Occasional high line pressure alarm after shot

Did you have an issue or question about operation of your plumbed Dream machine on Day One right out of the box? If so, report it here and also keep us abreast of the resolution.
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goodboyr
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Occasional high line pressure alarm after shot

Post by goodboyr » Thu Jan 17, 2013 3:04 am

Just got my Dream. Occasionally after pulling a shot, the line pressure indication goes to 6.1 bar and the alarm sounds. Then the pressure indication slowly decays to the actual line pressure which looks to be about 3.9 bar. Any ideas as to whats wrong?
Bob
La Spaziale Dream and Baratza Sette 270W

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chas
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Re: Occasional high line pressure alarm after shot

Post by chas » Thu Jan 17, 2013 9:28 am

I think you may have to call Chris Coffee and ask about that. Since the older S1s indicated errors by combinations of steady lights or blinking lights on the front panel, the user's manual indicated was those meant. However, since the Dream is supposed to give you a verbal error message, nothing is documented. Also, as far as I know, there was never any kind of sensor and therefore no alarm for this condition on models prior to the Dream. If you do call CCS, let us know what they say about this.

Typically the line water first flows through a one way valve. With this spring loaded valve, water can only flow from higher to lower pressure. Normally this lets water flow into the machine. However, when the pump turns on and pressure is higher on the machine side of the water line, this valve closes so that water can't flow back into the water mains. Any line pressure sensor should be on the water mains side of that one-way valve. The two most obvious options would be that either that valve isn't working properly or that the water mains pressure really is spiking higher for a period of time.

What do you have in the water path between the water line and the machine? Filters, shut off valves, pressure gauge, pressure regulator???? Are you on "city water" or a well?
Chas
LM GS/3 & LaSpaziale Dream v 1.23 (US 120V)
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goodboyr
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Re: Occasional high line pressure alarm after shot

Post by goodboyr » Thu Jan 17, 2013 9:45 am

Duh!!! I'm a noob! I realized this happens because i left the pf in the machine instead of removing immediately and rinsing. The pressure gets locked up in the portafilter (especially when you're experimenting with grinds and are running too fine). When you remove the pf and do a short rinse, the pressure returns to normal. Chock that one up to the learning curve! What an awesome machine, though.
Just for your info, I am hooked up to the house line through a combined carbon, ix filter through 1/4 inch JG lines. All is good now and I've finally dialled in the grind.
Thanks!
Bob
La Spaziale Dream and Baratza Sette 270W

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chas
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Re: Occasional high line pressure alarm after shot

Post by chas » Thu Jan 17, 2013 9:57 am

Something still sounds a little off about this...assuming the error message is a true indication of what is going on. Keep an eye on it and let us know what happens, if anything, going forward.

1) If this is really a high line pressure alarm, then as I noted in the last post, the sensor should be on the water mains side of a one way valve and it should be isolated from and unaffected by the PF/pump pressure.

2) If the sensor really is on the machine side of that one way valve, then a high pressure alarm could indicate that the 3-way valve isn't releasing all the pressure from the portafilter. However, if that happened,the PF would be hard to get off and would probably spray you with espresso grounds when you removed it.

Even though the alarms are supposed to be clearly stated on screen in English now, I hope to eventually work with Chris Coffee and LaSpaz to come up with a full list of alarm messages and what exactly triggers them.
Chas
LM GS/3 & LaSpaziale Dream v 1.23 (US 120V)
Mazzer Kony E, Customized Rocky
Hottop P/B

goodboyr
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Location: Canada

Re: Occasional high line pressure alarm after shot

Post by goodboyr » Thu Jan 17, 2013 10:20 am

The pressure slowly decays with the pf on. When you remove the pf, the high pressue starts decaying a bit quicker, and then when you flush without the pf it quickly returns to line pressure. It appears the "high line pressure" alarm is set for greater than 6 bar, for a certain time (maybe 5 or 10 seconds). I don't get any spray or difficulty removing the pf, so the 3 way seems to be working fine. I think its the location of the pressure sensor. I wonder if there's a check valve between the pump and the 3 way and head and the pressure sensor is between the pump and the check valve. That would explain why you don't see this high pressure when removing the pf, but flushing opens the check and equalizes the pressure.
Bob
La Spaziale Dream and Baratza Sette 270W

goodboyr
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Re: Occasional high line pressure alarm after shot

Post by goodboyr » Thu Jan 17, 2013 10:42 am

Looking at the flow diagram in the Vivaldi manual, I think it is as I described. There is a backflow prevention check valve between the pressure sensor and the pump. The 3 way is downstream of this at the group head. So, either the backflow check valve is a bit sticky, or when the 3 way operates, it is too low a flow to open the check valve. The 3 way doesnt have to open very long to relieve group head pressure, just a 'burp". So, that could be insufficient flow to open the check. Now that I am removing the pf and flushing immediately, I no longer have the alarm.
Bob
La Spaziale Dream and Baratza Sette 270W

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