went the other way, everything turned out well.  Maybe down under things are reverse, just like with the water going down the drain. 

    Leave a comment:


  • wcliam
    replied
    Re: Classic Pressure?

    Certainly didnt come across as condescending at any point, Who me. I needed the small words, and KIS explanations, as evidenced by the fact that Id understood the OPV to operate in exactly the opposite manner from reading the previous posts!

    Gradually experimenting with grind and tamp to get the best out of the new pressure, and enjoying it immensely.

    Leave a comment:


  • emckissock
    replied
    Re: Classic Pressure?

    I hope nobody thinks Im talking down to you, or others, with putting it in such simple terms - just following the KISS principle.
    Most things in the gaggia classic are pretty straightforward really, but the engineering is seriously robust and IMNSHO it has all the right things to let you pull a good shot - the adjustable OPV is one of them.

    The main downside would be the small boiler.


    Leave a comment:


  • wcliam
    replied
    Re: Classic Pressure?

    Thanks Who me, Im a lot more comfortable with the bean, grind and tamp variables, just wanted to make sure I was getting as much as possible out of the Classic. I appreciate the method will just get you in the right ballpark, but with this mod being no cost, I thought Id be a fool not to start there.

    Also appreciate the explanation in small words of the operation of the opv -- very helpful to understand what Ive done. Youve been very generous with your time and knowledge, and I and all who drink coffee from my machine are much obliged!

    Leave a comment:


  • emckissock
    replied
    Re: Classic Pressure?

    Yep, tightening should reduce the flow, and this increases the maximum possible pressure at the group head. If youve tightened the opv, then you would expect your shots to pour quicker if all other variables are unchanged.
    All the opv is, is a rubber bung on the end of a spring. The tighter you screw it down, the harder the water has to be pushed to squeeze past it. The higher the water pressure required, the slower the pump runs.

    Dont forget that this is only a rough way of setting pressure, different pumps will vary and also wear over time. But as some gaggias have started with flow rates of 50-60 ml, it is well worth checking and adjusting when things are way out of line.

    You are probably at the stage now that you need to work on some of the other variables. Plenty of threads to look at for further info on improving shot quality.

    Leave a comment:


  • wcliam
    replied
    Re: Classic Pressure?

    Thanks yet again, Who me. Really, really clear and helpful advice. As you may have guessed from my questions, I am not a naturally technically-minded or mechanical soul (I just love coffee machines and tinkering with them). Your suggestions were spot on, and it was a simple process once youd laid it out for me.

    Ive adjusted the opv so that Im getting 100ml in 30 seconds, down from about 130ml out of the factory. Perhaps Ive completely misunderstood the above posts, but I found tightening (turning the opv clockwise) reduced the flow, and loosening (counter-clockwise) increased it.

    Im happier with the results, but my shots still pour a lot quicker than Id like (certainly faster than 30ml in 30 seconds). Im playing with the grind and tamp at the moment, with some good results. During the week Ill do what I should have done at the start, which is determine which pump I actually have, and whether I should adjust further to get in the range of 9 bar.

    Again, many thanks. If even I can follow your instructions they are clear indeed!

    Leave a comment:


  • emckissock
    replied
    Re: Classic Pressure?

    Im making assumptions again here, your machine may be different, so check if this makes sense before following my guidance.

    The silicone tube is a push fit over the output pipe of the opv, it may also have a spring clip to keep it in place. Sometimes they get stuck in place over time. Remove the spring clip if fitted and slide up the tube out of the way.  A regular pair of pliers usually has a curved as well as a flat section, the curved part is great for gripping round objects, use this to firmly grip the part of the tube over the output pipe, twist about thirty degrees in each direction - this will free the pipe and allow it to pull off relatively easily.

    I think I just used a 17mm ring spanner on the opv nut. It may also be frozen in place - try a sharp tap (or several) with a hammer to free it up, you shouldnt need a lot of sustained force. This nut does not need to be very tight when reassembling -  flow through here is not under any pressure.

    Leave a comment:


  • wcliam
    replied
    Re: Classic Pressure?

    Thanks WM?, that was really helpful. Had another look, and my machine is exactly as you describe. Slid it out from between the tabs, removed the earthing cable, and its all good. I was just being a bit slow and precious with the machine.

    Consistent with this approach, Im having trouble getting the hex nut off to expose the OPV. Ive tried a spanner, but cant get the torque needed, as its not possible to approach horizontally. Others have suggested removing the silicon tube, and using a 17mm socket. Ive had a bit of a tug on the tube, but Im worried that if I use too much force Ill split it.

    What method did you use to get the hex nut off? Should I stop worrying, and just pull hard on the silicon, having faith that Ill be able to re-attach without too much trouble? Or put a bit more muscle into the spanner method, without removing the tube?

    Again, many thanks for the reply, and apologies if these are stupid questions.

    Leave a comment:


  • emckissock
    replied
    Re: Classic Pressure?

    Sorry, only just spotted this.
    Originally posted by 5F4B44414945280 link=1143118905/111#111 date=1298072862
    Hi all, great thread, and Im very keen to perform the mod on my Classic. Ive hit a snag at the very first step, however. Theres a small metal tab attaching the cup warmer / top plate to the rest of the machine, at the front.
    Doesnt sound like mine, but then my classic is mounted in a different case and is a 1994 model.
    Can you take a photo? I would have thought youd remove all top screws, lift from the rear and slide out of the tabs, but am just guessing based on your description.

    Leave a comment:


  • wcliam
    replied
    Re: Classic Pressure?

    Hi all, great thread, and Im very keen to perform the mod on my Classic. Ive hit a snag at the very first step, however. Theres a small metal tab attaching the cup warmer / top plate to the rest of the machine, at the front.

    In order to take the top off, Id have to snap it, or otherwise bend the tab all the way back, and work on the machine with the top plate still attached. Just wondering if anyone else has encountered this, and whether theres a simple solution that doesnt involve breakage.

    Apologies if this is a hopeless newbie question and Im missing something obvious, and thanks in advance.

    Leave a comment:


  • emckissock
    replied
    Re: Classic Pressure?

    Originally posted by 7D7A7F6A7D7B677B0F0 link=1143118905/109#109 date=1295117546
    I jut tried the mod on my (1yr old) classic, but only just got 100ml/30 secs return before I changed anything! Is something wrong?
    Sounds perfectly OK to me. If it is working fine, dont mess with it.

    Leave a comment:


  • rupertht
    replied
    Re: Classic Pressure?

    Hi Guys,
    How much variation is there in the factory settings? I jut tried the mod on my (1yr old) classic, but only just got 100ml/30 secs return before I changed anything! Is something wrong?
    Rup

    Leave a comment:


  • Wayno
    replied
    Re: Classic Pressure?

    Did the quick mod to mine today, tested the flow rate and it was at just over 80 mm in 30 secs made a couple of adjustments and settled on setting it at 110 MM in 30 seconds. WoW what a difference, Just made a great shot so im happy. Thanks for all your info every one, it has been a great help.

    Cheers
    Wayne

    Leave a comment:


  • scarey
    replied
    Re: Classic Pressure?

    Im no expert either but I think youve at least misread the specs - the 650ml/min is at 0bar (which matches my recollection of the "water debit test" being 90ml in 10sec for freeflow).

    With a blind filter in the group all water flow will be diverted by the OPV so Im guessing you would expect the flow for the OPV setting - ie 250ml/min for an OPV set to 9bar.

    Leave a comment:

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