OPV return options

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tcaton
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Joined: 13 years ago

#1: Post by tcaton »

Having "converted" my single-boiler Alexia to a "double boiler" (2nd boiler being a PV Export), I may never need to trade her for a higher-end machine. The only thing I may ever miss is the ability to plumb. CCS offers a kit to plumb an Andreja that can theoretically be applied to an Alexia. However, I believe one complication is what to do with the OPV waste water. The recommended solution is to run the OPV line to the drip tray, which requires a bit of internal surgery I'd rather not perform. Plus, I have a habit of forgetting to empty the tray as it is - I don't copious amounts of additional water flowing in there.

Why can't the OPV return line simply T junction with the water intake line just prior to the pump, rather than being dumped to the tray? I can see why this would not work in certain HX designs where the OPV is after the HX, as that would feed hot water into the pump. However, given a SB or an "early-OPV" HX design, is there a technical reason this would be a bad idea or simply wouldn't work?

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pizzaman383
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#2: Post by pizzaman383 »

I found a post somewhere describing how to do exactly what you're describing. I installed it in my VBM DDv2 about a year ago and love it.
Curtis
LMWDP #551
“Taste every shot before adding milk!”

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Teflon1064
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#3: Post by Teflon1064 »

The only issue that comes to mind is that the pump inlet isnt at atmospheric pressure, when plumbed in its at water supply pressure. Since the OPV operates on differential pressure (say 12barg - 0barg = 12bar), if you connected the outlet to a 3barg supply, youd have to adjust the OPV down to a differential pressure of 9bar to have it still open at 12barg. I dont know for sure but im guessing theres enough adjustment to do this. You may well need to upgrade the tubing to a higher pressure grade in line with the pump inlet/outlet since it would be permanently exposed to supply pressure post mod. When the pump is on, there will be pressure drop in the inlet pipework, reducing the pressure at the point the opv returns. I dont think this will be significant enough to be concerned about though.

Sounds like a good mod, as long as you dial in the opv setting once its done

jonr
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#4: Post by jonr »

I agree with Teflon1064, although it might be easier to regulate the supply down to a few psi, at which point it wouldn't have enough effect to worry about (and you could use the existing low pressure tubing).

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pizzaman383
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#5: Post by pizzaman383 replying to jonr »

Since I tried using the float-valve-in-reservoir plumb-in approach first, I had already put a pressure regulator on the supply line and had set it lower than normal. When I put this mod in place with my vibe-pump VBM I think I had to make a 1-bar adjustment to my OPV as was noted above.

I used the kit from Chris Coffee that includes a solenoid so that any of the rubber lines are only under pressure when the pump is running. I did need to use zip-ties on the barb fittings to that there was no seepage.

The other mod I made at the same time was to route the output of my steam boiler vacuum breaker to the drip tray. I installed a vacuum breaker that had a barb fitting, drilled a hole behind the bottom section of the E61 output stack, and routed a silicone tube to go out the hole and into the drip tray. I've seen a fitting that some machines use to run a water line through the front of the machine into the drip tray but couldn't find a place to order the part.
Curtis
LMWDP #551
“Taste every shot before adding milk!”

Loper77
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Joined: 12 years ago

#6: Post by Loper77 »

Does anyone have a link or a walkthrough how to achieve this? I've searched but can't seem to find the info.

Tia
pizzaman383 wrote:I found a post somewhere describing how to do exactly what you're describing. I installed it in my VBM DDv2 about a year ago and love it.