# OPV ( expansion valve) fault and reset on Alex duetto



## rocky66 (Jul 28, 2019)

Hi, I recently plumbed in my duetto after many good years service via the reservoir. I fitted a pressure regulator with the pressure just under 3 bar ( within manufacturer spec). As soon as I opened up the water it began to pour out via the OPV outlet above the drip tray. It eventually stopped when the machine warmed up but then started to flow out when it cooled down.

I decided to remove the spring and plunger from the OPV ( with a struggle) and noticed debris making it stick. The end of the plunger and o ring were in very good codition for a six year old machine. I cleaned everything with citric acid and reassembled. It now only shows a few drips as it reaches temp and stops. No water escaping when switched off as before. Job done I thought. But......how do I know if the OPV is tightened to the right level? I phoned Bella Barista and spoke to Chris who said I should put a blind filter and screw it in or out till the brew pressure is between 8-9 bar. That does not seem right to me. It is a rotary pump and the OPV on rotary pump machines are factory set so do not need adjusting ? All I want to know is how can I tell if I have screwd the plunger down to the right level. Can someone help please.


----------



## Nikko (Aug 20, 2014)

The pressure relief valve going to the drip tray should be set to ca. 12barg. Using the bypass on the pump to set the pump pressure to 12 barg, adjust the pressure relief valve so it opens at 12 barg.


----------



## DavecUK (Aug 6, 2013)

http://coffeetime.wikidot.com/rotary-pump-pressure-adjustment


----------



## rocky66 (Jul 28, 2019)

Dave Thank you for the link. The only thing I am not sure is do I tighten the OPV it if the pressure is not been relieved at 12 bar and loosen it if the OPV lets go earlier?

To summarise I switch on the machine.

Let it reach working temp

Fit a blind filter and activate the brew lever

Turn the pressure brew regulating valve clockwise till it shows 12 bar

If the OPV lets go before 12 bar then I loosen the OPV and conversely if at 12 if it has not opened then I tighten the OPV?

Finally adjust the brew regulator valve down to 9bar

Does the above seem right?

Many thanks for your help


----------



## DavecUK (Aug 6, 2013)

> If the OPV lets go before 12 bar then I loosen the OPV and conversely if at 12 if it has not opened then I tighten the OPV?


 Only this bit is the wrong way round...tighten/loosen


----------



## rocky66 (Jul 28, 2019)

Thanks


----------



## rocky66 (Jul 28, 2019)

Thanks Dave got the job now done. For my education does the setting of the OPV in any way influence the extraction or is it purely a safety mechanism. Sorry if it sounds a stupid question but I Am forever trying to learn more.


----------



## DavecUK (Aug 6, 2013)

It doesn't affect extraction at all unless it's set lower than the pump pressure. It's function is to allow expanding water (when it's heated) out of the sealed brew system rather than fracturing the pipes/fittings or boiler. You will see water exit the expansion valve tube after a shot as cold water entering the boiler warms up and expands.

Pump pressure should be 9 bar and expansion valve 11-13 bar, it's not super critical the exact pressure as long as it's 11 bar or over.

I used the term safety mechanism as the articles are simplified for all users....because if hydraulic pressure fractures a pipe, it's a relatively sedate (although expensive) event..


----------

