HX waterline solenoid not staying open

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
qntnclrk

#1: Post by qntnclrk » Nov 09, 2019, 4:17 pm

I have Rocket Giotto Evo V1 plumed to my RO system and about 2 months ago my pump/group head started getting starved for water. I quickly switched to tank mode, shut off the waterline, and made sure there were no kinks in the water delivery system. The line pressure checked out on my incoming water (around 1 bar) and the machine worked as expected when switched to tank mode, so I did some investigation and replaced the waterline solenoid value with this solenoid from espressotec:
https://www.espressotec.com/rocket-sole ... -5234.html

After the install and switch back to plumb mode and the machine works, but it seems like there is still a blockage between the water delivery system and the group head. When I engage preinfusion, the heat exchanger delivers about 20ml and stops. There's no line pressure at the group head, my group head thermometer reads +220C frequently, and my group head often emits only a ton of steam in preinfusion mode as if there's a big air bubble in there.

Is there a difference between the waterline and tank solenoid valves? Do I have a controller problem? Any help is appreciated!

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homeburrero
Team HB

#2: Post by homeburrero » Nov 09, 2019, 6:07 pm

qntnclrk wrote:After the install and switch back to plumb mode and the machine works, but it seems like there is still a blockage between the water delivery system and the group head. When I engage preinfusion, the heat exchanger delivers about 20ml and stops. There's no line pressure at the group head, my group head thermometer reads +220C frequently, and my group head often emits only a ton of steam in preinfusion mode as if there's a big air bubble in there.
Just to be clear, when you say 'engage preinfusion', are you saying that you lift the lever midway to the point where the pump is not engaged? If so, be aware that on the Evo you don't expect line pressure into the HX and group because the solenoid does not open until the lever switch (which tells the controller to engage the pump) is closed. Unless you rewire that solenoid all you get here is the same pre-infusion that you'd get in tank mode, i.e., the pressure that is built up inside the HX and TS due to thermal expansion.

In general, if you have a leak in the expansion valve, brew valve, or check valve that is draining water out of the HX, that might cause your symptom. A small leak leads to a bubble causing a thermosyphon stall, but a large leak can drain enough out that the system starts heating the group via circulating condensing steam, which can cause the group to go way hot. If this were your issue though you would expect it to occur in both tank mode and plumb mode.

Be aware that testing pre-infusion by leaving the brew valve at midway for a while to observe flow will drain the HX and cause your symptom.
qntnclrk wrote:Is there a difference between the waterline and tank solenoid valves? Do I have a controller problem?
Parts list shows the same solenoid valve for both. I doubt that it's a controller problem -- those two solenoids simply get energized whenever the pump is energized. The autofill solenoid is different - has its own pin on the controller.
Pat
nínádiishʼnahgo gohwééh náshdlį́į́h

qntnclrk

#3: Post by qntnclrk » Nov 09, 2019, 8:36 pm

Thanks for your reply! I really appreciate the help.

homeburrero wrote:Just to be clear, when you say 'engage preinfusion', are you saying that you lift the lever midway to the point where the pump is not engaged?
If so, be aware that on the Evo you don't expect line pressure into the HX and group because the solenoid does not open until the lever switch (which tells the controller to engage the pump) is closed. Unless you rewire that solenoid all you get here is the same pre-infusion that you'd get in tank mode, i.e., the pressure that is built up inside the HX and TS due to thermal expansion.
When I say 'engage preinfusion' that is what I mean. But this part has me a bit stumped as I used to be able to lift the lever to that stage and get running water, even if the machine was off. Sounds like I need to find a way to wire the solenoid "open."

homeburrero wrote:In general, if you have a leak in the expansion valve, brew valve, or check valve that is draining water out of the HX, that might cause your symptom. A small leak leads to a bubble causing a thermosyphon stall, but a large leak can drain enough out that the system starts heating the group via circulating condensing steam, which can cause the group to go way hot. If this were your issue though you would expect it to occur in both tank mode and plumb mode.
Ok, thanks for the walkthrough. This gives me a few places to check on and see if I have a blockage or leak. If I had a small leak in the check valve or brew valve I'd see more water than expected in the drip tray, right? I didn't have this in tank mode, but I've also had the machine apart a couple times through this process.

homeburrero wrote:Parts list shows the same solenoid valve for both. I doubt that it's a controller problem -- those two solenoids simply get energized whenever the pump is energized. The autofill solenoid is different - has its own pin on the controller.
Agreed, I looked everywhere and did a bit of digging but I was never able to find anything that said differently. That's really what prompted me to wonder if I had made the mistake.

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homeburrero
Team HB

#4: Post by homeburrero » Nov 10, 2019, 3:56 pm

qntnclrk wrote:Sounds like I need to find a way to wire the solenoid "open."
You would need to power the solenoid with a hot wire from anywhere after the power-on switch.** You don't want to take it from the element circuit, because I think that gets switched off when the water is low. You may need a regulator on your water line if you do that. It may be kludgy and not well integrated with the tank/plumb switch (I think that switch has only one power-in wire for the two solenoid alternatives.)
qntnclrk wrote:If I had a small leak in the check valve or brew valve I'd see more water than expected in the drip tray, right?
A leaking brew valve or expansion valve will end up in the drip tray. A bad check valve would let water flow back towards the pump. A leaking HX might let water drain into the steam boiler - fortunately unlikely. (If you do a long series of blind backflushes and get a boiler overfill that might indicate a leaking HX or a leaking autofill solenoid.)

** Or maybe not. See JRising's comment below about overheating solenoid coils.
Pat
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JRising

#5: Post by JRising » Nov 11, 2019, 10:31 am

A constantly on solenoid coil will overheat after a few minutes. There is a check valve adjacently upstream of that solenoid valve. You could just replace the solenoid valve with a 1/8 1/8 FF coupling. (Or just take the plunger out of the valve and make it a 1/8 1/8 FF coupling).
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qntnclrk

#6: Post by qntnclrk » Dec 02, 2019, 11:37 pm

This did the trick! I never thought to take the plunger out of a new solenoid valve. It maintains pressure consistently on the right group head pressure gauge and allows for the mid-lever lift preinfusion.

Do these plungers come removed from the factory? Or does the button behind the lever get 'bumped' at the mid-point and activate the water-line solenoid?

JRising

#7: Post by JRising » Dec 03, 2019, 11:31 am

qntnclrk wrote: Do these plungers come removed from the factory? Or does the button behind the lever get 'bumped' at the mid-point and activate the water-line solenoid?
They need that solenoid in place (And closed) in order to operate off of the reservoir, otherwise the pump would suck bubbles through the check valve unless the plumb-inlet was perfectly capped. You will want to put the plunger back in if you ever want to make the machine operable from the reservoir.

The machine simply works by opening one or the other solenoid valve (Plumb or Reservoir) whenever the pump is on, depending on which position the toggle switch is set. I'd never thought of it before but since you mentioned it, it would be cool to have a pair of switches behind the cam lever. One to open the solenoid at mid-point, the second to activate the pump at fully open. Be the first to do it, Rocket. It's a cooler idea than a needle valve in an oversized gicleur.